bluuebunny/crossref_metadata_2025 huggingface dataset:
A simplified microwave instrument for measuring particle volumes and densities
Authors: Hrubesh L. W.
Published: February 2004

An instrument is described that allows the direct and simple measurement of small particle volume and density. Volumes of 150 μ glass spheres have been measured and the technique is shown to be applicable to particles as small as 50 μ.
Large multimode rectangular cavities for microwave spectroscopy
Authors: Bridges Frank
Published: February 2004

A simple rectangular cavity is described for use over a 6–1 range of frequencies using the TEm,o,n modes. These modes give a convenient set of operating frequencies and can easily be obtained using copper plates in the cavity as mode suppressors. High voltage leads enter the cavity through choke joints.
Reststrahlen crystals as wavelength-selective laser reflectors
Authors: Lynk E. T. , Major L. B.
Published: February 2004

In this Note, we point out that the high-reflectance reststrahlen bands of many crystals may be used as wavelength-selective mirrors for far-infrared lasers (8–150 μ). Wavelength coincidences between selected laser transitions and the peaks of some crystal reststrahlen bands are given. Using the reststrahlen band at 9 μ in fused quartz, we have produced oscillation on the 9.0065 μ transition in XeI, with the exclusion of all other transitions.
A simple method for cleaning the surface of mercury
Authors: Davidson Howard L. , Rinker Robert
Published: February 2004

Surface dust and oxidation may be easily removed from a pool of mercury by embedding the material in a film of collodion which is poured onto the mercury and then removed.
A cryopumping system for balloon-borne mass spectrometers
Authors: Woods R. O. , Devlin T. K.
Published: February 2004

A change in geometry from that of the usual laboratory zeolite pump provided more efficient thermal insulation. Zeolite was packaged in a manner which gave a large surface-to-volume ratio and effective heat transfer during bakeout and cooling.
A technique for measuring film thickness on curved substrates
Authors: Hile John W.
Published: February 2004

A technique for measuring the thickness of thin films deposited on curved substrates is described. Conventional multiple beam interferometry with a flat Fizeau plate normally cannot be used with great precision on curved surfaces since the Fizeau fringe spacing is not constant. The technique described in this note takes into consideration the modified Newton's rings which result from such a measurement and gives a precise method of calculating the film thickness.
Inexpensive laser diode pulse generator for optical waveguide studies
Authors: Andrews James R.
Published: February 2004

An inexpensive GaAs laser diode pulse generator is presented. This generator has found application in the evaluation of optical pulse dispersion in glass fiber optical waveguide studies. It is capable of producing optical impulses as narrow as 110 psec at a wavelength of 0.9 μ and a pulse repetition rate of 50 kHz. With a slight modification, it may be used to produce optical pulses of considerably longer duration at reduced repetition rates.
The wavelength dependence of the response of a pulse fluorometer using the single photoelectron counting method
Authors: Wahl Ph. , Auchet J. C. , Donzel B.
Published: February 2004

We study the apparatus response function g (t) which must be known in order to deconvolute the fluorescence decay experiments obtained by the single photon counting method. Due to the flash and the PM characteristics, g (t) depends on the excitation and emission wavelengths. The PM contribution is analyzed qualitatively and found to be in agreement with the properties of the photoelectric effect. Therefore, the accurate determination of the ``true fluorescence decay'' cannot be obtained by the process commonly used, which consists in replacing g (t) by the apparatus response obtained with the PM receiving the light of the exciting pulse. The function g (t) may be obtained in using a reference fluorescent solution with a known fluorescence decay-time.
Contribution to the interferometric measurement of sub-angstrom vibrations
Authors: Kwaaitaal Th.
Published: February 2004

A Michelson interferometer is described for the measurement of low-frequency vibrational amplitudes in the sub-angstrom range (down to 10−3 Å) as a function of temperature. For this purpose a temperature stabilizing circuit has been developed. The use of a condensor microphone as an electromechanical feedback transducer opens up the possibility to relate the amplitude measurements to the wavelength of light. By these means the accuracy, reliability, and versatility of the interferometer are considerably improved and the draw-backs of existing set ups are effectively eliminated.
A low noise amplifier with application to noise thermometry between 300 and 4 K
Authors: Anderson P. T. , Pipes P. B.
Published: February 2004

A low noise FET amplifier has been constructed and applied to noise thermometry. The amplifier noise is less than 1 nV/(Hz)1/2 above 5 kHz. Temperatures between 300 and 4 K have been measured to better than 1% with a time constant of 5 sec. A description of the complete noise thermometer system is given.
Measurements of the vapor pressure of cesium by absorption of resonance radiation, λ = 8521 Å
Authors: Pradel P. , Roussel F. , Spiess G.
Published: February 2004

We have measured using optical means the absolute density of the saturated vapor pressure of cesium by absorption of resonance radiation corresponding to the 62P3/2→62S1/2 transition. Experimental results are compared with those obtained with a surface-ionization gauge and with the Taylor-Langmuir equations. Density was measured between 12.5°C and 39.2°C; in this temperature range the experimental error is about 10%. For higher temperatures, the absorption increases with the temperature but is not in a simple fashion related to the atom density in the absorption cell. A different method is proposed which permits density to be measured up to temperatures above 100°C, but this requires calibration using the Taylor-Langmuir formulae.
A ``plasmascope'' using light emitter diodes
Authors: Ejima S. , Novinski A. , Marshall T. C.
Published: February 2004

A ``plasmascope'' device which permits visual display of the floating potentials from a 7 × 7 matrix of Langmuir probes immersed in a low-density plasma is described. The probe potential, which is proportional to the plasma space potential, is sampled through a high impedance FET circuit. These potentials are displayed by a matrix of light emitter diodes such that the light intensity at a point on the matrix is proportional to the corresponding probe floating potential. This device is useful to determine the qualitative location of the plasma, its configuration, and slow motion.
Precision measurements of the thermal conductivity, electrical resistivity, and Seebeck coefficient from 80 to 400 K and their application to pure molybdenum
Authors: Moore J. P. , Williams R. K. , Graves R. S.
Published: February 2004

A longitudinal heat-flow technique for precise measurement of thermal conductivity, electrical resistivity, and Seebeck coefficient over the temperature range from 80 to 400 K is described. The basis of the technique is the use of a calibrated platinum resistance thermometer to provide in situ calibrations of specimen thermocouples. The total determinate errors at 273 K are ± 0.23% for electrical resistivity, ± 0.49% for thermal conductivity, and ± 0.07 μV/K for the Seebeck coefficient when Pt wire is used as the reference. Experimental results on two high-purity molybdenum specimens with cross-sectional areas differing by a factor of four are presented to demonstrate the system precision and low level of indeterminate erros.
A vacuum cell and associated optics for obtaining a single-reflection infrared spectrum using reflection-absorption spectroscopy
Authors: Tompkins Harland G. , Allara David L.
Published: February 2004

A compact vacuum cell and associated optics used to obtain a single-reflection infrared spectrum of a thin film on a metal surface is described. Reflection-absorption spectroscopy, in the past, has usually involved multiple reflections. Single reflection setups offer advantages of simplicity, the ability to generate and/or clean the sample surface, and the ability to use other surface studies techniques along with ir. An optical setup is described which will allow the above three advantages to be obtained, and in addition is simple and compact. Along with the optics, a vacuum cell housing the sample is described. This cell fits conveniently with a standard infrared spectrometer and no additional modification to the spectrometer is required.
A torsional pendulum technique using solid state devices to measure internal friction and stress relaxation
Authors: Welch W. D. , Barker B. D. , Carpenter S. H.
Published: February 2004

Two original and unique optoelectronic systems used to measure the anelastic properties of materials are described. The systems are used in conjunction with a standard inverted torsional pendulum. One system measures low frequency internal friction and the other measures stress relaxation at constant strain. The circuit diagrams and mechanical setups for these systems are given and typical data are shown.
Improved apparatus for the NMR measurement of self-diffusion coefficients using pulsed field gradients
Authors: Webster D. S. , Marsden K. H.
Published: February 2004

The characteristics of some quadrupole coils are examined to determine their suitability for NMR pulsed field gradient diffusion measurements. They are found to be capable of acceptable field gradient uniformity, low ratio of inductance to field gradient strength, low dc resistance and their windings are as far as possible from adjacent pole faces, thus minimising eddy current formation. An improved current pulser using SCR's is also discussed.
New simple circuits to eliminate time slewing
Authors: Bui Ai , Sneij George
Published: February 2004

A new idea is put forward which reduces considerably the timing errors arising out of the photomultiplier pulse-amplitude variations. A bipolar signal, obtained at the output of a simple electronic circuit, intersects the time-axis at a point determined by the amplitude of the input pulse. This amplitude-dependent displacement of the intersecting point along the time-axis helps reduce considerably the time fluctuations of the final output signal. Output pulse-amplitude variations from more than 3 V down to 0.15 V show an almost complete suppression of the time fluctuations of the output signal, while this is only of the order of 25 psec for an input variation of 0.15–0.10 V. The influence of the variation of temperature on the circuit behavior has also been investigated.
Calorimetry below 1 K: The specific heat of copper
Authors: Sellers G. J. , Anderson A. C.
Published: February 2004

A technique is described which permits the accurate measurement of heat capacities to very low temperatures without the use of a heat switch. As a test of this technique the specific heat of Cu, with and without hydrogen impurities, has been measured in the temperature range 0.04–1 K. The presence of hydrogen increases the specific heat by ≈ 1% as has been reported previously at higher temperatures. Above 0.3 K the data for hydrogen-free copper are in good agreement with the copper reference equation. At lower temperatures there is an additional contribution to the heat capacity which may be associated with oxygen impurities.
Low temperature, thin film NiCr thermometers
Authors: Griffin E. L. , Mochel J. M.
Published: February 2004

Thin metal film thermometers, typically 20 Å of Chromel A sandwiched by SiO, have been developed for use below 4 K. These thermometers have good low temperature stability (drift less than ± 0.0005 K/2 days), low noise, small heat capacity (0.1 erg/K·cm2), are insensitive to magnetic fields (less than ±0.001 K/25 kG), and are easily fabricated. Thermometers made with Chromel A are marginally stable at room temperature with a typical shelf life of several weeks.
A sensitive tipping-bucket rain gauge
Authors: Mink J. W. , Forrest E. P.
Published: February 2004

A sensitive tipping-bucket rain gauge has been developed which measures rainfall in increments of 5×10−3 mm with an accuracy of better than 0.1%. The gauge is being used to determine the relationship between millimeter wave attenuation caused by rainfall and rainfall rates from 0.3 to 30 mm/h.
Third-order asymptotic aberration coefficients of electron lenses. III. Formulas and results for the two-tube electrostatic lens.
Authors: Kuyatt C. E. , DiChio D. , Natali S. V.
Published: February 2004

The third-order asymptotic aberration coefficients of round electrostatic electron lenses are formulated, following Hawkes, in a form independent of object and aperture positions. Six quantities are sufficient to specify completely the third-order aberration properties of electrostatic electron lenses. Equations for these six quantities are derived in the form of integrals involving derivatives of the axial potential no higher than the second. Using these equations and our previously calculated potentials and first-order trajectories we have computed the six aberrations coefficients for the two-tube electrostatic lens for voltage ratios from 1.1 to 10 000. The results are believed accurate to better than 0.2%.
A procedure for making small metal spheres
Authors: Lang R. J. , Smith T. , Koren H. W.
Published: February 2004

A procedure is described for producing metal spheres with diameters of about 13 μ.
Carbon rod furnace infrared source
Authors: Boyd W. J. , Jennings D. E. , Blass W. E. , Gailar N.M.
Published: February 2004

A carbon rod furnace infrared source has been built and has proven to be a reliable and trouble-free source despite the high rod temperature of 2500 K. The furnace offers several advantages over previous furnaces. These include an increase in usable rod length to 6.35 cm, and extended rod life (up to 400 h), and a fully automated power supply for the furnace. Construction and operational details are discussed.
Construction of an einzel lens capable of high voltage operation
Authors: Aberth William H. , Schnitzer Rafael , Engesser Ferdinand C.
Published: February 2004

Construction details are given for a relatively inexpensive einzel lens capable of high voltage operation.
A gas flow system for esr measurements between 5 and 300 K
Authors: Reuveni A. , Maniv S.
Published: February 2004

Standard esr equipment for measurements at liquid helium temperature is used as a base for a gas flow system. The system operates at X and Q bands at temperatures down to 5 K. Temperature control is achieved by regulating the flow rate of the gas. It is stabilized to ±1 K. The helium flow rate required to maintain the lowest temperature is 0.12 liters/h.
An omnidirectional pressure transducer
Authors: Futral J. G. , Verma B. P.
Published: February 2004

Diaphragm type pressure transducers are inadequate in the measurement of pressures in deforming media such as soil, because they are too rigid and uniform pressure application is difficult. The omnidirectional pressure transducer is designed to overcome these shortcomings by encasing a cell in a hollow flexible walled sphere filled with an incompressible liquid.
A multiprobe miniature thermistor system for the measurement of temperature profiles
Authors: Lior Noam , Leibovitz Jacques , Laird Alan D. K.
Published: February 2004

A new instrument for the determination of fine temperature profiles in hot, corrosive, electrically conductive, unsteady two-phase fluid systems under vacuum or pressure is described. It features simultaneous measurement of temperatures at close locations, by a column of miniature (0.25 mm diam) thermistors mounted at the tips of supporting hypodermic tubes, and streamlined design that minimizes hydrodynamic and thermal disturbances at the measured locations. Some of the techniques used in the construction, such as the welding, insulation, and handling of fine wires (0.025 mm diam), are of interest in many other applications. The instrument has been used to measure temperature distributions with an accuracy of ±0.02°C in a model of a flash-evaporator stage used for the desalination of saline water, and thus provided new and quantitatively significant data about the process.
Irradiance uniformity and power loss with a spatially filtered laser beam
Authors: Pernick B. J.
Published: February 2004

Improvement of irradiance profile uniformity by choosing only a limited, central region of a laser beam is frequently used. The associated transmitted power loss is computed in dimensionless form for general utility. For example, a factor of 3 improvement in uniformity at the outer beam radius can be achieved with only about 35% power loss.
A compact multichannel spectrometer for field use
Authors: Walker G. A. H. , Buchholz V. L. , Camp D. , Isherwood B. , Glaspey J. , Coutts R. , Condal A. , Gower J.
Published: February 2004

Details are given of a Littrow-mounted grating spectrometer which uses a cooled linear array of silicon diodes as a detector (0.4–1.1 μ) and an Erfle eyepiece as collimator/camera. The slit is illuminated by a standard 35 mm camera lens. Analog diode output signals are multiplexed, digitized, and either recorded on magnetic tape for later processing or signal-averaged by a small on-line computer, then recorded on magnetic tape, and displayed on an oscilloscope. Test data are presented. The device has no moving parts, is competitive with existing devices based on photomultipliers and television cameras, and can be readily modified to increase the number of channels and improve wavelength and spatial resolution and throughput.
Versatile high pressure cell for use at low temperatures
Authors: Schilling J. S. , Klein U. F. , Holzapfel W. B.
Published: February 2004

An economical technique for maintaining pressures up to 100 kilobar in a volume of 10 mm3 at temperatures of 4.2 K and lower is discussed together with its application in resistivity measurements and Mössbauer spectroscopy. Modifications for the use in optical spectroscopy and for studies including external magnetic fields are indicated.
Determination of the Gaussian and Lorentzian content of experimental line shapes
Authors: Wertheim G. K. , Butler M. A. , West K. W. , Buchanan D. N. E.
Published: February 2004

The approximation of the Voigt line shape by the sum of a Gaussian and a Lorentzian of equal width is explored. The relative intensities of these two lines in the approximate function are related to the widths of the components of the Voigt function using nonlinear least-squares fitting. The useful range of the approximation includes lines sharper than Lorentzian and flatter at the top than Gaussian.
Effects of angular beam dispersion on performance of slotted-disk velocity selectors
Authors: Frankl D. R.
Published: February 2004

The disk-type velocity selector is analyzed to obtain the effects of angular dispersion on velocity resolution and sideband elimination.
Low temperature thermometry in high magnetic fields. IV. Allen-Bradley carbon resistors (0.5–4.2 K)
Authors: Sample H. H. , Neuringer L. J.
Published: February 2004

The transverse magnetoresistance of six 1/8-W Allen-Bradley carbon resistors with nominal room temperature resistances of 2.7, 3.9, and 5.6 Ω was measured at various temperatures between 0.5 and 4.2 K in static magnetic fields up to 140 kG. Below 1.5 K, the magnetic field induced temperature errors of the resistors are small, less than 25%, and are very reproducible, i.e., ±0.8% in the case of the 2.7 Ω units. Hence, these resistors are useful as low temperature thermometers in strong magnetic fields.
High pressure dialysis cell
Authors: Pusch W. , Wolff H.-J.
Published: February 2004

An apparatus is described which permits the determination of the mechanical permeability and the reflection coefficient of synthetic membranes at different hydrostatic mean pressures in the pressure range 1 up to 100 atm. Thus, it is possible to measure the volume flux across a membrane at pressures up to 100 atm using small pressure differences, ΔP, across the membrane. Therefore, the linear relations of the thermodynamics of irreversible processes can be used for the evaluation of the transport properties at large mean pressures. Furthermore, it is also possible to perform measurements at large pressure and osmotic pressure differences where the usual linear relations of thermodynamics of irreversible processes may no longer apply. Some preliminary results obtained with asymmetric cellulose acetate membranes which were annealed at different temperatures are reported. These results show that the transport coefficients of the membranes depend on the mean pressure.
Vacuum operating thermoluminescence spectrometers
Authors: Aramu F. , Maxia V. , Muntoni C.
Published: February 2004

Two instruments are described suited for recording thermoluminescent glow spectra respectively below and above room temperature. Their most remarkable property is the fact that the samples are kept under vacuum. Thermal insulation, thus, is good enough to allow samples to be placed only 15 mm from the light detector, even if they are heated up to 500 °C or cooled down to liquid N2 temp. Consequently, the light collection efficiency turns out to be very high. These instruments are equipped with both analog and digital recorders, thus obtaining an accurate gathering of data.
Optimized interpolation fitting to Ge resistance thermometer characteristics
Authors: Greenfield A. J. , Lieberman D. , Zair E. , Greenwald S.
Published: February 2004

The interpolation fitting method using cubic splines to represent a Ge resistance thermometer characteristic is compared to the commonly used least-squares fitting method. For a ``poorly behaved'' thermometer characteristic, the spline function is demonstrated to give considerably better interpolation accuracy. For a ``well-behaved'' thermometer characteristic, the spline function gives comparable or slightly better accuracy. Also, it is shown that by choosing a more efficient interval spacing distribution for the calibration points, one may obtain this improved accuracy even with fewer calibration points.
High pressure cells for the study of optical properties of liquid systems
Authors: Fleischmann F. K. , Conze E. G. , Kelm H. , Stranks D. R.
Published: February 2004

In order to investigate optical properties of liquid systems under high pressure two cells were constructed and tested. Special attention was given to the possibility of investigating equilibria or rates of reactions of corroding liquids.
The use of NMR for the continuous measurement of the concentration of orthohydrogen in the solid phase
Authors: Schmidt F.
Published: February 2004

A simple NMR system was used for measurement of the o–H2 concentration in the solid phase. It was found that the system must be calibrated, as the integral of the NMR absorption curve is not proportional to the o–H2 concentration, which was suggested earlier. The influence of the quantum diffusion below 4 K and 0.35 o–H2 content on the results is reported.
A proportional thermostat with 10 microdegree stability
Authors: Dratler Jay
Published: February 2004

The general problem of designing active proportional thermostats is discussed, and a design philosophy is deduced. The application of this philosophy to the construction and operation of a precision proportional thermostat for geophysical accelerometers in boreholes is described in detail. The thermostat discussed is of small size and weight, is simple to operate, and requires less than 5 W of power. It maintains the temperature of an instrument and its vacuum enclosure of 1688 cm3 total volume and 7 kg mass constant within 10 μ°C over periods of days in the presence of fluctuations in the ambient temperature of several degrees. Various models of the thermostat, with several different configurations of thermal insulation, have been tested extensively in both laboratory and borehole environments. Stable proportional operation has been achieved with setpoint temperatures ranging from 15 to 35 °C and with the difference between the setpoint and mean ambient temperatures varying from 4 to 10 °C. The electronic circuitry is designed to provide a maximum heater power of 15 W, and the thermistor is calibrated over the range −40–150°C. With suggested modifications, the thermostat is applicable to a variety of instruments over a fairly wide temperature range.
A camera for photography of atomospheric particles from aircraft
Authors: Cannon Theodore W.
Published: February 2004

A special camera has been installed on a research sailplane to take in situ photographs of atmospheric particles. Ice particle shapes, sizes, and concentrations; raindrop sizes and concentrations; and estimates of cloud droplet concentrations and maximum sizes are obtained from the photographs. The camera is capable of photographing particles as small as about 4 μ radius; the size of the largest particle completely imaged is limited by the 24×36 mm projected area photographed. Liquid particles can be distinguished from ice particles for radii greater than 50 μ. Techniques are described for calibrating the camera so that both in-focus and out-of-focus images are used for obtaining concentration and size data. Examples of photographs of ice particles, raindrops, and cloud droplets are shown. Camera improvements for getting more data for a given length of flight are suggested.
A shadow mask for sputtered films
Authors: Ingle Frank W.
Published: February 2004

Use of a magnet to clamp a magnetic metal mask to the substrate during sputtering resulted in good edge definition in thin film patterns.
A vacuum-tight, all-metal feedthrough for superconducting current leads
Authors: Mueller R. M. , Adams E. D.
Published: February 2004

An all-metal feedthrough which permits superconducting leads to pass from the 4He bath into the vacuum region of a cryostat is described. The all-metal construction facilitates rapid assembly and enables the seal to withstand rapid temperature changes resulting from the precooling of the apparatus with liquid nitrogen. Use of the device is limited to those applications, such as operation of superconducting magnets, in which the presence of normal connections between the various leads or to the metallic structure of the cryostat can be tolerated.
A differential transformer as a position detector in a magnetic densimeter
Authors: Greer Sandra C. , Moldover M. R. , Hocken R.
Published: February 2004

We describe the use of a differential transformer to detect the position of the buoy in a magnetic densimeter, an instrument for precise measurement of fluid densities. This detector can be used in cases where the buoy is not visible and it can be assembled from commercial electronic components.
A differential ellipsometer
Authors: Treu Jesse I.
Published: February 2004

A system is described which provides for direct measurement of the difference between linear dichroism, circular dichroism, or phase shifts (in transmission or reflection) of two adjacent samples. A uniaxial crystal is used to produce two incident light beams of mutually orthogonal polarization. The total intensity is analyzed by a single detector to give the differential quantities.
Trigger circuits for use in flash photolytic experiments
Authors: Wiesenfeld J. R.
Published: February 2004

Two trigger modules suitable for use in flash photolytic apparatus are described. One generates a 30 kV pulse for overvoltage triggering of flash lamps or control of spark gaps. The other produces high voltage, high current pulses for initiating conduction in mercury ignitrons.
Fast pulsed discharge switching in the 10 kJ range using commercial gaps
Authors: Saint-Hilaire G. , Guay J. M. , Dimoff K.
Published: February 2004

A moderately powered, multipurpose, fast pulsed discharge source is described in which standardized components are used to ``parallel switch'' a condenser bank. The system is virtually maintenance free, exhibits an overall jitter of less than 0.2 μsec in current breakdown and can operate flexibly over a range in storage energy from 0.8 to 8 kJ.
A rigid microwave access lens into copper-shielded plasma physics experiments
Authors: Hugenholtz C. A. J.
Published: February 2004

In this note, a microwave lens is described giving easy access through the copper shell of the SPICA experiment without disturbing the shielding effect. The lens consists of a number of small holes drilled in a solid plane metal disk. With increasing radius, the holes in the lens become smaller in diameter, so the phase velocity will increase towards the edge which produces a focusing effect for microwaves.
Resistivity measurements with samples in the form of a double cross
Authors: Jandl Serge , Usadel K. D. , Fischer Gaston
Published: February 2004

Samples in the shape of a double cross are analyzed, both theoretically and rheographically, as to their suitability for resistivity measurements. It is found, provided certain geometrical limitations are observed, that the presence of lateral arms instead of true point contacts has very little effect on the resistance observed. Typically, the voltage measured between the ends of lateral arms with half the cross section of the main sample body and separated by eight sample widths, is only 1% less than the voltage between two point contacts of similar separation placed on the main sample body. For known dimensions the effect of the side arms is calculated rigorously. Excellent agreement is found with measurements. The rheographic experiments also show that current and voltage arms need only be two or three times as long as they are wide to ensure the validity of the calculation.
Use of the quartz crystal thermometer for absolute temperature measurements
Authors: Benson Bruce B. , Krause Daniel
Published: February 2004

Tests of a quartz crystal thermometer over a period of two years indicate that with yearly NBS calibration and appropriate weekly ice point and other calibration checks, it is a reliable secondary standard for absolute temperature measurements. Over a range of at least 0–60°C it is accurate to better than 0.005°C and perhaps as good as 0.003°C. Descriptions are given of the absolute calibrations and of the tests for internal consistency of the quartz probes.
Low temperature application of commercial strain gauges
Authors: Alterovitz S. , Mapother D. E.
Published: February 2004

Commercial strain gauges are found to give linear reproducible results as pressure monitors for low temperature experiments. Calibration done at 77 K remains correct with 2% absolute accuracy at 4.2 K. The independent pressure calibration at low temperatures was done by precise measurements of the change in the critical magnetic field of indium.
Continuously direct-reading polarimeter for density contrast measurements in optically active solutions
Authors: Lambert R. B. , Davey M.
Published: February 2004

An instrument using a polarized laser beam has been designed for the purpose of measuring the horizontally averaged concentration of optically active solutes in experiments in which the vertical distribution of dissolved components, and the vertical transport of these components, is of interest. An analyzer, rotating at 500 rpm, samples the beam after it passes through the solution, producing a signal whose phase shift is proportional to the angle through which the polarized beam has been rotated. The signal is amplified, integrated, and processed such that the output is directly proportional to the solute concentration.
Measurements of spatial reactant and product concentrations in a flow reactor using laser-induced fluorescence
Authors: Stewart Thomas B. , Judeikis Henry S.
Published: February 2004

A system capable of measuring heterogeneous and homogeneous reactions inside cylindrical flow reactors is described. In this system, the laser-excited fluorescence of reactant gas molecules is used to measure the spatial concentration of these molecules down the length of a cylinder coated with a suitable catalyst. The laser beam can be placed either on axis or off axis of the cylinder to measure the gas distribution. From the spatial concentration and certain experimental parameters, the rate constant can be determined. This technique is more versatile than a gas sampling probe because the gas flow is not disturbed. Also, an instantaneous reading of the relative gas concentration and a high degree of sensitivity are obtained. This technique is applicable to most gases, but, for this study, it was used to examine NO2 solid reactions in polluted atmospheres.
Application of an LVDT to an analytical balance
Authors: Primak William
Published: February 2004

The secondary voltage of an LVDT (linear variable differential transformer) is proportional to the primary voltage. The force exerted on the core varies as the square of the primary current or voltage. Thus, the scale sensibility of the balance equipped with an LVDT decreases with applied voltage. The voltage sensibility possesses a maximum, where, of course, the system is insensitive to fluctuations in the primary or excitation voltage. With a suitable voltmeter to read the secondary voltage, speed of operation is increased somewhat and precision is increased by an order of magnitude over that obtained when the balance is used conventionally.
A LEED goniometer
Authors: De Bersuder L.
Published: February 2004

An hemispherical display type low energy electron diffraction apparatus, having complete freedom of incident and diffracted beams directions with high angular precision, high resolution, and high sensitivity, is described.
An apparatus for high pressure Raman spectroscopy
Authors: Hawke R. S. , Syassen K. , Holzapfel W. B.
Published: February 2004

This paper describes an apparatus that can be used to study the Raman and fluorescence spectra of liquids and solids up to pressures above 80 kilobar and in the temperature range between about 100 and 500 K. Basically, the pressure is produced by two opposed Bridgman anvils, whereby at least one anvil is made out of transparent sapphire material. This allows back scattered Raman measurements from a sample which is in the same environment as a small ruby crystal. The fluorescence lines of the ruby crystal at 14432 and 14404 cm−1 are frequency shifted by pressure and temperature and this effect is used to accurately measure the pressure in the cell. Raman spectra of water in the liquid, ice VI, VII, and VIII phases are given here to illustrate the capability of this apparatus.
An improvement of nanosecond fluorimeters to overcome drift problems
Authors: Hazan Gershon , Grinvald Amiram , Maytal Moshe , Steinberg Izchak Z.
Published: February 2004

For the processing of fluorescence decay data it is often necessary to obtain the time profile of the flash lamp which excites the fluorescence as well as the variation with time of the fluorescence intensity. If these intensity profiles are collected in consecutive experiments, instrumental drift may introduce serious errors. This problem is shown to be minimized by alternate collection of the data for the fluorescence and for the excitation lamp. An automatic setup for performing such experiments is outlined.
A new method of Johnson noise thermometry
Authors: Borkowski C. J. , Blalock T. V.
Published: February 2004

A new method of Johnson noise thermometry was developed and experimentally evaluated. The absolute temperature Ts was determined by measuring the available thermal noise power, i.e., the product of the open-circuit thermal noise voltage and the short-circuit thermal noise current generated by a sensing resistor at temperature Ts. The measured thermal noise power from the thermometer is a linear function of absolute temperature. This new method is independent of the sensing-resistor composition, the mass and nature of the charge carriers, and, in principle, the ohmic value of the resistor. Consequently, the method has a wide range of application, including use in the realization of an absolute thermodynamic temperature scale and especially in the measurement of high temperatures, particularly in nuclear reactors where the properties of sensor materials not only change due to the aging effects induced by the high temperatures but also change drastically because of radiation damage and transmutation. An evaluation of the method was performed with the sensor and signal processor both located in an area of high electrical background noise. The signal cable connecting the sensor to the signal processor was about 0.5 m in length. The deviations of the experimental data were not more than ± 0.10% from a straight line calibration through absolute 0 K in the temperature range ΔT from 725 to 1275 K. In the range ΔT, the maximum error in the indicated temperature for a 100% increase in the value of the sensing resistor at a fixed temperature was ± 0.60% and for a 50% decrease, was −1.00%. The feasibility of separating the thermal noise signal from electrical background noise induced in a long signal cable was demonstrated with the sensor and signal processor connected with a 30 m long coaxial cable. With the extraneous noise power in the cable, more than an order-of-magnitude greater than the thermal noise power, the uncertainty in temperature due to the extraneous noise was less than 1% at 100 C.
A time resolved spectrometer for high intensity relativistic electron beams
Authors: Walker Jack V. , Stevens Jack
Published: February 2004

A spectrometer system designed to measure the time-dependent kinetic energy of electrons from high current pulsed relativistic beam accelerators is described. The spectrometer, consisting of a three-element vacuum Compton diode, is simple, rugged, and self-driving. Calibration data are presented covering the energy range of 150 keV to 16 MeV. Applications and limitations of the spectrometer are discussed.
Model of response of an electric field mill operating during suborbital flight
Authors: Sheahen Thomas P.
Published: February 2004

A rotating-vane electric field mill was used to measure the electric field at the base of a series of vehicles as they passed through the ionosphere and reentered the atmosphere. Anticipated rapid and large variations in measured electric fields required a time response of a few milliseconds and a dynamic range from 40 to 50 000 V/m. These conflicting goals were met by using a bipolar logarithmic amplifier with limited memory. Presented here is a mathematical model of the electronics, which was used to unfold the electric field values from the telemetered outputs. The instruments also met other design constraints and functioned correctly on all flights.
A continuous two-photon-fluorescence monitor
Authors: Palmer Richard E.
Published: February 2004

A technique is described in which two-photon-fluorescence traces are recorded by means of an image-intensified vidicon instead of photograph techniques. The traces can be recorded directly at a rate up to 60 Hz for use in aligning a repetitively pulsed mode-locked Nd+3:YAG laser.
Low natural frequency vibration isolator or seismograph
Authors: Lorrain Paul
Published: February 2004

This passive vibration isolator, or stable table, attenuates horizontal displacements as well as tilt due to bending of the floor under shifting loads. It has a transmissiblity of 0.1 for horizontal displacements at a frequency that can be as low as 0.1 Hz. Higher frequencies are attenuated as 1/f2. The stable platform floats on a simple air bearing that rests on a pair of I beams supported on the concrete beams of the building. A weak horizontal restoring force is exerted on the platform by two light vertical springs. The device can also be used as a two-dimensional seismograph, or as a sensitive tilt meter.
Electronic circuit using charged pins for determining impact planarity in shock wave experiments
Authors: Shuler E. J. , Mock W. , Holt W. H.
Published: February 2004

An electronic circuit using charged pins has been designed to permit the accurate determination of the impact planarity (tilt) in shock wave experiments. The tilt circuit generates voltage pulses with risetimes of approximately 3 nsec. The circuit is described and its operation is discussed.
The electron beam fluorescence method as applied to molecular scattering experiments
Authors: Scott P. B. , Mincer T. R. , Muntz E. P.
Published: February 2004

A molecular beam system using electron beam excitation to observe the rotational state distribution of incident and scattered beams of nitrogen is described. The incident nitrogen beam is skimmed from a nozzle source and has low translational and rotational temperatures. Cryopumping of the scattering chamber is necessary to maintain a sufficiently low partial pressure of wall scattered nitrogen in the detection region. The electron gun is of special design for attaining (typically) 15 mA at 1200 eV energy in a millimeter diameter beam. Recording instrumentation is of analog type, the signal to noise ratio of a scattered beam is typically of order 40 using a 5 sec integration time constant. The system has been used to infer the anisotropy of nitrogen-rare gas intermolecular potentials.
Stability of fringe counting interferometers
Authors: Edgerton John W. , Andrew Kenneth L.
Published: February 2004

Two configurations of an automatic bidirectional, fringe-counting corner-cube interferometer are compared. They differ only in the method of quadrature phase introduction. The one using polarization coding has good phase stability at optical path differences as large as 955 mm, the one using adjacent beams has such poor phase stability as to render it useless at path differences greater than 700 mm. A useful well-defined alignment procedure is given for the corner-cube interferometer.
Measurement of totally depleted silicon solid state detector thickness by x-ray attenuation
Authors: Hanser Frederick A. , Sellers Bach
Published: February 2004

A method for measuring the thickness of silicon detectors by x-ray transmission is described. The method has been calibrated by using silicon disks of known thickness. Use of a 10 keV fluorescent Ge K x-ray source excited by a 10 mCi 238Pu source can give 1% accuracy from 50 to 700 μ Si, including a correction for an assumed, or independently measured, thickness of the front Au layer. With 14.4 keV nuclear γ rays from 400 μ Ci of 57Co 1% accuracy can be obtained from 200 to almost 1500 μ Si. With the two x-ray measurements both the Si and the Au layer thicknesses can be measured. The method has been used to make an accurate thickness measurement of a nominally 100 μ Si detector which was used to make stopping power measurements for heavy (z > 1) ions in Si.
Effect of rf field inhomogeneities on spin-echo measurements
Authors: Bull T. E.
Published: February 2004

The effect of radio frequency inhomogeneities on nuclear magnetic transverse relaxation time (T2) measurements has been investigated experimentally and numerically. Measurements using the Meiboom-Gill modification to the Carr-Purcell sequence have been emphasized; however, some other methods have been considered. The calculations have been performed assuming that the magnetization obeys (a) the Bloch equations and (b) the modified Bloch equations. In case (a) the errors resulting from rf field inhomogeneities were found to be small to moderate, and a method is presented whereby the upper limits to these errors can be determined experimentally. Furthermore, the errors are decreased considerably in a homogeneous main magnetic field adjusted to resonance and go to zero when T1 = T2. In case (b) the errors were considerably larger than in case (a) and the presence of a homogeneous main magnetic field did not necessarily decrease these errors. Even quite small rf field inhomogeneities were found to produce significant errors in the exchange times, chemical shift differences, and activation parameters derived from the transverse relaxation times.
Instrumentation for direct microscopic elemental analysis of frozen biological tissue
Authors: Hutchinson Thos. E. , Bacaner Marvin , Broadhurst John , Lilley John
Published: February 2004

A system has been devised to provide direct observation of frozen biological tissue in the scanning electron microscope. Both transmission and secondary electron methods of signal collection have been obtained. In combination with energy elective fluorescent x-ray analysis, the elemental constituents of subcellular regions less than 1000 Å in diameter have been analyzed in the transmission mode of operation. Transmission scanning electron micrographs of frozen muscle shows significant microstructural differences with conventionally obtained electron micrographs although dark bands, possibly corresponding to z zones of classically observed spacing, are seen.
A work-accelerated electron beam gun for optical measurements on molten zones
Authors: Rötzer Gunther
Published: February 2004

An electrostatically operated electron gun of the shielded filament type is described which embraces the advantages of no need of cooling the gun, relatively high collimation, and complete visibility of the zone of the sample which is heated by the gun.
An inexpensive nanosecond light pulser for use in photomultiplier system testing
Authors: McFarlane W. K.
Published: February 2004

A nanosecond light pulser of modest cost is described, which is suitable for use in the testing of large photomultiplier systems, where each phototube requires an individual pulser. Timing stability (of 200 psec) and light pulse amplitude stability (of 4% from 10° to 40°C) are adequate for all but the most demanding applications. Yellow light emitting diodes are used to obtain satisfactory matching to photomultipliers with S-11 response curves.
Miniature diamond anvil pressure cell for single crystal x-ray diffraction studies
Authors: Merrill Leo , Bassett William A.
Published: February 2004

A new miniature gasketed diamond anvil high pressure cell has been constructed to perform optical and x-ray diffraction studies on single crystals under hydrostatic pressure. For x-ray studies the cell is mounted on a standard goniometer head which may be attached to either a standard precession camera or single crystal orienter taking advantage of counting methods. The pressure cell has been used successfully in the study of the two high pressure phases of calcium carbonate, CaCO3(II) and CaCO3(III).
An automatic voltage control circuit
Authors: Sokoloski M. M. , Blackburn J. , Schifano J.
Published: February 2004

A simple automatic voltage control circuit is described which uses a photon coupler in the feedback loop to regulate the voltage drop across a varying load.
Effect of electron beam pulse width on time-of-flight spectra
Authors: Misakian Martin , Mumma Michael J.
Published: February 2004

A simple mathematical relationship is developed which describes the effect of electron beam pulse width on measured time of flight spectra. Application is made to thermal helium time-of-flight distributions.
A simple dual DVM Teletype terminal interface
Authors: Bradley George E.
Published: February 2004

A simple interface for reading the output of a two parameter experiment into a computer Teletype terminal is described.
A sample cell for low temperature optical absorption studies of frozen aqueous solutions
Authors: Pattison M. R. , Kim Y. W.
Published: February 2004

A sample cell for optical absorption studies of frozen aqueous solutions from 68 to 300 K is described. The use of very thin samples reduces undesirable scattering and the cell design permits both vacuum sealing to ∼ 10−6 Torr and the elimination of optical window breakage.
A stabilized electron-bombardment ion source
Authors: Isler R. C.
Published: February 2004

An electron-bombardment ion source which produces currents that fluctuate less than 0.25% over a period of 10 min is described.
Uniaxial stress apparatus with analog pressure readout
Authors: Vogelmann Helmut , Fjeldly Tor A.
Published: February 2004

A uniaxial stress apparatus with analog pressure readout is described. The apparatus allows measurements under vacuum and at low temperatures.