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'Vau Of * NBS TECHNICAL NOTE 939

U.S. DEPARTMENT OF COMMERCE/ National Bureau of Standards
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards 1 was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and

technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the

Office of Experimental Technology Incentives Program.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Center for Radiation Research — Laboratory Astrophysics 2 — Cryogenics 2 — Electromagnetics 2 — Time and Frequency'.

THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational insti- tutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists of the Office of Standard Reference Materials, the Office of Air and Water Measurement, and the following divisions:

Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor Radiation — Physical Chemistry.

THE.INSTITUTE FOR APPLIED TECHNOLOGY provides technical services developing and promoting the use of avail- able technology; cooperates with public and private organizations in developing technological standards, codes, and test methods; and provides technical advice services, and information to Government agencies and the public. The Institute consists of

the following divisions and centers: Standards Application and Analysis — Electronic Technology — Center for Consumer Product Technology: Product Systems Analysis; Product Engineering — Center for Building Technology: Structures, Materials, and Safety; Building

Environment; Technical Evaluation and Application — Center for Fire Research: Fire Science; Fire Safety Engineering.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effectiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the principal focus wthin the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer

languages. The Institute consist of the following divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE OF EXPERIMENTAL TECHNOLOGY INCENTIVES PROGRAM seeks to affect public policy and process

to facilitate technological change in the private sector by examining and experimenting with Government policies and practices in order to identify and remove Government-related barriers and to correct inherent market imperfections that impede

the innovation process. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS; promotes the development of the National Standard Reference Data System and a system of in- formation analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services

to ensure that the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following organizational units:

Office of Standard Reference Data — Office of Information Activities — Office of Technical Publications — Library —

Office of International Standards — Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

2 Located at Boulder, Colorado 80302.
i 6 1977

^&3

Ml

NBS Reactor: Summary of Activities

July 1975 to June 1976

Frederick J. Shorten, Editor

Reactor Radiation Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

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v>

'°*£A\J Of *

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Betsy Ancker-Johnson, Assistant Secretary for Science and Technology

uC NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Issued May 1977
National Bureau of Standards Technical Note 939

Nat. Bur. Stand. (U.S.), Tech. Note 939, 140 pages (May 1977) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1977

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C- 20402 - Price $2.76

Stock No. 003-003-01769-8
FOREWORD

The National Bureau of Standards Reactor was built not only to serve the needs of the NBS but also those of other government agencies

and the greater Washington Scientific Community . The Reactor Radiation

Division was established to operate the reactor and to foster its scientific and technological use. Toward this end, the Division has a small

nucleus of scientists experienced in the use of reactors for a wide range

of scientific and technical problems. In addition to pursuing their own research and developing sophisticated experimental facilities, they ac- tively seek out and encourage collaboration with other scientists, engaged

in challenging programs, whose work can benefit from use of the reactor,

but who as yet do not have the reactor experience necessary to take full

advantage of the facilities available. The Division also provides irradiation services to a wide variety of users as well as engineering and

other technical services.

The reactor operates at 10 MW and is designed to provide more than

20 experimental facilities ranging from intense neutron beams to extensive

irradiation facilities, making it one of the most versatile high flux

research reactors in the country. Thus it is able to serve a large number

of scientists and engineers in a broad range of activities both within

and outside the NBS.

This report attempts to summarize all the work done which is dependent on the reactor including a large number of programs outside the

Division. The first section summarized those programs based primarily

>n Reactor Radiation Division (RRD) initiatives whereas the second and

third sections summarize collaborative programs between RRD scientists

and other NBS or non-NBS scientists respectively. The fourth section

summarized NBS work originating entirely outside the RRD which requires

no collaboration with RRD scientists. The section entitled, "Service

Programs" covers those programs originating outside NBS but for which

RRD provides irradiation services. The remaining sections are selfexplanatory.

iii
FOREWORD

Appreciation is extended to F. J. Shorten of the Reactor Radiation

Division for his extensive contributions to the editing, organization

and preparation of this report, and to L. Sprecher, C. O'Connor and

P. Lewis for efforts in typing manuscripts.

iter Radiation Divisii

J . J . Rush

Chief, Reactor Radiation Division (Acting)

National Bureau of Standards

IV
ABSTRACT

This report summarizes all those programs which depend on the NBS

reactor. It covers the period from July 1975 through June 1976. The

programs range from the use of neutron beams to study of the structure

and dynamics of materials through nuclear physics and neutron standards

to sample irradiations for activation analysis, isotope production and

radiation effects studies.

Key words: Activation analysis; crystal structure; diffraction;

isotopes; molecular dynamics; neutron, nuclear reactor;

radiation.

v
TABLE OF CONTENTS

FOREWORD • iii

ABSTRACT v

A. REACTOR RADIATION DIVISION PROGRAMS 1

Neutron Scattering Studies of Hydrogen in Metals 1

1. The Lattice Dynamics of VD_

7 1

2. Inelastic Neutron Scattering Line Shapes in PdD.. ,„ . . 4

3. Lattice Dynamics of Cerium Deuteride 7 Crystal Dynamics, Phase Transitions and Orientational

Disorder in Ionic Crystals 9

1. Alkali Cyanides 9

2. Ammonium Halides 12

Order-Disorder Phase Transition in KCN 13

Neutrino Scattering 15

Spin Waves in Ferrimagnetic Erbium-Iron 19

Order-Disorder in V Ga 22

Application of Robust/Resistant Techniques to Crystal

Structure Refinement. 23

A Flat-Cone Diffractometer Utilizing A Position-Sensitive

Detector 26

Conversion of the Spectrometer Control System to the

DECLAB 11/40 27

The Neutron Radiography Program . 28

Thermal Neutron Flux Measurements 41

Solutions of the Klein-Gordon Equation 41

B. RRD-NBS COLLABORATIVE PROGRAMS 42

Separation of Overlapping Peaks in Neutron Diffraction

Powder Patterns 42

Powder Neutron Diffraction Analysis of the Crystal Structures

of LiNb

3 g

, M-LiTa

3 g

and H-LiTa-Og 47

vi
TABLE OF CONTENTS

Application of Simultaneous Diffraction Studies to

the Analysis of X-Ray Spectra 55

The Conformation of PS-PMMA Diblock Copolymer in Toluene

by Small Angle Neutron Scattering 59

Studies on the Structure of Defective Hydroxyapatite .... 61

C. INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS • 62

Deuterium-Site Occupancy in the a and 3 Phases of TiDx ... 62

Small Angle Magnetic Scattering From A Dilute Amorphous

Fe(Tb) Alloy 64

Diffraction Measurements From Rapidly Sputtered Bulk

Fe(Tb) and Ni(Dy) Alloy Samples 65

Nondestructive Determination of Grain-Orientation of Metal

Liners for Shaped-Charge Munitions .... 67

Reinvestigation of Crystal Structure of a-P, (N„)_ 69

b 5 2. Phase Transition Study of NaN by Powder Neutron

Diffraction 70

Quasi-Elastic Neutron Scattering Study of Single

Crystal Ammonium Perchlorate .... 72

Reinvestigation of the Crystal Structure of NH.C10,

at 298 K '...;.. 76

Small Angle Scattering: Instrument and Applications .... 78

Structure of the Antiferroelectric Phase of Copper

Formate Tetrahydrate 82

D. NON-RRD NBS PROGRAMS 84

Activation Analysis: Summary of 1976 Activities 84

Filtered Beams 99

Intercomparison of Fission Rate Measurement: Karlsruhe

Reactor Physics and Los Alamos Radiochemistry .... 100

Precision Measurement of the Wavelength of Nuclear Gamma

Lines and the Compton Wavelength of the Electron . . . 103

E. SUMMARY OF REACTOR OPERATIONS 107

vn
TABLE OF CONTENTS

F. SERVICE PROGRAMS 108

Activation Analysis Program of the Food and Drug

Administration at the NBSR 108

Improved Material for Solar Energy Cells 110

ATF's Forensic Activation Analysis Program Ill

Lunar Sample Analysis for 20 Trace Elements H2

Activation Analysis Program of the U. S. Geological Survey . . H2

Trace Elements in the Environment and Radioactive Decay

Studies - 116

The Non-destructive Determination of Trace Element Concentrations

Concentrations by Neutron-Capture Gamma-Ray

Spectrometry 117

G, STAFF ROSTER 119

H. PUBLICATIONS 123

vm
A. Reactor Radiation Division Programs

NEUTRON SCATTERING STUDIES OF HYDROGEN IN METALS

Our long range program to study the binding and diffusion of

hydrogen in metals, and related properties of metal-hydrogen systems has

provided new results particularly in the study of the lattice dynamics

of metal hydride crystals. Our collaborative interactions with the

Argonne and Oak Ridge National Laboratories have continued and a new

collaborative effort has been initiated with scientists at the Allied

Chemical Materials Research Center. New results have been obtained on

the crystal dynamics of VD and CeD„ - ~ and on a detailed comparison of

phonon lineshape profiles in a non-stiochiometic deuteride (PdDn

,„)

with computer simulation calculations of the lattice dynamics of this

disordered high density "defect" structure. We have also continued our studies of the structure and dynamics of the low concentration (a & 3)

phases of TiH , as discussed in another part of this report.

X

1. The Lattice Dynamics of VD - J. J. Rush, C. J. Glinka and J. M. Rowe

\J • / The lattice dynamics of a single crystal of a(bcc) VD has been

investigated by coherent inelastic neutron scattering measurements in

collaboration with H. E. Flotow of Argonne National Laboratory. Due to

the very small vanadium coherent cross section, essentially all the

coherent scattering by this compound is associated with the deuterium

(located in tetrahedral interstitial sites) . Thus a study of this

system provides a unique opportunity to measure the "in-band" and

optical modes associated with the vibrational displacements of the

deuterium (light atom) interstitials as a function of q and to. The VD„ , Q7 crystal prepared for these experiments had a "mosaic

spread" of <1° . Some example of neutron groups measured under both

constant AE and constant Q conditions are shown in figure 1. Also

present as a shoulder in figure lb is the incoherent "density of states"

scattering which is present in all phonon scans at higher energies and
REACTOR RADIATION DIVISION PROGRAMS

Q • (1.9, 1.9, 2.1)

[III] TA

"535—5T5 «[2,2,2+«] ( [2+f,2+{,2+{]

Figure 1. Examples of phonon groups measured for a-VDg.y. The arrow

and dashed line in group c. ([111]TA at £-0.25) indicate the

incoherent "density of states" peak.

makes the observation of coherent phonon peaks above ""20 meV quite

difficult. The phonons measured thus far at ?£0.5 in the three symmetry

directions are shown in figure 2. The results in figures 1, 2 represent

a direct measurement of the "in band" vibrations of the interstitial

deuterium atoms.

It is interesting to note from these results that: a) the observed

neutron groups are well defined, with little apparent broadening (for

•hto<20 meV) due to the random distribution of interstitials, b) the

phonon frequencies measured for VD_ _ are in general higher than those

for pure vanadium, indicating a general increase in interatomic forces

o on hydriding in spite of a ~5% expansion of the lattice (a (V) = 3.03A,

o O a (VD_ n ) = 3. 145 A). In fact the elastic constants obtained from the

o 0.7

long wavelength (low Q) slopes of the present measurements (figure 2) are 30-50% larger than the measured values for vanadium.

As a further attempt to elucidate the changes in vibration spectrum

which occur on deuteration we have made energy transfer scans at constant

2
REACTOR RADIATION DIVISION PROGRAMS

Q and fixed E for both VDn n and pure vanadium. These results were

r U. / used to derive phonon "density of states" distributions for V and VD„

7

, assuming one-phonon incoherent scattering. The results are shown in

figure 3. Both of these "distributions" reflect primarily the vibrational

displacements of the vanadium atoms (although the contribution of D

complicates this analysis) . It is clear from the results that the

addition of deuterium has considerably altered the frequency distribution,

In particular the cutoff of phonon energies is apparently shifted to

higher energies for the VD_ 7 crystal.

0.1 0.2 0.3 REDUCED

^1 0.4 0^6 » 0.1 0*2 03~" WAVE VECTOR (q/q^J

Figure 2. Partial dispersion curves in the three symmetry directions

for a-VDQ 7. Dotted lines indicate the long wavelength slopes

of the dispersion curves predicted by the measured elastic

constants of vanadium.

As discussed above the coherent inelastic scattering from VDn reflects only the D vibrational displacements so that the measurements

in figures 1, 2 allow a direct test of the coupling of interstitial

deuteriums to the host metal lattice. We have derived integrated

intensities from careful measurements of neutron groups in several

crystal directions up to phonon energies of 20 meV. The relative

intensities of the groups vs. q and AE show no variation within the
REACTOR RADIATION DIVISION PROGRAMS

10 20 30

fio) (meV)

40

Figure 3. Phonon "density of states" - G' (hco) derived from energyspectra measured at constant Q in V and aVDo.7. The pure

vanadium results represent a smooth line drawn through many

data points. The phonon densities are only approximately

normalized. Energy resolutions (FWHM) are indicated by the

horizontal bars.

estimated errors, thus providing clear evidence that the D atoms are strongly coupled to the acoustic vibrations of the vanadium lattice.

No adequate force model fit to the data in figure 2 is possible

without information on phonon frequencies at larger E, values. Such

measurements are quite difficult due to the superposition of the phonon

"groups" on the density of states scattering at energies >20 meV, but

further work is in progress.

2. Inelastic Neutron Scattering Lineshapes in PdD

J. M. Rowe, and J. J. Rush

0.63

C. J. Glinka,

In a previous coherent neutron scattering study of the lattice

dynamics of the non-stiochiometric metal hydride PdD ,„, severely

broadened lineshapes were observed for the optic phonons even at low

temperature (80K) . While the phonon peak positions observed in this
REACTOR RADIATION DIVISION PROGRAMS

3000-

30 40

fiu)(meV) 40 50fico(meU)

Figure 4. Representative constant-Q scans of the scattering in the optic

mode region from PdD „ at 77K. The solid curves are the intensity profiles calculated from the structural model for

PdD ,,. .63

earlier work could quite adequately be derived from a second near neighbor Born-von Karman model in which the crystal was treated as stoichiometric PdD (NaCl-structure) , such a model predicts sharp phonon

lineshapes and thus gives no insight into the nature of the observed

linebroadening . Recently however, A. Rahman has completed calculations

of the coherent "one-phonon" scattering for PdD ,.., based on a model for

the lattice dynamics which incorporates the large number of vacancies in

the actual structure. The calculations entail computing the normal

modes of vibration of a large unit cell of 108 Pd atoms with 68 deuterium
REACTOR RADIATION DIVISION PROGRAMS

atoms situated at random on the deuterium sublattice. The frequencies

and polarization vectors obtained by repeating the computations for a statistical ensemble of such cells are then used to evaluate the one- phonon cross section. In order to critically test these calculations,

new, more extensive, measurements have been made of the inelastic

scattering in the optic mode region. These measurements and calculations,

2 (which have been reported in a preliminary publication )

, have helped to

elucidate not only the dynamics of PdD ,„, but also the more general

problem of the effects of vacancies on the lattice dynamics of solids.

In figure 4 three typical inelastic scattering lineshapes, measured

with a triple-axis spectrometer at 80K, are shown with corresponding

calculated lineshapes (solid lines) . Although the structural detail in

the calculated lineshapes is dependent on the choice of unit cell size

used in the computations, and therefore must be discounted, the overall

widths are not and can be seen to satisfactorily account for the observed

width in each case. This agreement demonstrates that the observed

widths are primarily the result of the defect structure rather than a manifestation of anharmonic effects, for example. These results strongly

suggest that the character of the excitations in a highly defected

structure is markedly different from the plane-wave behavior found in

stoichiometric crystals.

Efforts are now underway to produce a higher concentration single

crystal sample of PdD with XM3.9. For X>0.8, PdD becomes superconducting and there is currently much interest in the role of lattice

vibrations in this material in the inducement of superconductivity. To

achieve this higher concentration, a crystal of Pd will be loaded under

a deuterium pressure of 2 kbar in a high pressure sample cell which has

been especially designed for this purpose and may subsequently be

mounted in a cryostat for the low temperature measurements. Further

studies along these lines are planned for the alloy-hydride system

Pd T7Cu.. D for which Tc's as high as 18 K have been reported, but these

y i_y x

& are awaiting the preparation of appropriate single crystals.
REACTOR RADIATION DIVISION PROGRAMS

1. J. M. Rowe, J. J. Rush, H. G. Smith, M. Mostoller, and H. E. Flotow,

Phys. Rev. Letters 33, 1297 (1974).

2. C. J. Glinka, J. M. Rowe, J. J. Rush, A. Rahman, S. K. Sinha, and

H. E. Flotow, Proceedings of the Conference on Neutron Scattering,

Gatlinburg, TN. 1976 (in press).

3. Lattice Dynamics of Cerium Deuteride - C. J. Glinka, J. M. Rowe,

and J. J. Rush

A comprehensive study of the phonon dispersion curves of CeD„ , in

collaboration with A. Maeland and G. Libowitz of Allied Chemical, has

been initiated and thus far preliminary coherent scattering measurements

have been made on a single crystal of CeD„ -_. It should be noted that

CeD_ has the same fee (CaF„) structure widely exhibited in transitionmetal hydrogen systems (e.g., Ti, Zr, Hf, Y) whose physical, thermodynamic and electronic properties have been extensively studied. The

cerium hydrogen system has received considerable attention due in part

to the occurrence of composition-dependent metal-to-semiconductor phase

600

CO3O

O

400

200

CeD2 | 2 Q=(3,3,5)r

60 80 100

"hco (meV)

Q=(4.2,4.2,0) -

80 100

Figure 5. Neutron groups observed in constant-Q scans at room temperature

in CeD2. 12

•
REACTOR RADIATION DIVISION PROGRAMS

transitions at low temperature. Our measurements represent the first

coherent inelastic scattering study of a nearly stoichiometric metal

hydride and should, therefore, afford the opportunity to investigate the

crystal dynamics (including anharmonic deuterium vibrations) and related

physical properties, virtually free from any perturbation of the phonons

due to nonstoichiometry. This study is also expected to provide a definitive test of the restricted central force model (in which "bond

2 bending" forces are neglected) which has been used in fitting to

specific heat data and time-of-f light neutron spectra on this material.

Figure 5 shows two typical optic phonon scans from our preliminary

data on CeD_ 1? . The six optic mode branches all lie within 74 to 84 meV

and the coherent scattering from these modes is superimposed on a considerable background of incoherent scattering which reflects the high

density of states in this region. Although more detailed measurements

will be needed to establish the connectivity of the closely spaced optic

branches, our present results indicate that a restricted central force

model is not adequate to describe their dispersion.

The peak seen in the neutron groups in figure 1 at Rid = 94 meV is

present in all of our scans and may arise from localized vibrations of

hydrogen atoms randomly distributed among the deuterium sites (our

sample contains a few atomic percent hydrogen) . The observation of

such a mode is potentially a very exciting development since the

hydrogen represents a light mass substitutional defect with (presumably) no change in the atomic forces. This system may, therefore, provide

the first real test case for mass defect theory in the dilute limit.

Measurements at room temperature on the CeD2.i2 crystal are continuing. We also intend to extend our phonon measurements to low

temperature and to a higher concentration of CeD . X

1. W. M. Mueller, J. P. Blackledge and G. Libowitz, Metal Hydrides*

Academic Press, New York (1968).

2. P. Vorderwisch et al., Phys. Stat. Sol. (b), 65, 171 (1974).

8
REACTOR RADIATION DIVISION PROGRAMS

CRYSTAL DYNAMICS., PHASE TRANSITIONS AND ORIENTATIONAL DISORDER

IN IONIC CRYSTALS

We have continued and extended our studies of the dynamics and

structure of orientationally disordered crystals. It is unfortunately

still correct to say that these systems are poorly understood, although

some progress has been made.

Our research during the past year has been centered on a study of

the structure of KCN and NaCN in all three phases, on extending our measurements of the crystal dynamics of KCN and on measurements of both

crystal dynamics and reorientational dynamics of deuterated ammonium

halides

.

1. Alkali Cyanides - J. M. Rowe, J. J. Rush, E. Prince,

N. J. Chesser, S. Susman and D. G. Hinks

We have completed a study of the crystal structures of KCN and

NaCN in all three phases by neutron powder diffraction. A set of characteristic powder patterns of KCN in all three phases is shown in

figure 1. The salient feature of the results shown in this figure is

the lack of observable peaks in cubic KCN for scattering angles greater

than about 62°. This is a reflection of the very large mean square

displacements of both metal and cyanide ions in the cubic phase which

arise from the soft shear mode (C, ,) previously observed. The extra

peak is a superlattice reflection characteristic of the low temperature

fully ordered orthorhombic structure.

The intensity of this superlattice line is proportional to the

square of the order parameter for this order-disorder phase transition.

The temperature dependence of the intensity is shown in figure 2.

In the ordered low temperature structure the two (CN)- ions in the

unit cell are ordered antiparallel to each other along the b axis.
REACTOR RADIATION DIVISION PROGRAMS

In addition, we have completed a more detailed study of the

dynamics of KCN. The dispersion relation for acoustic phonons has been

observed over a larger fraction of the Brillouin zone as shown in

figure 3. This extended information was obtained on the new BT4 threeaxis spectrometer, and it was the extra intensity and flexibility of

this instrument which allowed us to obtain the new data. However, it

must be emphasized that many of the neutron groups (especially at the

larger energies) were very poorly defined and that the dispersion curve

shown should not be interpreted in terms of harmonic or quasiharmonic

models. The characteristic feature of the dynamics of KCN is the strong

anharmonicity evidenced in the neutron lineshapes observed.

Finally, we have refined our measurements of the temperature dependence of the soft shear modes characterized by C, , . As was shown

previously, the elastic constant C,, tends to zero as the temperature is

lowered towards the first order phase transition at 168K. Our previous

measurements of the neutron scattering associated with these soft

modes was complicated by the large elastic scattering associated with

the Bragg peak about which the measurements were made. By changing the

experimental conditions, we have been able to remeasure these modes

with very little contamination and have shown that there is no detectable elastic component in the scattering for reduced wave vectors as low as 1/10 the distance to the Brillouin zone. At this wave vector the

energy of the phonon is approximately 0.2 meV just above the phase

transition. Recent theories have predicted the existence of elastic

scattering (central modes) for these phase transitions, so that the

present results were not expected. However, the predicted behavior may

only occur at smaller wave vectors than could be reached in this experiment, or the first order phase transition may occur at a temperature

too far above the point at which C,, extrapolates to zero. We intend to check these and other possibilities by extending our research to mixed alkali halide-akali cyanide crystals, beginning with

10
REACTOR RADIATION DIVISION PROGRAMS

20 30 40 50 60

SCATTERING ANGLE (DEG) 90

Figure 1. The observed powder diffraction patterns for the three

crystal phases of KCN. Note the comparative intensities

of high angle reflections in the cubic and intermediate

phases and the superlattice peak (blown up in insert in

the low temperature phase)

.

.0

CM

0.5-

i

1

TC =82.9K

i i i 1 20 40 60

T (K)

80 100

Figure 2. Temperature dependence of superlattice intensity in the low

temperature phase of KCN. Solid lines are result of theory

described elsewhere (R. Casella)

.

11
REACTOR RADIATION DIVISION PROGRAMS

Figure 3. Dispersion relation for "phonons" in KCN at 295K. Solid

lines are guide to the eye. (o) longitudinal acoustic modes

(o>A) transverse acoustic modes.

(K Br)_

75 (KCN)Q 2

_ and proceeding to higher cyanide concentration.

2. Ammonium Halides - J. M. Rowe, J. J. Rush and N. Vagelatos

We have successfully completed our program to grow large deuterated single crystals of ammonium iodide and ammonium bromide, and have

made detailed lattice dynamical measurments on the NaCl phase of ND.I

(see last years report) . In addition we have completed preliminary

measurements on the lattice dynamics of ND, Br in the CsCl phase at room temperature. We intend to study this system as a function of temperature and hope to make measurements in the low temperature tetragonal

phase. We have also made preliminary measurements of the quasilastic

scattering from ND.I in an effort to establish the reorientation mechanism in this high temperature phase. These preliminary measurements

indicate that the experiments are feasible, but also point up the

difficulty associated with the large amplitude motions of the ND, ions

and the broad distribution of equilibrium orientations in this phase.

12
REACTOR RADIATION DIVISION PROGRAMS

ORDER-DISORDER PHASE TRANSITION IN KCN

R. C. Casella

Experimental work of Rowe, Rush, Prince, and Chesser has indicated that below T — 83 K the CN dipoles undergo antiferroelectric

ordering. Earlier attempts to fit the temperature dependence of the

order parameter r\ deduced from their data met with difficulties. I was

led to consider the analogue to the Ising model in magnetism. It turns

out that their data for the intensity of neutrons from the superlattice

reflection (« n

2

) lie midway between what one expects for a twodimensional and a three-dimensional Ising model and is fit (within

errors) by the expression

n

2 = - (

sinh t)

1/3

(1)

roughly the square root of what one expects for the 3-D Ising model

100

Figure 1. Data of reference 1 compared with various idealizations of

the Ising model. Upper curve: n

2 = [1 - (sinh (Ti/T)) -4

] 1 '

1 *. exact Ising-model square- lattice result in two dimensions.

Lower curve: n

2 = [1 - (sinh (Tj[/T))" 3

] 2 /3, an approximate

global description of the three-dimensional simple-cubiclattice Ising-model result (c.f., figure 3). Middle

curve: equation (1) of text.

13
REACTOR RADIATION DIVISION PROGRAMS

1.0 -

CM

Figure 2.

0.5

-*_ 1

, 1

T

C

= 82.9K

i i

" 1 20 40

T (K)

60 80 100

Data from reference 1 compared with Ising model predictions:

lattice symmetry corrections. The CN~ sites lie in a slight

orthrombic distortion of what would otherwise be facecentered-cubic positions. Here the quasi-f.c.c. structure

of the lattice is taken into account. Upper curve: Twodimensional square lattice as in figure 1 (for comparison)

.

Lower curve: n

2 for f.c.c. Ising lattice, as calculated

numerically. Middle curve: the square root of the lower curve

.

H I

Figure 3. Comparison of the approximate analytical expression (a)

n = [1 - (sinh (tj/t)) -3] 1 / 3 for the three-dimensional

simple-cubic Ising lattice with (b) numerically calculated

extrapolations of same, (t = T/T , t, = T-./T )

14
REACTOR RADIATION DIVISION PROGRAMS

(see figures 1-3). Since T (= 82.9 K) is determined from specific

heat measurements, there are no free parameters in these fits. The

physical origin of this "anomalous-dimensional" behavior is not clear,

but is possibly associated with long range aspects of the forces, not

included in the Ising model.

1. J. M. Rowe, J. J. Rush, E. Prince, and N. J. Chesser, elsewhere in

this report.

2. D. M. Burley, Phil. Mag. 5_, 909 (1960).

NEUTRINO SCATTERING

R. C. Casella

The neutrino, postulated by Pauli in 1930 to save the principles

of conservation of energy and momentum in nuclear $ decay and experimentally confirmed by Reines, Cowan, and coworkers using a fissionreactor source of electron antineutrinos v in the period 1950-1960,

e is a unique probe of matter over a range of scales differing by at

least 24 orders of magnitude. Because of its weak interaction, the

neutrino carries information from the interior of stars (R ^ 10 9 m) as well as entering deep into nucleons (r < 10" 15 m) , where the next

layer of building blocks (postulated quarks and par tons) can be probed.

By modifying the quark-parton model of Feynman and of Bjorken and Paschos

in the so-called wee region of the kinematic variable x, I have been

able to account quantitatively for the high-y anomaly in antineutrinonucleon scattering experiments, the rise in the ratio of antineutrino

to neutrino charged-current cross sections with energy, and qualitatively to explain the surprising high-strangeness multiplicity associated

with neutrino-induced ye production. [u = muon and y is the

fractional energy loss in the laboratory frame of the lepton in the

15
125

REACTOR RADIATION DIVISION PROGRAMS

i i

| i I ^

i i i i i

j « i i 1 1 i i 200

X<0.6(Z/) 10<E<306eV

0.30 0.60

y

0.90

i i

I

i '

I

' s

| i

i 1

1

1

1 1 1 |i -X<0.6(i7) IO<E<306eV0.30 0.60

y

0.90

Figure 1. da/dy vs. y for vN and vN scattering. Experiment, as labeled. Theory, E = 20 GeV, normalization relative to

data arbitrary. Data from references 1 and 2. Crosshatched regions indicate detection-efficiency corrections

incomplete.

I !

| I I |

I I

| I I

| I I |

I I | I

. X<0.6(I/) E>706eV

(a)

i i I

i i 11 i

| i i

1 1 i

|

i i |

i

X<0.6(z7) E>706eV

0.30 0.60 0.90

y

0.30 0.60 0.90

y

Figure 2. da/dy vs. y for vN and vN scattering. Experiment, as labeled,

Theory, E = 100 GeV, normalization relative to data arbitrary,

Data from references 1 and 2. Cross-hatched regions require

further data reduction.

16
REACTOR RADIATION DIVISION PROGRAMS

50

?

40

GO

-s 3

</)

hS

20

"

10

VH X<.I5

E>50 GeV

(0)

J i

* "oTrf

r

0.5

y

°o

I>N .15<X<.6

E> 50 GeV

(b)

Figure 3. da/dy vs. y for vN scattering (a) in small x region only,

(b) excluding x < 0.15. Experiment, as labeled. Theory

(a) upper curve, E = 100 GeV, lower, E = 50 GeV, x < 0.14,

normalization fixed relative to that in (b) . Theory (b)

all E > 10 GeV, 0.14 < x < 0.6, normalization relative to

data arbitrary. Data from reference 2.

process, v + nucleon -> y~ + anything; i.e.,y=(E - E )/E ].

I have done so without the necessity of introducing right-handed

(V + A) currents not contained in the standard (V - A) version of

Fermi's weak interaction theory as formulated after the discovery of

parity violation in 1956 by Wu, Ambler, Hayward, Hoppes, and Hudson

1 2

at NBS. Theoretical fits to the data ' span an energy range, 10 GeV

to 150 GeV (see figures 1-4)

.

17
REACTOR RADIATION DIVISION PROGRAMS

50 100 150

E (GeV)

200

Figure 4. Absolute value of the total charged-current-induced neutrinonucleon cross section vs. energy. Theory, E > 10 GeV,

heavy curve. The straight line is an extrapolation from

lower energy Gargamelle data, not shown. Solid circles,

HPWE data, open circles, CF data.

1. A. Benvenuti, et al. 3 Phys. Rev. Lett. 36, 1478 (1976).

2. A. K. Mann, paper presented at Orbis Scientiae, Univ. of Miami,

Coral Gables, Florida (1976).

18
REACTOR RADIATION DIVISION PROGRAMS

SPIN WAVES IN FERR MAGNETIC ERBIUM-IRON

J . J . Rhyne

and

N. C. Koon and J. B. Milstein

(Naval Research Laboratory, Washington, DC)

H. A. Alperin

(Naval Surface Weapons Center, White Oak, MD)

The group of compounds RFe„, where R is a heavy rare earth, crystallize in the close-packed Laves phase or MgCu« structure. These compounds

have high Curie temperatures (T >550K) and show extraordinarily large

1

C

magneto-elastic interactions . The iron moments are ferromagnetically

aligned, and are antiparallel to the R moment (ferrimagnetic order).

The iron moment as determined from both bulk measurements and neutron

2 scattering on polycrystalline samples shows an anomalous reduction from

the expected 2u,, to approximately 1.6u_. The rare earth moments have

their free ion values.

We have studied the spin wave dispersion in ErFe~ using inelastic

neutron scattering and have compared the results to a theoretical model.

Inelastic scans along three principal axis directions were made at room

4

temperature (T for ErFe~ = 574K) on a single crystal approximately

3 c Z 0.5 cm using a triple axis spectrometer.

ErFe~ has 6 atoms per unit cell with the Er atoms arranged on sites

of tetrahedral symmetry and the Fe atoms on octahedral sites. One thus

expects six spin wave branches, one acoustic and five optic. As the

results in figure 1 show, only three of these branches have energies

easily studied by neutron scattering. The data in figure 1 for spin waves propagating in the [q,q,o] and [q,q,q] directions show isotropic

spectra consisting of (1) an acoustic mode with no measurable anisotropy

energy gap, (2) a very flat optic mode of energy 5.1 meV degenerate with

the acoustic mode at the zone boundary and (3) a highly dispersive

higher optic mode starting from an energy gap of 8.75 meV. This latter

i 1

2

mode has quadratic dispersion (Kw = D|q| ) in the q range shown with

2 5 2

D = 240 meV-A only slightly smaller than pure iron metal (D = 280 meV-A")

19
REACTOR RADIATION DIVISION PROGRAMS

and would represent the iron acoustic mode in the absence of rare earth

spins and the R-Fe exchange interaction, This mode is shown over only a small portion of the Brillouin zone due to the very high energy transfers

involved. The model calculation gives an energy of 172 meV at the zone boundary. The vanishing dispersion in the lower optic mode is a conse- quence of negligible Er-Er exchange in this compound; rather the Er

simply sits in the molecular field from the iron spins. Data were also

taken in the [q,o,o] direction which again indicated no evidence of a dependence of the dispersion on propagation direction.

A nearest neighbor interaction spin-wave model has been applied to

explain the data of figure 1. The Hamiltonian included exchange and

crystal field terms (the latter are negligible at room temperature) and

had the form

H =

I j 2^ S. n

.S.

m

+ H . L h . ii i j c.f

n,m x,j

where J., describes the interaction between the i'th ion of spin S. in

cell n with the j ' th ion of spin S. in cell m (i and j thus range from 1

to 6 and n, m were restricted to only nearest neighbors) . The spin wave

energies were calculated from Fourier transforms of the equations of

motion for the spin raising and lowering operators S— = S +iS as follows:

6 x ^

noKq) S+

(q) = -2j <S^>

( )g

+ _ <S Z, +

j=l iJ J 3 ij i

where J..(q) = Y JTM exp [iq (r ,-r .)] ij • ij mi m

and the six equivalent relations for S . In fitting the spectra the

spins on the Er and Fe atoms were fixed at 3.6 y_ and 0.66 y respectively

D ii as obtained from a combination of neutron diffraction and bulk magneti1-2

zation data . At the zone center the energies of the two optic modes

are given simply by u>° P = 24J

£r_Fe

<S^> and u)°P

= l 2J

Er.ge

(< SEr

~2<^V&

respectively. These relations and the known values of <S > thus allowed

the rare earth-iron exchange° constant J„ ^, = -0.32 meV to be determined.

Er-Fe

20
REACTOR RADIATION DIVISION PROGRAMS

ErFe2 295 K

9F,-F# = 30 meV

9F#_ Er = -0.32 meV

»Er-Er=0 O EXPT. — MODEL

Cq.q.03 Cq,q,q3

0.8 0.4 0.2 0.4 REDUCED WAVE VECTOR (X comp.)

Figure 1. Magnon dispersion of ErFe„ along [q,q,o] and [q,q,q]

symmetry directions. The solid line is the result of

a nearest neighbor spin wave calculation.

The remaining exchange constant J„ = 30 meV was adjusted to obtain

the correct dispersion in the higher optic mode. These values were

3 similar to those for the analogous compound Ho QOTb 10Fe

. oo . iZ Z JR-R

iS

equal to zero in both cases to an accuracy of approximately +.01 meV as determined from the maximum dispersion in the lower optic mode. Within

the restricted q-range of the higher energy data, this model fits the

experimental results extremely well. Its success in predicting accu- rately the E and q dependence of the remaining magnon branches is not

known.

The measurements are currently being extended to lower temperatures

to examine the effects of the strongly enhanced anisotropy and magnetoelastic interaction on the spin wave spectrum.

1. A. E. Clark, A.I. P. Conf. Proc. Series 18, 1015 (1974).

21
REACTOR RADIATION DIVISION PROGRAMS

2. J. J. Rhyne, to be published; M. 0. Bargouth and G. Will, Jovimal

de Physique CI 32, 675 (1971).

3. R. M. Nicklow, N. C. Koon, C. M. Williams, and J. B. Milstein,

Phys. Rev. Letters 36_, 532 (1976). (Note: Due to a difference in

definition of the Hamiltonian, exchange constants quoted in this

reference are larger by a factor of two than those in the present

paper.

)

4. E. Burzo, Z. Angew, Phys. 32. 127 (1971).

5. H. A. Mook and R. M. Nicklow, Phys. Rev. B ]_. 336, (1973).

ORDER-DISORDER IN V3 Ga

J . J . Rhyne

and

B. N. Das and R. A. Meussner

(Naval Research Laboratory, Washington, DC)

It is known that the superconducting transition temperature of

compounds of stoichometry near V„Ga can be varied by appropriate heat

treating. In an effort to discover if a correlation exists between the

T and the degree of atomic order of the V and Ga atoms a neutron

c diffraction study was undertaken of several samples of different heat

treating and also of slight composition variation from stoichometric

V„Ga. Neutrons are significantly superior to x rays for this type of

investigation due to the very similar x-ray scattering factors of V and

Ga which makes separate site occupancy factors difficult to determine.

In the neutron case V and Ga scattering amplitudes have opposite signs

and differ by more than a factor of 10.

Initial results have indicated that compounds even in the "as cast"

state are highly ordered with long range order parameters as high as

0.95 and that heat treatment annealing at 1400° C produces only a slight increase in the long range order parameter while it lowers the

super-conductivity transition temperature by about 0.5 K.

22
REACTOR RADIATION DIVISION PROGRAMS

As a result, first indications suggest that the variations in T

c are not strongly correlated with long-range crystallographic order in

V„Ga and certainly that T does not increase with crystallographic order

as previously predicted.

APPLICATION OF ROBUST/RES I STANT TECHNIQUES TO

CRYSTAL STRUCTURE REFINEMENT

W. L. Nicholson

(Battelle Pacific Northwest Laboratories, Richland, WA)

and

E. Prince

A technique for fitting a theoretical model to a set of experimental data points and estimating the best values of adjustable parameters in the model is said to be "robust," or, more precisely,

"robust of efficiency," if the parameter estimates have near minimum

variance for a broad class of distributions for the errors in experimental data. A technique is "resistant" if the estimates are not

highly dependent pn any small subset of the experimental data. To

date, all techniques that are robust of efficiency are also resistant.

Many data analysts feel that this is inevitable, hence, the splice

word, robust /resistant.

The technique of least squares, the one most commonly used for

refining crystal structures, is neither robust nor resistant. Least

squares was designed specifically by Gauss for normally distributed

errors. With broad- tailed error distributions and/or the presence of a few bad data points in a large data set, least squares can give

anomalous results. In recent years, statisticians have been developing

methods of fitting and parameter estimation which work nearly as well

as least squares for ideal data sets, but which are robust /resistant.

The purpose of this research is to apply these methods to crystal

23
REACTOR RADIATION DIVISION PROGRAMS

structure refinement, both as a non-trivial test of the robust/resistant

approach and as a development in calculational crystallography.

The technique of least squares is based on finding the minimum

value of the quantity £w . (y . -y ) 2

, where y. is the value of the

observed data, y. is a calculated value of that point based on some theoretical function containing adjustable parameters, and w. is a weight. For the method to work well, the weight, w., must be proportional to 1/a. 2

, where a.

2 11 is the variance of the observation y. . J 10

This variance is, however, usually not known a priori, but is

approximated by a formula containing a term arising from an assumed

Poisson distribution of random counts and one or more other terms

which estimate additional experimental error associated with the

observed value, y. . 1

10

Tukey describes a robust/resistant alternative to least squares

estimation which is particularly attractive for crystal structure

refinement. In the least squares program, the response of a refinement

is modified by adjusting the weight according to the formula w' . = w.W(x), where x = (y. -y. )/Ka.. a. is the standard deviation

l

y io •'ic 1 i

approximation described above and K is a robust/resistant estimate of

scale. The function W(x) is called a "W-function." Characteristics

that a W-function should have in order to create a robust/resistant

2 refinement are discussed elsewhere by the authors. To perform the

refinement, an initial set of parameters is used to form normalized

residuals r = (y. -y. )/a.. These are used to construct K.

10 1C x

3 4 Independent work of Andrews and Beaton and Tukey suggest a K of

6 times the median absolute residual. With K specified, W(x) is

calculated and the weighted least squares iteration performed. After

each iteration, K is recalculated as above.

The crystallographic least squares program RFINE4 was modified

to include, as options, several different W-functions. One of these

W-functions was used to investigate the operational characteristics

of the robust/resistant approach using a lead deuterium orthophosphate

24
REACTOR RADIATION DIVISION PROGRAMS

p f. data set. The details of the investigation are described elsewhere. ' A second option is the biweight W-function W(x) = (1-x2

) 2 (|x| <_ 1); = (otherwise)

.

RFINE4 with the Tukey biweight W-function is being used to

repeat the refinements of the structure of D(+) tartaric acid originally

carried out by Hamilton and Abrahams as part of the single-crystal

intensity project of the International Union of Crystallography.

Three of the 17 experiments considered by Hamilton and Abrahams,

selected on the basis of reasonably large numbers of reflections,

have been analyzed so far. The refinement for each data set has

three stages: 1) attempt to "recreate" the results of Hamilton and

Abrahams by repeating as closely as possible the condition of their

refinements; 2) add secondary extinction to the classical weighted

least squares refinement; and 3) incorporate the biweight W-function

and do a robust/resistant refinement. The results of Hamilton and

Abrahams are not reproduced exactly, possibly because of small

differences in the handling of atomic scattering factors in the

original refinement. Inclusion of the Zachariasen model for secondary

extinction significantly improves the refinements of all three experiments. Inclusion of the biweight function again significantly improves

the refinement with weighted r indices decreasing by up to 40%.

Based on the refinement of these three experiments, the robust/

resistant approach looks very promising. Individual atom positions

and thermal vibration parameters agree more closely than in the

original analysis. For each experiment, a small fraction of the data

fail to fit the robust/resistant estimated model and, hence, are identified as extreme outliers. These outliers can be identified on

theoretical grounds as very imprecise reflections. For example, for one experiment the extreme outliers were mostly weak reflections.

Such residual patterns suggest that the biweight approach succeeds in

minimizing the influence of poor data on the refinement. The above

work was reported at the 1976 winter meeting of the American Crystallo25
REACTOR RADIATION DIVISION PROGRAMS

graphic Association, Clemson, SC. A written version is being submitted

for open literature publication.

Work is now in progress on refinement of the remaining experimental data sets reported by Hamilton and Abrahams. Several of their

refinements give very discrepant individual atom parameter estimates.

Elimination or a least reduction of these discrepancies would establish

robust/resistant techniques as a viable approach to crystal structure

refinement.

1. J. W. Tukey in Critical Evaluation of Chemical and Physical

Structural Information, National Academy of Sciences, Washington;

DC, 1974.

2. E. Prince and W. L. Nicholson, NBS Tech. Note 896 (1976).

3. D. F. Andrews, Teohnometvics , 16, 523 (1974).

4. A. E. Beaton and J. W. Tukey, Teohnometvics3 16, 147 (1974).

5. L. W. Finger and E. Prince, NBS Tech. Note 854 (1975).

6. C. S. Brickenkamp and E. Prince, NBS Tech. Note 860, 55 (1975).

7. W. C. Hamilton and S. C. Abrahams, Acta Cryst. } A26 , 18 (1970).

A FLAT-CONE DI FFRACTOMETER UTILIZING A

POSITION-SENSITIVE DETECTOR

E. Prince, J. C. Norvell, and A. Santoro

The use of flat-cone geometry to take advantage of linear

position-sensitive detectors for single crystal neutron diffractometry

was described in last year's progress report. An instrument employing

these principles is under construction. The detector itself has been

received and tested, and most of the electronic components are in

hand. Work on hardware and software is proceeding.

1. E. Prince and A. Santoro, NBS Tech Note 896, 17 (1976).

26
REACTOR RADIATION DIVISION PROGRAMS

CONVERSION OF THE SPECTROMETER CONTROL SYSTEM

TO THE DECLAB 11/40

E. Prince, J. J. Rhyne, J. M. Rowe

and

S. F. Trevino

(Picatinny Arsenal, Dover, NJ)

It was apparent several years ago that the existing data acquisition system for controlling beam tube experiments would be inadequate

for controlling the new 4-axis spectrometer being installed at BT-4.

More recently, various developments made it desirable to phase out

the existing system, which was installed in 1967, and which was based on obsolete equipment that was becoming more and more difficult to

maintain adequately. After extensive consideration of the alternatives,

the new system chosen was a Digital Equipment Corporation DECLAB 11/40,

supplemented by an industrial control subsystem (ICS-11) provided by

the same manufacturer. A major effort to adapt a DEC supplied operating

system (RSX11M) so that it could handle spectrometer and dif fractometer

operations was nearly complete at the end of the year. Most of the

task of adapting user programs to the new system was also complete,

and the work of rewiring the instruments was proceeding. It is

anticipated that the conversion will be complete well before the end

of calendar year 1976.

The new operating system possesses much greater flexibility

than the existing system. It can accommodate an arbitrary number of

motors for each instrument, and also an arbitrary number of detector

scalers. Furthermore, it is now possible to do program development,

including compiling and linking of programs and editing of source

text, without interrupting the data collection process.

27
REACTOR RADIATION DIVISION PROGRAMS

THE NEUTRON RADIOGRAPHY PROGRAM

D. Garret, H. Berger, M. Ganoczy, M. Dorsey

and

W. Parker

(Reed College, Portland, OR)

The goals of the Neutron Radiography Group of the Reactor Radiation

Division are to develop neutron radiographic standards, techniques and

hardware and to participate in the National Bureau of Standards Nondestructive Evaluation Program. In these capacities, the group provides

assistance to both the public and private sectors in the development of

neutron applications.

Accomplishments of the Neutron Radiography Group during the past

year consist of a number of collaborative efforts with outside agencies

in the public sectors. Internal efforts have been devoted to the development of three dimensional laminagraphy, three dimensional image enhanced

laminagraphy, extensive beam diagnostics on the thermal column, modifications to the thermal column beam facility and fabrication of the new

vertical beam facility. Preliminary conceptual design work has been

completed on the external hardware for both the thermal and fast vertical

facilities.

1. Three-Dimensional Inspection by Thermal-Neutron Laminagraphy

Radiographic inspection of thick, complex objects presents problems

because overlaying radiographic shadows from different object depths

complicate interpretation and because it is often difficult to assign an object depth to an observed shadow. Three-dimensional (3-D) radiographic

methods including computerized image reconstruction optical and holographic

methods, and multiple-film laminagraphy mimimize these inspection problems.

In this work, multiple-film laminagraphy has been demonstrated with thermal neutrons, thereby expanding the capability of neutron radiography to

inspect complex objects.

28
REACTOR RADIATION DIVISION PROGRAMS

In this technique, radiographic views from several angular orientations are obtained and superimposed to bring a desired object image

plane into registration (focus) while information from other planes is

blurred. New developments reported here include the use of thermal

neutrons as the imaging radiation and the rotational movement of the

object-detector assembly as opposed to the usual trans lational source movement to obtain the angular views.

One object used to demonstrate the method was a simulated EBR-II

fast reactor fuel subassembly. A hexcan, 5.7 cm across the flats,

normally holds 91 rod-shaped fuel elements in 11 rows. For our tests

the can was filled with solid aluminum rods and occasional Bakelite rods.

These neutron attenuating rods were used to demonstrate spatial resolution

at various locations in the assembly. To aid in that determination sev- eral through holes varying in size from 0.5- to 2.5- mm diam were drilled

in each Bakelite rod.

Thermal-neutron radiograph of the fuel subassembly were obtained

over a 40-deg angular coverage, with a 5-deg rotation between exposures.

These nine individual neutron radiographs were viewed superimposed to

focus on any desired plane. Since it is necessary to view through all

the films, a light exposure on each film (typical density 0.4) and a clear base are desirable. This was accomplished by one of two methods.

In one approach the neutron radiographs were obtained on a clear base

x-ray film. In the other, neutron radiographs were obtained with con- ventional x-ray film; the films were then copied on clear-base graphic

arts film (Kodak types 6127 and 4135 were used). In both cases, neutron

radiographs were prepared with gadolinium vapor-deposited screens in

vacuum cassettes.

Figure 1 pictures example of two laminagraphic views from these

tests. The results show that one can focus on individual fuel rows and

that detail as small as 0.5 mm can be resolved in the hexcan assembly.

In tests with a high-contrast cadmium test object, a spatial resolution

of 0.25 mm was obtained for a similar thickness object.

29
REACTOR RADIATION DIVISION PROGRAMS

Figure 1. Photographs of 9-film thermal neutron laminagrams of an EBR-II

fuel subassembly hex-can containing aluminum and Bakelite rods

instead of fuel. View a focuses on a plane adjacent to one hex-can face and shows a single Bakelite rod in focus; four

holes 2.5 mm, 1.5 mm, 1.0 mm and 0.5 mm (left to right) are detectable. View b focuses on the middle row of simulated

fuel rods; one Bakelite rod is in focus. Three holes (1, 1.5

and 2.5 mm in diameter) are visible on the print. Note the

different images of the radiographic markers at the left of

each view. These two laminagrams were obtained with one set

of neutron radiographs.

Three-dimensional thermal-neutron radiography with a spatial resolution better than 1 mm can now be accomplished with a technique re- quiring minimum equipment investment. This broadens the application of

thermal-neutron radiography. The 3-D method will prove useful for assem- bly inspection. Additional capabilities of isotopic differentiation and

radioactive material inspection make this neutron laminagraphic method

particularly attractive for nuclear problems.

30
REACTOR RADIATION DIVISION PROGRAMS

2. Film Investigations

Work has continued on the investigation of the suitability for

neutron radiography of other emulsions than the standard x-ray emulsions,

Most of this work has been done with an electron-sensitive emulsion developed for transmission electron microscopy. This film is now produced

on a regular basis by Eastman Kodak as Type SO 163. It has from two and

a half to three times the speed of Type SR, depending on the development.

Qualitatively the resolution approaches that of SR, but a radiograph on

SO 163 does not have the "snap" of one of the same density done on SR.

The ratio of neutron sensitivity to gamma ray sensitivity is definitely

better than that for the double emulsion x-ray films.

We have also looked at the possibility of using graphic arts films

for neutron radiography. Generally these are high contrast emulsions

with extremely fine grain with resulting high resolution. They are also

single emulsion on a clear base. With proper development they will produce a gray scale satisfactorily. Preliminary work indicates that the ones tried so far are much too slow when used with a gadolinium foil con- verter to be useful. There does appear to be a possibility that they

can be used for certain applications with a scintillating screen such as LiFZnS:Ag or Gd

? S:Tb. They may also be useful for neutron laminagraphy where low density and a clear base are required.

3. Image Enhancement

A Spatial Data Image Enhancement system has been installed and

placed in operation in the image analysis laboratory of the Neutron

Radiography Group. The purpose of this unit is to perform various operations on the radiographic image which causes subtle details to become

more easily visible to the eye. This image enhancement system operates

strictly in the analog mode, utilizing a standard video camera and monitor. The signal from the video camera is routed to the enchancement

circuitry which manipulates the image in such a way that it can be dis31
REACTOR RADIATION DIVISION PROGRAMS

played in one of three ways, i.e. (a) edge enchancement in which the

first derivative of the black and white image is displayed, (b) a normal

enlargement of the original image is displayed and (c) color enhancement

in which the shades of gray of the radiograph are divided into the hues

of twelve colors. A standard radiographic image is illustrated in

figure 2 . Color enhanced and edge enhanced images of this radiograph

are illustrated in figure 3 and figure 4 respectively.

Figure 2. Normal neutron radiograph, no image enhancement,

32
REACTOR RADIATION DIVISION PROGRAMS

Figure 3. Neutron radiograph, edge enhancement mode,

Figure 4. Neutron radiograph, color enhancement mode,

33
REACTOR RADIATION DIVISION PROGRAMS

4. Image Enhanced Laminagraphy

A successful demonstration has been made to adapt the color image

enhancement system to three dimensional laminagraphy viewing. The video

camera of the image enhancement system views the laminagraph image as

the depth below the surface of a test object is viewed. As the layer

image comes into view, the enhanced image of the structure under observation is displayed on the video output of the enhancement system.

The method can be employed to view complicated structures or it can be employed to view in three dimension microstructure below the surface

of components. Figure 5 illustrates microshrinkage below the surface of a stainless steel casting covering a depth of approximately 1/4 in. in

equal depth steps.

Figure 5. Color enhanced laminagraph microshrinkage in stainless steel

casting showing the shape of the cavity at various depths

below the surface.

34
REACTOR RADIATION DIVISION PROGRAMS

5. Pacemaker Studies

The Food and Drug Administration requested the group to investigate

the feasibility of using neutron radiographic techniques to inspect pacemakers and the individual components used in their manufacture. Specifically, the FDA hoped to have developed a method for detecting leaks

between the insulation surrounding the electrodes and the seal entering

the pacemaker module. A second series of studies was to be conducted on neutron radiography of mercury and lithium iodide batteries used to power

the pacemaker.

a. Seal Leakage Studies

The pacemaker was inspected by neutron and x-radiography in an attempt to visualize water that had been injected between the module seal

and the electrode insulation. Neither technique could be used to visualize details of the water. In the case of neutrons, the hydrogen content

of the insulation was probably very close to that of the water. In the case of x rays, the density of the insulation was possibly very close to

that of water.

b. Mercury Cell Studies

A set of two new and four depleted mercury cells were radiographed

with neutrons and x rays. Two views of the cells were taken for each

specimen - one view along the cell axis and the other at right angles to

the cell axis. A schematic diagram of a typical cell is illustrated in

figure 6.

In the case of neutron radiography good detail could be visualized

in the views taken down the cell axis; some detail could be visualized

but not as satisfactorily at right angles to the axis. In both cases,

migration of the mercury toward the cell axis could be observed in the

depleted cells, but not in the unused cells. The new cells could unam- biguously be identified by the absence of the mercury migration.

35
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CERTIFIED CELL

INSULATOR RING

INNER BARRIER

ZINC ANODE

CATHODE

BOTTOM INSULATOR

VENT

Figure 6. Schematic diagram of mercury cell for pacemaker application.

The mercury cells were x-rayed at an optimum energy. Although no detail could be observed in the right angle shots, mercury migration

could be observed in the axial x-rays of the depleted cells.

The possibility of a microbeam neutron or x-ray transmission measure- ment along the cell axis to determine remaining battery life remaining

in the cell appears to be a real one. No method exists to produce this

specification at this time. A microbeam gamma ray backscatter gauge

could possible be considered for insitu measurements.

c. Lithium Battery Studies

Lithium batteries are being seriously considered as power sources

for pacemakers because of their long life - 13 years as compared to 5

years for a mercury cell. X-radiography is unsatisfactory for lithium

battery evaluation because of the double stainless steel case and the

relativley low atomic number of the materials used in the electrolyte.

With neutrons it was possible to observe a phenomenon which appeared

to be a function of cell life. This apparent electrolyte migration or

36
REACTOR RADIATION DIVISION PROGRAMS

Figure 7. Neutron radiographs of lithium iodide pacemaker batteries

showing gas pocket formation as a function of depletion.

gas pocket production is not understood at this time. The cell is fabricated in a slab geometry consisting of a rectangular lithium slab sandwiched between two slabs of iodine. As the battery becomes depleted,

lithium iodide is formed causing no change in the total attenuation to

the neutron beam.

A series of four lithium batteries was subjected to use tests

ranging from 10% to 105% of the expected life. Neutron radiographs of

the four units are shown in figure 7. It can be seen that as the use factor increases, the formation of gas pockets appears to take place.

Further study on this project will continue once a set of new batteries

from the same manufacturing batch are received from the FDA.

37
REACTOR RADIATION DIVISION PROGRAMS

6. Pair Production Generated In Objects Under Inspection

A lack of contrast sensitivity has been observed from film fogging

when thin Al (a few mils) window cassettes are used. We believe it is

due to pair production products generated in the object under inspection.

Presumably the radiation products generated do not possess great penetrating power in Al since the effect caused by an object in front of the

cassette appears to disappear when aluminum of 0.125 in thickness is

employed as an entrance window. We attribute the effect to the high

energy prompt gamma rays resulting from radiative capture of thermal

neutrons in D„ (6.2 MeV) and graphite (4.4 MeV) . Experiments are in

progress to determine the cause of the phenomenon and the effect it may

have on cassette design.

The magnitude of the film fogging is illustrated in figure 8 which

is a copy of a radiograph made in a neutron-free beam, i.e., when the

thermal column curtain was in the closed position.

Figure 8. Film fogging due pair production in specimen under inspection.

38
REACTOR RADIATION DIVISION PROGRAMS

7. Standard Measurements

Preliminary design work has been started on two standard measurements which will make it possible to compare individual neutron radiographic facilities. These standard measurements are:

1. Thermal Neutron to Gamma Ray Ratio

A means to measure the thermal neutron to gamma ray ratio of a neutron beam for radiographic purposes. At the present time, these

measurements are made using a gold foil to measure the thermal neutron

flux and TLDS to measure the gamma content . The gamma measurement is the

most inaccurate since the presence of the neutrons has an effect on the

readings.

The effect of the gamma ray content on the image recorder is the

important factor to be considered, and not necessarily the mr content.

Both the mr and the energy spectrum of the gamma beam will have an effect

on the gamma film fogging.

We propose to accomplish this measurement using a standard package

which will consist of a film in contact with a Gd converter screen sufficiently thick to stop the neutron beam. This will be backed by an aluminum filter sufficiently thick to stop the electrons generated by the

Gd. A second film will be employed to determine the effect of the gamma

ray content of the beam plus the effect of knock on protons created in

the film base by fast neutrons. The ratio of these two numbers at the same front film density would be the meaningful number for comparison of

facilities.

2. Beam Divergence Meter

One requirement that has been presented to the NBS Neutron Radiography group has been that of measuring the new beam divergence of a radiographic facility. Preliminary design work has been started on such

a device which essentially measures the L/D ratio of the beam. The concept is illustrated in figure 9.

39
REACTOR RADIATION DIVISION PROGRAMS

Beam Energy Monitor

\ Gd Single Zone Plate

Spectrometer

Distributed Neutron Source

Figure 9. Schematic diagram of the beam divergence meter.

8. Facilities

Extensive modifications to the thermal column neutron radiography

facility. Swellage of the magnetite concrete outer shield caused the

collimator to shift, directing the neutron beam into neighboring experiments. A new outer shield box fabricated from 0.5 in. thick welded

steel plate and filled with lead has been installed. Larger beam pipes

have been designed into the new system to produce a larger beam and to run cryogenic cooling to crystal beam filters.

LEAD SHIELD

T/i///j///////mm

////////////////.

SHUTTER-

-LEAD BEAM DUMP

<gZZZZZZ2ZZZZZZZZZZZZZZZZZZZZI

7ZZ7ZZZZZZZZZZZZZZZZZZZZZZZZZ

Figure 10. The components comprising the meter consist of a pancake

fission beam monitor, two single zone plates of Gd, and the

distributed neutron source. As C is moved in the direction

of the source, the counts above background in the stop when

the neutron beam can no longer be seen by the fission chamber,

The distance x can then be used as a measure of the beam

divergence.

40
REACTOR RADIATION DIVISION PROGRAMS

Pinhole radiographs of the thermal column aperture have exhibited

extensive haloing at the image plane. Further diagnostic work will be

necessary to determine the cause of this effect.

A problem has arisen in that gamma scatter from the object being

radiographed raise the background to an unacceptable level. A new lead

lined cave is being designed to eliminate this problem. In addition,

the design of a gravity-operated shutter mechanism for the thermal column

facility A schematic diagram of the proposed shield and shutter is illustrated in figure 10.

THERMAL NEUTRON FLUX MEASUREMENTS

V. W. Myers and M. Ganoczy

Analysis of the data for calibrating boron loaded cobalt glass

beads in a known thermal neutron beam is being completed. An unknown

thermal flux can then be determined by comparing the Co-60 counting

rate from a bead activated in the unknown flux to a calibrated bead.

SOLUTIONS OF THE KLEIN-GORDON EQUATION

V. W. Myers

The time- independent Klein-Gordon equation for a particle of rest

mass m is (E-V) 2 ^ = (m2 -V2

)i|j. This equation is valid in the classical

field limit for a spin zero particle, for example a II meson in an

2 —r —

r

external field. Solutions for ty such as e , e have been investigated to determine if they conform to a real potential V over all

space <: r $ °°. There are rather stringent limitations on solutions

because of the presence of (E-V) 2 rather than E-V of the non-

— x relativistic Schrbdinger equation. For example, e

" corresponds to a -r 2 real potential over all space, but e does not. There are similar

restrictions on solutions of the Dirac equation.

41
B, RRD-NBS Collaborative Programs

SEPARATION OF OVERLAPPING PEAKS IN NEUTRON

DIFFRACTION POWDER PATTERNS

A. Santoro

and

P . Brown

(Center for Building and Technology)

1. Method

Important applications of powder diffraction data, such as quantitative analysis and determination of lattice parameters, lattice distortions, crystallite sizes etc.,. are possible only if the patterns contain

a large number of single, non-overlapped peaks. This requirement constitutes a serious limitation in most cases and, not surprisingly, attempts

have been made to circumvent the problem. In the case of x-ray diffraction the possibility of separating overlapping peaks has been analyzed

in detail, especially by Parrish and co-workers. A major difficulty in

the use of x-ray patterns is due to the fact that the x-ray peak shapes

are not well known and therefore cannot be accurately described by means

of a simple mathematical function. However because the neutron diffraction peak shapes are nearly gaussian, the treatment of overlapping re- flections relatively simple in this case. The use of neutron powder

patterns for the characterization and the analysis of the crystalline

components of Portland cements has been considered in this laboratory

for this reason. With this approximation the total intensity y. observed

at the angular position 20 . is given by the expression

m m

( r (28.-29 ) 2

-. -.i

y-r = E yn

- n =£ 5 a 1-p / n ns exp -b (28,-26) 1

t~r n i,n ~njn[_ tanG J

v

|_ n l n J I

where y. is the contribution of reflection n to the intensity measured

x,n J at 20., 9 is the Bragg angle of reflection n, a the peak height and

b = (4£n2)/H where H is the full width at half maximum (fwhm) . P is n n n

42
RRD-NBS COLLABORATIVE PROGRAMS

6000

4000-

2000

9000-

20 22 24 30 31

5000

00

M-LiTa

3 8 •

m \\

(c)

00 4 iT

m*

/

[ l \

A A

00

jL

/ V\i 7 * 999 / v. V*.

•

1 1 1 20

Figure 1

21 22 23

3000-

1000

Observed values (dots) and least-squares profiles (continuous

lines) for the compounds indicated on each figure. The broken

lines represent the separated gaussians. The experimental

conditions are indicated on figure la. In all the figures

the abscissas are the 26 angles and the ordinates the number

of counts.

43
RRD-NBS COLLABORATIVE PROGRAMS

80

60

KBr

a,<a2

< a3=/3 = 2l'' 24'< 23'<20' --THEORETICAL

U=724l V=-4875

W=27l5' — LEAST SQUARES

U=II760 (240) V=-778l (325) W=3546 (95) • EXPERIMENTAL

POINTS

40

20,

120

100

^ a,<a2

< aj /3 = 19' ^ 25'< 35' 13' --THEORETICAL

U = 30000

V=-IOOOO W=4600 — LEAST SQUARES U=37300

V=-I0700 W=5500

• EXPERIMENTAL

POINTS

20,

Ni Pb MON 26_ = 33.03°

1.0 2.0 3.0

Figure 2. Comparison between the theoretical and the experimental values

of the full widths at half maximum of neutron diffraction

peaks. The "experimental" points of figure la. have been obtained by least-squared fitting of the peaks of KBr by assuming

gaussian shapes. The points of figure lb. are those given by

Caglioti et al. (loc. cit.). The broken lines represent the

theoretical preditions according to the equation

H

2 = Utan2

9 + Vtan9 + W. The continuous lines are the leastsquares lines through the experimental points. The parameter

a is given by a = tan6/tan8 where 29 is the take-off angle

the so called "asymmetry parameter", introduced to correct for the distortions caused by the vertical divergence and s = -1,0,+1, depending on

the sign of 20 in. - 20 . m is the number of reflections contributing° to

the intensity y.. A least-squares program has been written which minimizes the function

F =]P W. y. (observed) - y. (calculated)

with respect to the parameters H, a, 2R and P of each reflection. In

the above expression W. are weights, assigned according to the expression

W. = l/(y. + background). The main difference between Rietveld method

(J. Appl. Cryst. , 2, 65, 1969) and the one described here is that the

latter does not require any structural information.

44
RRD-NBS COLLABORATIVE PROGRAMS

6.600

4

a 6.590

6.580

2.0

Figure 3. Lattice constant of KBr calculated from the indicated re- flections and plotted against the function

(cos 2 6)/sin9 + (cos 2 6)/9. The extrapolated value of the

lattice parameter - a = 6.596 - is in good agreement with

the literature values which range between 6.596 and 6.599,

2. Results

Examples of the application of the least-squares program are illustrated in figures la, b, c, and d for cases of increasing degree of over- lapping. The data obtained after refinement are given in table 1 and

compared, whenever possible, with the theoretical predictions.

The powder pattern of KBr contains good quality, non overlapped

peaks. Therefore, a detailed analysis of these peaks has been carried

out in order to clarify a number of questions related to the profile

fitting procedure proposed by Rietveld and now widely used. Preliminary

results of this study seem to suggest the following conclusions:

a. The neutron diffraction peaks are very nearly gaussian. The analysis of all the peaks, however, shows that with our experimental arrangement the least-squares fit results in a value of the R^ factor around

4-5%, This means that the so called "expected" R factor cannot be evaluated on counting statistics alone and that it is unrealistic to expect

i structural refinements with R factors lower than 4-5%.

b. There is a discrepancy between the theoretical values of the full

widths at half maximum (fwhm) calculated with the procedure of Caglioti

45
RRD-NBS COLLABORATIVE PROGRAMS

Table 1. Results from the least-squares separation of overlapping peaks

KBr

25L1

2

0:75T10

2

\

= 3.6%

M-LiTa

\

= 8.2%

C.AF+e-C S 4 2

M

LS

2fi THEORY

H

LS

H

THE0RY

20.56° 20.53 30' 27'

23.78 23.76 29 26

31.34 28 26

32.12 38 26

32.99 31 26

20.62 20.63 32 27

21.51 21.51 32 27

22.08 22.05 32 27

35.45 33 26

36.39 35 26

36.94 37 26

*w

= 5.2%

et al. (Nucl. Instr. } _3, 223, 1958) and the experimental data. The nature

of the discrepancy is illustrated in figures 2a, b. These figures show

that the functional relationship between fwhm and dispersion parameter

seems to hold. It is clear, however, that more careful analysis of the

equation relating the fwhm and 6 is required before we can apply with any

confidence the equation to a profile fitting procedure such as that of

Rietveld.

c. In figure 3 the lattice parameter of KBr obtained from each diffraction line is plotted against the Nelson and Riley extrapolation function (Klug & Alexander, "X-Ray Diffraction Procedures," 2nd Edition,

Wiley, 1974, p. 594). While the choice of this function may not be quite

appropriate for our particular case, the figure shows clearly that the

peak positions are affected by systematic errors as in the x-ray case. The nature of the systematic errors does not have to be necessarily the same in x-ray and neutron diffraction, however. For example, the vertical

46
RKD-NBS COLLABORATIVE PROGRAMS

component of the eccentricity error cannot be eliminated experimentally

in the neutron patterns (as it is done in the x-ray patterns) because

this would require measurements of peak positions in the unfavorable

anti-parallel geometry. According to our preliminary results, this error unfortunately varies with 6 according to cos29 cotan6, making it difficult

to apply the ordinary extrapolation procedures. Another significant difference between x rays and neutrons is that in the latter case the problem of absorption is only rarely important, while in the former case is

the major source of errors. The refinement procedure of Rietveld does

not take into account systematic errors in the lattice parameters. The

above results strongly indicate that this is another area where further

study is required.

POWDER NEUTRON DIFFRACTION ANALYSIS OF THE

CRYSTAL STRUCTURES OF LiNb

3

O

g

, M-LiTa 3 8 AND H-LiTa 3 8

A. Santoro

and

R. S. Roth and D. B. Minor

(Inorganic Materials Division)

The principles of the crystal chemistry of Li in oxide structures

is largely unknown, as this ion generally cannot be located with any

accuracy by x-ray diffraction methods. However, neutron diffraction

offers unique advantages over x rays in scattering of both Li and oxygen

and opens up the promise of learning some of the details of the Li-oxygen

coordination scheme. The compound LiTa„0 o was found to be trimorphic

(Roth et al. in Fast Ion Transport in Solids, p. 218, Ed. W. vanGool,

North Holland Publish Co., Amsterdam, 1973). As the crystal structures

of all the polymorphs are known in principle, it appeared that these three

phases might be appropriate to use as a starting point in this study.

However, the lowest temperature polymorph has never been synthesized as

47
RRD-NBS COLLABORATIVE PROGRAMS

a pure single phase, so the apparently isostructural compound LiNb„0o J o was substituted. Stoichiometric LiTao o was prepared from LiTa0„ and JO J Ta^Oj., and converted to the M- and H-polymorphs by heating at 1025°C and

1200°C respectively. The LiNb o o was prepared from LiNb0o and Nb o c by jo j Z j

reaction at 1100°C. All heat treatments were performed in open containers

of pure platinum.

Neutron diffraction measurements were made at room temperature on

a powder dif fractometer of moderate resolution at the National Bureau of

Standards reactor. The details of the experimental conditions are sum- marized in table 1.

Table 1. Experimental conditions used to collect powder diffraction data

Monochromatic beam: reflection 220 of a Cu monochromator

o Mean neutron wavelength = 1.358(1)

A

Take-off angle = 63.8°

Horizontal divergences: (a) In-pile collimator a =21 min. arc

(b) Monochromatic beam collimator a =24 min. arc

(c) Diffracted beam collimator a =23 min. arc Monochromator mosaic spread ^10 min. arc

(*) Theoretical values of full width at half maximum (fwhm) parameters:

U = 7200, V = -4650, W = 2420 x 10

4

deg

2

Sample container: Vanadium can of ^1 cm. diameter

(*) The parameters U,V,W appear in the expression

H

2 = Utan 6 + Vtan9 + W

n n n where H is the fwhm of reflection n with Bragg angle 9 Their theo- n n. retical values are calculated with the expressions given by Caglioti

et al. (Nucl. Instr., 3, 223, 1958).

48
RRD-NBS COLLABORATIVE PROGRAMS

The structural models of the title compounds were refined by using

the profile fitting procedure proposed by Rietveld (J. Appl. Cryst., _2,

65, 1969).

Starting Models

a. LiNb„0„ - The structure of lithium triniobate has been determined

by single-crystal x-ray techniques by Lundberg (Acta Chem. Scan. , 25 , 3337, 1971) and by Gatehouse & Leverett (Cryst. Struct. Comm. , 1, 83,

1972) . It has been re-considered in this work not only to provide a useful comparison between x-ray and neutron diffraction results, but also

to test if the total profile analysis proposed by Rietveld can be ex- tended to the refinement of crystal structures of the complexity en- countered in the study of this class of compounds. The results of the

refinement, reported in table 2, show that the method can be safely applied to the study of oxide structures. Figure 1 shows the calculated

and observed profiles for this compound.

b. M-LiTao o - The x-ray analysis of the intermediate temperature

J o phase of lithium tantalate (Gatehouse, Negas & Roth, J. Solid State Chem.

18 , 1, 1976) failed to reveal the exact location of the Li atoms.

An attempt made by powder neutron diffraction techniques showed immediately that the lithium ions are located in the octahedral sites indicated

by the idealized structure represented in figure 2. The results of the

profile refinement are summarized in table 3.

In figure 3 are shown the calculated and observed profiles for

M-LiTa o o

. A comparison between the atomic coordinated obtained by

J o single-crystal x ray analysis and by powder neutron diffraction is shown

in table 4.

49
RRD-NBS COLLABORATIVE PROGRAMS

Table 2. Results of the refinement of the structure of LiNb-O

J o

LiNb o o -P2./c, a = 7.457(2), b = 5.033(1), c - 15.270(2) A, 6 = 107.34(1) Jo 1

26. .„. . = 6.00°, 29^. . = 64.50°, step = 0.1°

xnxtial final

No. of reflections = 269, no. of observations above background = 519

-12

Scattering amplitudes: b =0.711, b

Q=0.575, b =-0.194x10 cm U = 15700(1400), V = -11600(1100), W = 4300(200)

R = 6.3%, R

p pw

7.6%, R , expected

= 4.2% (**)

Atom X y z B(*)

Nbl 0.493(2) 0.228(3) 0.331(1) 0.56

Nb2 0.751(2) 0.232(4) 0.073(1) 0.60

Nb3 0.987(1) 0.247(4) 0.333(1) 0.56

01 0.998(2) 0.055(4) 0.098(1) 0.74

02 0.413(3) 0.079(4) 0.216(1) 0.74

03 0.767(3) 0.096(3) 0.345(1) 0.74

04 0.539(2) 0.419(4) 0.105(1) 0.74

05 0.911(3) 0.418(5) 0.216(1) 0.74

06 0.641(2) 0.384(3) 0.461(1) 0.74

07 0.149(2) 0.071(3) 0.453(1) 0.74

08 0.275(3) 0.417(4) 0.345(1) 0.74

Li 0.245(9) 0.245(20) 0.082(4) 2.3

(*) The isotropic temp, factors were kept fixed at the values found by

x rays.

(**) For the definitions of R , R and R , see Hewat, ILL report

p' pw expected

#74H62S, April 1974.

50
RRD-NBS COLLABORATIVE PROGRAMS

Table 3. Results of the refinement of the structure of M-LlTa

M-LiTa_0o - C2/c, a = 9.409(1), b = 11.519(1), c = 5.050(1) A

J o

3 = 91.11(1)° 26. ._. . = 9.00°, 26.. . = 78.00°, step = 0.1°

initial final

No. of reflections = 247, no. of observations avove background = 641

bm

= 0.691xl0~12 cm

Ta

U = 15000(1100), V = -10900(900), W = 4300(200)

R = 6.1%, R =7.3%, R ,=5.3%

p pw

Atom x

(*) Tal v ' 0.2415

Ta2 v J

01 0.3533(5)

02 0.3839(5)

03 0.1322(5)

04 0.1187(5)

Li

All thermal parameters and the positional parameters of the Ta

atoms were kept fixed during refinement.

c. H-LiTa o Jo - The structure of the high temperature phase of LiTao o

j o has not been determined previously, but lattice parameters measurements

indicated that the structures of H-LiTa„0 o and LiNb,0nc F (Lundberg, Acta Jo b id

Chem. Scan., JL9, 2274, 1965) must be closely related. A refinement based

on this assumption gave a final R factor of 15%, i.e. significantly higher

than the expected value. These preliminary results indicate that the

gross structural features of the two compound are. the same. The high

value of the R factor, however, suggests that the symmetry of H-LiTa„0

fi may be lower than that of the space group Pmam reported for LiNb,0nc F.

b ±_)

Single-crystal measurements do in fact show that many reflections h0£

with h = 2n + 1 have appreciable intensity, thus indicating that the

structure does not contain the glide plane. Further study on the structure of this compound by neutron single-crystal and powder techniques is

still in progress.

51

°' expected

y z B

v ;

0.0864 0.2466 0.27

0.3299 1/4 0.27

0.4502(5) 0.4386(11) 0.62

0.1794(5) 0.4226(10) 0.61

0.4366(5) 0.0834(12) 0.48

0.1961(4) 0.1050(10) 0.64

0.8357(20) 1/4 0.70
RRD-NBS COLLABORATIVE PROGRAMS

<

.00

. 5;

CO O

CO

u

o

H-lG

U

CD •UU

cOOuU

CD&O

exco

nu

G

01C

CD

3

O

i-HCOa

c

CO

cd>

u

<u

en o

CDU

G

W)

•H

„(Olx) AilSN3J.NI N0Hin3N

52
RRD-NBS COLLABORATIVE PROGRAMS

LAYER I

LAYER 2 6 4

LAYER 3

Figure 2. Layers of octahedra which build up the structure of M-LiTa_Og

Table 4. Comparison of x-rays and neutron atomic parameters for oxygen

and lithium atoms in the structure of M-LiTao o J o

X RAYS HEUTRONS Atom X y z B X y z B

0(1) 0.3541(20) 0.4516(17) 0.4413(37) 0.62(28) 0.3533(5) 0.4502(5) 0.4386(11) 0.62

0(2) 0.3846(22) 0.1788(17) 0.4270(39) 0.61(27) 0.3839(5) 0.1794(5) 0.4226(10) 0.61

0(3) 0.1332(20) 0.4375(18) 0.0792(36) 0.48(26) 0.1322(5) 0.4366(5) 0.0834(12) 0.48

0(4) 0.1185(22) 0.1967(18) 0.1069(38) 0.64(28) 0.1187(5) 0.1961(4) 0.1050(10) 0.64 LI - - - - 0.8397(20) 1/4 0.7

53
RRD-NBS COLLABORATIVE PROGRAMS

00

CO

CO H

•H

hJ

I a

O

(3

J-i <u 4JU

cdex

S-i 0)&o

p-c

o

(-1 4-1 3

01C

0)

3

O

rH

COO

X)C

cd

0)>

cd

en o

cu

00 •H

ft,

( t OI)« JkllSN3J.NI

54
RRD-NBS COLLABORATIVE PROGRAMS

APPLICATION OF SIMULTANEOUS DIFFRACTION STUDIES TO

THE ANALYSIS OF X-RAY SPECTRA

A. Santoro

and

R. D. DesLattes, R. LaVilla and A. Henins

(Optical Physics Division)

1. Introduction

X-ray spectra from the sun are now being intensely studied as they

are rich in structural details of importance for the understanding

especially of flare phenomena. As the time of maximum solar activity

approaches, large scale plans for sophisticated multi-spectral measurements are well underway. One of these, the Solar Maximum Mission (SMM)

,

a 300 kg satellite containing more than a dozen spectrometers, is being

pursued under NASA sponsorship by a group at Mullard Industries and

Appleton Laboratories in England and Lockheed Research Laboratory in

Palo Alto, California.

This group has asked the NBS for assistance in the quantitative

characterization of the dispersion crystals and for comment on the crystallographic choices which must be made. X-ray spectroscopic resources

(232.06) provided help in optimizing diffraction characteristics for the

several spectral features to be studied on SMM. One additional feature

of crystal choice, namely the avoidance of simultaneous diffraction, was

studied at the Reactor Division (31A.03).

Simultaneous, or multiple, diffraction of x-rays takes place whenever two or more sets of crystal planes are in position to diffract the

incident beam. The occurrence of this effect produces complicated variations in the measured intensity of reflections (Zachariasen, Acta Cryst.

18 , 705, 1965) and it has to be avoided in structural investigations

(Santoro and Zocchi, Acta Cryst. 17, 597, 196A; Acta Cryst. 21, 293, 1966

Acta Cryst. 22, 331, 1967) as well as in x-ray spectroscopy work.

55
RRD-NBS COLLABORATIVE PROGRAMS

In what follows we will outline the method employed in this study

and we will point out some properties of the diffraction geometry which

may be of general interest.

2. Method

The crystal is initially oriented so that the reciprocal lattice

vector (scattering vector) corresponding to the selected "primary reflection" h k 1 , is perpendicular to the incident beam. The orientation

o o o needed to bring h k 1 into reflecting position is then achieved by means

o o o of the appropriate rotation 6 about the direction perpendicular to the

"equatorial plane", i.e. the plane defined by incident and diffracted

beams. Obviously the diffraction condition continues to be satisfied

also if we rotate the crystal of any arbitrary angle i/j (azimuthal ro- tation about the scattering vector. Since the crystal orientation, the

lattice parameters and the values of 8 and ijj are all known quantities,

it is possible to evaluate the matrix T which transforms the coordinates

h of a reciprocal lattice point, expressed in the reciprocal lattice

system, into the coordinates expressed in an appropriate Cartesian system

attached to the laboratory

x = Th

From this equation it is easy to derive the geometrical conditions (that

is the value of ty or that of the wavelength X) under which a second

reciprocal lattice point hkl is in simultaneous diffraction with the

primary reflection hkl. Starting from the same equation it is also

o o o possible to prove a number of theorems which have been found useful in

interpreting the geometry of multiple diffraction and in designing ex- periments which minimize its effects on the measured intensities. These

are the following:

a. Simultaneous diffraction may be X-dependent or X-independent . (In

the first case the angle ^ at which a node hkl is in simultaneous diffraction with the primary reflection hkl is a function of X, in the

o o o second case it is not)

.

56
RRD-NBS COLLABORATIVE PROGRAMS

a>i re

roa>'

ii <o

C\J CM

LU

CM

•8 5o

ro

CvjO of ooCMoo f o ^.

00o

CDoo

CM o I CM

CM CO 4-J <r ro cd C • 1M O H 3

•h a

4-> rH

O

u cd o

0)

H CJ

aj o u -H e j-1 ^- CO

cd 4-1 mh

•rl C «H M QJ TJ

On iH

qj oj OJ > rH

XJ CfJ Qh

4-1 & «H

4-1 ,£ QJ rH

4-1 ,£J CJ H 4-1

S-i 14-1 pi o o O <4H H QJ 4J T3 <i) o a ^

cd cd m-i

4-> O

,0

cd

4-1 cd

$-1 oH

cd too cd

M-l -H O T3

<u a) o ^

CJ 4->

<4H ^H

M-l Cd •H13 u a> O ptj CO3o

QJa . cd -next;

4-» CJ H cd <t 3 <r a ft cti MOH

QJU3

00

•H

1*4

a) o H CO a j-i 4-1 cd

qj ai rH o O m• CO CO «H CO o o r-» <j- • • O

CN <t H H

J_

cm cr> <x> ro

ro cvi cvi cvi

O o <1 o

CMoo

00o

CDoo

CM

cdm 1 CN rH

U

M-l • O O CO O I •H CN O

cn r^-

U

00 M-J cd a • O CM QJ MH

•H QJO

4-J rH

U

O Cd M-l 4-J 3 B CO

CJ

QJ mh a) S MH

QJ 4-J M-l H c •H QJ H 4J h cd QJ U rG 4-J 42

cd 4-1 c 4-1 00 QJ H C •H CO

J-l QJ

n £

CX >H

O

0) rC

QJ > CO

,fl cd CJ

4-J &

QJ cd

,fl QJ I-lu

4J ^ cd 00

•H 4J cd £ QJ •H H u "T3 a QJ O MH X QJ •H 4J ^J

4-J 13

H

CJ CJ •> cd cd r< M < •

14-1 rH CJ

•4-1 Cd QJ

O

•H 4-J 00 •H

13 CO

u 4J !* cd O

CD

U rH cd 3 O r4 O QJ <4H QJ X MH

cj 3 4-J •H • cd -H t3

4-> fi

O

O

rH Cd 4-1 QJ CT\ IB rH

CU CX II •H QJ 3 •H

CO

OO 4J -9-

CN

QJU

CJ00

•H

F*4

57
RRD-NBS COLLABORATIVE PROGRAMS

b. Simultaneous diffraction X-independent takes place if, and only if,

the points h k 1 and hkl lie on a vertical net, i.e. on a net perpendicular to the equatorial plane.

c. If h k 1 and hkl are in simultaneous diffraction X independent,

o o o

r > then also the reciprocal lattice point

h' = h - h, k'=k-k l'=l-l o o o diffracts simultaneously with hkl and hkl. In addition, the three

o o o nodes all lie on the same vertical net.

d. If h k 1 , hkl and h'k'l' are in simultaneous diffraction X-indepeno o o

r dent, the net of these three nodes is rectangular.

e. If a node hkl diffracts simultaneously with the primary reflection

hkl at a value ii of the azimuth, then the node

o o o

r '

h

1 « h - h, k' = k - k, 1' = 1 - 1 o o o diffracts simultaneously with hkl at the azimuth

o o o

tJ>* = 180° + $

3. Results

A computer program which evaluates the azimuthal coordinates ty of

multiple reflections has been developed. The values of ty were calculated

for the lower and upper limits of each wavelength interval to be studied

and for each dispersion crystal employed in SMM. When these values are plotted as indicated in figure 1, one often finds orientation intervals

entirely free of multiple diffraction. When possible, it is obviously

desirable to choose such orientations for spectroscopy. Sometimes, however, there are no such regions, as indicated in figure 2, or the desired

orientation is not accessible because of growth morphology. For these

cases a second program has been developed which enumerates the Bragg

angles (or wavelengths) at which trouble might be expected.

Other x-ray spectroscopy programs are benefitting from this work

also. For example, the spectra of magnetically confined and laser driven

58
RRD-NBS COLLABORATIVE PROGRAMS

plasmas are rich in this region and need quantitative spectrophotometry,

Work done in support of the ERDA supported studies at the Princeton

Plasma Laboratory will include use of this systematic approach to the

avoidance of multiple diffraction effects. Finally, an NBS experiment

destined for installation at the Stanford Storage Ring was recently

troubled by this effect because of a failure to apply the systematic

tests in advance.

THE CONFORMATION OF PS-PMMA DIBLOCK COPOLYMER IN TOLUENE

BY SMALL ANGLE NEUTRON SCATTERING

C. C. Han

(Polymers Division)

and

B. Mozer

A deuterated polystyrene-poly (methyl methacrylate) (dPS-PMMA)

diblock copolymer and its deuterated polystyrene homopolymer precursor

were studied by small angle neutron scattering and light scattering ex- periments using toluene as the solvent.

The radii of gyration of the deuterated PS homopolymer (M=88,000)

measured by both methods and that of the PMMA block (M=203,000) in the

diblock copolymer measured only by neutron scattering were determined as

o o 210A and 85A respectively. In addition, the second virial coefficients

and the chain excluded volume exponents were also obtained.

The copolymer chain configuration in toluene at 23° C is inferred

from these measurements. It is suggested that the PMMA block forms the

interior core from which the PS block exudes out as an expanded chain.

59
RRD-NBS COLLABORATIVE PROGRAMS

co

CO

^CM sj- H toO 1 ctf "^ O

•H 4J H !-i C SrHK

•H <U <*-* ^^ > -H • o co

CJ rH • hJ TJ -H O rH ^-

'

C «w 6 +1 O <W v«-' CM U 0) • CD O CM m

co o <C s^

G) /"^ <*S /-s B CO CO CO 3 S5 S3 53 iH > \_x N»^ >«• o> 4Je

13 0) O

o) a CM m CO

T3 O • o o

3 0- tH • • «H X <? +i +1 O W m CO rH X rH o rH W • • • rH rH rH

/-S /""N /"\ /~\ o o<f CO CO CO CO

hJ S3 (H 53 CM s-x «>«• s-^ %.•

iH CO o O

A iH sr «*

CM +i +i +1 r^ CD m o m +l or rH rH CM m

V CM CM CM co

, , e s-^ •-s /-N

4-) CO CO <d

ES rJ •H w .v-^ ^^ v—' M

CO CO CO

rH o o

3 rH a

CO o a CO O

0) /-N /—

s

o rH

«H CO CO rH X

O +1 +1 X VO a 00 m CO • CO CJ\ o O N-*' CM vO

/-s /-\

X-N ^S .Sd <""N o o o .. 2

s o <| O <g B

CO o CO rH S H § o

PL. £1 Ph 43 § -£> S rC! TJ s_/ tTj V Pu *-» Pm ^

60
RRD-NBS COLLABORATIVE PROGRAMS

STUDIES ON THE STRUCTURE OF DEFECTIVE HYDROXYAPATITE

A. Santoro

and

L. Schroeder

(Polymers Division)

Structural studies of defective hydroxyapatite using the method of

total profile analysis have continued in the past year. The results so far obtained do not permit to determine the nature of the defects present

in the structure, mainly because a "standard" sample with which comparisons can be made is not yet available. Attempts are now being made at

preparing non defective samples of the compound.

61
C, Interagency and University Collaborative Programs

DEUTERIUM-SITE OCCUPANCY IN THE °< AND B PHASES OF TiDx

H. Alperin

(Naval Surface Weapons Center, White Oak, md )

and

H. Flotow

(Argonne National Laboratory, Argonne, IL )

and

J. Rush and J. Rhyne

A neutron diffraction study on polycrystalline samples of the

a (hep) and B(bcc) phases of TiDx has been completed. The objective was

the determination of the sites that are occupied by deuterium atoms in

each of the two phases. The compositions and temperatures chosen to

achieve the a and 3 phases were TiDrt -..,.. at 375C and TiDn ,-, at 400C reu .u/ J u .o / spectively. The results show that both phases exhibit considerable

mixed - octahedral (y) - tetrahedral (1-y) site occupancy. The results

are for the a-phase: y=0.68±.02 while for the B-phase: 0.15<y<0.30. A

comparison of observed and calculated intensities are given in Tables 1

and 2. The uncertainty in y for the B-phase is due to a strong correlation with the octahedral deuterium temperature factor. The site occu- pancy results may be correlated with the Ti-D distances for each site.

In both phases it appears that the deuterium atoms predominantly occupy

sites with the larger holes

.

Single crystals of titanium have been obtained and diffraction

measurements will be made to further refine the octahedral and tetrahedral temperature factors. Work is underway using the time-of-flight

spectrometer to measure the quasielastic scattering from TiH in the a and B phases in order to determine the diffusion of hydrogen in the

lattice. Finally we expect to measure the phonon spectra on single

62
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Table 1. Comparison of observed and calculated neutron scattering

intensities for TiD

n n

__ at 375C—a (hep) phase.

hkl

"obs "calc

100

002

101

102

110

103

51370

54575

199045

21085

34498

48779

53024

53068

196319

23269

34694

47774

Calculated with B

Tl

= 1.875, B°ct= 4.6, B*

et

= 3.0 and deuterium

octahedral site occupancy, y = 0.68.

Table 2 . Comparison of observed and calculated neutron scattering

intensities for $-phase (bec) TiD.

6

_ at 400C.

hkl

"obs calc

110

200

211

220

230700

4529

28822

24936

237573

5001

28566

23784

a Ti not fpf Calculated with B = 2.5, b" =5.0, B^ = 2.5 and deuterium

octahedral site occupancy, y = 0.20.

63
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

crystals of pure a-Ti and aTiH n7C. to obtain information on how the

presence of hydrogen affects the metal-metal bonds. This work has

already begun with the measurements of several phonon branches for pure

a-Ti at room temperature.

SMALL ANGLE MAGNETIC SCATTERING FROM A DILUTE

AMORPHOUS Fe(Tb) ALLOY

H. Alperin and S. Pickart*

(Naval Surface Weapons Center, White Oak, MD)

and

J . J . Rhyne

Low temperature neutron scattering measurements on a rapidly

sputtered bulk sample of composition Tb A An Fe_ noo reveal anomalous

u. uio u. yttz

small-angle magnetic scattering similar to that observed in the more

rare earth-rich amorphous alloys TbFe„ and HoFe„ reported previously . The data in figure 1 show a broad hump (as distinct from a sharp critical

2

peak) about T (determined from magnetic measurements ) and the anomalously

large magnetic component below T . Above T the scattering can be

fitted to a Lorentzian from which we deduce a correlation length which

increases from 13A at 260K to 38A at T . Below T the scattering can be

c c fitted by the asymptotic Porod Law for a random distribution of spherical

particles.

* Physics Dept., University of Rhode Island

1. S. Pickart, J. Rhyne and H. Alperin, Phys Rev. Lett. _33, 424 (1974);

AIP Conf. Proc. _2_4, 117 (1975).

2. H. Alperin, J. Cullen, A. Clark AIP Conf. Proc. 29, 186 (1976).

64
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

40K

30Kc

'EW20K

IOK-

' .018 .982

Vo6

- ^08 \ °-l L-q=.04A

*V!?

^JL

1 1 100 200

TOO

300

Figure 1. Scattered neutron intensity, background subtracted as a function of temperature. The data at lower temperatures

for q = .04, which are not plotted for reasons of con- venience, scale very closely to the square of the observed

spontaneous moment .

DIFFRACTION MEASUREMENTS FROM RAPIDLY SPUTTERED BULK

Fe(Tb) AND Ni(Dy) ALLOY SAMPLES

H. Alperin

(Naval Surface Weapons Center, White Oak, MD.)

and

J . J . Rhyne

3 3 We have previously measured bulk samples (50 mm to 150 mm in

volume) of Tb Fe, (x = 0.118, 0.25, 0.33, 0.45 and 0.75) alloys pre65
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Tb Fe

^^

0.018 0.982

uj 6

_

_i u < X= 1.194 A T=295K

>-or<

a: .

<r- 4 m

a:<

V

i- _

c75 2 2

LdH

H ,. , ,

n

bcc Fe —^- 110 200 211

i i 220

3 4 Q = 47rSin 8/\

Figure 1. Diffraction pattern of amorphous Tt> n ..„ Fe_ qR9 at room temperature. If the pattern were due to small

polycrystalline particles of pure bcc iron the peaks

would have to appear at the locations indicated.

pared by dc rapid sputtering. Diffraction patterns were found with very

broadened peaks. The atomic 'structure' that can give rise to such

patterns has been described as amorphous, arising from a random close

packed atomic arrangement. We have now made similar measurements on the

compositions Tb Fe., for x = 0.018, 0.167 and also for Ni(lwt.%Dy)

which corresponds to Dy~ ^^Ni,. nnr ,

. The terbuim content in the 0.0036 0.9964

x = 0.018 sample was analyzed by neutron activation to an accuracy of

+2% by the Activation Analysis Section of the Analytical Chemistry

Division. The diffraction pattern for this composition shown in figure 1,

is most likely also due to an amorphous random close packed atomic

arrangement. However, if one should try to attribute the broadened

diffraction peaks to small-size crystalline iron particles, these

particles could be no larger than an average diameter of 15A if we

analyze only the broadening about the (110) Fe position. The displacement of the measured peaks from the (211) and (220) Fe positions however

makes even such a crystalline interpretation doubtful. For the x = 0.167

composition, if the particles are crystalline they could be no larger

than 10A. The Ni(Dy) sample exhibited sharp diffraction peaks indicative

of a crystalline atomic structure.

66
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

NONDESTRUCTIVE DETERMINATION OF GRAIN-ORIENTATION OF

METAL LINERS FOR SHAPED-CHARGE MUNITIONS

C. S. Choi and H. J. Prask

(Picatinny Arsenal, Dover, NJ)

The optimum functioning of shaped-charge ammunition requires that

the projectile have essentially zero spin (i.e., axial rotation) at

impact with the target. This requirement is very difficult to achieve

in practice. It has been generally accepted that at relatively low

spin rates (£ 50 r.p.s.) optimum functioning can be achieved in spite

of spin if the liner cone is manufactured in a specific way. That is,

by preferentially aligning the individual grains of the liner such that

as the liner collapses along preferred slippage directions, a counterrotation equal and opposite to that of the in-flight projectile is

imparted to the explosive blast jet. It has also been suggested that

residual stresses are induced in liners by the same manufacturing

technique which produces grain orientation (i.e., shear spinning), and

that it is residual stress, not grain orientation, which causes "spin

compensation" in collapsing liners. The principal difficulty which has

prevented the resolution of this conflict has been the lack of non- destructive test methods to measure grain orientation and residual

stress, which would then allow test firing of the characterized liners.

In the present program, we have explored the feasibility of

neutron diffraction as a nondestructive probe for grain orientation

determination in intact, copper shaped-charge liners. Initial measurements were performed on a piece cut from a liner which had been flattened

and examined by x-ray diffraction. Neutron and x-ray results were

found to be comparable. Subsequent neutron diffraction studies were

made on twelve intact liners from a current production batch. In

figure 1 are shown pole-figure representations of the neutron diffraction results for (111) and (220) planes for two of the copper liners.

67
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

COA/E / (///) coaje i (eeo)

COAJE2(///) COAJE 2 (220)

Figure 1. Pole figures for (111) and (220) grain orientation in

intact shaped charge liners from neutron diffraction

measurements. The heavy solid contour corresponds to

"random" grain orientation; lighter counters correspond

to increases in orientation by approximately 30% of

random per contour.

These data represent the extremes of the differences observed for the

twelve liners, which in the case of (111) reflections are rather

significant. If grain orientation is the critical parameter, one would

expect the performance of these two liners to be measurably different.

Further studies to establish grain orientation as a function of

depth (total thickness ^ 3 mm) and to examine the feasibility of

nondestructive residual stress measurements using neutrons are in

progress.

68
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

REINVESTIGATION OF CRYSTAL STRUCTURE OF

a-P

b

(N

3

) 2

C. S. Choi

(Picatinny Arsenal, Dover, NJ)

and

E. Prince

Lead azide is a well-known primary explosive. The explosive

nature of the azide compound is known to be correlated very closely

with the degree of covalency in the azide bond in the crystal.

Therefore, it is very important to know the structure of the azide

groups and their surroundings accurately in order to understand the

explosive properties. The crystal structure of a-P ^3)2 was determined

previously by using a partial three-dimensional neutron diffraction

data set. The present study was aimed at improving the accuracy of

the structure by collecting a complete set of three-dimensional data.

A total of 1466 independent reflections were measured within the

limiting sphere defined by a maximum 20 angle of 106° and a neutron

o wavelength of 1.226A. With this new set of data, the refinement of

the structure converged rapidly to the final discrepancy indices,

R = 0.038 and wR = 0.043 for 1328 observed reflections. The structure

obtained in this study is essentially the same as that of previous

study, except for the detailed values of some parameters and their

accuracy. The configurations of the four different azide groups in

a-Pb(N3)2 are given in table 1. The azide I and azide III are essentially symmetric, azide II is slightly asymmetric and azide IV

is quite asymmetric. The azide structure becomes more symmetrical

when the bond lengths are corrected for the effect of the thermal

vibration by using the riding model.

69
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Table 1. The structure of four diiiferent <

Type Bond Bond Length (A)

Raw Riding

I Ni-N2 1.166(1) 1.179

II N3-N4

N5-N4

1.181(2)

1.160(2)

1.186

1.173

III N6 -N7 N8 -N 7

1.172(2)

1.167(2)

1.181

1.176

IV N9 -N 10

Nji-Nio

1.191(2)

1.149(2)

1.196

1.164

N-N-N Angle (°)

177.9(2)

178.2(1)

179.2(1)

178.3(2)

PHASE TRANSITION STUDY OF NaN 3 BY POWDER

NEUTRON DIFFRACTION

C. S. Choi

(Picatinny Arsenal, Dover, NJ)

Sodium azide undergoes a phase transition at approximately 14 °C

from 3-phase (rhombohedral R3m) to a-phase (monoclinic C2/m) with

decreasing temperature. Iqbal and Christoe have studied the phase

transition by a method of polarized Raman scattering and concluded that

the phase transition is a second order type. Subsequently, they

proposed a mechanism for the phase transition based on the soft mode

2 model developed by Chihara et al. ; the azide axis, in the phase

transition, gradually changes its orientation with temperature over a wide temperature range, and this uniform tilt of the azide axis is

coupled anharmonically to its librational mode in accordance with the

formulas given by Chihara et al. The present study was aimed at

determining the tilt of the azide axis at various temperature by the

o neutron powder diffraction method. Using 0.948A neutrons, powder

diffraction data of NaN3 were collected at four different temperatures;

270 K, 174 K, 78 K, and 4 K, within the scanning range of 8° to 60° in

70
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

scattering angle with a 0.1° interval. The portion of the spectrum

contaminated by the aluminum container was excluded from the refinement. The structure and lattice parameters were refined by the Rietveld

technique of profile refinement using a program modified by Hewat. The

profile residuals, R and R as defined by Reitveld, are 0.10 and 0.12 w

for 270 K, 0.067 and 0.114 for 174 K, 0.048 and 0.066 for 78 K, and

0.055 and 0.069 for the 4 K structure, respectively. The structure of

a-NaN3 are very similar to that of 3-phase in general atomic arrangement,

except for slight distortions due to a shear movement of the lattice

(or $-angle changes) and an internal rotation of the azide axis. The

tilt of the azide axis is the compounded effect of these two distortions.

Table 1. The distortion parameters of NaN3 at various temperatures. The

parameters are 3 for the angle of monoclinic cell, for the

internal rotation of the azide axis measured from the c-axis,

and the tilt angle of the azide axis measured from the normal

direction of the cation layer. The 300 K data refer to the

equivalent monoclinic cell of the rhombohedral structure.

Tilt(°)

Temperature 3 (°) e<°) Tilt(°) (soft mode Model)

300 K 112.54 22.54 0.0 0.0

270 K 110.7(1) 25.88(4) 5.2 4.4

174 K 108.63(4) 28.80(1) 10.17 9.9

78 K 107.63(1) 29.64(1) 12.01 12.2

4 K 107.46(1) 29.94(1) 12.48 12.48

The tilts of the azide axis obtained in this study agree well with

those obtained by Iqbal et al. based on the soft mode model as shown in

table 1. The rate of tilt is largest at near transition temperature

and therefrom it decreases gradually until it saturates at near 78 K.

1. z. Iqbal and C. W. Christoe, Solid State Commun. 17, 71 (1974).

2. H. Chihara, N. Nakamura, and M. Tachiki, J. Chem. Phys. 59, 5387

(1973).

71
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

QUASI-ELASTIC NEUTRON SCATTERING STUDY OF

SINGLE CRYSTAL AFWONIUM PERCHLORATE

N. J. Chesser and H. J. Prask

(Picatinny Arsenal, Dover, NJ)

The rotational motions of the ammonium ions in ammonium perchlorate (NH CIO.) have been the subject of considerable study for more than

a decade, primarily because this salt has been thought to provide a prototype for quasi-free rotation in an ionic solid. An earlier quasielastic neutron scattering (QNS) study of polycrystalline NH.C10, indicated that in the temperature range 78 to 130K the ammonium ions were

reorienting via "instantaneous" 120° jumps about C„ axes of the ion.

Thus three protons would move 120°, about an axis containing the nitrogen and fourth proton, to a new configuration identical to the original.

2 A recent crystal structure determination at low temperature has established that three of the four NH, protons are in non-equivalent equilibrium positions and that their thermal amplitudes differ. It would seem

likely, therefore, that the jump probability for a proton is site dependent and that a QNS study of single-crystal NH.C10, might differentiate the different jump probabilities, and the present report summarizes

the results of such a single crystal study. This work represents the

most complex material for which QNS has been applied to establish the

details of orientational disorder in a crystalline solid.

As a guide to the analysis of our experimental data, we have ex-

•• 3

tended the "instantaneous" jump reorientation model of Skold to include

the possibility of three different residence times, x., associated with

2 X +

the three non-equivalent hydrogen equilibrium sites of an NH, - appropriate to NH.C10, . This model yields three different Lorentzian contributions and a 6-function contribution to the scattering law. Of these,

the 6-function and one of the Lorentzians have structure factors independent of residence times whereas the structure factors of the second

and third Lorentzians depend on the relative ratios of the residence

times. Eased upon average xs obtained from QNS studies of polycrystalline

72
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

^^,

iC\ AY. . /c

1 2*3

FED

C

D

E

F

^»—

Figure 1. Intensity contour map for the h0£ and 0k£ planes of NH4CIO4

at 120K. Areas marked A represent intensities which are, on

the average, approximately ten times those of areas marked F.

Diamonds indicate the value of Q selected to obtain relatively

pure Lorentzian contributions. While these contours are those calculated for the residence times derived from 120K

data, they are similar to those derived for all of the temperatures examined.

Table 1. Activation Energies E and Arrhenius Prefactors t for each

o o atom.

Hydrogen

Site

(kcal/mole)

o (psec)

1

2

3(3')

.58±.04

,61±.04

.52±.05

,15±.03

.15±.03

.28±.03

73
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

T(K)

120 100 80

—x r2 ° POWDER

.004 .006 .008 .010 .012 .014 .016 .018

l/T(K)

Figure 2. Residence times derived from analysis of the Lorentzian

widths (see text) . The lines are obtained under the assumption of an Arrenhius temperature dependence for the residence

times (x=T exp(E /T) for each proton. Parameters are listed

in table 1. Powder data are from reference 1.

1. H. J. Prask, S. F. Trevino and J. J. Rush, J. Chem. Phys. 62_, 4156

(1975).

2. C. S. Choi, H. J. Prask and E. Prince, J. Chem. Phys. 61, 3523

(1974).

3. K^Skold, J. Chem. Phys. 49, 2443 (1968).

4. V. F. Sears, Adv. Phys. 24, 1 (1975).

74
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

NH.C10, and the ratios of librational amplitudes inferred from the low

temperature neutron diffraction study the structure factor contour map

of figure 1 is obtained.

Constant Q scans of the quasielastic scattering were made for

3 single crystals of NH.C10, using a triple axis spectrometer configured

such that FWHM (ful-width-at-half-maximum) - 0.1 meV. Measurements were

made at temperatures of 60 to 120K, at the reciprocal lattice points

indicated in figure 1.

The data were fit using a non-linear least squares fitting routine

with six adjustable parameters: the Lorentzian width, Lorentzian and

6-function intensities, "thermal" (i.e. analyzer efficiency dependent)

and "fast" (i.e. flat) neutron background levels, and offset of the

peaks from the nominal elastic position. The calculated curves were

folded with the appropriate Gaussian resolution function and corrected

3 for analyzer efficiency (K

f cot0.)

.

From the structure factor map and the limitation that the model

requires the width of Lorentzian two to be greater than that of

Lorentzian three, residence times for the different sites were obtained

at each temperature as shown in figure 2. Assuming Arrenhuis behavior,

activation energies and prefactors as shown in table 1 are obtained.

The results shown in figure 2 and table 1 clearly indicate the anisotropic character of ammonium uon reorientations in NH.C10, . Work is in

progress to further examine this behavior.

75
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

REINVESTIGATION OF THE CRYSTAL STRUCTURE OF

nh

4

cio

4 AT 298 K

C. S. Choi and H. J. Prask

(Picatinny Arsenal, Dover, NJ)

and

E. Prince

A refinement of the structure of ammonium per chlorate at room

temperature has been reported by Peyronel and Pignedoli, who concluded

that the structure cannot be refined in the centrosymmetric space group

Pnma, but can be refined in the space group Pna2^. Since this con- clusion is in disagreement with our study at low temperature using

neutron diffraction data, we have performed further least-squares

refinement of the room temperature structure in the centrosymmetric

space group Pnma using their published data. Two cycles of refinement

with isotropic temperature factors, followed by three more cycles of

refinement with anisotropic temperature factors and an isotropic

secondary extinction parameter, reduced the R indices to R = 0.044 and

R = 0.049 for the 800 observed reflections. A comparison of this

centrosymmetric structure result (R = 0.044 for the 35 parameters) with

their acentric structure refinement (R = 0.055 for the 55 parameters)

shows clearly that Pnma is the correct space group for NI^CIO^ at room temperature as it is at lower temperatures. The bond parameters and

rigid body motions of the perchlorate group obtained in this study are given in table 1. The librational motion of the perchlorate group, as obtained from the rigid body refinement, is almost isotropic and causes

o the apparent Cl-0 bond length to be shortened by about 0.02A. The

translational motion, however, is extremely anisotropic and closely

resembles the thermal ellipsoid of the nitrogen atom of the ammonium

group.

76
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Table 1. The bond parameters and rigid body motions of the

group

.

perchlorate

Bond length (A) Uncorrected (A) Corrected (A)

Cl-O(l) 1.432(3) 1.452

Cl-0(2) 1.4^4(3) 1.445

Cl-0(3) 1.4*2(2) 1.462

Bond angle (°) Uncorrected (°) Corrected (°)

0(l)-Cl-0(2) 111.3(2) 111.2

0(l)-Cl-0(3) 108.7(1) 108.7

0(2)-Cl-0(3) 109.7(1) 109.7

0(3)-Cl-0(3) 108.6(2) 108.6

Principal Amplitudes Directions based on crystal syst<

axis r.m.s. (A) a (°)

89.

8 (°) Y (°)

T(l) .314 1.

T(2) .171 1. 91.

T(3) .168 1.0

r.m.s. (°)

L(l) 7.1 1.

L(2) 6.9 138.

L(3) 6.5 48.

N-atom

U(l) .325(3) 88.(1) 90

U(2) .191(3) 90 180

U(3) .179(3) 2.(1) 90

132.

138.

2.(1)

90

92.(1)

1. G. Peyronel and A. Pignedoli, Acta Cryst. B31, 2052 (1975).

77
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

SMALL ANGLE SCATTERING: INSTRUMENT AND APPLICATIONS

C. S. Schneider

(U. S. Naval Academy, Annapolis, MD)

The double perfect crystal dif fractometer has been considered for

measuring the scattering of thermal neutrons from a Christiansen filter

1 2

to determine the scattering amplitude of the powder atoms. The scattered intensity, as a function of the difference ANb for powder and

liquid, changes in form with the phase shift across the particle,

<J> = 25kR = 2XRANb and the probability of scattering from particles in

the sample, P = N a x where x is the powder thickness. In the single

P P

. 2 diffraction region <J><1 and P = x<j) /4R<1 for a packed powder of particle

radius R. Thus

I, = Pfl = (ANb) X xRfI

where I is the central peak intensity and f<l accounts for absorption

e and slight broadening from the initial resolution to X/R. When P

exceeds unity the central peak is completely diffracted and multiple

diffraction begins causing reduction in the intensity seen at the base

of the central peak: in region two where (j><l and P>1

I

2 = fI c //P = flo/X/xR ANb.

Finally, as <}> exceeds unity the scattering becomes multiple refractive

being broadened through roughly X /p ANb/2ir where P = x/R. Thus

I = f'I /Xv^R ANb

continuing the (ANb) decrease with a small change in coefficient f.

The precision of using the double crystal dif fractometer to determine Nb by finding the center of equal intensities in region one from

the plot in figure 1, is one part in 2/n7 where N is the total counts

recorded. In one day's counting using perfect Ge crystals, X = 0.4 nm,

R = 40 um and x = 1 mm for highly absorbing powders, the precision

approaches a few parts per thousand.

78
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

Because a rapidly decreasing tail of the resolution in a diffractometer is necessary to observe small angle scattering, which decreases as

4 2

, Darwin reflectivities are not ideal with their 6 decrease soon over powering the sample scattering. Bonse-Hart triple reflection monochromator and analyzers have been made of Ge single crystals with the hope

of exploiting their 9 tail drop-off, but the modest peak intensities of

10 n/min made the advantage marginal. Several modifications have been

considered: first, highly assymetric channel cutting (beam incident

upon monochromator nearly parallel to the channel) can largely reduce

the rocking width but the intensity would stay nearly the same. Second, inducing thermal gradients perpendicular to the reflecting

planes can broaden the integrated reflectivity to — = a AT where a is

the thermal expansion coefficient and AT the temperature difference

across the crystal. Due to the small value of a, the large thermal con- ductivity and the large temperature dependence of a, power densities of

2

20 W/cm did not cause a significant reflectivity increase from Si (111)

planes. The techniques of adhering a graphite wafer to the back surface

and preparing a resistive pathway proved a very effective method of

applying several hundred watts to the crystal. Air jet cooling appears

sufficient but is not highly uniform.

4 Finally, strain induced reflectivity is being intensively studied

with a strained perfect crystal spectrometer recently fabricated, with

reversible dialable strain normal to the reflecting plane

Ad at

max 2d P

existing furthest from the neutral axis of the crystal sheet where a is

Poisson's ratio. Slices of both Si and Ge have been optically polished

and their curvatures measured as a function of the strain device micrometer reading, by observing the focussing of a nearly parallel laser

beam. Anticlastic (saddle shaped) curvature is 25 percent of the applied curvature between constraint lines. Strain is applied vertically

79
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

-I/2XR -I/X/XR" l/X/XR I/2XR ANb

Figure 1. Intensity scattered by a Christiansen filter as viewed at

the base of the central peak in the double perfect crystal

dif f ractometer

.

so that the defocussing of the double crystal dif fractometer is minimized: two smearing effects are present. First is the permanent

smearing due to finite horizontal collimation (3 and second crystal curn vature, 1/p

2H"

A6 = 3Hx /p 2H

:

where x is the separation of monochromator and analyzer crystals. Second is the relative curvature smearing which can be eliminated by setting

p„ = p.. -2x, the focus condition: w

2 = ^Hp 2H

(P2H

"PlH+2X)

where W_ is the width of the monochromator crystal. If the smearing is

not to affect the induced mosaic, A9 = 2ef tan 8 where f<l is due to

dynamical effects then in the focussed condition for p>>x,

A6 = fttane/p >A9 1 = B^x/p^

or t>3uxcot0p /p„f. Since p /p„ < .25 and $ = 0.01 and x = 50 cm is

rl V H V n — n ample sample and shielding space, then t>1.2 mm/f. Present studies on

80
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

12

8

4h

IKn/min

* O.I mm Si o 0.2mm Si D 0.7mm Si

• 1.2mm Si + 2.4mm Si

Jd»

+ « D

O *

a

o

if*

x+»

L

0.4 0.8

nl

16

8

Kn/min

I.6XI0"3

« 0,6 mm Ge

o 1 .6 mm Ge

• 3.0mm Ge

t/£

4? O x o o

J 1 I L =L 0.4 0.8 1.2 1.6x10

Up

-3 v

Figure 2. Intensity reflected from various thicknesses of 18x25 ram area Ge (some imperfect) and Si crystals. Note saturation

of thin crystal reflectivity.

ft 1 piezoelectrically strained crystals ' should eliminate focussing

problems.

Deeper penetration of the beam into a mosaic or strained crystal

also requires a minimum thickness to reflect fully. This thickness is

roughly one millimeter as above and can be extracted from the intensity

measurements made with the Si and Ge crystals on the strain device. The

intensity saturates either due to beam penetration of the thin crystals

or to yield of the thicker crystals, which was at a strain of roughly

81
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

-3

10 , corresponding to a few minutes arc mosaic. Preliminary data is

shown in figure 2.

Insertion of the 2 mm thick amorphous TbFe~ sample into the beam of

the perfect crystal dif fractometer caused severe attenuation, largely

from scattering. This suggests the need for the broader resolution of

the bent crystal dif fractometer. Critical scattering in iron is also

under consideration as the very fine q resolution allows direct observation of long correlation lengths.

1. L. Koester and H. Ungerer, Z. Physik, 219 300 (1969).

2. L. Koester and K. Knopf, Z. Naturforsoh 262, 391 (1971).

3. B. Alefeld, A. Physik, 22J3 454 (1969).

4. A. Boeuf and F. Rustichelli, Acta Cryst. A30, 798 (1974).

5. M. Kuriyama and T. Miyakawa, Acta Cvyst, A26 667 (1970).

6. T. F. Parkinson and M. W. Moyer, Nature, 211, 400 (1966).

7. A. G. Klein et al., Appl. Phys. Letters, 10, 293 (1967).

STRUCTURE OF THE ANTI FERROELECTRIC PHASE OF

COPPER FORMATE TETRAHYDRATE

M. I. Kay

(Puerto Rico Nuclear Center, Mayaguez, PR)

and

E. Prince

A three-dimensional neutron diffraction data set was collected

from a crystal of copper formate tetrahydrate in the antiferroelectric

phase at 77 K. The antiferroelectric phase is characterized by small

deviations, in alternate unit cells, from more symmetric positions in

the room temperature, paraelectric phase. Consequently, reflections

with odd values of I are much weaker, on the average, than reflections

with even values of I. Nevertheless, some of the odd £ reflections

82
INTERAGENCY AND UNIVERSITY COLLABORATIVE PROGRAMS

have appreciable intensity. Attempts to refine the structure using

conventional least-squares techniques have met with difficulties,

particularly with respect to reflections of the class 5, k, I with I odd. There may be features in the structure not included in the model

which have a particularly strong effect on these reflections. Work is

continuing on refinement of the structure using robust/resistant

methods.

1. M. I. Kay and R. Kleinberg, Fevvoelectr>ies3 4-, 147 (1972)

83
D. Non-RRD NBS Programs

ACTIVATION ANALYSIS: SUMMARY OF 1976 ACTIVITIES

Harry L. Rook and Thomas E. Gills

(Analytical Chemistry Division)

This summary of the activities of the Activation Analysis Section

covers the period of July 1975 to June 1976. During this period the

Section has continued its efforts to attain a high degree of versatility

in activation analysis and has directed efforts toward developing a greater expertise in multielemental analysis particularly coupled with

automation and computer data reduction. In addition, research is

continuing in the area of the investigation of parameters which affects

accuracy and precision in activation analysis.

While the majority of the activation analysis work is in support of

the Analytical Chemistry Division's programs, a large portion of the

Section's activities this year has been spent in service analyses for

organizations outside the Bureau of Standards and for groups within the

Bureau of Standards. Such cooperation affords an opportunity to transfer

analytical capabilities or expertise to the analytical community.

The Activation Analysis Section has at present eleven members and

has programs in a variety of areas related to the trace elemental

characterization of materials. These areas include research projects,

SRM certification analyses and service analyses. Summaries of the work

in these areas are included.

1. Basic Research in Activation Analysis

a. A Method for the Determination of Iodine in Biological and

Environmental Matrices

H. L. Rook

Iodine is an element with excellent intrinsic sensitivity when

determined by thermal neutron activation. However, in most real samples,

84
NON-RRD NBS PROGRAMS

the preponderance of chlorine and bromine, relative to iodine, makes the

direct determination of iodine virtually impossible. Over the past 20

years, there probably have been as many publications on the separation

of iodine as there have been for any other radionuclide. Upon review,

however, the methods are essentially the same. After irradiation, the

samples are subjected to a rapid destructive process to free the iodine

from the matrix and then the iodine is separated from the other halides

either by liquid-liquid extraction or by liquid ion exchange. Both of

these procedures are, however, rather complex and do not effect a com- plete separation of the halides in one pass. Also, most of the separations are not quantitative in the recovery of iodine, thus, they require

a radiochemical yield determination, with its associated problems and

additive errors. The best assessment of the present ability of NAA to determine

iodine in real matrices is the published results of iodine in Bowen's

Kale and in certain NBS SRM's such as Orchard Leaves, Bovine Liver and

Coal. These matrices have been widely studied and numerous publications

have appeared with data on their trace element compositions. In Bowen's

Kale, no consensus iodine result was obtained, because values reported

by cooperating laboratories varied by more than two orders of magnitude.

In the NBS SRM's, no iodine values have appeared in open literature,

except on Coal, and they appear to be in error.

In the work presented here, a simple, rapid procedure is developed

for the quantitative determination of iodine in botanical, biological

and environmental matrices.

For the separation of iodine from general matrix activity, the

sample is burned in a flowing oxygen atmosphere using a quartz combustion tube, similar to the one described for mercury separations.

Following combustion, the sample is heated to 1100° C with a resistance

oven to completely distill the volatile elements. During this process,

the iodine is separated from the chlorine and bromine, in the gas phase,

by a trap containing hydrated manganese dioxide (HMD). A second trap,

85
NON-RRD NBS PROGRAMS

of silvered glass wool, is placed downstream from the HMD trap to collect

the iodine. The HMD trap, heated to 80° C, has been found to completely

remove chlorine while quantitatively passing iodine through to the

final collector trap. With this separation system, samples can be

processed in 10-15 minutes with separations of greater than 10 6 for

chlorine and 10*4 for bromine.

The described procedure has been used for the determination of

iodine in numerous new and old SRM's at the NBS. Table 1 gives some representative data on SRM 1571, Orchard Leaves. From this work, it is

estimated that <10 9 g of iodine can be easily determined in real

matrices.

Table 1. Iodine Concentration in SRM 1575 Orchard Leaves

Sample yg/g

Iodine

Sample

#

Ug/g

Iodine

1 0.176 5 0.160

2 0.165 6 0.166

3 0.171 7 0.153

4 0.180

Mean

0.167 ± 0.009

b. The Measurement of Radial Efficiency Gradients in Ge(Li)

Gamma Detectors

R. M. Lindstrom

In the decade since the introduction of lithium-drifted germanium

detectors, their availability from commerical suppliers with steadily

increasing counting efficiency has led to their nearly universal use in

measuring gamma-rays from radioactive substances. The rapid replacement

of the sodium iodide scintillation detector for gamma assay is due almost

entirely to the forty-fold sharper energy resolution of the newer

detectors. In addition to assuring qualitative identification of gamma

emitters, this resolution allows a forty-fold reduction of the background

86
NON-RRD NBS PROGRAMS

area under a peak, with the result that despite a two to ten-fold decrease

in counting efficiency the Ge(Li) detector is still superior to Nal for

quantitative determination.

In order to minimize the counting time required for a given

statistical precision, the analyst is often impelled to place the source

close to the detector, often in contact with the end cap. But, because

of the small size of the crystal, small differences in shape or positioning of the counting sample compared to a standard may lead to significant

differences in counting efficiency. It is the intent of the present work

to examine this position sensitivity where the source is in contact with

the detector can. With a Cs point source directly on the vacuum can

of 80 cm Ge(Li) detector, the radial gradient in efficiency (i.e., across

the can) is 1.6%/mm at r = 10 mm; this is three times the efficiency

gradient of a 7.6 x 7.6 cm Nal(Tl) detector. The present work extends

these considerations to different detector configurations.

c. Selective Radiochemical Separation for the Activation Analysis

of Biological Standard Reference Materials

T. E. Gills

New biological materials such as Tomato leaves, Pine Needles and

Spinach are currently being characterized at the National Bureau of

Standards as part of the Standard Reference Materials Certification Program. Of the elements whose concentrations are usually certified, Copper,

Arsenic, and Antimony could be determined accurately and precisely by

activation analysis if sensitivity were the only consideration. However,

the matrix radioactivities in most cases prevent instrumental determination

of those elements or nuclides. The most useful (n,y) reactions involve

short-lived nuclides of Cu, As and Sb thus requiring chemical separation

of those elements from the activated matrix. Separation procedures by

Kosta et. al. for Cu, As, and Sb are capable of producing accurate results

at the sub-ppm level of concentration. However, such procedures are highly

87
NON-RRD NBS PROGRAMS

dependent upon the pH of the extraction system and are not easily

adaptable to multielemental analyses.

Among possible radiochemical procedures and reagents for group

separation of elements, inorganic ion exchangers have received increased

interest arising from the high selectivity which can often be obtained

by their use. Furthermore, by separating elements in groups instead of

individually, and utilizing the high resolution of semiconductor detectors,

simple, low cost and rapid analyses can be achieved.

Table 1

A Comparison of NAA Results Using The Described

Separation Procedure to other Independent Methods

Code Element Spinach Pine Needles Tomato Leaves

1 Cu 10.8 ± .2 2.98 ± .16 11.1 ± .2

4 Cu 12.7 ± .4 3.2 ± .4 11.5 ± .2

3 Cu 11.5 2.9 10.6

1 As .12 ± .01 .20 ± .02 .23 ± .03

2 As .17 ± .05 .21 ± .04 .29 ± .05

1 Sb .043 ± .004 .22 ± .01 .12 ± .03

Codes: 1 - Neutron Activation Analysis with Chemical Separation.

2 - Colorimetry.

3 - Isotope Dilution Spark Source Mass Spectrometry,

4 - Atomic Absorption Spectrometry.

88
NON-RRD NBS PROGRAMS

This work involved the use of two chromatographic columns separately

filled with Cuprous Chloride and Tin Dioxide. The columns were placed in

series to provide a selective separation procedure for Cu, As and Sb from

neutron activated biological materials. This separation scheme, was initially tested by reanalyzing previously certified NBS Orchard Leaves

(1577). The procedure was then used to determine Cu, As, and Sb in new proposed Standard Reference Materials; Spinach, Pine Needles and Tomato Leaves.

A comparison of NAA results using this procedure to other independent

methods is given in table 1.

d. Evaluation by Activation Analysis of Elemental Retention in

Biological Samples After Low Temperature Ashing

G. J. Lutz, J. S. Stemple and H. L. Rook

Low temperature ashing (LTA) is the low temperature CVL00 C) decomposition of organic or biological samples using atomic oxygen produced

by an electrodeless radio-frequency discharge. There are a number of

advantages in using LTA as the first step in a general analytical method

such as the avoidance of contamination during wet or high temperature

ashing. With respect to activation analysis, freeze-drying followed by

LTA has the advantage that with the elimination of organic carbon, the

possibility of charring a sample with a very high neutron flux is removed,

In addition, wet digestions can be substantially speeded up and hence

short-lived nuclides can be more readily separated for counting.

The possibility exists in the LTA method of the loss of some volitile elements during ashing. We have studied, using activation

analysis, loss or contamination of trace elements during LTA.

A commerical model LTA apparatus capable of 100 watts forward power

was used in these experiments. A schematic of the apparatus is shown in

figure 1. The sample was placed in a borsilicate glass ashing chamber

which was briefly rotated by hand to induce the organic sample to spread

as evenly as possible on the inside surface. The cold trap was filled

89
NON-RRD NBS PROGRAMS

with crushed dry ice (liquid nitrogen would condense explosive ozone)

.

The system was pumped down to 1.3 - 2.6 Pa (10-20 millitorr) . The

oxygen flow rate was adjusted so as to maintain a pressure of 13-40 Pa

(100-300 millitorr) . Forward power was usually set to the maximum of

100 watts. Tuning to optimum was accomplished by observing the maximum

intensity in discharge glow in the tube.

Preliminary experiments involving addition of tracers to biological

materials and determining retention of each isotope after ashing verified

previously published data and served to establish and perfect the basic

ashing technique. After these experiments, it was decided to study three

NBS Standard Reference Materials in detail: 1571-Orchard Leaves, 1577-

Bovine Liver, and 1632-Trace Elements in Coal.

Samples of about one gram were ashed for a period of several hours.

The relative amounts of the elements in ashed and unashed samples were

determined by nondestructive neutron activation analysis with the NBS 10

megawatt nuclear reactor and photon activation analysis with the NBS

electron linear accelerator. Suitable irradiation and counting schedules were arranged to detect and quantify both long- and short-lived activities.

In the activation analysis experiments, the losses of iodine, bromine,

chlorine and mercury in addition to carbon were observed.

Figure 2 shows, in the format of the periodic chart, the elements

detected and not lost during ashing in all experiments. The symbols in

the individual square of each element, OL, C and BL stand for orchard

leaves, coal and beef liver, respectively, in which the element was

determined. In addition, some elements reported retained in the literature determined by neutron activation analysis, atomic absorption

spectrometry, or spectrophotometry are included.

It is also significant to note that, equal in importance to loss of

trace elements, there was no pick-up of contamination during the ashing

process as would be evidenced by an increase in the amount of the element

after ashing. This is in spite of the fact that only very ordinary precautions were taken to guard against contamination during cleaning of the

90
NON-RRD NBS PROGRAMS

borosilicate glass ashing tube with ordinary laboratory detergent followed by rinsing with water, hot dilute hydrochloric acid and finally

deionized water and drying in an oven at 110° C.

BOROSILICATE GLASS ASHING CHAMBER

VACUUM GAUGE I

> 1 &=

A h

. DRY ICE

COOLED TRAP

VALVE

"> \ X®=Q

FLOW GAUGE —

RF GENERATOR AND

TUNING CONTROLS

PR

V

Figure 1. Block diagram of LTA apparatus

OXYGEN CYLINDER

2. Cooperative Research Projects

a. The Determination of the Absorption of Metallic Ions on Tooth

Tissue

The American Dental Association Health Foundation Research Unit

at NBS (ADA-NBS) is involved in a research effort to improve adhesive

bonding between hard tooth tissues and materials for use in preventive

and restorative dentistry. The initial direction of this project is to

determine which candidate metallic ions, are the best suited to serve as

a mordant to improve the adhesion of dental resins and composites to hard

tooth tissues. Success in this objective could save millions of teeth

annually from decay and the costly procedure of drilling and filling with

expensive silver alloy restorations.

Neutron activation analysis is currently being used to determine

the concentration of four elements (Al, Cu, Fe and Zn) in hard tooth

91
NON-RRD NBS PROGRAMS

Table 1. Trace Element Variations in a Whole Bovine Liver Compared to

Replicate Analysis of NBS Bovine Liver.

As Se Cu

e uoncentr*

Co

itionsipptnj Zn Mo La Whole Bovine

Liver

n - 12 (2-gram samples)

(wet wt .

)

.004+. 001

(25%)

<.l 25.9+2.3

(11%) .056+. 003

(6%)

240+18

(8%)

42+5

(12%)

1.3+.2

(15%)

1.7+.3

(18%)

NBS Bovine Liver

Standard

n - 6 (gm dry wt. ).055+. 003

(5%)

1.2+.1

(8%)

193+14

(7%)

. 18+. 01

(6%) .027+. 002

(7%)

125+5

(4%)

3.0+.3

(10%)

NBS Certified

Certificate Value

or recommended

Interim Value

.055 l.l+.l 193+10 .18 .027+. 002 130+10 3.2

L6

NA

c

CL

BL

BE

MG

C

OL

8L

AL

C

OL

BL

SI CL

HE

NE

AR

K

c

OL

CA

c

OL

BL

sc

C

OL

CR

cOL MNcOL

3L

FE

cOL

BL

CO

c

OL

BL

CU

5 ZN

C

OL

BL

GA

C GE AS

C

OL

SE

c

OL KR

RB

C

OL

BL

SR

C

OL

ZR

c

OL

N3 mo

CL TC RU RH PD AG CD

5

IN SN SB

cOL

BL

TE XE

cs

c

OL BA

COL

LA

c

OL

EL

TA

c RE IR PT AU

T 5 PB

C

OL

Bl PO RN

FR RA AC

CE

cOL

BL

PR NO PM SM EU

c

2L

GO TB DY KO EP. TM Y8 LU

TH

cOL

PA U NP PU AM CM BK CF ES FM MO NO LW

Figure 2. Elements retained during LTA.

92
NON-RED NBS PROGRAMS

tissue. Metallic salts of these four metals were chosen to study as mordants (chemicals which serve to fix a colorless surface active coupling

agent on the surface of enamel or dentin) because ions of these metals

form more stable chelates with organic completing compounds than calcium

ions, which are dominant in tooth tissue. Improved bonding might be

obtained if appropriate metal cations are placed on the tooth surface,

and in effect replace or supplement calcium ions as sites for bonding

by means of chelating or coupling agents.

The results obtained in this study will be published later in

cooperation with the ADA-NBS.

3. Analytical Research Applied to Specific NBS Programs

a. The Use of Neutron Activation Analysis in the Evaluating of

Sampling, Storage and Analysis of Samples for the National

Banking System*

T. E. Gills and L. T. McClendon

When reviewing the literature for trace element concentrations in

similar biological materials the range of the results are enormous.

Several orders of magnitude in analytical data are not uncommon, even

from laboratories using comparable (though not ridgidly standardized)

techniques for biological materials. The need to make accurate and precise measurements of selected metals in biological samples such as human, plant and animal tissue is important to agencies who have the

responsibilities to monitor trace element pollution trends and establish

pollution guidelines. The National Bureau of Standards (NBS) has been

cooperating with the Environmental Protection Agency (EPA) in the

evaluation and improvement of methods for sampling and storage of environmental and biological materials. This research is in support of the

proposed National Environmental Specimen Bank (NESB) . It is the purpose

of NESB to preserve samples for long periods so that retrospective

analyses can be made.

93
NON-RKD NBS PROGRAMS

One important part of this research is to gain a better understanding of trace element variations within whole organs or tissue

biopsies. Since many of the biologically active elements are present at

the ultra trace levels, the utmost in analytical sensitivities are necessary to study and evaluate many of these trace elements. Neutron

activation has been extensively used in this study due to its sensitivity

and specificity for many elements in a variety of matrices. A typical

analysis of a fresh whole bovine liver compared to an NBS SRM (liver

matrix) is given in table 1 as an illustration of elemental variation

within a tissue compared to analytical variability.

b. Prompt-Gamma Activation Analysis

R. M. Lindstrom, W. B. Walters*, and W. Zoller*

In the past year, a cooperative venture was initiated between the

University of Maryland nuclear and atmospheric chemistry group and the

Activation Analysis Section to design and evaluate a prompt-gamma-ray

counting facility dedicated to chemical analysis. The intense, wellthermalized neutron flux available in the National Bureau of Standards

Reactor (NBSR) makes it likely that this prompt-gamma facility will be

the best ever operated for analytical usage.

After examining several possible ports, it was decided that a vertical beam tube in the reflector could offer the best combination of

high flux (^2.2 x 10 8 /cm2 sec) good thermalization (CR ^,20) and low flux

of scattered gamma-ray. A thimble and shutter have been designed by

R. S. Carter and J. Sturrock for insertion into V5 and is currently being fabricated in the NBS Shops. An order has been placed for a large

computer-based multiparameter pulse height analyzer, and designs for the

target holder and beam stop, primary Ge(Li) gamma-ray detector and splitannulus coincidence detector are being completed. Initial experiments

are planned for early in 1977.

94
. NON-RRD NBS PROGRAMS

c. A Study of Lithium Uptake and Location in the Brain Using the

Nuclear Track Technique

B. S. Carpenter, D. Samuel, I. Wassermann and A. Yuwiler

It is well established that lithium salts are a most effective

treatment for some mental disorders, particularly for mania and forms of

depression. In spite of their widespread use, both therapeutically and

prophylactically, their mode of action is still poorly understood. One

aspect of lithium treatment in man seems to be its mono- and bi-polar

forms. An understanding of the neurochemistry and psychopharmacology of

this disease may help in the understanding of other forms of mental disorder. In spite of research on the effect of lithium electrolytes, on various neurotransmitters and other biochemical systems, little is known

about their mode of action or their distribution in mammalian brains.

One reason is the absence of a suitable, sufficiently long-lived radioactive tracer which would enable the site and rate of turnover release

of lithium to be studied by classical biochemical techniques of labeling,

autoradiography, etc. A second problem is the difficulty of studying,

in vivos metabolic processes in the brain, and the dearth of suitable

animal models of affective mental disorder.

In order to determine the lithium concentration, rate of uptake and

location in the brain, rats were injected interperitoneally with doses

of 99.6% enriched 6 Li2C03 in an inert carrier (carboxymethyl cellulose).

The doses of 6 Li2C03 varied from 50 to 100 mg/kg body weight. The rats were sacrificed at 0, 0.5, 1, 3, 5, 8, 12, 24, and 48 hours after injection. The brains were then excised, fixed, and two sections made:

(a) a transverse section through the hypothalamus region and (b) a trans- verse section through the pons. These sections were sandwiched between

dyed cellulose nitrate (CN) detectors and prepared for thermal neutron

irradiation. The tissues were irradiated for 90 seconds (1.33 x 10

n»cm

2 »s

-1

) to produce a-tracks in the CN detectors from the 6 Li(n,a) 3 H

reaction. The tissues were separated from the detectors and the CN detectors were etched in a caustic solution. The entire area that the

95
NON-RRD NBS PROGRAMS

brain tissues occupied on the detector was scanned, VL3 mm by 19 ram for

each detector, by the use of an optical light transmission microscope.

Visual observation of the a-track density indicated that the

lithium was dispersed between the cortical and the subcortical regions

nonuniformly. The distribution of the track densities in the tissues

is believed to be indicative of the fact that the Li is not bound chemically in the brain to plasma protein, but remains free in plasma water.

Microscopically, the results of lithium uptake study showed that Li

reach its maximum concentration level in both the hypothalamus and the

pons region of the brain 8 hours after injection of the Li2CC>3. Finally,

from this study the biological half-life of Li in the brain was determined by assuming they followed a first order exponential decay 12 hours

after injection. The Li biological half-life in the hypothalamus region

was found to average 29.4 ± 2.9 hours. This value is in close agreement

with the 30.9 hour value obtained from Ebadij et al3 data. The halflife in the pons region was longer, 132.5 ± 17.2 hours. There are no other results available on the biological half-life of Li in the pons

region.

4. Analytical Support for the SRM Program

a. Standard Reference Materials

Much of the Section's efforts have been in support of the Standard

Reference Materials Certification Program. A wide variety of SRM's were

analyzed by NAA and the table below lists those in which activation

analysis was responsible for a significant fraction of the trace element

certification data.

96
NON-RRD NBS PROGRAMS

Table 1

Matrix SRM/Ref erence Sample Name

(a) Copper Copper Benchmark

su\ t? An • /Wheat Flour

(b) Food Graxn <

\ Rxce Flour

(c) Body Fluids (Serum

\Freeze-Drxed Urine

(d) Water Toxic Metals in Water

!

Spinach

Tomato Leaves

Pine Needles

(f) Biological Brewer's Yeast

(g) River Sediment Sediment

(h) Rock Obsidian Rock

b. SRM Feasibility Studies - SRM Mixing

R. M. Lindstrom, B. S. Carpenter and S. S. Fine

The intent of the project was to establish and test procedures by

which an analyst can prepare from two different SRM's a standard sample

of known intermediate composition.

The first pair of SRM' s examined was pine needles and tomato leaves

due to their similar particle size and density and their dissimilar trace

element content. Mixing known (weighed) proportions of these two materials

and analyzing each of nine mixes resulted in a satisfying predictability

of concentration.

Similar mixtures have been made from pine needles and river sediment,

a pair of materials that might be expected not to mix well nor stay homogeneous once blended. These experiments should give an indication of how

well the simple procedures used here can be expected to predict the composition of mixtures. The final output of the work, to be completed during

the transition quarter 1976, will be a manuscript describing the

experiments and detailing expected variations in resultant compositions.

97
NON-RRD NBS PROGRAMS

5. Service Analyses

In addition to analyses on SRM's, a large number of analyses were

made on non-SRM Materials. These include cooperative analyses, where

the analyses were made on samples furnished by other laboratories in the

past year. The following analyses were done:

1. Mercury in Soil and Calcium Chloride - G. J. Lutz, H. L. Rook

2. Mercury in Sea Water - G. J. Lutz, H. L. Rook

3. Trace Elements in Antimony Trioxide - R. M. Lindstrom, S. Fine

4. Platinum in Iron Oxide - T. E. Gills, H. L. Rook

5. Impurities in Lithium Hydroxide - T. E. Gills

6. Trace Elements in Raney Nickel - R. H. Filby

7. Trace Elements in Fiber Samples - R. M. Lindstrom, S. H. Harrison

8. Titanium in Sapphire - G. J. Lutz

9. Analysis of Gold Films - S. H. Harrison, R. M. Lindstrom

10. Trace Metals in Polyethylene Inplant Standards - T. E. Gills

11. Trace Elements in Dental Materials - L. T. McClendon, T. E. Gills

12. Boron in Silicon Detectors - B. S. Carpenter

6. Facilities

Two major enhancements to our ability to analyze large numbers of

samples were added in the past year. First, our two best Ge(Li) detectoranalyzer systems were equipped with automatic sample changers

(Ref: Shideler and Suddueth, in prep.), allowing unattended counting of

many samples over evenings and weekends. The two sample changers are electrically similar in operation, but mechanically different so as to

handle 55 mm x 12 mm petri dishes with one system and 20-ml scintillation

counting vials with the other. The first system offers the ability to

count samples at 5 to 10 cm from the detector face, as well as at 1 cm.

98
NON-RRD NBS PROGRAMS

The second major strengthening of the analytical system is the

addition of several additional capabilities to QLN1, the activation

analysis computer code written and maintained for this Section under

contract by H. P. Yule of the NUS Corporation. These features include

the quantitative as well as qualitative use of the code's multiplet

resolution abilities, and the estimation of upper limits for components

sought but not found. The code will now handle up to 4096 channels of

data per spectrum.

FILTERED BEAMS

R. B. Schwartz and I. G. Schroder

(Nuclear Sciences Division)

A 136 cm long silicon filter was placed in through tube GT-2,

viewing a graphite scatterer placed at the center of the tube. This

Figure 1. "Phantom" in position in front of the 2 keV beam.

99
NON-RRD NBS PROGRAMS

arrangement produces an intense collimated beam of 144 keV neutrons.

The addition of ^ 3 cm of titanium removed a low-energy contaminant peak,

resulting in an essentially pure beam of 144 keV neutrons. The beam

intensity is ^ 3 x 10 6 neutrons/s, in an one- inch diameter beam. The

gamma ray contamination is ^ 30 mR/hr. This 144 keV beam, together

with the very pure 2 keV and 25 keV filtered beams, gives the NBS

Reactor a unique facility for instrument and dosimeter calibration in

the keV neutron energy range.

Typical uses for the facility include testing the response of

albedo dosimeters by placing them on our anthropomorphic phantom and

irradiating them under carefully controlled conditions in the various

beams. Figure 1 shows the phantom in position in front of the 2 keV

beam during such an irradiation.

INTERCOMPARISON OF FISSION RATE MEASUREMENTS

!

KARLSRUHE REACTOR PHYSICS AND LOS ALAMOS RADIOCHEMISTRY

D. M. Gilliam

(Nuclear Sciences Division)

Fission rate measurement scales at two laboratories engaged in

quite different branches of nuclear energy development have been intercompared via NBS initiative and cooperative execution. The Reactor

Physics Group at GfK (Gessellschaf t fur Kernforschung) in Karlsruhe,

Germany, submitted fissionable deposits for direct comparisons with

NBS reference deposits, and the Radiochemistry Group at Los Alamos

participated in joint fission rate measurements with NBS at Los Alamos.

For the basic uranium fissionable isotopes, both laboratories are within 2% of the NBS fission rate measurement scale. This is marginally

adequate for some programmatic goals; more serious, however, is a discrepancy between Los Alamos and NBS of nearly 6% for Pu-239 fission

rate measurements.

100
NON-RRD NBS PROGRAMS

With the cooperation of Dr. Werner Scholtyssek of GfK, fissionable

deposits of U-235, Pu-239, and normal uranium were sent to NBS for com- parisons with the corresponding NBS reference deposits. The mass assay

of the NBS reference deposits has been described in detail by Grundl,

et al. 1 The GfK deposits were received and maintained in sealed fission

chambers of the type used at Karlsruhe. The NBS reference deposits were

mounted in nearly identical gas flow chambers. Both chambers were of

the parallel plate type with the deposit positioned flush against a thin

aluminum wall. The chambers were mounted so that the two deposits would

be back-to-back with only the thin aluminum walls separating them. In

this configuration, the chambers were positioned so that the deposits

were at the center of a 4-cm-wide beam from the thermal column. The

angle between the beam axis and the deposit normal was not determined

to high precision, but a very accurate 180° rotation was possible by

alignment of the holder base against a fixed plate on the supporting

table. The relative fission rates from the two orientations were averaged in the following way:

(FGfK

/FNBS ) AV

= V

(FGfK/FNBS)

Q

(FGfK

/FNBS } e+180 <,

where 6 is the angle between the beam axis and the chamber axis. A

choice of = 55° was made for the final deposit comparisons, based on

Table 1. Variation of the orientation in the beam.

(Fv /F ) GfK' NBS

AV

1.185 + .001

1.185 + .001

1.188 + .001

1.175 + .003

1.255 + .001

e (FGfK/FNBS'

e

(FGfK

/FNBS^

e+180

70° 1.3235 + .0004 1.062 + .001

55° 1.267 + .001 1.108 + .001

35° 1.2446 + .0006 1.1334 + .0005

20° 1.215 + .002 1.136 + .003

0° 1.385 + .001 1.137 + .001

101
NON-RRD NBS PROGRAMS

the data of table 1 for enriched uranium deposits at a variety of angles.

Consistency with ± 0.25% is seen over the range 35° to 70°. The odd

ratios at small angles are not at all surprising, since gross scattering

effects from insulators, cables, support structures, and the gas line

are expected at these angles.

Table 2 shows the results of the comparison and the estimated

uncertainties. The largest uncertainties were the quoted errors (1.2%

to 1.5%) for the NBS reference deposits themselves. Other systematic

errors contributed about 0.5% uncertainty or less.

Table 2. Comparison of results.

Mass Mass Mass Scale

Principal Determined Determined Ratio

Isotope by NBS by GfK GfK/NBS

ug ug

U-238 325.1 + 1.6% 325 .0.9997

U-235 309.4+1.3% 31-1 1.0052

Pu-239 28.62 + 1.3% 28.98 1.0126

The intercomparison of absolute fission rate measurements between

NBS and the Radiochemistry Group responsible for weapons diagnostics at

Los Alamos Scientific Laboratory (LASL) was carried out at LASL. After

calibrations and temperature effects testing at the National Bureau of

Standards Reactor, double fission chambers developed at NBS were operated in the BIG-10 critical facility at LASL simultaneously with the

irradiation of an activation fission foil pack which was later destructively analyzed by the Radiochemistry Group. Table 3 shows the results

of the comparison. The striking discrepancy in Pu-239 fission rates is

receiving careful study by both groups.

102
NON-RRD NBS PROGRAMS

Table 3. Fission rates (per nucleus) in BIG-10 test C-LASL.

Isotope Studied

U-235 U-238 N -237 Pu-239

P

NBS Measurement 110.4±1.5% 4.14±1.8% 35.2±1.9% 132.3±1.6%

(10 15 sec 1 ) LASL Measurement 112 ±1.6% 4.21±3.8% 35.3±5% 140 ±2%

(10~ 15 sec 1 ) LASL/NBS 1.014 1.017 1.003 1.058

1. J. A. Grundl, D. M. Gilliam, N. D. Dudey, and R. J. Popek,

"Measurement of Absolute Fission Rates," Nuclear Technology

25, 237 (1975).

PRECISION MEASUREMENT OF THE WAVELENGTH OF NUCLEAR

GAMMA LINES AND THE C0MPT0N WAVELENGTH OF THE ELECTRON

R. D. Deslattes, E. G. Kessler,

W. C. Sauder, and A. Henins

(Optical Physics Division)

The wavelengths of nuclear y-lines and the Compton wavelength of

the electron are being measured in terms of the wavelength of a molecular ly stabilized visible laser. The wavelength measurements use a two

crystal transmission spectrometer equipped with angle-measuring

interferometers to determine the crystal diffraction angles. The y-rays

are diffracted by nearly perfect Ge and Si crystals whose spacings have

been accurately measured in terms of the above-mentioned stabilized

laser. A more detailed description of the experimental procedure has

1 2 been given in other reports. '

. Our activity over the past year has been primarily centered in

three areas: (1) the reduction of systematic uncertainties associated

with the vertical divergence correction, the angle interferometer

calibration, the temperature sensitivity of the angle interferometers,

and the crystal lattice spacing; (2) the irradiation of several

103
NON-RRD NBS PROGRAMS

y-sources of Au-198 and Ir-192 and the measurement and data analysis of

the wavelengths of the associated y-radlations; and (3) the design and

manufacture of a transfer cask for nuclear y-sources and the design of

a transfer cask for the Compton wavelength measurement.

1. Reduction of Systematic Uncertainty

Several new Soller collimators have been manufactured which allow

the vertical divergence correction to be varied and be more accurately

calculated.

The interferometers have been recalibrated under more controlled

conditions to obtain an interferometer constant accurate to 0.06 ppm.

The calibration procedure involves summing to closure measurements of

the interfacial angles of a 72-sided optical polygon and provides

absolute angle measuring capability.

One of the angle interferometer zeroes was found to drift with

temperature. This drift resulted from a temperature sensitive dove

prism in the interferometer which has now been replaced with good

effect. An interferometer design which eliminates the dove prism is

planned for the future. Temperatures are controlled to better than

0.01 °C so that sub ppm measurements are possible even with the present

interferometer

.

The crystal lattice spacing was determined by first measuring the

spacing of a standard Si crystal by simultaneous optical and x-ray

3 interferometry . Then, the ratios of the lattice spacings of this

standard Si crystal and of the crystals used for y-ray diffraction are measured. This transfer has been completed to the 0.5 ppm level.

However, y-ray wavelengths measured with Ge and Si crystals differ by 1

to 2 ppm as indicated below. An unknown systematic error of this

magnitude is thus associated with the crystal lattice measurements or the y-ray angle measurements. This systematic error is under investigation.

104
NON-RRD NBS PROGRAMS

2

.

y-ray Measurements

Three Au sources were irradiated with activities up to 4 x 10 3 Ci.

These sources were used for measurement of the wavelength of the 412

keV Au-198 line. Measurements were obtained for diffraction with Ge

crystals in two orders and Si crystals in three orders. Measurements

in different orders are consistent. However, wavelengths measured with

Si crystals are approximately 2 ppm larger than those measured with Ge

crystals.

A 2 x 10 3 Ci Ir-192 source was produced and used for measurement

of eight y lines (205, 295, 308, 316, 468, 588, 604, 612 keV) by

diffraction with Ge crystals in two different orders. Five of these

lines were used in two tests of consistency by the combination principle

(295 + 316 = 612 keV and 295 + 308 = 604 keV) . Closure was found

within 0.5 ppm. The wavelengths of four other lines (136, 416, 484,

and 884 keV) were determined by use of the combination principle. The

strongest four lines (295, 308, 316, and 468 keV) were also measured

using Si crystals. Wavelengths measured with Si crystals are approximately 1.5 ppm larger than those measured with Ge crystals.

Although there is a 1 to 2 ppm unknown systematic associated with

our wavelength measurements, our results are nonetheless 10 times more

4 accurate than previous results. A detailed summary of all our y-ray measurements will appear shortly in reference 5.

3. Design and Manufacture of Transfer Casks

A 41 cm diameter transfer cask for intense (several kilo-Ci)

nuclear y sources was designed and constructed. The cask allows

convenient irradiation of samples from the vertical ports on the NBSR.

A large diameter transfer cask for a multi kilo-Ci Cu-64 source

has been designed and is under construction. This source will serve as a positron emitter in the measurement of the Compton wavelength of the

electron.

105
NON-RRD NBS PROGRAMS

1. R. D. Deslattes, E. G. Kessler, W. C. Sauder, and A. Henins, Atomic

Masses and Fundamental Constants 53 J. H. Sanders, A. H. Wapstra,

eds., Plenum Press, New York, p. 48 (1976).

2. R. D. Deslattes, E. G. Kessler, W. C. Sauder, and A. Henins, Nat.

Bur. Stand. (U.S.), Tech. Note 896, 114 (Jan. 1976).

3. R. D. Deslattes and A. Henins, Phys. Rev. Lett. 31, 972 (1973).

4. R. G. Helmer, R. C. Greenwood, and R. J. Gehrke, Atomic Masses and

Fundamental Constants 53 J. H. Sanders, A. H. Wapstra, eds.,

Plenum Press, New York, p. 30 (1976).

5. R. D. Deslattes, Proceedings of the School of Physics3 'Enrico

Fermi ' s Metrology and Fundamental Constants Course (1976)

.

Preprints will shortly be available.^

106
E, Summary of Reactor Operations

Operating productivity and fuel utilization efficiency for the

past year were the best in the history of the facility. The newly

installed heat exchangers functioned well. Otherwise, this operating

cycle was uneventful. Four papers dealing with the operation of the

NBSR were presented at the August 1975 meeting of the Reactor Operations

Division of the American Nuclear Society.

A summary of the overall operating statistics for this and

previous years is presented in the following table.

NBSR Operating Summary

Reactor Operations to date, MWh

Reactor Operations for year, MWh

Hours Reactor Critical

Number of Days at 10 MW

On-line Time at 10 MW

Number of fuel elements used

Average U-235 Burnup

Number of Refueling Operations

Number of Unscheduled Shutdowns

Number of Irradiations

Irradiations, Total Hours

Hours per irradiation

Number of Visitors

1973 1974 1975 1976

229,000 290,000 328,000 396,000

67,000 61,000 38,000 68,000

7,000 6,600 3,900 6,900

279 254 157 283

77% 70% 43% 78%

28 24 16 24

52% 54% 53% 55%

7 6 4 6

14 6 2

4,300 3,000 1,550 2,360

5,250 4,300 1,800 7,250

1.2 1.4 1.2 3

3,000 5,000 3,000 7,000

107
F, Services Programs

ACTIVATION ANALYSIS PROGRAM OF THE

FOOD AND DRUG ADMINISTRATION AT THE NBSR

J. T. Tanner and M. H. Friedman

(Food and Drug Administration, Washington, DC)

1. Analysis of Chlorine in Japanese Rice Oil

During 1968 an incident in Japan (the so-called "Yusho" poisoning)

resulted in the contamination of a large quantity of rice oil with polychlorinated biphenyls (PCB) . Several people died and many were injured

ppermanently as a result of consuming this contaminated cooking oil.

The FDA has recently been reviewing regulations governing the amount of

PCB allowable in foods. Since much of the data on the effect of PCB on man was gathered as a result of this accidental contamination incident

in Japan, it was very important that there be an accurate analysis of

this oil for PCB.

A sample of this rice oil was analyzed at the FDA headquarters

laboratory for PCB's and compared with an earlier analysis of PCB done

in Japan. The results differed by almost a factor of two. The analytical procedure used by FDA was the official method of analysis for PCB

currently listed by the A.O.A.C. The Japanese data were based on earlier methodology and on neutron activation analysis for total chlorine.

In support of the pesticide analysis unit of FDA, the NAA unit

analyzed the contaminated oil for chlorine. The NAA results supported

the original Japanese analysis. Since control rice oil contained virtually no chlorine, the chlorine detected was assumed to be bonded to the

PCB (approximately 50% chlorine) or another yet unknown contaminant.

To resolve the factor of two discrepancy, the pesticides unit then

succeeded in separating the chlorine containing compounds by adsorption

chromotography and GLC into two fractions. One fraction contained PCB

and results from NAA chlorine determination and the A.O.A.C. PCB method

were equivalent. The second fraction was a group of later components

108
SERVICE PROGRAMS

'

from a GLC column and contained an equivalent amount of chlorine. This

resolved the factor of two discrepancy between analyses at FDA and in

Japan. To date, the other chlorine containing compound (s) have not been

identified.

2. Analysis of Animal Waste Material

Recently it has become common practice to use animal waste as a feed ingredient for animal feeds. This practice has been approved by

Table 1. Elemental concentration of animal waste material (yg/g)

Element

Dried

Cattle Manure

(low fiber)

Dried Dried

Cattle Manure Processed Waste

(high fiber) Pellets

Dried

Poultry Waste

(with litter)

Dried

Poultry

Waste

Dried

Sewage

Sludge

Fe 2394±444 45651611 18901125 895184 1838114 154141444

Zn 109±11 79H0 6913 16513 140112 17521113

Rb 19±2 37+1 14.710.2 8.8H.1 12.711.3 32111

Co 1.7±0.5 2.210.5 1.1+0.2 2.010.3 1.210.1 7.112

Sb 0,2810.02 0.2910.05 0.2210.02 0.3710.02 0.3810.02 6.3±1.8

Br 29±4 29+2 56+3 912 2012 3013

Cr 20±7 3119 5H 6H 4.9+0.3 280H05

Se 0.5±0.2 0.6±0.1 0.2910.01 0.410.1 0.710.2 4.8H.2

Ba 0.09±0.02 0.17+0.01 0.0710.01 <0.2 <0.1 0.810.2

Sc <0.7 <2 <0.4 0.1910.02 0.310.1

Cs 0.13+0.02 0.3310.05 0.2510.06 0.0610.02 0.1010.04 0.5810.03

La 2.6±0.4 1111 2.510.5 2.410.4 1.910.2 2718

Eu 0.13±0.02 0.510.2 0.0910.03 0.05+0.02 0.0710.03 0.610.1

V 1.6±0.4 915 2H 2.9+0.3 2.910.3 2H2

Ca 10500±700 105001700 1250012000 48000+3000 6200017000 27000+6000

CI 78001600 605011300 5200+400 34001100 53001400 570HOO

Al 6300±300 12000+5000 2600+600 1070H5 2400H00 190001900 Mg 2300±800 29001700 40001500 3200H000 36001400 400012000

Cu <100 <100 <50 <50 <100 500160 Mn 40117 10319 5716 130+50 160120 210+40 Na 5600+700 6800+1500 3300+900 16001400 35001900 34001800 K 21000+8000 16000+4000 2000014000 1500013000 1500013000 1400017000

As <1.4 <1.6 <1.2 <1.2 <1.4 4+1

*The above

air dried. samples were collected from the feed lots (except sludge) and air dried. The sludge w;

109
SERVICE PROGRAMS

seven states for animals in intrastate commerce, but has not been

approved by FDA for animals in interstate commerce. In order to establish base line information about trace metals in typical animal waste

products, samples of dried waste from animals with a known diet history

and a sample of processed waste pellets composed of a mixture of animal

feed and dried animal waste were obtained for analysis. In addition a sample of sewage sludge, which is being tested as an animal feed ingredient on an experimental basis, was analyzed. The results of these

analyses are given in table 1. The high levels of many metals in both

animal waste products and sewage sludge indicate that the practice of

using animal waste or sewage sludge as animal feed ingredients should

be carefully evaluated before being fully sanctioned.

IMPROVED MATERIAL FOR SOLAR ENERGY CELLS

T. M. Raby

Neutron Transmutation Doped (NTD) silicon is beginning to assume

a position of major importance in the semiconductor device field and

may have wide ranging application in the development of solar energy

cells.

It has been recognized in recent years that silicon is almost an

ideal material for transmutation doping. Normally available silicon

contains 3% Si-30 which transmutes to P-31 on the capture of a thermal

neutron. This process produces a uniform concentration of phosphorus,

a paramount factor in the material's performance and use. The NBS reactor, with its extensive and versatile facilities and

its intense highly thermalized neutron flux, is ideally suited for

transmutation doping of materials. Over the past several months,

together with the Oak Ridge National Laboratory, numerous silicon

samples have been irradiated at the NBS reactor. . Extensive research is

currently being carried out to study the use of NTD silicon in power

110
SERVICE PROGRAMS

devices and solar cells and to expand its application into other semiconductor fields. The success of this work could mark a new era in the use of reactor produced materials in important energy fields.

atf's FORENSIC ACTIVATION ANALYSIS PROGRAM

CM. Hoffman

(U.S. Treasury Department, Washington, DC)

Although the use of NAA for detecting barium and antimony in gunshot residues has been replaced by flameless atomic absorption spectrophotometry, NAA still plays a valuable role in the analysis of trace

evidence. The method's sensitivity and non-destructive nature make the

technique very attractive for the analysis of certain types of physical

evidence commonly found at crime scenes. During the past year, our Laboratory used NAA to examine evidence

in 175 cases. This evidence consisted of hair, paint, glass, soil and

metal particles.

The conclusions drawn by a Laboratory examiner concerning the relative origins of questioned and known evidentiary materials depends

upon the analytical background data available for the type of material

under examination. Characterization of the material requires that a significant quantity of data be available for this evaluation. Studies

of various materials , such as paint and glass , are being conducted by

our laboratory scientists to meet this need. For example, glass samples

which cannot be discriminated by their refractive index, density or elemental composition as determined by x-ray flourescence, will be studied

by NAA to assess the worth of this method as it applies to this type of

problem.

Ill
SERVICE PROGRAMS

LUNAR SAMPLE ANALYSIS FOR 20 TRACE ELEMENTS

E . Anders

(University of Chicago, Chicago, IL)

During the last year, numerous samples were analyized for 20 trace

elements (Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os , Pd, Rb , Re, Sb, Se,

Te, Tl, U and Zn) by radiochemical neutron activation using the NBS

Reactor. This is part of a continuing extensive program to determine

the origin and constituents of lunar samples. The analysis involved

trace levels as low as one part in

obtained from meteorite specimens.

15 trace levels as low as one part in 10 and will be compared with those

ACTIVATION ANALYSIS PROGRAM OF THE U. S, GEOLOGICAL SURVEY

J. J. Rowe and P. A. Baedecker

(U. S. Geological Survey, Reston, VA)

Activation analysis is being applied by the Radiochemistry Project,

Reston to the determination of trace concentrations of elements in geological materials. The technique is used for the analysis of rocks,

minerals , waters and coals for geochemical studies related to ore formation, magmatic differentiation, hydrothermal alteration and transport,

energy reserves and environmental problems.

Coals are being analyzed as part of a program to study the trace

element content of U. S. coals. More than 1000 coal samples per year

are being analyzed for 24 elements. This is possible through the use of

automated counting equipment and computer data reduction. The system

operates 24 hours per day, 7 days per week to collect gamma ray spectra

onto magnetic tape. Samples are counted 4 days after irradiation and

then again 6 weeks later. The data from the two counts are processed by

computer to provide the final analytical report (Table 1) . Through the use of epithermal neutron irradiations at the JEEP reactor, Kjeller,

Norway we were able to instrumentally determine U, Sr, Mo, and Ni and

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SERVICE PROGRAMS

f* <». r\j IA n »h -4- eg M -O O * O *< eg o ao *%* tft m -toof-in *0<

jt < eg V

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113
SERVICE PROGRAMS

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114
SERVICE PROGRAMS

improve the determination of Co, Zn, As, Se, Br, Rb , Cs , Ba, Sm, Tb, Hf,

Ta, W and Th to supplement the thermal irradiations done at the NBS

reactor.

The project has been analyzing a wide variety of geological materials for numerous programs of the Survey. Gold has been determined in

2 sediments and igneous rocks using a fire assay radiochemical method.

Ruthenium and iridium were studied in chromites using a fire assay radio3 4 chemical method with collection into a platinum bead ' followed by

Ge(Li) or coincidence counting.

The NBS reactor facility has been utilized to provide thermal

neutron irradiations leading to the determination of 22 to 24 elements in

many geologic matrices (Table 2) . In some cases the thermal irradiations have been supplemented by epithermal irradiations to instrumentally determine tungsten, cesium, rubidium, barium, uranium and thorium

when they occur at low concentrations.

1. Rowe, J. J. and Steinnes, E., "Determination of 30 elements in

coal and fly ash by thermal and epithermal neutron activation

analysis". (submitted to Talanta)

2. Rowe, J. J. and Simon, F. 0., "Determination of gold in geologic

materials by neutron activation analysis using fire assay for

radiochemical separations". U.S.G.S. Circ 599.

3. Greenland, L. P., Rowe, J. J. and Dinnin, J. I., "Application of

triple coincidence counting and of fire-assay separation to the

neturon-activation determination of iridium". U.S.G.S. Prof Paper

750-B, p. 175-179 (1971).

4. Page, N. J., Rowe, J. J. and Haffty, J., "Platinum metals in the

Stillwater Complex, Montana" (submitted to Econ. Geol.).

115
SERVICE PROGRAMS

TRACE ELEMENTS IN THE ENVIRONMENT

AND RADIOACTIVE DECAY STUDIES

W. H. Zoller, G. E. Gordon and W. B. Walters

(University of Maryland, College Park, MD)

Our group has made extensive use of the NBSR for the irradiation

of numerous samples for trace-element analysis using instrumental neutron

activation analysis (INAA) . We have had our computer-based Northern

Scientific analyzer system and two Ge(Li) Y-ray detectors at the Reactor

for periods of several weeks during the last year to count short-lived

radioactive products. Most of the other samples are returned to the

university for counting long-lived activities.

In our "local" air pollution studies we have applied INAA to particles collected in the stacks of coal and oil-fired power plants and

municipal incinerators. We have also analyzed particles collected with

airplanes in the plumes of the Vienna oil-fired plant, and the Chalk

Point (Md.), Dickerson (Md.) and Four Corners (New Mexico) coal-fired

plants. (The latter is a joint venture with Lawrence Livermore Laboratory and some of the analyses have been done there.) We have also analyzed ambient aerosols collected from several sites in Washington, D. C.

during the summer of 1975. Briefly we find that:

(1) We can now account almost quantitatively for the sources of

about thirty elements observed in the Washington atmosphere.

(2) Coal combustion does not appear to be the major source of most

toxic elements, exceptions being As, Se and vapor-phase Hg.

(3) From previous years' work, motor vehicles are the major sources

of atmospheric Pb, Br, CI and, possibly, Ba.

(4) Oil-fired plants are major sources of V, Ni and possible Se.

(5) Municipal incinerators release little total mass, but the

particles are so rich in many trace elements that they are often a major

source of urban, ambient Zn, Cd, Sb and, possibly, Ag and Sn. Since Sb

and Cd are clearly toxic, this finding raises a serious question about

the proposed use of urban refuse as a supplement to coal in power plants.

116
SERVICE PROGRAMS

Recently we have begun studies on additional sources: cement

plants and steel mills.

We are also continuing our studies of global atmospheric particulate samples. We have analyzed additonal particulate samples collected

from the very clean air of the South Pole. Since there is essentially

total snow cover there, the particles have had to be transported long

distances. The enrichment factors of many elements are the same as for

urban air, so one might be tempted to assume that those particles originate from anthropogenic sources. However, one cannot assume that without investigating particles from natural sources, of which volcanoes are

a major example. In order to obtain better information on volcanic

emissions, we collected aerosols from the Jan. /Feb. 1976 Mt. Augustine

eruption in Alaska with the use of an airplane operated by the

National Center for Atmospheric Research in Boulder. Preliminary analyses

of these samples indicate that a number of moderately volatile elements

are highly enriched on the volcanic particles.

In our decay scheme studies we have completed work on the yy angular

correlations in Rh-105 following the decay of A. 4-hr Ru-105 and published

the results in Physical Review C. The results of earlier studies of the

decay of Te-134 to levels of 1-134 have also been published. New coincidence data have been taken for the decay of 100-min Nd-149 to levels of

Pm-149, 12-min Nd-151 to levels of Pm-151, 5-hr and 20-min Pd-111 isomers

to levels of Ag-111, and 3.4-hr and 2.6-hr Cd-117 isomers to levels of

In-117.

THE NON-DESTRUCTIVE DETERMINATION OF TRACE ELEMENT

CONCENTRATIONS BY NEUTRON-CAPTURE Y-RAY SPECTROMETRY

G. E. Gordon, W. H. Zoller, D. Anderson,

M. Failer, and W. B. Walters

(University of Maryland, College Park, MD)

In cooperation with Dr. Richard Lindstrom of the NBS Activation

Analysis Section, efforts are underway to develop a neutron-capture

117
SERVICE PROGRAMS

y-ray spectrometer for the purpose of non-destructive trace-element

concentration measurements. The system is to include a split-annulus

Compton-suppressed Ge(Li) pair spectrometer whose pulses are automatically collected and analyzed by an 80K PDP 11/34. Construction of the

reactor beam tube is underway (with design help and some machining by

the Reactor staff) and the fabrication of external shielding is being

planned.

The computer system has been ordered and the development of the

software system is advancing.

118
6. Staff Roster

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119
STAFF ROSTER

NON-RRD NBS STAFF LOCATED AT REACTOR

Division 240.01

P. R. Cassidy

H. E. DeSpain

J. J. Shubiak

F. Moore

Division 241.05

R. A. Dallatore

C. Eisenhauer

R. Fleming

D. Gilliam

J. A. Grundl

I, G. Schroder

R. Schwartz

V. Spiegel

Division 310.08

B. S. Carpenter

B. J. Clipper

K. M. Cunningham

B. N. Garrigues

T. E. Gills

R. R. Greenberg

C. A. Grimm

S. H. Harrison

R. M. Lindstrom

G. J. Lutz

L. T. McClendon

N. Sato

H. L. Rook

GUEST WORKERS AND COLLABORATORS

Division 213.04

D. G. Eitzen

Division 232.06

R. D. Deslattes

E. G. Kessler

W. C. Sauder

J. Snyder

Division 241.05

C

.

Bowman

K. Duval

1

H. Heaton

G. Tamaze

Division 242.06

L. L. Lucas

F. J. Shima

Division 311.05

W. Brown

M. Mathew

L. Schroeder

Division 312.02

R. Reno

Division 313.03

D. B. Minor

R. S. Roth

Division 313.04

G. J. Rosasco

Division 313.06

A. B. Mighell

Division 311.03

C. Han

Building Technology

P. Brown

120
STAFF ROSTER

Argonne National Laboratory

H. Flotow

D. L. Price

K. Skold

S. Susman

Battelle, N. W.

L. Brachenbush

G. Endres

W. Nicholson

Federal Bureau of Investigation

B. Davies

Haverkost

W. Kilty

Mitchell

P. Riley

Food and Drug Administration

M. Friedman

J. T. Tanner

Harry Diamond Laboratory

C

.

Heimbach

D. McGarry

National Institutes of Health

D. Davies

R. Frank

W. Hagins

W. Robinson

Naval Air Defense Command

M. Stellabotte

W. Williams

Naval Air Rework Facility

R. Chavez

Naval Engineering Center

P. Soltis

Naval Research Laboratory

P. D' Antonio

B. Das

A. Erlick

J. Karle

R. Meussner

J. Milstein

Naval Surface Weapons Center

(Dahlgren Laboratory)

R. Buckingham

(White Oak Laboratory)

H. Alperin

P. Hesse

D. Polansky

R. Williams

Oak Ridge National Laboraitory

H. A. Mook

M. Mostoller

H. G. Smith

Picatinny Arsenal

N. Chesser

C. S. Choi

M. K. Farr

H. J. Prask

S. Trevino

Smithsonian Institution

T. Chase

J. Mishara

U. S. Geological Survey

P,

J. Baedecker

J . Rowe

121
STAFF ROSTER

U. S. Treasury Department

J. M. Hoffman

W. Kinard

L. Reid

American University

R. Abbundi

R. A. Segnan

Colorado State University

C. E. Patton

Georgetown University

K. Barkigia

C. Quicksall

Howard University

G. A. Ferguson

Reed College

W. Parker

University of California

(Lawrence Livermore Laboratories)

J . Browne

S . Hankins

University of Chicago

E. Anders

University of Maryland

D. Anderson

C. Choquette

W. Cunningham

M. Failey

P. Gallagher

M. Germani

B. Glagola

M. Glascock

D. Glotfelty

G. Kowalczyk

E. Lepel

J. Levkoff

J. Muhlbaier

D

.

Reamer

E. Schneider

M. Small

P. Solomon

E. Sombrito

K. Steffansson

W. Walters

W. Zoller

U. S. Naval Academy

C. S. Schneider

University of Rhode Island

S. J. Pickart

Allied Chemical Corporation

G. Liebowitz

A. Maeland

R. 0' Handy

General Electric Company

F. Lubursky

Idaho National Engineering

Laboratories

H. D. Reeder

J. R. Smith

Old Delft Corporation

D. Bracher

122
PUBLICATIONS

COLLABORATIVE PROGRAMS

ALPERIN, H. A., FLOTOW, H. , RUSH, J.J., RHYNE, J.J., "Deuterium-Site

Occupancy in the a and $ Phases of TiDx," (in press).

ALPERIN, H. A., CULLEN, J.R., and CLARK, A.E., "Magnetic Properties of

Bulk Amorphous Tb Fe1 ," A. I. P. Conf. Proa., 29, 186, (1975).

BERGER, H., "Calif ornium-252 As A Source For Thermal Neutron Radiography,"

Symposium International Sur L 'Utilization Du Calif'ornium-252 , (to be

published)

.

BERGER, H., "Nondestructive Evaluation: A Review of Nuclear Methods,"

Instrumentation in the Aerospace Industry, Vol. 22, (1976).

BERGER, H., "Practical Applications of Neutron Radiography and Gaging,"

ASTM STP 586, American Society for Testing and Materials, (1976).

BERGER, H., "Detection Systems for Neutron Radiography," Proc. Symposium

on Practical Applications of Neutron Radiography and Gaging3 ASTM

STP 586, (1976).

BERGER, H., PARKER, W. L. , LAPINSKI , N. P., REIMANN, K. J., "ThreeDimensional Inspection by Thermal Neutron Laminagraphy ," Transactions

American Nuclear Society, Vol. 23, (1976).

BERGER, H. , "Nondestructive Measurements: How Good Are They," Materials

Evaluation, 34, 18A-24A, 33A-34A (1976)

.

BERGER, H. and MOTZ, J. W. , "A Qualitative Discussion of Quantitative

Radiography," in Prevention of Structural Failure, No. 5 Materials/

Metalworking Technology Series (1975)

.

CASELLA, R. C, TREVINO, S. F., and ROWE, J. M. , "Determining the Number

of Independent Real Parameters in the Phonon Dynamical Matrix,"

Phys. Rev. B12, 4573 (1975).

CHESSER, N. J. and PRASK, H. J., "Quasielastic Neutron Scattering Study

of Single Crystal Ammonium Perchlorate , " Proceedings Conf. on Neutron

Scattering, Gatlinburg, TN (in press).

CHOI, C. S., PRASK, H. J., and PRINCE, E. , "Ammonium Perchlorate: Reinvestigation of the Crystal Structure at 298°K," Acta. Cryst.

(in press)

.

123
PUBLICATIONS

CHOI, C. S., "Crystal Structures of the Inorganic Azides," Chapter 73

in Physios and Chemistry of the Inorganic Azides, Vol. 1, (R. Walker

and H. Fair, Editors), Plenum Press (in press).

CHOI, C. S., SANTORO, A., and MARKINKAS , P. L., "l,3,5-Triacetye-2 ,4,6-

heradhydro-S-triazine (TRAT) ," Acta, Cryst. , B31, 2934 (1975).

CHOI, C. S., SANTORO, A., and ABEL, J. E., "The Crystal Structure of 3,

7-diacetyl 1,3,5,7 tetraza-bicyclo [3,3,1] nonane (DAPT)," Acta.

Cryst., B32, 354 (1976).

CHOI, C. S., and PRINCE, E. , "A Neutron Diffraction Study of Structure

and Thermal Motion in Several Monovalent Metal Azides," J. Chem.

Phys., 64-, 4510 (1976).

FARR, M. K. and TREVINO, S. F., "Mode Gruneisen Parameters of KBr

Determined by Inelastic Neutron Scattering," Proceedings of the

Conference on Neutron Scattering, Gatlinburg, TN. (in press).

FARR, M. K., GIGUERE, P. A., and ARNAU, J. L., "The Lattice Dynamics of

Deuterium Peroxide," Proceedings of the Conference on Neutron

Scattering} Gatlinburg, TN. (in press)

.

GLINKA, C. J., ROWE, J. M. , and RUSH, J. J., "Inelastic Neutron Scattering

Lineshapes in PdD, ," Proc. Conf. on Neutron Scattering, Gatlinburg,

TN. (in press) .

GLINKA, C. J., MINKIEWICZ, V. J., and PASSELL, L., "Absolute Measurement

of the Critical Scattering Cross Section in Cobalt," AIP Conf. Proc,

29_, 499 (1976).

IQBAL, Z., PRASK, H. J. and TREVINO, S. F., "Molecular Vibrations and

Lattice Dynamics of Inorganic Azides," Physics and Chemistry of the

Inorganic Azides, (R. Wlaker and H. Fair, editors) Plenum Press (in

press) .

IQBAL, Z., CHOI, C. S., CHRISTOE, C. W. , FORSYTH, A. C, PRASK, H. J.

and TREVINO, S. F. , "Advances in Techniques for Structural and

Dynamical Studies of Stability in Energetic Materials, and Applications to Diverse End-Item Problems," Proceedings of 1976 Army

Science Conf. , DA Publication (in press)

.

PRINCE, E., TREVINO, S. F. , CHOI, C. J., and FARR, M. K. , "A Refinement

of the Structure of Deuterium Peroxide," J. Chem. Phys., 6_3, 2620

(1975).

124
PUBLICATIONS

PRINCE, E., "Dimethyl Sulfone Diimine, A Neutron Study," Acta Cryst.

B31 , 2536, (1975).

PRINCE, E., MIGHELL, A., SANTORO, A., and REIMANN, C, "Neutron Diffraction

Structure Determination of Dichlorotetrapyrazole Copper (II)," Acta.

Cryst. , B31, 2479 (1975).

RHYNE, J. J., KOON, N. C, MILSTEIK , J., and ALPERIN, H. A., "Spin Waves

in Ferrimagnetic ErFe„," Proceedings of Conference on Neutron

Scattering3 Gatlinburg, TN (ir press).

RHYNE, J. J., ABBUNDI, R. , SEGNAN, R. , and SWEGER, D., "Hyperfine Fields

in the Absence of Order in DySc Alloys," AIT Conf. Proc. 3 29_, 352

(1976).

RHYNE, J. J., "Curie Temperatures of Amorphous RFe Alloys," AIP Conf.

Proc. , 29 , 182 (1976)

.

ROWE, J. M. , "Neutron Scattering Studies of the Diffusion of Hydrogen

in Metals," Proceedings of the Conference on Neutron Scattering3 Gatlinburg, TN (in press).

ROWE, J. M. , RUSH, J. J., PRINCE, E., and CHESSER, N. J., "Neutron

Scattering Studies of Crystal Dynamics and Order-Disorder Phase

Transitions in Alkali Cyanides," Ferroelectrics , (in press).

ROWE, J. M., VAGELATOS, N., RUSH, J. J., and FLOTOW, H. , "The Acoustic

Modes of the Phonon Dispersion Relation of NbD Alloys," Phys. Rev. 3 12, 2959 (1975). x

RUSH, J. J., ROWE, J. M., GLINKA, C. J., VAGELATOS, N. , and FLOTOW, H.

,

"Coherent Neutron Scattering Study of the Vibrations of Interstitial

Deuterium in a VD o.7'" Proceedings of the Conference on Neutron

Scattering3 Gatlinburg, TN (in press)

.

RUSH, J. J., ROWE, M. J., VAGELATOS, N. , "Crystals Dynamics of KCN and

NaCN in the Disoriented Cubic Phase," J. Chern. Phys. s Q, 4551,

(1975).

SANTORO, A., PRINCE, E., "The Use of Position-Sensitive Detector in

Single Crystal Dif fractometers," J. Appl. Cryst., (in press).

SANTORO, A., "Powder Neutron Diffraction Analyses of the Crystal Structures of LiNb^Og & H-LiTa ," Collected Abstracts Third European

Crystallographic Meeting, PI05, Zurich, Switzerland, (1976).

125
PUBLICATIONS

SANTORO, A., NIEGHELL, A., PRINCE, E. , and REIMANN, C, "Neutron Diffraction Structure Determination of Dichlorotitra-pyrazolcopper

(II), Acta. Cryst. 3 B 31, 2479, (1975).

SANTORO, A., CHOI, C.S., and ABEL, J. E. , "1 ,5-Diacetyl-3 , 7-Dinitro-l,3,

5,7 Tetraazacyclooctane (DADN) , " Acta. Cryst. B31 , 2126, (1975).

SCHNEIDER, C.S., "Coherent Nuclear Scattering Amplitudes of Germanium,

Copper and Oxygen for Thermal Neutrons," Acta Cvyst. s A32 , 375

(1976).

SCHNEIDER, C, "A Precise Refractometer for Thermal Neutrons," Rev. Sci.

Instr. 3 44, 1594, (1975).

SHEN, T. Y., MITRAS, S. S., TREVINO, S. F. and PRASK, H. , "Order-Disorder

Phenomenon in Sodium Nitrate Studied by Low Frequency Raman

Scattering," Phys. Rev . 3 B12, 4530-4533 (1975).

SHORTEN, F. J., "Nuclear Science Education Day," NBS Technical Note, 888,

(1975).

VAGELATOS, N., ROWE , J. M. , and RUSH, J. J., "Lattice Dynamics of Nd,I

in the NaCl phase (I) at 2960° K," Phys. Rev. B, 12/10 , 4522 (1975).

126
PUBLICATIONS

INDEPENDENT PROGRAMS

CARPENTER, B. S., MYKLEBUST, R. L. , "Comparative Boron Analysis by Ion

Microproble Mass Analyzer and the Nuclear Track Technique,"

Analytica Chemioa Actas (in press)

.

DESLATTES, R. D. , KESSLER, E. G., SAUDER, W. C, and HENINS , A., Atomic

Masses and Fundamental Constants S3 Plenum Press, New York, p. 48

(1976).

FARBER, T. M. , RITTER, D. L. , WEINBERGER, M. A., BIERBOWER, G.

,

TANNER, J. T., FRIEDMAN, M. H. , CARTER, C. J., EARL, F. L., and

VANLOON, E. J., "The Toxicity of Brominated Sesame Oil and Brominated

Soybean Oil in Miniature Swine," Toxicology3 5, 319-336 (1976).

FRIEDMAN, M. H. , and TANNER, J. T., "Trace Elements in Food by Neutron

Activation Analysis," Trans, of the American Nuclear Society} 21 , 97 (1975).

GLADNEY, E. S. and ROOK, H. L. , "Simultaneous Determination of Tellurium

and Uranium by Neutron Activation Analysis," Analytical Chemistry3 47, 1554-1556 (1975).

GROS, J., TAKAHASHI, H. , HERTOGEN, J., MORGAN J. W. , and ANDERS, E.,

"Composition of the Projectile That Bombarded the Lunar Highlands,"

Proc. 7th Lunar Sci. Conf. 3 Geochim. Cosmochim. Acta, Suppl. 7,

(in press)

.

GRUNDL, J. A., SPIEGEL, V., EISENHAUER, C. M. , HEATON , H. T.

,

GILLIAM, D. M. , and BIGELOW, J., "A Californium-252 Fission Spectrum

Irradiation Facility for Neutron Reaction Rate Measurements,"

Nuclear Technologys (in press)

.

GRUNDL, J. A., and EISENHAUER, C, "Fission Rate Measurements for Materials

Neutron Dosimetry in Reactor Environments," Proceedings of ASTMEURATOM Symposium on Reactor Dosimetry_, Petten, The Netherlands.

HARRISON, S. H., LaFLUER, P. D. and ZOLLER, W. H. , "Sampling and Sample

Handling for Activation Analysis of River Water," Accuracy in Trace

Analysis: Sampling, Sample Handling, Analysis, Vol. 1 NBS Special

Publication ^22 (1976)

.

HARRISON, S. H., LaFLUER, P. D. and ZOLLER, W. H. , "An Evaluation of

Lyophilization for the Preconcentration of Natural Water Samples

Prior to Neutron Activation Analysis," Analytical Chemistry3 47 , 1685-1688 (1975).

127
PUBLICATIONS

HARRISON, S. H. , "Neutron Activation Analysis: A Useful Tool for Evaluating Water Sampling and Analysis Techniques," Transactions of the

American Nuclear Society, 2_1, 110-111 (1975)

.

HIGUCHI, H. and MORGAN, J. W. , "Ancient Meteoritic Component in Apollo

17 Boulders," Proc. 6th Lunar Sci. Conf., Geochim. Cosmochim. Acta,

Suppl. 6, 1625-1651 (1975).

JAMES, 0. B., BRECHER, A., BLANCHARD, D. P., JACOBS, J. W. , BRANNON, J. C,

K0R0TEV, R. L., RASKIN, L. A., HIGUCHI, H., MORGAN, J. W. , ANDERS, E.,

SILVER, L. T., MARTI, K. , BRADDY D., HUTCHEON, I. D., KIRSTEN, T.,

KERRIDGE, J. F. , KAPLAN, I. R. , PILLINGER, C. T., and GARDINER, L. R.

,

"Consortium Studies of Matrix of Light Gray Breccia 73215," Proc.

6th Lunar Sci. Conf., Geochim. Cosmochim. Acta, Suppli. 6, 547-577

(1975).

McGARRY, E. D., ROZI , A. H. , DAVID, G. S., GILLIAM, D. M. , "Absolute

Neutron-Flux Measurement at Fast Pulse Reactor with Calibration

Against Calif ornium-252," IEEE Conf. on Nuclear and Space Radiation,

San Diego (1976)

.

MORGAN, J. W., GROS, J., TAKHAHSHI , H. , and HERTOGEN, J., "Lunar Breccia

73215: Siderophile and Volatile Elements," Proc. 7th Lunar Sci. Conf.,

Geochim. Cosmochim. Acta, Suppl. 7, (in press).

MORGAN, J. W. , "Chemical Fractionation in the Solar System," Proc. 1976

Int. Conf.: Modern Trends in Activation Analysis, J. Radioanal. Chem.

,

(in press)

.

MORGAN, J. W. , GANAPATHY, R. , HIGUCHI, H. , KRAHENBUHL, U. , "Volatile and

Siderophile Trace Elements in Anorthositic Rocks from Fiskenaesset

,

West Greenland: Comparison with Lunar and Meteoritic Analogues,"

Geochim. Cosmochim. Acta 40, 861-887 (1976)

.

MORGAN, J. W. , HIGUCHI, H. , and ANDERS, E., "Meteoritic Material in a Boulder from the Apollo 17 Site: Implications for its Origin,"

The Moon 14, 505-517 (1975).

REIMER, G. M. , and CARPENTER, B. S., "Fission-Track Determination of

Uranium in Solutions," Abstract, EOS Transactions, American Geophysical Union, _56, No. 6, (1975).

ROOK, H. L., SUDDUETH, J. E. and BECKER, D. A., "Determination of Iodine129 at Natural Levels Using Neutron Activation and Isotopic

Separation," Analytical Chemistry, 4_7, No. 9, 1557-1562 (1975).

128
PUBLICATIONS

ROWE, J. J. and STEINNES , E. , "Determination of 30 Elements in Coal and

Fly Ash by Thermal and Epithermal Neutron Activation Analysis,"

Talanta (in press)

.

ROWE, J. J. and SIMON, F. 0., "Determination of Gold in Geologic Materials

by Neutron Activation Analysis Using Fire Assay for Radiochemical

Separations," U.S.G.S. Civo 599.

TANNER, J. T., and FRIEDMAN, M. H., "Trace Elements in Food," Modern

Trends in Activation Analysis, (to be published) J. Radioanal Chem.

TANNER, J. T., "Instrumentation in Applied Nuclear Chemistry," Krugers

(Editor) , Journal of the Association of Official Anlaytioal Chemists

5_8, 626 (1975).

TANNER, J. T. and FORBES, W. S., "Determination of Mercury in Total Diet

Samples by Neutron Activation," Analytioa Chimioa Acta , _74, 17-21

(1975).

WAGNER, G. A., REIMER, G. M. , CARPENTER, B. S. , FAUL, H., VAN der LINDEN, R. and GIJBELS, R. , "The Spontaneous Fission-Track Rate of U-238 and

Fission-Track Dating," Geochimioa et Cosohimioa Acta3 39, 1279-1286,

Pergamon Press (1975)

.

129
1*B$-114A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO. NBS Technical Note 939

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

NBS REACTOR: Summary of Activities

July 1975 to June 1976

5. Publication Date May 1977

6. Performing Organization Code

7. AUTHOR(S)

Eradarick J- Short- p.n

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Worlc Unit No.

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP) 13. Type of Report & Period Covered

7/1/75 to 6/30/76

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) This report summarizes all those programs which depend on the NBS reactor.

It covers the period from July 1975 through June 1976. The programs range from

the use of neutron beams to study the structure and dynamics of materials through

nuclear physics and neutron standards to sample irradiations for activation analysis,

isotope production and radiation effects studies.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Activation analysis; crystal structure; diffraction; isotopes; molecular dynamics;

neutron; nuclear reactor; radiation

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CRYSTAL

DATA

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In 1954, the first edition of CRYS- TAL DATA (Determinative Tables and Systematic Tables) was published as Memoir 60 of the Geological Society of America. In 1960,

the second edition of the Determinative Tables was issued as Monograph

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