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Sep 1973

Volume 44, Issue 9, pp. 1167-1438

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A High Precision Scanning Ratio Calormimeter for use Near Phase Transitions

M. J. Buckingham, C. Edwards, and J. A. Lipa

Rev. Sci. Instrum. 44, 1167 (1973); http://dx.doi.org/10.1063/1.1686346 (6 pages) | Cited 16 times

Online Publication Date: 6 November 2003

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Near a phase transition the rate of change with temperature of the specific heat and the thermal relaxation time can both become very large with resulting difficulties in the measurement of specific heat by conventional methods. This paper describes a calorimetry method specially adapted to overcome these difficulties, which has proved successful for measurements near the critical point of fluids.

Experimental Study of a Sintered‐Copper Heat Exchanger

N. Pundak, Y. Winograd, and Ralph L. Rosenbaum

Rev. Sci. Instrum. 44, 1173 (1973); http://dx.doi.org/10.1063/1.1686347 (5 pages) | Cited 1 time

Online Publication Date: 6 November 2003

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The inlet and outlet temperatures and the block temperature of a discrete heat exchanger in a dilution refrigerator have been measured. Temperatures measured on the outgoing 3He☒4He stream were higher than temperatures predicted theoretically; this discrepancy has been attributed to viscous effects within the dilute 3He☒4He channel which degrade the performance of the heat exchanger significantly below 80 mK.

``Boxcar'' Attachment for Oscilloscopes Useful for Low Level Signals

Frank G. Collins and Ronald Katchinoski

Rev. Sci. Instrum. 44, 1178 (1973); http://dx.doi.org/10.1063/1.1686348 (4 pages) | Cited 6 times

Online Publication Date: 6 November 2003

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The design of an inexpensive ``boxcar'' integrator for improving the signal‐to‐noise (S∕N) ratio of low level repetitive signals is described. The design is simplified by using the timing circuits of an oscilloscope to generate the gate and delay for the boxcar. The S∕N ratio can be improved up to 60 dB. It is useful for signals from 500 μV to 30 mV rms containing frequencies up to 50 kHz, at repetition rates to several kHz. Examples of its use for sine and square waves are included.

Modified Poppet Valve for Quasisteady Gas Injection into Vacuum

Sinji Morimoto and Kyoichi Kuriki

Rev. Sci. Instrum. 44, 1182 (1973); http://dx.doi.org/10.1063/1.1686349 (4 pages)

Online Publication Date: 6 November 2003

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A fast acting valve has been developed for quasisteady gas injection with a short rise time. The valve has a structure which is a combination of the conventional poppet and piston valves. From gas density measurements by a fast ionization gauge, the rise time was found to be limited by the expansion of the gas front. The minimum rise time is 70 μsec for a specific geometry of gas exit. The design criteria are also discussed.

A Sensitive Magnetometer and its Application to Nuclear Magnetic Thermometry in the Compound AuIn2 at Ultralow Temperatures

K. Andres and J. H. Wernick

Rev. Sci. Instrum. 44, 1186 (1973); http://dx.doi.org/10.1063/1.1686350 (3 pages) | Cited 16 times

Online Publication Date: 6 November 2003

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A method is described with which small magnetic moments of samples can be measured using a superconducting transformer and a commercial flux gate magnetometer. It is applied to nuclear magnetic thermometry in the temperature range from 1.7 mK to 0.5 K using the intermetallic compound AuIn2, which is particularly suitable for this purpose.

Computer Controlled NMR Spectrometer for Two‐Pulse Experiments

David A. Wright and Max T. Rogers

Rev. Sci. Instrum. 44, 1189 (1973); http://dx.doi.org/10.1063/1.1686351 (4 pages) | Cited 7 times

Online Publication Date: 6 November 2003

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A general method has been developed by which two‐pulse experiments may be largely automated by interfacing a minicomputer to an NMR pulse spectrometer. The necessary pulses and time delays are supplied by the computer and the interface converts these to the levels necessary for the rf oscillator and power amplifier of the spectrometer. Values of the relaxation times (T1, T2, T1ρ) are extracted from the collected data by data analysis subroutines which perform a least‐squares fit of the data to an exponential decay. Deviations of the data points from the least‐squares slope are displayed to permit an immediate visual check for experimental errors. The advantages of the simple pulse sequences are retained while their disadvantages, particularly inefficient data collection for very long or very short relaxation times, are greatly reduced. The lower limit of relaxation times which may be measured by this method is about 100 μ sec.

Size Spectrometry of Aerosols Using Light Scattering from the Cavity of a Gas Laser

R. Schehl, S. Ergun, and A. Headrick

Rev. Sci. Instrum. 44, 1193 (1973); http://dx.doi.org/10.1063/1.1686352 (4 pages) | Cited 3 times

Online Publication Date: 6 November 2003

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A gas laser cavity beam is used as monochromatic radiation source for detecting and sizing aerosol particles. The aerosol is forced through the cavity of a (1∕2) mW open cavity He☒Ne laser having one plane mirror and one spherical mirror. Light scattered from individual particles is collected by a hemispherical mirror and is focused onto a detector. The system has good resolution and sensitivity and has the capability of measuring high aerosol concentrations without dilution.

An Analysis of the Transmission Properties of Spherical Electrostatic Electron Spectrometers

P. C. Kemeny, A. D. McLachlan, F. L. Battye, R. T. Poole, R. C. G. Leckey, J. Liesegang, and J. G. Jenkin

Rev. Sci. Instrum. 44, 1197 (1973); http://dx.doi.org/10.1063/1.1686353 (7 pages) | Cited 28 times

Online Publication Date: 6 November 2003

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A detailed analysis of the transmission properties of low‐energy spherical electrostatic electron spectrometers employing preacceleration or preretardation is presented, which shows that the transmission efficiency of such instruments is not necessarily related inversely to electron energy nor directly to analyzer pass energy. A prescription, which enables observed spectra to be corrected over a wide energy range for intensity variations resulting from instrumental effects, is provided, and a detectable shift (≤ 0.1 eV) in the apparent position of electron lines under certain conditions is predicted. The theory is applied to the design and performance of two spherical photoelectron spectrometers employing ultraviolet and soft x‐ray sources. The analysis may readily be extended to other forms of electrostatic spectrometers employing preacceleration or preretardation.

Measurement of Complex Permittivity of Liquids at Frequencies from 5 to 40 GHz

R. Van Loon and R. Finsy

Rev. Sci. Instrum. 44, 1204 (1973); http://dx.doi.org/10.1063/1.1686354 (5 pages) | Cited 18 times

Online Publication Date: 6 November 2003

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Computer analysis of reflected power profiles allows accurate determination of complex dielectric permittivity of low, medium, and high permittivity liquids by one single method if nonideal plunger properties are taken into account. For low loss measurements account is taken of the losses in the waveguide walls. For medium and high permittivity liquids, dumbell plunger design leads to important errors due to higher mode excitation and propagation.

Time‐of‐Flight Measurements of Metastable State Lifetimes

David E. Kaslow and Jens C. Zorn

Rev. Sci. Instrum. 44, 1209 (1973); http://dx.doi.org/10.1063/1.1686355 (4 pages) | Cited 2 times

Online Publication Date: 6 November 2003

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A time‐of‐flight method for measurement of the lifetime of metastable molecules is described. The method is applicable to a molecules in several different metastable excited states. As compared to methods used previously, the method has the advantages that it does not require selective excitation or quenching of the different states; moreover, it does not require a determination of the relative populations or velocity distributions of molecules in the excited states. The feasibility of the method is demonstrated with a measurement of the lifetime of the a 1πg state of N2.

Method for Plotting Work Function Distribution of a Thermionic Emitter

R. Haug and J. Lebas

Rev. Sci. Instrum. 44, 1213 (1973); http://dx.doi.org/10.1063/1.1686356 (4 pages)

Online Publication Date: 6 November 2003

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A plotter of the work function distribution of a thermionic emitter has been designed with analog circuits connected to a plane diode. In the best conditions, a full width at half‐maximum (FWHM) of 160 meV has been measured. The apparatus has been tested with a plane tantalum emitter.

A High Speed Microprogrammed System for Generation and Acquisition of Signals

J. G. Zornig and J. F. McDonald

Rev. Sci. Instrum. 44, 1217 (1973); http://dx.doi.org/10.1063/1.1686357 (6 pages)

Online Publication Date: 6 November 2003

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A high speed microprogrammed system has been constructed to perform the synthesis and recording of high frequency nonrepeating pulse signals. The system can drive an analog device with arbitrarily designed waveforms and record individual pulses from several sensors in return. The present design operates at frequencies up to 1.5 MHz and can accept pulse durations of up to 16 000 samples. Accuracy is limited by the availabe ADC and computer word size and is presently 8 bits (0.3%). A primary advantage of the design is the reliance to the maximum extent on the hardware of a small general purpose computer. Very little more external hardware is required than the ADC, DAC, and multiplexer. Waveforms are read directly from and stored directly in the host computer core memory. This enables the maximum flexibility in the design of service programs for particular experiments. At present the system is used for an experiment in which a fast pulse input is to be adjusted adaptively in real time based on the measured outputs of a system.

Direct Reading Mobility Indicator

M. J. Howes

Rev. Sci. Instrum. 44, 1223 (1973); http://dx.doi.org/10.1063/1.1686358 (3 pages)

Online Publication Date: 6 November 2003

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Performance evaluation studies of a simple instrument which indicates directly the carrier mobility in extrinsic semiconductor samples of small aspect ratio is presented. Experimental results on Ge, Si, GaAs, and InP samples and encapsulated microwave devices (transferred electron oscillator structures) indicate a maximum variation of ±5% as compared with measurements using the Hall effect.

Cavitation as Artifact in Stopped Flow Experiments

Mo‐Mui Wong and Z. A. Schelly

Rev. Sci. Instrum. 44, 1226 (1973); http://dx.doi.org/10.1063/1.1686359 (5 pages) | Cited 3 times

Online Publication Date: 6 November 2003

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The time resolution of stopped flow devices is limited by the time required for homogeneous, rapid mixing. At high enough flow velocities cavitation occurs in the liquid, which at high sensitivity obscures optical detection in the early history of the reaction mixture. In a Gibson‐Milnes type stopped flow apparatus, in the flow rate range of 5–10 m sec−1, forced vortex or inertial breakdown is the major mechanism of bubble formation, depending on the way of stopping. The amplitude and lifetime of the effect are reported in pure water, methanol, and benzene as a function of mixer design, flow velocity, mixing ratio, temperature, way of stopping, as well as way of detection.

A Method for Correcting Curved‐Pipe Flow Effects Occurring in Coiled Capillary Viscometers

R. A. Dawe

Rev. Sci. Instrum. 44, 1231 (1973); http://dx.doi.org/10.1063/1.1686360 (3 pages) | Cited 4 times

Online Publication Date: 6 November 2003

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The error in viscosity measurements caused when using coiled tubes has been experimentally assessed. Previous methods for obtaining a correction factor are shown to be unreliable. A method for calculating the Dean number for an unsteady state viscometer is proposed with which the flow data obtained in a curved‐pipe can be satisfactorily correlated. Experimental results obtained using a new coiled viscometer are used to illustrate how such a correction can be applied.

An Improved Adiabatic Titration Calorimeter

S. Amdur and J. A. Marinsky

Rev. Sci. Instrum. 44, 1234 (1973); http://dx.doi.org/10.1063/1.1686361 (5 pages) | Cited 2 times

Online Publication Date: 6 November 2003

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The complexity and cost of instrumentation that has been necessary to provide the ability to measure the complete temperature profile of a chemical reaction without heat loss has been sizeably reduced in the improved adiabatic titration calorimeter that is described. Its design is such that even large changes in temperature during reaction can be accommodated without transfer of heat into or out of the calorimeter. This is accomplished simply by matching such changes in the calorimeter temperature by simultaneous and equivalent changes in the temperature of a surrounding water bath. This capability of the calorimeter eliminates the special instrumentation that is required in other calorimeters to measure the small temperature change that can be tolerated without significant loss of heat. The titrant is stored in a glass coil in thermal contact with the solution in the calorimeter prior to its controlled transfer into the solution by displacement with air. By this approach the heat capacity of the calorimeter is essentially unchanged during calorimetric study of a reaction. This simplification removes the need for repetitive calibration inherent in the operation of other calorimeters.

Absolute Length Measurement at High Pressure

R. C. Lincoln and Arthur L. Ruoff

Rev. Sci. Instrum. 44, 1239 (1973); http://dx.doi.org/10.1063/1.1686362 (8 pages) | Cited 10 times

Online Publication Date: 6 November 2003

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A length measurement system is described which can make absolute length change measurements of a meter long specimen within a pressure vessel (to pressures of 8 kilobar) with a fractional 3σ random error of ± 6 × 10−8 and a possible systematic error of less than 4 × 10−7 for changes in length of 1 cm. Possible uses of such a system for measuring the volume thermal expansivity (at pressure) and the isothermal bulk modulus (at pressure) are described. Moreover it is noted that when this system is combined with an ultrasonic velocity measurement system, the adiabatic bulk modulus (at pressure) and Grüneisen parameter as a function of pressure can be directly determined and the absolute pressure itself can be measured.

Digital Microstress Gauge for Magneto‐Thermal Gas Transport Studies

J. Taboada and T. W. Adair

Rev. Sci. Instrum. 44, 1247 (1973); http://dx.doi.org/10.1063/1.1686363 (4 pages) | Cited 6 times

Online Publication Date: 6 November 2003

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A description is given of an extremely sensitive stress gauge system designed for studying rarefied gas transport in magnetic fields. A novel approach employing a vertical quartz cantilever with an associated optical electronic readout is used to detect changes in the Maxwell stress on a thin aluminum disk in the magnetic‐thermal field. Forces acting on the detecting disk as small as 10−5 dyn can be resolved.

Ohmic Contacts to Photoconducting CdS Single Crystal Samples Using Pure Indium

T. Zold

Rev. Sci. Instrum. 44, 1251 (1973); http://dx.doi.org/10.1063/1.1686364 (5 pages) | Cited 1 time

Online Publication Date: 6 November 2003

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See Also: Erratum

Show Abstract
We have prepared ohmic contacts to photoconducting CdS samples by either soldering or diffusing high purity indium into the samples. The electric field distribution was measured along the samples with an electric field measuring equipment of 40 μ resolution. From these measurements we found that spikes or contact fields appear at the ends of the sample when the contacts were made by soldering indium to the sample. These contact fields can be large enough to nucleate high electric field domains at the contacts which strongly influence the development of the electric field in the rest of the sample. Such contact fields were absent when high purity indium was diffused into the sample for times longer than 30 min, at 600 °C in He atmosphere. On the other hand, for diffusion times shorter than 30 min, same as in the case of the soldered indium contacts, contact fields were observed at the ends of the sample. Furthermore, for diffusion times longer than 30 min, the electric field distribution indicated the existence of heavily doped layers at the ends of the sample; the thickness of these layers being typically of the order of 100 μ. These layers changed distinctly with time since after three months the thickness of these layers has been reduced by about 50 μ. The reduction of the thickness of these layers is probably caused by the recapture of some of the electrons by the donors, since atomic diffusion in solids at room temperatures is known to be extremely slow.

Helical Resonator for VHF SQUID Operation

L. R. Corruccini

Rev. Sci. Instrum. 44, 1256 (1973); http://dx.doi.org/10.1063/1.1686365 (2 pages) | Cited 4 times

Online Publication Date: 6 November 2003

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A helical resonator for SQUID magnetometer operation in the 30 MHz‐1 GHz frequency range is described. The device offers a convenient means of utilizing the expected linear increase in SQUID sensitivity with operating frequency throughout this range. Experimental results which demonstrate this effect at 460 MHz are presented.

A Study of the Ion Beam Intensity and Divergence Obtained from a Single Aperture Three Electrode Extraction System

J. R. Coupland, T. S. Green, D. P. Hammond, and A. C. Riviere

Rev. Sci. Instrum. 44, 1258 (1973); http://dx.doi.org/10.1063/1.1686366 (13 pages) | Cited 73 times

Online Publication Date: 6 November 2003

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Experimental results are given for the perveance and beam divergence of a single aperture three electrode extraction system using helium ions at energies between 10 and 30 keV. The aperture radii, the electrode thicknesses, and the spacings were varied and from the results a preferred design was obtained for use in a multiaperture array. The most critical parameter was the ratio (S) of the radius of the first aperture to the distance between the first and second electrodes, the highest current density being obtained at values of this ratio less than 0.5. The optimum beam divergence observed corresponded to a Gaussian beam profile with a width (ω) of ± 1.2° at 2 m from the source. The measured perveance at small values of S and at minimum ω lay between 75% and 90% of the value predicted on the basis of a simple model using the Langmuir‐Blodgett formula for the spherical diode.

The Slip Correction in Accurate Viscometry

R. A. Dawe

Rev. Sci. Instrum. 44, 1271 (1973); http://dx.doi.org/10.1063/1.1686367 (3 pages) | Cited 5 times

Online Publication Date: 6 November 2003

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The slip correction in capillary viscometers can cause significant errors. Some of the factors which affect slip are described and suggestions are made so that inaccuracies may be avoided in future accurate viscosity determinations.

A New Ion and Electron Detector for Ion Cyclotron Resonance Spectroscopy

W. T. Huntress and W. T. Simms

Rev. Sci. Instrum. 44, 1274 (1973); http://dx.doi.org/10.1063/1.1686368 (4 pages) | Cited 4 times

Online Publication Date: 6 November 2003

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A new detector using an externally driven tuned circuit has been developed for use in ion cyclotron resonance spectroscopy experiments. Based on the ``Q‐meter'' circuit, this detector will operate at frequencies greater than 1 MHz at rf levels less than 1 mV. Operation in the frequency range 1–15 MHz allows the use of higher magnetic fields for more efficient storage of low mass ions in the trapping mode of operation. In the frequency range 2–6 MHz electrons can be detected in the ion cyclotron resonance cell by their resonant motion in the trapping plane.

A Multiple Sweep, Floating Langmuir Probe System for Pulsed Discharge Diagnostics

J. Lacoste and K. Dimoff

Rev. Sci. Instrum. 44, 1278 (1973); http://dx.doi.org/10.1063/1.1686369 (4 pages) | Cited 2 times

Online Publication Date: 6 November 2003

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A multiple sweep probe and recording system is described which operates at floating potential. It is adaptable to measuring plasma characteristics generated by a high voltage discharge. Shielding problems are avoided by allowing the system to trigger with the initial transient and then recover automatically to predischarge settings. Duration, frequency, and number of sweeps are easily controllable to fit requirements of the postdischarge regime under study.

A Simple Flying Spot Scanner Design for Electron Lithography

C. M. Melliar‐Smith and A. R. Storm

Rev. Sci. Instrum. 44, 1282 (1973); http://dx.doi.org/10.1063/1.1686370 (4 pages) | Cited 2 times

Online Publication Date: 6 November 2003

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A simple, inexpensive flying spot scanner system is described which enables a conventional scanning electron microscope (SEM) to be used for research projects in electron beam lithography. The unit, built almost entirely from readily purchased parts, bolts onto the SEM without any modification of the microscope itself. The ultimate resolution of the system exceeds 45 line pairs∕cm over a 9 cm square frame, giving over 900 beam on, beam off operations per frame. The system has been used with electron lithography to etch thin films into patterns of considerable complexity with linewidths of less than 5000 Å.
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