itional Bureau of Standard:

Library, N.W. Eldg

DEC 9 1964

Reference book not to be

token from ry.

^ecknical ^lote 252

PROCEDURES FOR PRECISE DETERMINATION

OF THERMAL RADIATION PROPERTIES

NOVEMBER 1962 TO OCTOBER 1963

A Report to: Air Force Materials Laboratory

JOSEPH C. RICHMOND, DAVIS P. DEWITT,

AND WARREN D. HAYES, JR.

i

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assuring

maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. Its responsibilities include development and maintenance of the national stand- ards of measurement, and the provisions of means for making measurements consistent with those standards; determination of physical constants and properties of materials; development of methods

for testing materials, mechanisms, and structures, and making such tests as may be necessary, particularly for government agencies; cooperation in the establishment of standard practices for incorporation in codes and specifications; advisory service to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Government; assistance

to industry, business, and consumers in the development and acceptance of commercial standards and

simplified trade practice recommendations; administration of programs in cooperation with United

States business groups and standards organizations for the development of international standards of practice; and maintenance of a clearinghouse for the collection and dissemination of scientific, technical, and engineering information. The scope of the Bureau's activities is suggested in the following

listing of its four Institutes and their organizational units. Institute for Basic Standards. Electricity. Metrology. Heat. Radiation Physics. Mechanics. Applied Mathematics. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radio Standards Laboratory: Radio Standards Physics; Radio Standards Engineering.** Office of Standard Ref- erence Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.** Office of Standard Reference Materials.

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and Space Telecommunications. Radio Systems. Upper Atmosphere and Space Physics.

Institute for Applied Technology. Textiles and Apparel Technology Center. Building Research.

Industrial Equipment. Information Technology. Performance Test Development. Instrumentation.

Transport Systems. Office of Technical Services. Office of Weights and Measures. Office of Engineering Standards. Office of Industrial Services.

* NBS Group, Joint Institute for Laboratory Astrophysics at the University of Colorado. ** Located at Boulder, Colorado.
NATIONAL BUREAU OF STANDARDS

Technical Note 252

ISSUED NOVEMBER 20, 1964

PROCEDURES FOR PRECISE DETERMINATION

OF THERMAL RADIATION PROPERTIES

NOVEMBER 1962 TO OCTOBER 1963

Joseph C. Richmond, Davis P. DeWitt,

and Warren D. Hayes, Jr.

A Report to Air Force Materials Laboratory

Research and Technology Division

Air Force Systems Command

Wright-Patterson Air Force Base, Ohio

Project No. 7381, Task No. 738103

(Prepared Under Contract No. DO 33(61 6)-61 -02)

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price 40 cents

FOREWORD

This report was prepared by the National Bureau of Standards under

Amendments Nrs. 5 and 6 to Delivery Order (33-616) 61-02. The work

was initiated under Project Nr. 7381, "Materials Applications", Task Nr.

738103, "Materials Information Development, Collection and Processing".

The Contract was administered under the direction of the AF Materials

Laboratory, Research and Technology Division, United States Air Force,

with Mr, D. F. Stevison acting as Project Engineer.

This report covers work performed during the period 1 November, 19 62

through 31 October, 19 63.

Joseph C. Richmond,

National Bureau of Standards.

ABSTRACT

The preliminary design of an inter grating- sphere reflectometer,

utilizing a helium- neon continuous- wave gas laser as the source, for

measuring the reflectance of specimens at high temperature, was completed. Development work on an ellipsoidal mirror reflectometer for

measuring spectral reflectance in the wavelength range of 2 to 15 microns

of specimens at room temperature was continued. The study of equations

relating spectral emissivity of metals to other properties was continued.

Platinum- 13% rhodium and oxidized Inconel working standards of normal

spectral emittance were calibrated over the wavelength range of 1 to 15

microns at temperatures of 800, 1100 and 1300 °K. Several modifications

of the normal spectral emittance equipment were made to permit operation in the 15-35 micron range.

in
CONTENTS

PAGE

1. Objectives 1

2. High -Temperature Integrating Sphere Ref lectometer 1

3. Spectral Reflectance Equipment 4

4. Equations Relating Spectral Emissivity of Metals to Other

Properties 6

5. Calibration of Working Standards 7

6. Normal Spectral Emittance Equipment 19

7. Data-Processing Attachment 23

8. Summary and Future Plans 2 6

IV
ILLUSTRATIONS

FIGURE PAGE

1. Photograph of the Infrared Ref lectometer with Light Cover Panels

Removed. The Specimen is Mounted at the First Focus of the

Ellipsoidal Reflector and the Detector at the Second Focus . . 5

2. Normal Spectral Emittance of 0.484-in. Disc Working Standards

of Platinum- 13% Rhodium Alloy at 800° K 10

3. Normal Spectral Emittance of 0.484-in. Disc Working Standards

of Platinum-13% Rhodium Alloy at 1100°K 10

4. Normal Spectral Emittance of 0.484-in. Disc Working Standards

of Platinum-13% Rhodium Alloy at 1300°

11

5. Spectral Distribution of Two Categories of Standard Deviations,

Each Computed From Six Measured Emittance Values Obtained at

800°K, Three Each on Two Specimens of Platinum-13% Rhodium

Alloy 12

6. Spectral Distribution of Two Categories of Standard Deviations,

Each Computed From Six Measured Emittance Values Obtained at

1100° K, Three Each on Two Specimens of Platinum-13% Rhodium

Alloy 13

7. Spectral Distribution of Two Categories of Standard Deviations,

Each Computed From Six Measured Emittance Values Obtained at

1300° K, Three Each on Two Specimens of Platinum-137o Rhodium

Alloy 14

8. Normal Spectral Emittance of 0.484-in. Disc Working Standards of

Oxidized Sandblasted Inconel at 800°

15

9. Normal Spectral Emittance of 0.484-in. Disc Working Standards of

Oxidized Sandblasted Inconel at 1100° K 16

10. Normal Spectral Emittance of 0.484-in. Disc Working Standards of

Oxidized Sandblasted Inconel at 1300°K 16

11. Spectral Distribution of Two Categories of Standard Deviations,

Each Computed From 18 Measured Emittance Values Obtained at

800°K, Three Each on Six Specimens of Oxidized Sandblasted

Inconel 17

v
FIGURE PAGE

12. Spectral Distribution of Two Categories of Standard Deviations,

Each Computed From 18 Measured Emittance Values Obtained at

1100°K, Three Each on Six Specimens of Oxidized Sandblasted

Inconel 18

13. Spectral Distribution of Two Categories of Standard Deviations,

Each Computed From 18 Measured Emittance Values Obtained at

1300° K, Three Each on Six Specimens of Oxidized Sandblasted

Inconel , 19

14. Schematic Diagram of Atmosphere Purification System 22

vi
PROCEDURES FOR PRECISE DETERMINATION

OF THERMAL RADIATION PROPERTIES

NOVEMBER 1962 TO OCTOBER 1963

1. OBJECTIVES

The broad objective of this program is to develop standard procedures,

and to select or design suitable equipment for the measurement of normal spectral emittance±/and/or spectral reflectance of materials, particularly those

used in aircraft, missiles and space vehicles, at temperatures from below room

temperature to near the melting point of refractory materials of interest, and

over the wavelength range from the ultraviolet into the far infrared. The

specific objectives for the report period included (1) development of instrumentation and techniques for measurement of normal spectral emittance in the

temperature range of 2000 to 4000°F (1366 to 2478°K), and over the wavelength

range of 0.3 to 15 microns (2) extension of existing equipment and procedures

for measurement of normal spectral emittance in the temperature range of 1000

to 2000°F (811 to 1366°K) and wavelength range of 1 to 15 microns to the wavelength range of 15 to 35 microns and (3) preparation and calibration of working standards of normal spectral emittance in the temperature range of 1000

to 2000°F and the wavelength range of 15 to 35 microns. A further objective,

covered by Amendment No. 6 to the delivery order, called for the preparation

and calibration of disc standards of normal total emittance of polished platinum-13% rhodium alloy and oxidized, sandblasted inconel over the temperature

range of 1000 to 2000° F.

The work on development of equipment and procedures for measuring normal

spectral emittance at temperatures in the 2000 to 4000°F (1366 to 2478°K)

range has proceeded on another project sponsored by the George C Marshall

Space Flight Center of N.A.S.A. Reports covering work sponsored by the

Research and Technology Division of the Air Force Materials Laboratory have

been sent to both sponsors

2. HIGH-TEMPERATURE INTEGRATING SPHERE REFLECTOMETER

The accuracy of a direct measurement of emittance depends primarily upon

the accuracy with which the temperatures of the specimen and blackbody are

known. The percentage error in an emittance measurement that is due to the error in temperature measurement (or temperature difference between blackbody

and specimen) may be expressed as

dVft. K

dT m

-T£ - T

where dft^ is the change in emitted energy, W^, accompanying a change

1/ Emittance is a property of a specimen; it is the ratio of the emitted radiant flux per unit area to that of a blackbody radiator at the same temperature

and under the same conditions.
in temperature, dT . The factor K may be evaluated from the expression

r p C^^t

K = vs e (2)

where C2 is the second Planck radiation constant, e the base of the

natural logarithms, \ the wavelength and T the absolute temperature.

At XT = 0.29 cm °K, which is the peak of the Planck distribution function, K = 5.0. At shorter wavelengths, K increases rapidly with decreasing wavelength, and at longer wavelengths, K decreases slowly with

increasing wavelength.

Thus it can be seen that the errors in direct emittance measurements are inherently large at short wavelengths, below the peak of the Planck distribution function. Also, accurate temperature (or temperature difference) measurements are difficult to make at temperatures above those at which conventional

thermocouples can be used, particularly on materials whose spectral emittance

at the optical pyrometer wavelength is not accurately known. As a result, errors in direct emittance measurements at such temperatures are inherently

large .

In contrast to emittance, the accuracy of a reflectance measurement is

not affected by the accuracy with which the temperature of the specimen is

known. Hence, reflectance measurements appear to offer inherently greater ac- curacy than emittance measurements both at short wavelengths and at high temperatures .

Because of these apparent advantages of the reflectance approach, consideration has been given to the design of an integrating sphere ref lectometer

utilizing a continuous -wave gas laser as the illuminating source. The principal difficulty in making high-temperature spectral reflectance measurements

with conventional techniques and apparatus arises from the inability to detect

the dispersed reflected radiation in the presence of a large quantity of un- dispersed radiation emitted by a heated specimen. Even when the incident radiation is modulated (chopped) to facilitate detection, the signal to noise ratio is small unless the incident radiation is extremely intense. Utilizing a gas laser as the source removes this experimental difficulty, since the chopped

flux reflected from the specimen can be of an intensity many orders of magnitude larger than the flux emitted by the specimen. Consequently, the precision

with which the radiation detector can sense the reflected flux is greatly increased and high-precision reflectance measurements at high temperatures should

be possible. To be sure, there are disadvantages encountered in utilizing the

laser as a radiometric source, the principal one being that the high-intensity

output is available only at discrete wavelengths, making it impossible to obtain measurements over a continuous wavelength interval, as is possible with

conventional techniques. Notwithstanding this objection, it seems probable

that this difficulty may at least be partially overcome by future developments

in laser technology.

Even if measurements can be made only at a relatively few discrete wavelengths, the data thus obtained will be valuable. Available evidence indicates

that if no phase transition is encountered, the general shape of the spectral

reflectance curve of a material does not change appreciably with an increase in
temperature. Hence, it should be possible to interpolate between wavelengths

with the aid of continuous spectral reflectance curves obtained at room temperature by more conventional methods.

The basic objectives of the work with lasers are three-fold:

(1) To investigate and evaluate the practicability of utilizing the

continuous -wave gas laser as a radiometric source.

(2) To develop techniques and apparatus for high-precision reflectance

measurements on specular and diffuse specimens at elevated temperatures and at discrete wavelengths.

(3) To investigate coatings and coating techniques for integrating

spheres that will permit operation with this method into the far

infrared portion of the spectrum (from 3 to 15 microns or beyond).

There are many features of the continuous -wave gas laser in addition to

its high monochromaticity and intensity that make the laser desirable as a ra- diometric source. The output can be electronically modulated (chopped), re- moving the necessity for cumbersome mechanical chopping and rectifying assemblies. Outputs are available using various gas combinations at high intensities at discrete wavelengths in the spectral region 0.4 to 40u . These features - and others - will be given close scrutiny and, if possible, the advantages will be exploited to further advance techniques for making thermal

property measurements with greater accuracy, especially at the higher temperatures and the longer wavelengths

One immediate need is for high-accuracy spectral emittance data to further advance the art of optical pyrometry. Recently developed optical pyrometers are capable of high-precision measurement of brightness temperatures.

The accuracy with which these brightness temperatures can be converted to true

temperatures, however, is dependent on a knowledge of emittances at 0.65u. At

present there is no gas system which will lase at this wavelength, but by a series of measurements close to 0.65u, it should be possible to use the appropriate theoretical model to arrive, by interpolation, at an accurate emittance

at the optical pyrometer wavelength.

The integrating sphere technique for measurement of spectral data in the

visible and to 2.5u is well established. Such a sphere is usually coated with

smoked magnesium oxide which has high reflectance (> 95%) in the visible and

near infrared, and is in addition a good diffuser of radiation. The same coating is also used for a reflectance standard. Unfortunately no such coating has been developed for integrating spheres operating at wavelengths longer

than 2.5u. Flowers of sulphur is a possibility but more work is needed. One

of the principal goals in this phase of the program is to select and evaluate

a coating for an integrating sphere for use at long wavelengths.

During the report period a preliminary design was completed for an integrating-sphere ref lectometer to be used with a helium-neon source for measuring the spectral reflectance at 0.635 and 1.15 microns of specimens heated to

high temperatures.
3. SPECTRAL REFLECTANCE EQUIPMENT

Equipment for measurement of spectral reflectance under conditions approximating normal illumination and hemispherical viewing was described in WADC

Technical Report 59-510, Parts II and III. The equipment utilizes a 12 in.

diameter ellipsoidal mirror with the specimen placed at the first focus and the

detector at the second.

During the early part of the contract year construction of a light-tight

cover for the equipment was completed permitting the convenience of operating

the equipment in normal room lighting. Additional modifications were made on

the following features of the apparatus

.

(1) Optical system - mounts were designed and constructed to permit

greater ease in alignment or adjustment of optical components.

(2) Specimen mount - a mounting jig was designed and constructed to

allow convenient removal or installation of specimens; the specimen

holders allowed measurements to be made at various fixed angles of

incidence

.

(3) Detector mount - the method of mounting the detector was modified

with a gear rack and pinion mechanism so that the detector could

be moved between the ellipsoid first and second focus points

.

The principal effort in the past year has been directed toward improvement of the signal-to-noise ratio with the large area (1 cm diam.) Golay detector . It was found that operation of the equipment during the wavelength

scanning process did not yield data of the desired accuracy. The reason for

the poor performance was traced to mechanical vibrations rather than electronic

malfunctions or deficiencies. To eliminate transmission of air-borne vibration

to the cell, the interior surfaces of the light-tight cover were covered with

a 3/4" thick acoustic matting, and to reduce structure-borne vibration, the detector and mount were supported on an 800 pound seismic table which was independent of other parts of the equipment and rested on the floor. Figure 1 is a photograph of the modified equipment. Despite these precautions to isolate the:

Golay detector from external mechanical vibrations, the signal-to-noise ratio

remained unacceptable. Because of these poor results it seemed desirable to

investigate other types of detectors. Two thermopile detectors with 1 cm viewing areas have been ordered and these will be tested in the near future.

Tests on a heated specimen (a white porcelain enamel) were conducted using the Golay cell. The purpose of these tests was to determine the background

level of radiation emitted from the heated specimen that the detector could

withstand without damage from excessive temperature. It was anticipated that

the detector, because of its design, would fail when the specimen reached a moderately high temperature. However, quite surprisingly, the detector failed

when the specimen reached a temperature of only 70°C. Calculations indicated

that this corresponded to a background flux of about 500 microwatts. Such a result demonstrated that the Golay cell cannot be used in this equipment with

heated specimens and this again points to the need for another type of detector,

During the coming year efforts will be directed toward obtaining room-tempera

ture reflectance data on various materials through use of the large-area thermopiles .
Figure 1. Photograph of the infrared ref lectometer with light cover panels removed. The specimen is mounted at the

first focus of the ellipsoidal reflector and the detector at the second focus
4. EQUATIONS RELATING SPECTRAL EMISSIVITY OF METALS TO OTHER PROPERTIES

A summary of the background and current status of this phase of the work

follows. Equations relating the emissivity of metals to their electrical resistivities have been available for many years. The earlier attempts by Hagen and

Rubens have been modified through the years to produce relations that are generally applicable in the longer wavelength and elevated temperature regions.

While this approach to prediction of properties has been very successful for re- strictive conditions, it is not satisfactory for explaining the inflections and

irregularities observed in experimental emissivity and reflectivity data.

A more realistic approach to prediction of the property must consider the

mechanism of the transport process to be characterized by more than one family

of free electrons. Recent publications by Roberts !"l] and T. R. Harrison [2]

have given equations that are applicable or adaptable, including the effects of

several families of free and bound electrons on the transport process . This

classical approach is in harmony with quantum mechanics, as electrons in different energy zones are shown to have different behaviors

.

The equations suggested by Harrison, with terms to provide for the effects

of free and bound electron families, have been considered. Attempts were made

to compute values of the equation parameters from reliable normal spectral re- flectivity values of the metal rhodium at room temperature. As stated in a previous report (WADC TR 58-510 Pt IV), first only one category of free electrons

and one of bound were used. Within the wavelength range of visible radiation a curve obtained in this way gave very creditable agreement with experimental data

and followed the inflection corresponding to a maximum in emittance of about

0.45 micron. In the attempt to extend the range of good fit out to about lOu,

it became evident that additional parameters, making at least 10 in all, would

be required for insertion into more than one term for free electrons and more

than one for bound electrons

.

.

Work will continue on the rhodium data until parameters for proper theorydata comparison can be better determined. Special consideration will be given

to the effect on the parameters due to uncertainties in the reflectivity data.

Optical constants determined from the parameters derived from reflectivity data

will be computed and examined to determine the physical creditability of this

approach

.

With the fraction of total effort on this study that could be devoted to

this aspect, no set of parameters has yet been found that will produce a normal

spectral reflectivity curve which fits the observed data over a wide wavelength

interval both generally and in detail. However the findings have not been negative and show promise that further exploration could produce some useful results .

Several additional attempts to determine the proper parameters for the

theoretical expression using a different approach did not yield any significant

results. It was found impossible to theoretically fit the experimental data in

a general and detailed manner. Further study indicated that the experimental

reflectivity curve for rhodium might be at fault. Hence, the sources of the

rhodium reflectivity data were re-evaluated and several inflection points were

found to be caused by improper smoothing of data that were obtained in different]

6
determinations. Even when the data were readjusted, it was not possible to determine a set of parameters for the expression that provided a detailed match

with the experimental curve. Optical parameters (index of refraction and absorption coefficient) when computed from parameters that gave a general fit proved to

be physically unrealistic. This led to consideration of the Kramers -Kronig dispersion relations which permit calculation of the optical constants from knowledge of the reflectivity over the entire frequency (wavelength) spectrum. At

present a computer program is being developed which will perform these calculations. Further study of this technique reveals that the shape of the reflectivity

curve at very short wavelengths (vacuum ultraviolet) is quite significant. It is

also evident that the shape of the curve (or optical activity) in this region

has an important bearing in predicting the optical constants in other wavelength

regions

It is apparent that special consideration must be given to the reliability

of the reflectivity data at wavelengths in the ultraviolet and below. In this

region, the reflectivity is extremely sensitive to surface conditions. This is a serious consequence since there is not always an abundance of data in this region. This region is of primary significance to our study of optical behavior

in other regions of the spectrum where there is a comparatively large amount of

reliable reflectivity data.

It is expected that work on relation of spectral emissivity to other properties will continue to be only a small fraction of the total effort.

5. CALIBRATION OF WORKING STANDARDS

The platinum, oxidized Kanthal and oxidized Inconel working standards of

normal spectral emittance that had been transmitted to the Physics Laboratory,

Aeronautical Systems Division, in 1962 were returned to the National Bureau of

Standards early in 1963 with a request that the Bureau arrange to distribute

them as requested.

The standards are now offered for sale at a price of $175.00 each, plus a surcharge of $4.00 per gram for the platinum standards. It is anticipated that

the supply of working standards will be augmented from time to time, as required,

by preparation and calibration of additional standards . The sale price of the

standards is intended to cover the replacement cost. They are described in

WADC TR 59-510 Pt IV.

Two types of 0.484 inch diameter disc working standards were prepared for use at R.T.D. during the report period. These were of polished platinum-13%

rhodium alloy and oxidized Inconel, respectively. Preparation of these working

standards is described in the following section.

5.1. Platinum-137o Rhodium Working Standards

The platinum-13% rhodium specimens were received from the fabricator in

the form of 0.035-in. sheet, cut into two strip specimens 1/4 x 8 in. in size

and five discs 0.484 in. in diameter. The original sheet of alloy from which

the specimens were cut was approximately 1 1/16 x 8 in. in size. The 1/4 x 8

in. strips were cut from the two edges of the original sheet, and the discs were cut from the central portion of the remaining strip.
Each specimen was washed in hot tap water to which a commercial detergent

had been added, rinsed in running hot tap water, then in distilled water, and

finally in ethyl alcohol. Rubber surgical gloves were worn at all times while

handling the specimens, and they were touched only at the ends or edges after

cleaning. The specimens were dried in air and placed in a closed container,

supported by the ends or edges only, for storage prior to annealing.

All specimens were annealed in an electric furnace with silicon carbide

heating elements. The strip specimens were hung by means of platinum hooks,

suspended from aluminum oxide rods in the furnace; the disc specimens were supported by the edges only on ceramic forms resting on a rigid ceramic slab. All

of the specimens were then enclosed in a ceramic muffle. Starting with ambient

conditions, the temperature of the furnace was raised to 2282° F (152 3°K) over a period of six hours, and held at that temperature for one hour. The power was then turned off, and the specimens were allowed to cool in the furnace, which

required two days

.

The specimens were removed from the furnace by means of cleaned, platinumtipped tongs and were placed in individual cardboard boxes, supported by the

ends or edges only, to protect them from contamination.

The two 1/4 x 8-in. strips were prepared for measurement by welding a platinum-platinum 107o rhodium thermocouple to each specimen. A shallow groove

was scratched in each specimen, normal to its long axis and located at the midlength. The 10-mil thermocouple wires were separately welded to the specimen

by means of a condenser-discharge type of electronic spot welder. Each wire

was laid in the shallow groove to position it for welding, and the welding operation was observed through a low-power microscope.

Three sets of spectral curves were made for each strip specimen at each

of three temperatures, 800°, 1100° and 1300°K. Each set of curves consisted

of (1) a 1007o curve, obtained when the two blackbody furnaces at the test temperature served as sources for the respective beams, (2) a zero curve, obtained

with the specimen beam blocked near the specimen furnace, and (3) a specimen

curve, obtained with the comparison blackbody at the test temperature as source

for the comparison beam, and the hot specimen at the same temperature serving

as source for the specimen beam. The height of each curve was recorded on punched paper tape at each 0.1 revolution of the wavelength dial over the range

corresponding to approximately 1 to 15 microns

.

The punched paper tape containing the raw emittance data was fed into the

National Bureau of Standards SEAC computer, which then adjusted the recorded

emittance of the specimen at each wavelength on the basis of the recorded 100%

and zero curves

.

The adjusted emittance values for the six measurements, three each on two

specimens, were then fed back into the computer, and the following values were computed at each of the approximately 110 wavelengths: (1) E, the average
emittance (2) jm , the standard deviation— due to error of measurement, computed

as the average standard deviation of the three measurements on each specimen

about the mean for that specimen, and (3) cg

, the standard deviation principally due to differences in specimens.

The values obtained on the platinum-137 rhodium specimens are tabulated

in Table I, and are shown in Figures 2 through 7.

The spectral emittance curves for the plat inum-137o rhodium alloy, shown

in Figure 2 at 800°K, Figure 3 at 1100°K, and Figure 4 at 1300°K, are quite

similar to the corresponding curves for platinum.

1_/ All standard deviations in this study are precisely defined as "estimates

of the standard deviation of the parent population from which the measurements

were drawn." Mathematically

/n n n

; (x-xx)2 + 2 (x-x? ) 2 ... + E (x-x

p

) 2

(n-l)p

where x is an individual measurement, Xi is the average of n measurements

on specimen one, and p is the number of specimens. (For data in this

report, n = 3 in all cases, and p = 2 for platinum-137 alloy and 6 for

oxidised sandblasted Inconel.)

p

1 =

(x-x)a

where x is the overall average of the n x p measurements, n each on p spec imens
i r

.2 5

i i i i i i i r

PLATINUM 13% RHODIUM AT 800 °K

UJO

z .20h

_i .15

(E

.10

.05

o o

"<*>„

J I I L J I I I I L

I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 WAVELENGTH, MICRONS Figure 2. Normal Spectral Emittance of 0.484-in.

Disc Working Standards of Platinum-13%

Rhodium Alloy at 800° K.

The plotted values are averages of six

measured values , three each on two

specimens

.

.05

Figure 3. Normal Spectral Emittance of 0.484-in.

Disc Working Standards of Platinum-13%

Rhodium Alloy at 1100°K.

The plotted values are averages of six

measured values, three each on two

specimens

.

10
.25 -

1 1 1

<boo

o

1 1 1 1 1 1 1 1 1 1 1

PLATINUM 13% RHODIUM AT 1300 °K

o

o

.2 " o

o

o o°0

.15 — °o

°o

.10 ^^nznZm&SlBsP °

05

^^Qbatoayu

5 6 7 8 9 10 WAVELENGTH, MICRONS

J L

12 13 14 15

Figure 4. Normal Spectral Emittance of 0.484-in.

Disc Working Standards of Platinum-137

Rhodium Alloy at 1300° K.

The plotted values are averages of six

measured values, three each on two

specimens

The principal differences are that (1) in general, the emittance of the

platinum- 137, rhodium alloy is higher than that of platinum at the same temperature and at the same wavelength, (2) the maximum at about 1.4 micron at 800°K

is lower for the platinum-13% rhodium alloy than for platinum, (3) the maximum

at about 1.36 micron for platinum and 1100°K has moved to about 1.12 microns

for plat inum-137 rhodium, and (4) no evidence of a maximum at 15 microns or beyond is seen in the platinum-137 rhodium data.

The standard deviations as and <7m

are plotted as a function of wavelength

in Figure 5 at 800°K, Figure 6 at 1100°K, and Figure 7 at 1300°K.

There was considerable scatter in the individual standard deviations, as can be seen in Table I. A statistical technique known as a moving average was used to smooth the data and thus bring out more clearly the trend of t

s and nm

with wavelength. In applying this technique the standard deviations at five

11
adjacent wavelengths were averaged, and the average was plotted as a function

of the wavelength of the center point. In this way an average value was obtained for each wavelength at which data were available, except for the two

shortest and two longest wavelengths

.

In general, the Tm

values show less variation with wavelength than the

TS values. The average values of <jm

were 0.23 at 800°K, 0.19 at 1100°K, and

0.33 at 1300°K, and the corresponding values of ag were 0.25 at 800°K, 0.57

at 1100°K, and 0.91 at 1300°K. However, the ^

g values are based on only two

specimens, and hence are not highly reliable.

.U£U

.01 8 -

1 1 1 1 1 1 1 1 1 1 1 1 1 1 PLATINUM 13% RHODIUM AT 800 °K

.016 - -

.0 14 -

.0 12 -

.010 -

•#

.0 08 • • _

• • DUE TO DIFFERENCES BETWEEN SPECIMENS

.006 • o DUE TO ERROR OF MEASUREMENT

.004

.002 -

i i i i i i i i i i i i i S

6 7 8 9 10 II WAVELENGTH IN MICRONS

12 13 14 15

Figure 5. Spectral Distribution of Two Categories

of Standard Deviations, Each Computed

From Six Measured Emittance Values Obtained at 800°K, Three Each on Two

Specimens of Platinum-137o Rhodium

Alloy.

The upper curve represents standard deviations due to differences in emittance between specimens, identified as <j s in the

text. The lower curve represents standard

deviations due to random error, identified

as am

in the text . In both curves each

point represents the moving average of

five adjacent values.

12
The increase in precision (lower nm values) over what was obtained in the

tests on platinum reported in WADC TR 59-510 Pt IV can be ascribed in part to

the reduction in error due to direct recording of data by the data-processing

attachment as compared to reading the curves with a variable scale.

H .\JC\J

|

]

1

1 1 1 1 1 1 1 1 1 1 1 1 2

UJ2 PLATINUM 13% RHODIUM AT 1100 °K

UJ :oi 8 —

or3

U)<

UJ2

.016 —

UJ .014 _ _

O

2

.012 -

2 •••.-rf\• DUE TO DIFFERENCES BETWEEN SPECIMENS

UJ

u. .0 10 -

o \• •-"XX 2o

.0 08 -

• •*

t-< V.

> .006 — • • _

UJa

a .004 — o

ce % o°°„ • S < ^0 • o o QDUE TO ERROR OF MEASUREMENT „ Q # 2

If)

.002 \ •

1 * 1

1 1 1 1 1 1 1 1 1 1 1 1 1

I 2 3 4 5 6 7 8 9 10 1 1 12 13 14 15 WAVELENGTH IN MICRONS

Figure 6. Spectral Distribution of Two Categories

of Standard Deviations, Each Computed

From Six Measured Emittance Values

Obtained at 1100°K, Three Each on Two

Specimens of Platinum-137 Rhodium

Alloy.

The upper curve represents standard

deviations due to differences in emittance between specimens, identified as

ct s in the text. The lower curve re- presents standard deviations due to

random error, identified as 7 in the

text. In both curves each point re- presents the moving average of five

adjacent values

13
.020

.01 8

< .016

.014

.0 12

.010

.008

'i r ~i i—r —i—

r

PLATINUM 13% RHODIUM AT 1300 °K

~ \

* DUE TO *v

• DIFFERENCES X

.BETWEEN SPECIMENS V,

> .006 f LUa

.004^-

.002 -

• c^o9 _ •

• • • 1* 1

DUE

°o

O

° oo°

L L

TO ERROR

c D °oo<fe o°°

1 1

OF MEASUREMENT

<*>cP^ aasSzta „<

. 1 1 1 _

1 2 3 4 5 6 7 8 9 1

Figure 7

^ cboa3tfOxxcc»Dcc^^xocoP **"L

10 II WAVELENGTH IN MICRONS12 13 14 15

Spectral Distribution of Two Categories

of Standard Deviations, Each Computed

From Six Measured Emittance Values

Obtained at 1300°K, Three Each on Two

Specimens of Platinum-137o Rhodium

Alloy.

The upper curve represents standard

deviations due to differences in emittance between specimens, identified as

j in the text. The lower curve re- presents standard deviations due to

random error, identified as am

in the

text. In both curves each point re- presents the moving average of five

adjacent values

.

5.2. Oxidized Inconel Working Standards

Specimens were cut from 2x8 in. Inconel sheet. Six strips, 1/4 x 8 in.

in size, were cut from the two edges of the sheet, three from each edge.

Twelve discs, 0.484-in. in diameter, were cut from the center of the sheet.

All specimens were marked for identification, and the position and orientation

of each specimen in the original sheet was recorded. The specimens were sandblasted with 60-mesh fused alumina grit and an air pressure of approximately

70 ps i , care being taken to obtain a uniformly rough surface on all specimens.

The sandblasted specimens were cleaned ultrasonically in acetone, passivated

for one minute in 10% nitric acid at 109°F (316°K), rinsed in distilled water

and then in freshly distilled acetone. The cleaned specimens were subjected

to a minimum of handling. When handling was unavoidable, rubber surgical

gloves were worn, and the specimens were touched only by the ends or edges.

The strip specimens were suspended from a metal rack by means of oxidation-resistant metal hooks, and the rack was inserted into a cold furnace.

The disc specimens were supported by the edges only on special ceramic supports placed on the hearth of the furnace, and enclosed in a ceramic muffle.

14
The furnace was brought to 1952° F (1340°K) and held for 24 hours, then dropped

to 1520° F (1100°K) and held for an additional 24 hours, after which the specimens were allowed to cool in the furnace.

The specimens were removed from the furnace by means of cleaned stainless

steel tongs, and were placed in individual plastic holders, in which they were

supported by the ends or edges only. Each plastic holder, containing a specimen, was then placed in an individual cardboard box, to protect the specimen

against contamination.

The six 1/4 x 8 in. strips were prepared for measurement by welding a platinum-platinum 10% rhodium thermocouple to each specimen. A shallow groove

was scratched in each specimen near its midlength and normal to its axis, which

penetrated through the oxide coating to the bare metal. The oxide was also re- moved from each end of the specimen by grinding for a distance of approximately one inch from each end. The thermocouples were welded by a procedure similar to that used for the platinum-137o rhodium specimens.

The normal spectral emittance of each of the six specimens was measured

three times at each of three temperatures, and the data were analyzed statistically, as in the case of the platinum-13% rhodium specimens. The results

are shown in Table II and are plotted as a function of wavelength in Figures 8

through 13.

.9

1 1 1 1

/Soooo0000000(

1 1 1 1

1 1 1 1 1 1 1

o

o

.8

.7

.6 :

OXIDIZED INCONEL AT 800 °K V

.5

.4

.3

- -

.2

.1

1 1 1 1

1 1 1 1 1 1 1 1 1 1 1 5 6 7 8 9 10 WAVELENGTH, MICRONS

12 13 14 15

Figure 8. Normal Spectral Emittance of 0.484-in,

Disc Working Standards of Oxidized

Sandblasted Inconel at 800°K.

The plotted values are averages of 18

measured values, three each on six

specimens

15
1.0

.9

LjO7" .8

<tt-H

?

./ W

-I .6 <

.5

.3 -

~1 I I I

1

'ooooooooooooooocoooaioocca*11"

OXIDIZED INCONEL AT 1100 °K

1 1 1

cocoa,*TM***"

J L J I L

2 3 4 5 6 7 8 9 10 II 12 13 WAVELENGTH, MICRONS

14 15

Figure 9. Normal Spectral Emittance of 0.484-in,

Disc Working Standards of Oxidized

Sandblasted Inconel at 1100°K.

The plotted values are averages of 18

measured values, three each on six

specimens

.

1.0

.9

8

.7

.6

.5

.4

.3

.2

.1

1 1 1 1 1 1 1 1 1 1 1 1

° o o o o o o o o ooo axxt)o<x>aBoa&xpax*3^^ —

o

o

OXIDIZED INCONEL AT 1300 °K

-

I 1 1 1 1 1 1 1 1 5 6 7 8 9 10 WAVELENGTH, MICRONS

12 13 14

Figure 10. Normal Spectral Emittance of 0.484-in,

Disc Working Standards of Oxidized

Sandblasted Inconel at 1300°K.

The plotted values are averages of 18

measured values, three each on six

specimens

.

16
£ .040 z

HI§ .03 6

IE3

< .032

uisu .028 o

z

? .024 u .020

u.o

s, .016 -

< 012 >

ui° .008 Q

K

Q .004 z

<1-

(0

i i I i i i i i i i i r

OXIDIZED INCONEL AT 800 °K

**».

- <%oon

° iooo° O? rf*b(. ocscb

J L J I I I I L J L

I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 WAVELENGTH IN MICRONS

Figure 11. Spectral Distribution of Two Categories

of Standard Deviations , Each Computed

From 18 Measured Emittance Values Obtained at 800° K, Three Each on Six

Specimens of Oxidized Sandblasted

Inconel

The upper curve represents standard

deviations due to differences in emittance between specimens, identified as

rj s in the text. The lower curve re- presents standard deviations due to

random error, identified as Tm

i- n the

text. In both curves, each point re- presents the moving average of five

adjacent values

The general shape of the spectral emittance curves is similar to that

obtained on the previous standards, but the emittance at each wavelength is

somewhat higher. There was a slight increase in emittance with an increase

in temperature at each wavelength.

2/ , 2/

r and a

s~

1100°K in Figure 12, and at 1300°K in Figure 13.

The values of 7m— and a— obtained at 800° K are plotted in Figure 11, at

In general the values of ~

s were somewhat larger than those of a.m : and

showed greater variation with wavelength. The average values of am

were 0.70

at 800°K, 0.59 at 1100°K, and 0.63 at 1300°K, and the corresponding values of

2_/ See footnote 1 on page 9.

17
1— .utu z

w

S

1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

lu .03 6 —

3

OXIDIZED INC0NEL AT 1100 °K 3.032 —

• IDs

•

•

lu .028 o

• z

< •

t- .024 — —

l- • S • w .020 _ •

u.o

• • 2 .016 • • o •••- • • • H •• < .012 > ••^.-vn. : ~

tuo

.008 •**+

o

o00 a °o \

<Q .004 _ ^ooocooooooo^o °^^S^^V° _

<

1- 1

1 1 1 1 1 1 1 1 1 I1

I

1 1 10 1 1 1 1 1 1 1 1 1 1 i 1 1 1 1

I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 WAVELENGTH IN MICRONS

Figure 12 . Spectral Distribution of Two Categories

of Standard Deviations, Each Computed

From 18 Measured Emittance Values Obtained at 1100° K, Three Each on Six

Specimens of Oxidized Sandblasted

Inconel

.

The upper curve represents standard

deviations due to differences in emittance between specimens, identified as

ct s in the text. The lower curve re- presents standard deviations due to

random error, identified as amin the

text. In both curves, each point re- presents the moving average of five

adjacent values.

a s were 0.82 at 800°K, 1.04 at 1100°K, and 1.00 at 1300°K. This is a con- siderable improvement in reproducibility of specimens over what was obtained

in the tests reported in WADC TR 59-510 Pt IV, and is partly due to the

fact that the specimens were cut from adjacent portions of the original

sheet

.

There is also some improvement in precision over the corresponding data

reported in WADC TR 59-510 Pt IV, which can again be ascribed to a reduction

in the reading error due to use of the data-processing attachment.

18
£- .040 z

ui

uj .03 6 K3.032

UJ

.028

.024

.020

.016

.012 -

.008 -

.004 -

~l I I I I

I I

OXIDIZED INCONEL AT 1300 °K

i—

r

0000ooc^rf>M:>c

to

J_

Figure 13.

5 6 7 8 9 10 WAVELENGTH IN MICRONS

12 13 14 15

Spectral Distribution of Two Categories

of Standard Deviations, Each Computed

From 18 Measured Emittance Values Obtained at 1300°K S Three Each on Six

Specimens of Oxidized Sandblasted

Inconel

.

The upper curve represents standard

deviations due to differences in emittance between specimens, identified as a in the text. The lower curve re- presents standard deviations due to

random error, identified as Tm

in the

text. In both curves, each point re- presents the moving average of five

adjacent values

.

6. NORMAL SPECTRAL EMITTANCE EQUIPMENT

During the report period the major effort with the normal spectral emittance equipment has been to extend the wavelength range of satisfactory operation from 1 to 15 microns to 1 to 38 microns or beyond. A cesium bromide

prism and a thermocouple detector with a cesium bromide window were available

for use in the wavelength range of 15 to 40 microns.

The principal problem involved when working in this long wavelength range

is in maintaining a satisfactory signal-to-noise ratio. At a temperature of

800°K the radiant energy, per unit wavelength interval and unit area, emitted

by a blackbody radiator at 15 microns is about 33.6 times that emitted at 40

microns. At 1400°K, this ratio increases to about 43.5. Obviously, in order

to maintain a satisfactory signal-to-noise ratio, the noise will have to be

reduced proportionately. To further complicate the problem, absorption by

19
atmospheric carbon dioxide and water vapor greatly reduce the intensity of the

flux reaching the detector, particularly at wavelengths beyond about 34 micr ons .

In order to maintain a satisfactory signal-to-noise ratio, it was necessary to (a) keep the energy level as high as possible by reducing atmospheric

absorption, and (b) reduce all possible sources of noise to the lowest possible

levels. These sources include (1) Johnson noise in the thermocouple detector,

(2) noise from variable resistance of the rectifier contacts on the chopper

shaft, (3) noise from the preamplifier and amplifier, (4) background radiation

from the chopper blade and interior of the monochromator , and (5) scattered

radiation within the monochromator. Although the latter two tend to be of con- stant intensity, they represent a spurious signal and, hence,- may be considered

as noise.

The Johnson noise, item (1) above, could be reduced by cooling the detector, which was not considered desirable. Significant reduction of noise from

items (2) and (3) would involve major modifications in the electronic circuits

of the equipment, which is considered beyond the scope of the investigation at

this time. Noise from source (4) could be reduced by cooling the entire monochromator, which would make the cesium bromide optical elements particularly

vulnerable to attack by atmospheric moisture. Source (5), scattered radiation

within the monochromator, appeared to be one area where a sizeable reduction

in noise could be achieved without major changes in the equipment.

The two approaches selected to improve the signal-to-noise ratio, especially in the long-wavelength region, were (1) to reduce scattered radiation

within the monochromator as much as possible, and (2) to operate in a moisturefree C02 -free atmosphere.

6.1. Reduction of Scattered Radiation

A special filter kit accessory was purchased for use with the Model 13

spectrophotometer. This consisted of (1) a silver chloride disc, (2) a black

polyetheylene filter, and (3) a calcium fluoride reststrahlen plate. The

silver chloride disc transmits at wavelengths from 4.5 to 28 microns, but is

opaque to radiation of shorter wavelengths. The black polyethylene filter

transmits at wavelengths from 15 to 40 microns, but is opaque at shorter wavelengths. The calcium fluoride reststrahlen plate is a good mirror at wavelengths longer than 22 microns, but scatters radiation of shorter wavelengths.

A special filter holder was built to accommodate the silver chloride disc

and black polyethylene filter. The filter holder was arranged so that either

filter could be inserted or removed from a position immediately in front of

the entrance slit to the monochromator, without opening the optical path to

the atmosphere.

The restrahlen plate was mounted on the movable mirror mount in the monochromator, where it could be inserted or removed by a remote control lever

mounted on the exterior of the monochromator case.

At the time these changes were made, it was decided that two mirrors in

the specimen beam, mounted between the chopper and combining optics, could be

20
removed and thus reduce absorption losses in the specimen beam. In order to

accomplish this, it was necessary to redesign the opaque air-tight cover for

this portion of the optical path.

Several baffles had previously been installed in the monochromator to re- duce as much as possible the stray radiation reaching the detector. The design of these baffles was again examined, and several adjustments and modifications were made to improve their effectiveness.

6.2. Reduction in Atmospheric Absorption

A controlled atmosphere system, using super-dry nitrogen(dew point-100°C)

,

had previously been built for use with the normal spectral emittance equipment. This was found necessary for the attainment of the desired accuracy,

particularly in the spectral regions where the water vapor and carbon dioxide

absorption peaks occur.

The enclosure was designed to permit controlled leakage, so that during a measurement it could be continuously swept out with CQs -free super-dry nitrogen, which was supplied from a cylinder under a slight positive pressure.

With this system it was possible to maintain the relative humidity, as measured with a recording humidigraph, below 57o for periods of several hours at a flow rate of nitrogen of about 2.5 cubic feet per minute. These conditions

were satisfactory while working in the 1 to 15 micron wavelength range. However, serious absorption occurred under these conditions in the 35-40 micron

range

The plastic enclosure to the external optics was redesigned to reduce the

enclosed volume and all joints in the system were sealed to minimize leakage.

A new atmospheric purification system was designed and installed. The new train is shown schematically in Figure 14.

Air from the enclosure reaches the oil-less compressor by a pipe/ not

shown on the diagram. A valve in this pipe is adjusted to provide the desired

resistance to flow, so that a slight positive pressure is maintained in the

instrument enclosure, and a slight vacuum is maintained at the compressor inlet. A needle valve, connected to a tee in the vacuum portion of this line,

is adjusted to provide a controlled leak of room air into the compressor inlet, to compensate for the loss by leakage from the high-pressure portion of

the system. The loss is approximately 15 cubic feet per hour (CFH) , out of

approximately 185 CFH that is being circulated.

Air from the compressor goes to a tank that serves as a ballast for the

system. Air from the tank, at a pressure of about 75 psi, is fed through the coarse air filter (2), and air filter (6), where coarse dust and condensed liquid are removed. The pressure is then reduced to about 60 psi by the pressure regulator (7), and fed through the silica gel drying tower (10), Ascarite

carbon dioxide absorbent (11), the molecular sieve water filter (12), oil filter (14), and dust filters (15) and (16). The pressure drops from about 60 psi

to about 10 psi in passing through these units. A second pressure regulator

(18), is used to decrease the pressure to a few ounces per square in., after

which the air passes through a surge tank (20), and flow meter (21), and into

the instrument enclosure.

21
--HW- -c

£

« ©

^

^7

I c*

N. ^

Figure 14. Schematic Diagram of Atmosphere Purification System,

1. Air inlet from compressor and storage tank.

2. Coarse air filter. 3. Purge valve.

4. Combination temperature and pressure gage.

5. Valve. 6. Air filter. 7. Pressure regulator. 8. Gage, combination pressure and temperature. 9. Safety relief valve. 10. Water

filter - silica gel. 11. Carbon dioxide filter, Ascarite. 12. Water filter, molecular

sieve. 13. Moisture indicator. 14. Oil filter. 15. Dust filter, 11-15 micron.

16. Dust filter, 2-5 micron. 17. Gage, pressure, 0-30 psi, 18. Pressure regulator.

19. Gage, pressure, 0-15 psi. 20. Surge

tank. 21. Flow meter. 22. Discharge to

spectrometer enclosure.

The manufacturer of the drying towers used in this system indicated

that the dew point of the air entering the instrument enclosure should be

below -100° C. The humidity within the enclosure was below that measured by

the recording humidigraph.

22
Tests with the equipment have indicated that the water vapor absorption

peaks do not disappear until the equipment has been purged for several hours, even though the humidity of the atmosphere in the enclosure, as measured with

the humidigraph, drops quite rapidly. It is believed that the continued presence of these peaks may be due to films of water vapor, adsorbed on optical

elements and other surfaces within the enclosed volume, which require appreciable time for removal. Because of the relatively long period required for

purging, it is considered desirable to maintain the dry atmosphere continuously, except when the enclosure must be opened to permit adjustment of the

equipment or insertion of a new specimen.

The drying capacity of the system becomes exhausted in less than 24 hours

of operation. Most of the moisture and carbon dioxide enters the system with

the air admitted through the controlled leak. An automatically-cycled laboratory air dryer has been ordered to supply predried air to this leak, which

should remove at least 957 of the load from the silica gel drying tower

(10. in Figure 14) in the main purification train, and correspondingly lengthen the periods between recharges .

7. DATA -PROCESSING ATTACHMENT

The manufacturer of the data-processing attachment to the normal spectral

emittance equipment sent an engineer to the Bureau to correct the malfunctions

that had been noted. These malfunctions consisted primarily of unstable circuits which resulted in drift from the calibration settings of potentiometers

controlling corrections for zero-line and 100%-line errors. The trouble was found to be in the digital portions of the circuits, and was corrected. A

mechanical difficulty, binding of the gears in the correcting potentiometer

drive mechanism, was also found and corrected.

7.1. Computer Code for Making Corrections

Following these adjustments, the data-processing attachment operated satisfactorily for a time, after which intermittent trouble developed in the

automatic correction circuits. However, it was established that the attachment correctly recorded, on punched paper tape, the zero curve, 100% curve,

and specimen curve. A program for the Bureau's SEAC computer was therefore

designed by means of which the corrected spectral emittances could be computed

from the values that had been recorded on punched paper tape. Use of the

data-processing attachment and the computer in this way greatly reduced the

time .required in obtaining useful data with the normal spectral emittance

equipment

7.2. Errors in Correction Circuits

The errors in the correction circuits were difficult to locate and correct. During a calibration run the pulses, produced by the analog-to-digital

converter on the recorder pen shaft, are recorded on magnetic tape. During a subsequent specimen run the magnetic tape is played back synchronously and the

pulses are read from the tape, amplified, and used to drive a "100% line" and

a "zero line" potentiometer up and down scale by means of separate multistable

vibrator circuits which actuate reversible ratchet motors. The pulses appeared

23
to be recorded on the magnetic tape satisfactorily, but did not drive the potentiometers up and down scale as required to make the corrections.

The manufacturer sent the engineer who had designed the data-processing

attachment to the Bureau, in an effort to find and correct the remaining difficulties .

Plug-in amplifiers of a new design were installed. These amplify the

pulses from the tape, and the outputs drive the ratchet motors. The equipment

then appeared to operate satisfactorily for short periods of time, but over

the 30-minute period required for a complete scan of the spectrum, errors ac- cumulated that exceeded the design specifications. These errors could be due

to missed pulses, or spurious pulses (the overall effect of a missed positive

pulse or a spurious negative pulse would be the same)

.

A check of the ratchet motor circuits revealed some weak components,

which were replaced, but errors still persisted.

A check of the tape amplifiers indicated that at times the signal

strength was weak. The amplifiers were redesigned for more gain, and adjusted

for optimum response to the recording tape being used. The basic problem of

accumulation of errors over periods of 15 minutes or more was not eliminated.

It was noted that spurious signals were produced when the tape heads were

touched. This was attributed to insufficient grounding of the tape heads.

The mounting plate containing the tape heads was insulated from ground, and

the heads themselves were connected to the ground lead of the amplifiers, in

order to provide an adequate ground without the possibility of ground loop

pick-up. This change improved operation of the equipment, but did not eliminate completely the spurious counts.

A finite time is required to actuate the stepping motors . If two pulses occur within a time interval shorter than the "dead time", the second pulse is

lost. On long runs many of the pulses occur due to random backward or forward

steps of only one pulse, which can occur rather rapidly if the recorder pen

chatters . In order to reduce this rapid random correction, a buffer register

was introduced between the amplifier and stepping motor, which resulted in the

stepper motor not having to step for the first forward or reverse signal following a change in direction (the motor did step for the second and all subsequent pulses in one direction, however). This buffer register reduced the operation of the stepper motors by 60 to 807o , but the accumulated errors still

persisted

.

The pen position counter was temporarily connected to the output of the

read amplifier, to follow the pulses at electronic speed. This was done to

determine whether the errors were due to the steppers being unable to follow

the pulses from the tape, or were due to failure to properly record the pulses

on the tape originally. The count showed that the steppers were accurately

following the pulses on the tape, indicating that the trouble probably originated in the recording circuits

.

24
Observation of the output of the two recording multivibrators showed apparent spurious pulses . The multivibrators were adjusted by increasing the

safety margin against spurious triggering, and by reducing the output impedance. Operation was improved, but the accumulated errors still exceeded specification limits.

The buffer register was moved from between the read amplifier and stepping

motor to between the pen analog-to-digital converter and the write multivibrator. The effect of this change was to prevent the extra pulses from being recorded, rather than to record them and then eliminate them before they reached

the stepper motor. After this change was made, the equipment operated satisfactorily .

7.3. Computation of 100 Selected Ordinates

The rigorous method of computing normal spectral emittance from spectral

data may be expressed mathematically as follows:

ts

i w E , dX

o bX sX

o bX

dX

(3)

where E^g

e bX

•sX

total normal emittance of specimen

rate of blackbody energy emission (radiant flux)

per unit area, unit solid angle and unit wavelength

interval, within the wavelength interval X to

(X + dX), at temperature T

normal spectral emittance of specimen at wavelength

X and temperature T.

However, all computations from data are based upon finite wavelength intervals, t\X . The following equation applies to such computations:

E ti

^2

2 ^bXE SX^X

Li

S e b\AX

Xi

(4)

Xi and X2 being selected to include substantially all of the flux

emitted by a blackbody radiator at the test temperature T.

In the weighted ordinate method uniform values of AX are used, and each

value of E s\ must be weighted by a factor proportioned to sbX' This value of

ehX represents the flux emitted per unit area, unit solid angle and within the

wavelength interval X and (X + AX), by a blackbody at the test temperature, T.

In the 100-selected ordinate method, the area under the spectral distribution curve for the radiant flux per unit area and unit solid angle emitted

by a blackbody radiator at the test temperature T is divided vertically into

25
100 slices of equal area. The 100 selected ordinates are then the 100 median

wavelengths of the 100 areas. In this case A\ varies, but the quantity p b\k\

is held constant at 0.01 Under these conditions, equation (2) can be re- written:

E ts = 0.01 S

10G

E sX (5)

In practice any desired degree of precision in the computation of E ts can be attained by either the weighted ordinate method or the selected ordinate method, by taking a large enough number of ordinates. With any given

number of ordinates, the computation error will be smaller by the selected or- dinate method than by the weighted ordinate method. With solids, whose spectral emittance curves do not normally have sharp peaks or valleys, the 100-

selected ordinate method gives values that have no significant computation

error from this source.

The wavelengths representing the 100 selected ordinates referred to

above were computed for temperatures of 600°, 700°, 800°, 900°, 1000°, 1100°,

1200°, 1300° and 1400°K, and are given in Table 3.

The 100 selected ordinates for temperatures of 800°, 1100°, 1300° and

1400° K were converted to digital form and punched on paper tape for use with

the data-processing attachment for computation of total normal emittance during measurement of normal spectral emittance

.

8. SUMMARY AND FUTURE PLANS

Preliminary design was completed for an integrating sphere ref lectometer

for use with a continuous -wave gas laser as the source. Future plans include

(1) construction of the ref lectometer and procurement of a helium-neon laser

source, a detector-amplifier-recorder system and other accessory items, (2)

initial calibration and operation of the equipment at wavelengths of 0.632 and

1.15 microns, at which the helium-neon laser operates, and for which suitable

sphere coatings are available, and (3) eventual development of suitable sphere

coatings for operation over an extended wavelength range, from the ultraviolet

down to perhaps 0.25 micron into the infrared to at least 3.39 microns where

the helium-neon laser operates, and procurement of one or more additional

lasers to operate at wavelengths in this range.

Extensive tests with the ellipsoidal mirror ref lectometer have led to the

conclusion that the Golay cell detector is not suitable for use with this equipment. A new large-area thermopile has been ordered. Future plans include calibration of the ref lectometer and operation in the wavelength range of approximately 1 to 15 microns.

Attempts to fit parameters to the Roberts equations for the emissivity

of rhodium have so far been unsuccessful. A small amount of additional work

will be done to conclude this phase of the investigation.

26
Specimens of platinum- 13% rhodium alloy and oxidized Inconel were prepared and calibrated for use as standards of normal spectral emittance over

the wavelength range of approximately 1 to 15 microns.

A number of modifications were made in the normal spectral emittance

equipment to facilitate operation in the 15 to 38 micron range. These included (1) use of special filters to reduce scattered radiation, and (2)

construction of a special atmosphere purification system to reduce absorption

by COg and H2 0. Future plans include procurement of a more sensitive thermocouple detector and calibration of working standards of normal spectral emittance in this wavelength range.

The data -processing attachment has continued to give trouble. When one difficulty is corrected, another soon develops. It is believed that at least

part of this can be ascribed to the fact that this was the pilot model of the

data-reduction system. Many of the weaknesses that have been found have been

corrected in the production model. It is hoped that it will be possible to

exchange the present attachment for one of current production.

The wavelengths for use in the 100-selected-ordinate method of computing

total normal emittance from normal spectral emittance curves were computed for

temperatures at 100° intervals from 600° to 1400°K.

27
TABLE 1

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 800°

K

Wavelength Emittance— ^m ^s~

Microns X100 X100 X100

1.18 24.2 .16 .19

1.25 25.5 .49 .26

1.33 26.1 .29 .94

1.40 26.2 .30 .90

1.48 25.2 .15 1.06

1.58 23.7 .23 .97

1.68 22.1 .30 .78

1.81 20.6 .18 .73

1.98 19.2 .24 .64

2.23 17.7 .36 .42

2.51 16.5 .34 .33

2.73 15.4 .29 .26

2.92 14.7 .29 .07

3.14 13.8 .38 .05

3.35 13.2 .27 .07

3.56 12.6 .20 .14

3.77 12.2 .20 .26

3.98 11.7 .16 .19

4.20 11.3 .15 .38

4.41 11.0 .33 .14

4.58 10.8 .26 .19

4.76 10.5 .27 .19

4.91 10.2 .23 .31

5.07 10.1 .23 .35

5.21 9.9 .20 .21

5.34 9.7 .27 .31

5.47 9.7 .17 .42

5.60 9.5 .22 .40

5.76 9.3 .22 .40

5.90 9.1 .09 .45

6.04 8.9 .15 .40

6.16 8.7 .20 .35

6.28 8.7 .15 .28

6.41 8.6 .16 .31

6.53 8.6 .21 .24

2/

28
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM-13% RHODIUM WORKING STANDARDS AT 800°

Wavelength IT «-- l/ Emittance- 2/

XlOO

2/

^s~

Microns XlOO XlOO

6.64 8.5 .33 .31

6.76 8.4 .22 .33

6.87 8.4 .16 .38

6.97 8.4 .21 .42

7.07 8.4 .20 .28

7.19 8.3 .21 .40

7.32 8.2 .18 .47

7.44 8.2 .15 .40

7.56 8.1 .19 .45

7.66 8.0 .12 .49

7.77 8.0 .20 .33

7.88 7.9 .21 .35

7.98 7.9 .15 .35

8.08 7.9 .23 .33

8.18 7.8 .23 .26

8.28 7.8 .24 .28

8.38 7.9 .24 .33

8.47 8.0 .31 .12

8.57 8.0 .22 .19

8.66 8.0 .23 .26

8.75 8.1 .22 .14

8.84 8.1 .26 .16

8.93 8.1 .17 .24

9.01 8.0 .13 .12

9.10 8.0 .18 .19

9.18 8.1 .23 .33

9.26 8.1 .24 .16

9.35 8.6 .25 .02

9.43 9.1 .25 .02

9.51 9.4 .13 .05

9.67 9.3 .16 .26

9.83 8.6 .31 .21

10.00 8.1 .14 .19

10.15 7.8 .24 .19

10.30 7.6 .24 .19

29
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 800°

K

Wavelength Emittance - 2/

XIOO

2/

Microns xioo XIOO

10.46 7.3 .23 .07

10.61 7.2 .31 .14

10.76 7.1 .15 .09

10.91 7.0 .34 .14

11.05 7.0 .29 .16

11.19 6.9 .23 .24

11.32 6.8 .25 .16

11.45 6.8 .18 .05

11.58 6.6 .30 .16

11.72 6.6 .14 .14

11.84 6.5 .19 .09

11.97 6.6 .24 .26

12.09 6.4 .39 .21

12.22 6.5 .20 .12

12.35 6.4 .22 .12

12.48 6.4 .24 .12

12.60 6.2 .18 .12

12.72 6.2 .16 .09

12.85 6.2 .20 .16

12.98 6.2 .17 .19

13.10 6.2 .18 .09

13.22 6.2 .23 .05

13.34 6.0 .30 .09

13.46 6.0 .23 .05

13.58 6.0 .19 .09

13.69 5.9 .23 .09

13.81 5.9 .28 .12

13.93 5.8 .17 .07

14.03 5.8 .32 .26

14.14 5.8 .30 .24

14.25 5.7 .26 .21

14.36 5.7 .27 .19

14.47 5.7 .22 .14

14.58 5.6 .41 .09

14.68 5.5 .31 .09

30
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM-13% RHODIUM WORKING STANDARDS AT 800°

Wavelength Emittance 1/

XlOO

a y

Microns XlOO XlOO

14.79 5.6 .27 .02

14.90 5.6 .33 .07

15.01 5.7 .22 .02

15.11 5.6 .26 .07

1/ Average of 6 measured values^ three each on two specimens

2/ See footnote 1 on page 9 in the text.

31
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 1100°

K

2/

Wavelength

1/ Emittance- 2/ 2

CTs Microns X100 X100 xioo

1.07 23.1 .45 .14

1.12 23.3 .47 .24

1.18 23.1 .48 .02

1.25 22.5 .56 .14

1.33 22.3 .50 .24

1.40 21.8 .39 .09

1.48 21.3 .37 .02

1.58 20.7 .37

1.68 20.0 .34 .02

1.81 19.1 .29 .07

1.98 18.5 .26 .16

2.23 17.7 .29 .21

2.51 16.8 .24 .16

2.73 16.1 .17 .14

2.92 15.7 .22 .38

3.14 15.0 .27 .54

3.35 14.6 .34 .61

3.56 14.2 .38 .61

3.77 13.9 .34 .94

3.98 13.5 .35 1.11

4.20 13.1 .23 1.06

4.41 12.7 .16 1.15

4.58 12.5 .16 1.11

4.76 12.2 .21 1.13

4.91 12.0 .21 1.13

5.07 11.8 .10 1.13

5.21 11.6 .14 1.23

5.34 11.4 .20 1.15

5.47 11.2 .18 1.18

5.60 11.0 .24 1.30

5.76 10.9 .13 1.15

5.90 10.7 .12 1.06

6.04 10.5 .18 .97

6.16 10.5 .13 .94

6.28 10.4 .13 .94

32
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 1100°

1/ 2/ 2/

Wavelength Emittance

XlOO

°s

Microns XlOO •XlOO

6.41 10.3 .18 .99

6.53 10.1 .12 .75

6.64 10.0 .17 .80

6.76 9.8 .18 .78

6.87 9.8 .08 .94

6.97 9.6 .14 .94

7.07 9.6 .13 1.08

7.19 9.5 .22 1.04

7.32 9.5 .17 .99

7.44 9.4 .18 1.01

7.56 9.4 .20 1.01

7.66 9.3 .15 .97

7.77 9.2 .15 .94

7.88 9.2 .09 .92

7.98 9.1 .13 .94

8.08 9.0 .19 .90

8.18 9.1 .19 .90

8.28 9.1 .15 .80

8.38 9.0 .09 .82

8.47 9.1 .08 .90

8.57 9.2 .12 .78

8.66 9.2 .11 .87

8.75 9.3 .08 .75

8.84 9.2 .15 .73

8.93 9.2 .06 .73

9.01 9.3 .11 .68

9.10 9.3 .08 .61

9.18 9.2 .12 .64

9.26 9.2 .16 .66

9.35 9.3 .15 .68

9.43 9.7 .11 .73

9.51 10.0 .18 .52

9.67 10.2 .07 .42

9.83 9.8 .12 .31

10.00 9.4 .19 .31

33
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM-13% RHODIUM WORKING STANDARDS AT 1100°

K

Wavelength Emittance— 2/

CTm

XlOO

2

^s

Microns XlOO XlOO

10.15 9.0 .31 .35

10.30 8.6 .20 .28

10.46 8.4 .24 .54

10.61 8.4 .20 .52

10.76 8.2 .10 .42

10.91 8.1 .19 .40

11.05 8.0 .19 .38

11.19 7.8 .14 .38

11.32 7.8 .15 .54

11.45 7.7 .11 .61

11.58 7.6 .14 .54

11.72 7.5 .21 .45

11.84 7.4 .16 .33

11.97 7.4 .15 .47

12.09 7.3 .06 .40

12.22 7.3 .08 .38

12.35 7.2 .15 .42

12.48 7.2 .10 .49

12.60 7.2 .08 .38

12.72 7.1 .08 .26

12.85 7.0 .17 .26

12.98 7.0 .11 .24

13.10 6.9 .11 .38

13.22 6.9 .04 .16

13.34 6.9 .17 .21

13.46 6.9 .13 .19

13.58 6.8 .08 .05

13.69 6.8 .09 .14

13.81 6.7 .13 .16

13.93 6.8 .11 .26

14.03 6.6 .22 .19

14.14 6.6 .14 .21

14.25 6.5 .22 .05

14.36 6.5 .20 .31

14.47 6.4 .19 .19

34
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM-13% RHODIUM WORKING STANDARDS AT 1100°

1/ 2/ 2/

Wavelength Emittance <^m XlOO

cr s Microns XlOO XlOO

14.58 6.5 .16 .12

14.68 6.5 .22 .28

14.79 6.5 .17 ;19

14.90 6.4 .14 .19

15.01 6.4 .25 .21

15.11 6.4 .37 .31

1/ Average of 6 measured values, three each on two specimens

2/ See footnote 1 on page 9 in the text.

35
TABLE 1 cont'd

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 1300°

K

Wavelength Emittance

Microns X100

1.07 25.4

1.12 25.2

1.18 24.7

1.25 24.3

1.33 23.7

1.40 23.1

1.48 22.6

1.58 22.0

1.68 21.2

1.81 20.4

1.98 19.7

2.23 18.7

2.51 18.0

2.73 17.3

2.92 16.6

3.14 16.2

3.35 15.9

3.56 15.3

3.77 15.0

3.98 14.6

4.20 14.4

4.41 14.0

4.58 13.8

4.76 13.7

4.91 13.3

5.07 13.2

5.21 12.9

5.34 12.8

5.47 12.7

5.60 12.5

5.76 12.3

5.90 12.1

6.04 11.9

6.16 11.6

6.28 11.6

1/ 2/

X100

1.07

.94

.87

.68

.43

.40

.30

.29

.24

.43

.29

.39

.41

.32

.23

.21

.16

.15

.23

.26

.25

.23

.26

.31

.23

.26

.27

.18

.18

.19

.25

.21

.25

.29

.31

2/

X100

28

,14

02

,12

.02

.02

.19

.28

.19

.38

.40

.57

.57

.59

.75

.97

.87

1.06

1.11

1.3.8

1.30

1.53

1.65

1.72

1.81

1.77

1.74

1.74

1.65

1.70

1.60

1.63

1.60

1.65

36
TABLE 1 cont'd

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 1300°

Wavelength Emittance

Microns X100

6.41 11.6

6.53 11.3

6.64 11.2

6.76 11.1

6.87 11.0

6.97 10.9

7.07 10.8

7.19 10.8

7.32 10.7

7.44 10.7

7.56 10.6

7.66 10.4

7.77 10.4

7.88 10.4

7.98 10.4

8.08 10.4

8.18 10.3

8.28 10.3

8.38 10.2

8.47 10.2

8.57 10.2

8.66 10.2

8.75 10.2

8.84 10.3

8.93 10.2

9.01 10.3

9.10 10.2

9.18 10.2

9.26 10.2

9.35 10.2

9.43 10.2

9.51 10.5

9.67 10.9

9.83 11.0

10,00 10.5

1/ 2/ 2/

X100

36

,38

,29

,38

,27

,22

,20

,15

,13

,22

,18

,28

,24

,13

,25

,27

,29

,19

,19

,20

,15

,17

.17

.19

.17

.18

.22

.15

.15

.16

.13

.10

.12

.10

.12

X100

1.86

1.67

1.63

1.65

1.65

1.65

1.56

1.46

1.60

1.56

1.58

1.63

1.53

1.53

1.63

1.60

1.44

1.39

1.48

1.46

1.34

1.37

1.41

1.32

1.34

1.34

1.23

1.18

1.18

1.30

1.25

1.20

1.06

.99

1.06

37
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 1300°

K

2/ Wavelength Emittance — 2/

°m

XlOO

as

_ Microns XlOO XlOO

10.15 10.0 .27 1.04

10.30 9.7 .20 .92

10.46 9.5 .33 1.04

10.61 9.2 .15 .97

10.76 9.1 .15 .97

10.91 9.0 .08 .75

11,05 8.9 .12 .78

11.19 8.8 .16 .85

11.32 8.7 .25 .80

11.45 8.5 .09 .85

11.58 8.5 .09 .73

11.72 8.4 .17 .71

11.84 8.3 .14 .66

11.97 8.2 .19 .59

12.09 8.0 .20 .68

12.22 8.1 .09 .57

12.35 8.0 .15 .57

12.48 7.9 .13 .47

12.60 7.8 .20 .45

12.72 7.8 .16 .21

12.85 7.7 .15 .24

12.98 7.6 .14 .28

13.10 7.5 .11 .19

13.22 7.5 .17 .26

13.34 7.5 .28 .33

13.46 7.4 .19 .05

13. S8 7.3 .17 .21

13.69 7.2 .12 .16

13.81 7.3 .15 .02

13.93 7.3 .15 .16

14.03 7.2 .18 .16

14.14 7.2 .16 .02

14.25 7.2 .13 .05

14.36 7.1 .11 .02

14.47 7.2 .16

38
TABLE 1 cont'd.

NORMAL SPECTRAL EMITTANCE OF

PLATINUM- 13% RHODIUM WORKING STANDARDS AT 1300°

Wavelength

Microns X100 X100

Emittance

1/ 2/

7.0 .16

7.2 .21

7.1 .16

7.0 .23

7.2 .19

2/

14.58 7.0 .16 .09

14.68 7.2 .21 .07

14.79 7.1 .16 .05

14.90 7.0 .23 .07

15.01

15.11 7.2 .18 .05

1/ Average of 6 measured values, three each on two specimens

2/ See footnote 1 on page 9 in the text.

39
TABLE 2

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 800°

K

Wavelength

1/

Emittance

2/ am

XlOO

< 2/

7 —

S Microns XlOO XlOO

1.18 82.0 .77 1 .84

1.25 83.5 .88 1 .19

1.33 84.5 .97 1 .53

1.40 85.1 .70 1 .67

1.48 85.1 .82 1 .59

1.58 84.7 .85 1 .50

1.68 84.2 .58 1 .60

1.81 83.9 .66 1 .55

1.98 83.5 1.07 1 .66

2.23 84.5 .81 1 .22

2.51 83.3 .81 .98

2.73 83.2 .85 .88

2.92 82.8 .83 .88

3.14 82.7 .66 .78

3.35 82.6 .56 .73

3.56 82.5 .56 .75

3.77 82.4 .63 .76

3.98 82.1 .70 .89

4.20 82.1 .58 .93

4.41 82.1 .66 .76

4.58 82.1 .68 .65

4.76 81.9 .50 .61

4.91 81.7 .67 .64

5.07 81.6 .80 .39

5.21 81.7 .77 .45

5.34 81.6 .93 .52

5.47 81.6 .85 .52

5.60 81.5 .87 .55

5.76 81.3 .72 .64

5.90 81.3 .66 .67

6.04 81.3 .81 .58

6.16 81.1 .65 .58

6.28 81.1 .83 .48

6.41 81.1 .66 .55

6.53 81.1 .63 .57

40
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 800°

Wavel ength

Microns

6. 64

6. 76

6. 87

6. 97

7. 07

7. 19

7. 32

7. 44

7. 56

7. 66

7. 77

7. 88

7. 98

8. 08

8. 18

8 28

8 38

8 47

8 57

8 .66

8 .75

8 .84

8 .93

9 .01

9 .10

9 .18

9 .26

9 .35

9 .43

9 .51

9 .67

9 .83

10 .00

10 .15

10 .30

1/ Emittance —

m

XlOO

s XlOO XlOO

81.1 .65 .49

81.3 .63 .47

81.5 .62 .47

81.8 .76 .55

82.1 .70 .49

82.8 1.40 .80

82.8 .55 .59

83.1 .73 .60

83.3 .66 .61

83.6 .64 .56

83.9 .67 .60

84.2 .66 .61

85.0 .62 .66

85.9 .67 .60

86.5 .67 .62

87.1 .62 .64

87.5 .57 .65

87.5 .70 .75

87.7 .66 .80

87.9 .70 .84

88.1 .81 .95

88.2 .67 .88

88.4 .61 .92

88.4 1.60 1.15

88.9 1.04 .83

89.1 .73 .80

89.3 .78 .83

89.4 .72 .82

89.2 ;68 .73

88.8 .73 .76

88.4 .68 .82

88.3 .67 .80

88.3 .68 .72

88.6 .60 .75

88.9 .50 .82

41
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 800°

K

Wavelength Emittance—

m

XlOO

2

Microns XlOO XlOO

10.46 89.4 .56 .84

10.61 89.5 .78 .98

10.76 89.7 .74 .93

10.91 90.0 .57 .74

11.05 90.2 .73 .71

11.19 90.5 .57 .81

11.32 90.6 .64 .81

11.45 90.7 .79 .87

11.58 90.8 .67 .85

11.72 91.1 .67 .75

11.84 91.3 .65 .67

11.97 91.5 .57 .78

12.09 91.6 .68 .81

12.22 91.8 .77 .76

12.35 92.0 .70 .77

12.48 92.4 .64 .80

12.60 92.9 .60 .89

12.72 93.0 .65 .95

12.85 93.3 .68 .89

12.98 93.4 .55 .80

13.10 93.8 .52 .83

13.22 94.1 .53 .79

13.34 94.2 .59 .81

13.46 94.3 .59 .90

13.58 94.4 .59 .84

13.69 94.3 .61 .86

13.81 94.0 .61 .80

13.93 93.3 .53 .85

14.03 91.7 .59 .85

14.14 89.8 .67 .82

14.25 87.6 .69 .86

14.36 85.2 .79 .91

14.47 82.8 .79 .92

14.58 80.5 .74 .92

14.68 78.2 .70 .87

42
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 800°

1/ 2/ 2/ Wavelength Emittance— o^ a^~

Microns X100 X100 X100

14.79 75.9 .72 .91

14.90 73.9 .61 .84

15.01 72.3 .79 .89

15.11 70.8 .57 .89

1/ Average of 18 measured values, three each on six specimens

2/ See footnote 1 on page 9 in the text.

43
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1100°K

Wavelength Emittance— <% as Microns X100 X100 X100

1.07 89.4 1.10 3.13

1.12 89.5 .80 3.28

1.18 89.4 .76 3.17

1.25 89.3 .59 3.17

1.33 89.1 .57 2.87

1.40 88.9 .55 2.75

1.48 88.6 .66 2.51

1.58 88.1 .70 2.31

1.68 87.7 .77 2.05

1.81 87.4 .59 1.69

1.98 86.9 .50 1.61

2.23 86.7 .52 1.43

2.51 86.3 .55 1.53

2.73 85.7 .59 1.44

2.92 85.5 .60 1.48

3.14 85.4 .52 1.41

3.35 85.2 .53 1.36

3.56 85.0 .53 1.36

3.77 84.9 .58 1.25

3.98 84.8 .59 1.19

4.20 84.6 .66 1.11

4.41 84.5 .52 .92

4.58 84.4 .55 1.01

4.76 84.4 .60 .97

4.91 84.2 .81 1.32

5.07 84.3 .60 1.22

5.21 84.4 .63 1.17

5.34 84.5 .56 1.10

5.47 84.6 .53 1.11

5.60 84.5 .54 .97

5.76 84.0 1.21 1.45

5.90 83.9 .97 1.12

6.04 84.0 .78 .97

6.16 83.8 .69 .87

6.28 83.9 .54 .90

44
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1100°K

Wavelength Emittance— 2/

XlOO

2

Microns XlOO XlOO

6.41 84.0 .61 .93

6.53 83.9 .51 .95

6.64 84.0 .51 .99

6.76 84.2 .57 .99

6.87 84.6 .64 1.03

6.97 84.8 .52 .95

7.07 85.0 .55 .91

7.19 85.2 .53 .87

7.32 85.3 .47 .80

7.44 85.4 .46 .70

7.56 85.6 .44 .67

7.66 85.7 .50 .60

7.77 86.0 .50 .69

7.88 86.2 .57 .67

7.98 86.7 .51 .77

8.08 87.1 .49 .74

8.18 87.6 .51 .56

8.28 88.0 .62 .54

8.38 88.4 .49 .59

8.47 88.6 .53 .56

8.57 88.7 .62 .48

8.66 88.9 .50 .51

8.75 88.9 .57 .45

8.84 89.0 .64 .51

8.93 89.3 .46 .50

9.01 89.4 .42 .60

9.10 89.5 .43 .65

9.18 89.7 .38 .73

9.26 89.8 .44 .74

9.35 89.9 .47 .72

9.43 90.0 .49 .62

9.51 90.0 .62 .47

9.67 89.8 .58 .27

9.83 89.9 .50 .33

10.00 89.9 .53 .44

45
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1100°

K

Wavelength Emittance— 2/

Microns XlOO X100 XlOO

10.15 90.0 .39 .48

10.30 90.1 .39 .49

10.46 90.2 .47 .45

10.61 90.4 .54 .48

10.76 90.7 .46 .65

10.91 90.9 .38 .71

11.05 91.2 .43 .60

11.19 91.4 .42 .45

11.32 91.6 .47 .33

11.45 91.6 .54 .37

11.58 91.9 .50 .42

11.72 92.1 .37 .53

11.84 92.2 .33 .53

11.97 92.3 .58 .47

12 . 09 92.5 .57 .41

12.22 92.7 .59 .45

12.35 93.0 .59 .43

12.48 93.2 .52 .53

12.60 93.5 .44 .65

12.72 93.7 .48 .62

12.85 93.8 .53 .57

12.98 94.0 .61 .55

13.10 94.4 .56 .52

13.22 94.9 .62 .71

13.34 95.1 .51 .77

13.46 95.3 .51 .70

13.58 95.4 .63 .64

13.69 95.4 .71 .67

13.81 95.4 .59 .62

13.93 95.4 .46 .71

14.03 95.3 .38 .94

14.14 94.8 .37 1.11

14.25 93.8 .42 1.16

14.36 92.4 .66 1.44

14.47 90.9 .70 1.52

46
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1100°

Wavelength

Microns

14.58

14.68

14.79

14.90

15.01

15.11 80.3 4.68 3.36

Emittance 1/ 2/

XlOO

2

Ss~

XlOO XlOO

89.1 .58 1.57

87.3 .53 1.65

85.4 .48 1.80

83.3 .49 1.89

81.3 .63 2.04

1/ Average of 18 measured values, three each on six specimens

2/ See footnote 1 on page 9 in the text.

47
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1300°

K

Wavelength 1/ Emittance- 2/ a —

m XlOO

v -2

s Microns XlOO XlOO

1.07 91.7 1.57 2.87

1.12 91.4 1.59 2.68

1.18 91.2 1.45 2.52

1.25 91.0 1.63 2.37

1.33 90.8 1.53 2.10

1.40 90.4 1.22 1.90

1.48 89.8 1.26 1.71

1.58 89.4 1.13 1.57

1.68 88.8 .96 1.57

1.81 88.3 .88 1.45

1.98 87.9 .72 1.46

2.23 87.4 .93 1.38

2.51 86.9 1.15 1.53

2.73 86.5 .83 1.21

2.92 86.3 .83 1.15

3.14 86.1 .84 1.01

3.35 86.0 .72 .94

3.56 86.0 .71 .96

3.77 86.0 .63 .94

3.98 86.0 .66 .79

4.20 85.8 .42 .84

4.41 85.7 .67 .91

4.58 85.7 .73 .85

4.76 85.6 .54 .74

4.91 85.6 .54 .74

5.07 85.6 .49 .71

5.21 85.6 .61 .77

5.34 85.6 .61 .79

5.47 85.6 .63 .83

5.60 85.6 .65 .79

5.76 85.5 .75 .86

5.90 85.4 .49 .80

6.04 85.5 .53 .79

6.16 85.5 .56 .81

6.28 85.6 .31 .81

48
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1300°

a 1/ Wavel ength s Microns

6. 41

6. 53

6. 64

6. 76

6. 87

6. 97

7. 07

7. 19

7. 32

7. 44

7. 56

7. 66

7 . 77

7. 88

7. 98

oo 08

8 18

8 28

8 38

8 .47

8 .57

8 .66

8 .75

8 .84

8 .93

9 .01

9 .10

9 .18

9 .26

9 .35

9 .43

9 .51

9 .67

9 .83

10 .00

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85.7 .38

85.7 .63

85.7 .51

85.8 .56

86.0 .52

86.1 .60

86.1 .59

86.3 .70

86.5 .71

86.7 .65

86.9 .58

87.0 .61

87.3 .45

87.5 .42

87.7 .37

88.0 .40

88.2 .54

88.4 .42

88.8 .36

89.4 1.05

89.4 .64

89.5 .64

89.6 .59

89.7 .56

89.8 .56

90.0 .49

90.1 .58

89.9 .98

90.2 .68

90.3 .51

90.3 .57

90.4 .69

90.6 .99

90.4 .89

90.3 .83

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.69

87

95

97

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49
TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1300°

K

Wavelength Emittance

m

XlOO

s Microns XlOO XlOO

10.15 90.4 .72 .79

10.30 90.5 1.38 .93

10.46 90.8 .79 .79

10.61 90.9 1.36 .95

10.76 91.0 .54 .82

10.91 91.2 .55 .61

11.05 91.4 .59 .81

11.19 91.7 .50 .84

11.32 92.0 .54 .78

11.45 92.1 .58 .71

11.58 92.2 .47 .66

11.72 92.3 .58 .83

11.84 92.6 .53 .80

11.97 92.9 .51 .72

12.09 93.0 .56 .72

12.22 93.2 .52 .62

12.35 93.3 .54 .69

12.48 93.6 .51 .76

12.60 93.9 .45 .70

12.72 94.3 .38 .72

12.85 94.4 .48 .72

12.98 94.7 .74 .59

13.10 94.9 .60 .57

13.22 95.1 .52 .64

13.34 95.5 .67 .68

13.46 95.6 .40 .67

13.58 95.8 .50 .59

13.69 95.8 .57 .64

13.81 96.0 .85 .56

13.93 96.0 .50 .63

14.03 95.8 .46 .62

14.14 95.5 .53 .75

14-25 94.9 .62 .88

14.36 94.0 1.13 1.06

14.47 93.1 .79 1.40

50
USCOMM-NBS

TABLE 2 cont'd.

NORMAL SPECTRAL EMITTANCE OF

OXIDIZED INCONEL WORKING STANDARDS AT 1300°

Wavelength Emittance- 2/

CTm" a

-'2

s Microns X100 X100 X100

14.58 91.9 1.09 2.00

14.68 90.1 1.01 2.09

14.79 88.4 1.04 2.28

14.90 86.4 .99 2.51

15.01 84.5 1.07 2.57

15.11 82.7 1.05 2.73

1/ Average of 18 measured values, three each on six specimens

2/ See footnote 1 on page 9 in the text.

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