bluuebunny/crossref_metadata_2025 huggingface dataset:
A method for measuring very small conductances
Authors: Berberian John G.
Published: March 2003

A transient method for measuring extremely small conductances (specific conductance ∼10−14 mho/cm) is described. Long−time dielectric relaxation times can also be determined with the addition of a capacitance calibration. Direct current conductance data of commercially available cholesteryl linoleate are presented as a function of reciprocal temperature.
Beryllium windows joined by electroplating
Authors: Johnson H. R. , Dini J. W.
Published: March 2003

Beryllium windows, 76 mm diam and 0.25 mm thick, were joined to stainless−steel flanges by electroplating the joint area with nickel. The procedures for surface preparation of both materials and the technique used for joining the materials with nickel are described. Electroplated joints made with this method have proved to be vacuum tight to helium. By using this technique, shrinkage stresses, distortion, and recrystallization problems associated with high−temperature joining processes are eliminated.
A simple image intensifying system for Berg−Barrett topography
Authors: Vreeland T. , Lau S. S.
Published: March 2003

A simple imaging system to facilitate crystal orientation with respect to the x−ray beam for Berg−Barrett topography has been constructed. This system consists of an image intensifier tube with an x−ray phosphor deposited on its fiber−optic input plate and means to manipulate and indicate the crystal orientation. Applications of the system to studies of both
Low−cost apparatus for the determination of the refractive index of thin dielectric films
Authors: Brady James J. , Lewis Adolph L.
Published: March 2003

A relatively simple apparatus for determining the index of refraction of substrates such as ZnSe and the index of refraction of thin films deposited on a substrate is described. Use is made of a readily available Lansing mirror mount and two Lansing translational stages.
Thin films for x−ray astronomy
Authors: Williamson F. , Maxson C. W.
Published: March 2003

A method is described for producing thin, large area plastic films used for entrance windows of x−ray proportional counters in rocket−borne experiments. Sizes up to 1800 cm2 have been successfully prepared and flown.
Resonant cavities for the measurement of the surface resistance of conductors at millimeter wavelengths
Authors: Tischer F. J. , Jalali F.
Published: March 2003

Three cavity resonators for the investigation of the electrical surface characteristics of conductors at millimeter−wave frequencies are described. They are an H−guide resonator and two rectangular cavity resonators optimized to give high accuracy and good repeatability of measurements. The investigation in which these cavities are used involves Q−value measurements at 35 Ghz with polished and rough surfaces.
Automatic scanning of mica track recorders
Authors: Cohn Charles E. , Armani Roland J.
Published: March 2003

A computer−controlled microscope system previously developed for scanning plastic solid−state track recorders has been refined to allow scanning of mica recorders. Refinements were made in the automatic focusing, scan pattern, and light level threshold.
An automatic system for determining Seebeck coefficients of polymeric fibers and films
Authors: Grady P. L. , Hersh S. P.
Published: March 2003

An apparatus is described which greatly facilitates the measurement of Seebeck coefficients on materials with low electrical conductivity for use in charge transport studies. A temperature programmer is included in the system and data are recorded automatically, thereby eliminating the need for manual measurements. Special instruments and connections are used to reduce leakage of the thermally generated Seebeck voltage. The apparatus has been especially designed for polymeric films and fibers and a simple and inexpensive method for mounting and testing fiber specimens has been developed. The various types of Seebeck experiments that can be performed with this system and the problems encountered with low conductivity samples are described.
A simple rotating anode x−ray generator
Authors: Longley W. , Miller R.
Published: March 2003

A rotating anode x−ray generator has been constructed of simplified design, with the elimination of unnecessary complexities. The design incorporates magnetic fluid ’’Ferrofluidic’’ vacuum seals and Wilson water seals. The rotor is 10 cm diam and the tube body is 5 cm wide. The tube is demountable at several points for easy replacement of rotor and cathode assemblies. The complete unit is contained within a framework 1.52×0.61 m.
Tunable low−temperature NMR oscillator for magnetic field measurements
Authors: Wampler William R. , Matula Svatoslav , Lengeler Bruno , Durcansky Georg
Published: March 2003

A tunable low−temperature rf oscillator with Si MOSFETs as active devices is described. Tunability by a factor of 2 in frequency is reached by using GaAsP varactor diodes. Used as an NMR probe with 27Al and 51V, the oscillator allows magnetic fields to be measured in superconducting magnets with an accuracy of better than 0.1 G. We found the gyromagnetic ratio γ of 27Al and 51V at 4.2 K to be 1.11119±1 and 1.12555±1 MHz/kG, respectively, corresponding to a Knight shift of + 1.61×10−3 and + 5.58×10−3, respectively.
An ac capacitance bridge temperature controller for use in strong magnetic fields at low temperatures
Authors: Griffin J. A.
Published: March 2003

An ac capacitance bridge, using a strontium titanate capacitance thermometer, is used with phase sensitive detection for the control of temperature to ±5 m K/h between 4.2 and 25 K in strong magnetic fields.
A wide−time range pulse radiolysis system of picosecond time resolution
Authors: Jonah Charles D.
Published: March 2003

A stroboscopic pulse radiolysis system is described which detects the transient absorption generated by a 20 psec pulse from a 20 MeV linear accelerator. The time resolution is obtained by using, as the analyzing light, the short pulse of ?erenkov light generated by the portion of the electron beam which passes through xenon. The remaining portion of the electron beam is delayed by passing around a 270° magnet and the delay of the light may be varied by an optical delay line. Block diagrams for the electronics and the optics are given. The magnitude of sources of errors are discussed.
Laser-initiated krytron-switched Blumlein structure for pulse selection
Authors: Hyer R. C. , Sutphin H. D. , Winn K. R.
Published: March 2003

A method is described for the selection of a mode-locked pulse from a laser by the use of a laser-initiated krytron-switched Blumlein structure that replaces the usual high voltage spark gap. The main features are an all electronic circuit coupled to a longitudinal mode KD*P Pockels cell that has a fast risetime and high extinction ratio. The result is an inexpensive, noise-free pulse selector that provides a stable source of switched out pulses.
Variable temperature sample cell and optical mount for laser Raman studies of adsorbed species
Authors: Schrader G. L. , Hill C. G.
Published: March 2003

A sample cell and optical mount for use in laser Raman spectroscopic studies of adsorbed species at elevated temperatures is described. In situ Raman spectra of pyridine adsorbed on 60–120 mesh silica gel at room temperature, 75 °C, and 150 °C are reported. The cell has also been used in studies of other species adsorbed on silica, alumina, and platinum wire.
Precise measurement of dielectric properties at very high frequencies
Authors: Kakimoto A. , Ōchi M. , Matsushita T.
Published: March 2003

This paper describes an improved method and apparatuses based on it for the measurement of the dielectric constant and the dissipation factor at very high frequencies. This method is a combination of the Hartshorn and Ward, Lynch, and liquid immersion methods. The direct purpose is to measure low-loss polyethylene which is to be used in submarine telephone cables at 36 and 100 MHz in Japan. By using a 0.5∼2.0 mm thick disk specimen, the dielectric constant can be measured to an accuracy of 0.3%, the dissipation factor to several μrad, and the mean thickness to several μ without any kind of correction. The three equations for them are simple and independent of the frequency. This method is easy to use and takes little time, for the values to be measured for each specimen are only three in a series of measurements, and the mechanical thickness measurements are not required.
On the measuring and recording of transient phenomena in vibrating systems
Authors: Sachse Wolfgang
Published: March 2003

We describe in this paper a simple device which facilitates the measurement and recording of the response curve of vibrating systems. The method utilizes a digital counter to measure the period and a peak detector to measure the amplitude of vibration. Applications of the method to record the steady-state and transient response of linear and nonlinear vibrating systems are given.
Simple digital clipped correlator for photon correlation spectroscopy
Authors: Chen S. H. , Veldkamp W. B. , Lai C. C.
Published: March 2003

The detailed design and performance of a digital clipped correlator constructed as an integral part of a photon correlation spectrometer (PCS) is described. The correlator is of a modular design and easily expandable to several hundred channels. Each channel contains a 4-bit buffer storage, and the overflow bits from the storage are serially transferred into the memory of a multichannel analyzer. The dead time associated with the transfer is negligible. The sampling time of the correlator can be varied from 1 sec to 50 nsec. The principal features of the design are its simplicity, expandability, low cost, and optimal use of commercially available equipment.
Low-temperature heat-pulse calorimetry for self-heating radioactive samples
Authors: Trainor R. J. , Knapp G. S. , Brodsky M. B. , Pokorny G. J. , Snyder R. B.
Published: March 2003

A heat-pulse technique is described for measuring low-temperature heat capacities of radioactive self-heating samples in the range 2–60 K. The method also provides a simple alternative to traditional heat-pulse methods for measuring nonradioactive samples and is attractive because a heat switch is not required. Data for copper indicate an overall accuracy of about 1%. Heat capacity data for plutonium-242 between 4 and 13 K are also presented.
Time-share synthesizer NMR
Authors: Cary Lewis W.
Published: March 2003

A method using a frequency synthesizer to operate both the transmitter and local oscillator in an FT–NMR spectrometer is described. This method facilitates multi-nuclear operation.
New high pressure cell for neutron scattering at very low temperatures
Authors: Paureau J. , Vettier C.
Published: March 2003

An apparatus for inelastic neutron scattering experiments at low temperature is described. This pressure assembly consists of an autofrettaged aluminum 7075-T6 alloy cell and a shield. The rupturing pressures for some cells have been measured at different temperatures; the efficiency of the shield has also been tested. These studies demonstrate the feasibility and the safety of experiments under high pressure up to 4 kilobar even at very low temperature.
High precision capacitance bridge for studying lipid bilayer membranes
Authors: White Stephen H. , Blessum David N.
Published: March 2003

A simple ac bridge for the measurement of the capacitance of lipid bilayer membranes between 100 Hz and 10 kHz with a nominal accuracy of about 0.1% without corrections is described. The voltage across the unknown need be only 7 mV (rms). Using a simple calibration procedure, the capacitance can be determined with a nominal accuracy of 0.05%. The resolution of the bridge is about 1 part in 20 000. The novel features of the bridge are (1) 100:1 resistance ratio arms and a floating unknown, (2) a single-ended output and a balanced input utilizing a photocoupled isolator, and (3) a detector to monitor voltage across the unknown at balance.
Data acquisition system for laser Doppler velocimeters
Authors: Maynard J. A. , Gaylord T. K. , Rust J. H.
Published: March 2003

Instrumentation for rapidly acquiring, storing, and processing laser Doppler velocimeter data is described. Electrical pulses having amplitudes that are inversely proportional to the Doppler frequencies are generated and then counted with a multichannel analyzer. Velocity distribution data may then be printed out, graphically displayed, or computer processed.
Software correction for phase-sensitive detector misalignments in pulsed NMR
Authors: Jeener J. , Segebarth C.
Published: March 2003

A complete analysis of pulsed NMR signals requires the knowledge of the time dependence of the components of the signal in phase and out of phase with the pulse. In practice, the NMR signal is processed by a pair of (approximately) orthogonal phase-sensitive detectors, the filtered outputs of which can be sampled, digitized, and stored repetitively. The present paper describes a software technique for correcting these stored signals for the lack of orthogonality of the two phase-sensitive detectors, the difference between their sensitivities, the overall phase shift in the spectrometer, and the difference between the reference frequency of the spectrometer and the frequency of the center of a reference NMR line. The necessary information is derived (also by software) from measurements performed on a single symmetric NMR absorption line.
Torsion-equilibrium method for measuring twist in textile yarns
Authors: Grady P. L. , Lord P. R. , London C. R. , Smith G. E.
Published: March 2003

An electromechanical apparatus is described that was designed to determine the twist in textile yarns by measuring the number of turns a yarn untwists due to the torque created by a freely rotating axial load. The apparatus utilizes an optoelectronic system to count the number of turns in each direction so that the net number of turns needed to reach the equilibrium state is measured. The damping of the rotating unit was found to be noncritical. A mechanical support system has been designed which facilitates testing and improves reproducibility of results. The system can be used for staple and continuous filament yarns but the sample length for staple yarns must be shorter than the fiber length.
Apparatus for the measurement of angle-resolved spectra of electrons emerging from single crystals
Authors: Best P. E.
Published: March 2003

An apparatus to measure inelastic low-energy electron diffraction (ILEED) and energy- and angular-dependent secondary electron emission, (EADSEE), is described. The apparatus can measure EADSEE for incident beam energies of up to 200 eV and ILEED for beam energies up to 50 eV, with energy and angular resolutions of about 0.15 eV and 1.5°, respectively. General design criteria are discussed, and detail is provided where a little-known technique has been employed.
Composition analyzer for microparticles using a spark ion source
Authors: Auer Siegfried , Berg Otto E.
Published: March 2003

Iron microparticles were fired onto a capacitor-type microparticle detector which responded to an impact with a spark discharge. Ion currents were extracted from the spark and analyzed in a time-of-flight mass spectrometer. The mass spectra showed the elements of both detector and particle materials. The total extracted ion current was typically 10 A within a period of 100 nsec, indicating very efficient vaporization of the particle and ionization of the vapor. Potential applications include research on cosmic dust, atmospheric aerosols and cloud droplets, particles ejected by rocket or jet engines, by machining processes, or by nuclear bomb explosions.
Tesla transformer accelerator for the production of intense relativistic electron beams
Authors: Boscolo I. , Brautti G. , Coisson R. , Leo M. , Luches A.
Published: March 2003

A resonant transformer high-voltage (HV) generator is described that delivers a 1.1-MV peak on the HV head of the secondary circuit. The HV head feeds a field emission diode that gives out a 6-kA/20-nsec electron beam. High repetition rates, up to 3 pulses/sec (power supply limited), have been attained with foilless diodes. Design details and electron beam characteristics are given and discussed.
Inelastic electron scattering spectrometer
Authors: Gibbons P. C. , Ritsko J. J. , Schnatterly S. E.
Published: March 2003

The design and construction of an inelastic electron scattering spectrometer for the study of electronic excitations of solids is described. The spectrometer features high beam energy (300 keV) and fine energy loss resolution (<0.1 eV). Energy loss spectra in the range 0–1000 eV may be measured with momentum transfer from 0 to 2 Å−1.
Convenient electron spin resonance/optically detected magnetic resonance spectrometer
Authors: Murphy J. C. , Zarriello P. R. , Kues H. A. , Aamodt L. C.
Published: March 2003

A combined electron spin resonance (ESR)/optically detected magnetic resonance (ODMR) spectrometer is described. The microwave portion of the spectrometer is of the homodyne type and uses amplitude modulation of the reflected signal from the sample cavity for frequency stabilization and resonance detection. For ODMR spectroscopy microwave power incident on the resonant cavity can be pulse (Δt ≳ 100 μsec) or square wave modulated by a second modulating waveform.
Vibrating wire viscometer
Authors: Bruschi L. , Santini M.
Published: March 2003

A new technique, developed to measure the linewidth of a vibrating wire, is presented in this paper. After a discussion on the accuracy of the method, the theory of the vibrating wire is reviewed, with particular regard to the conditions under which the Stokes theory can be applied to real experiments.
Dilution refrigerator still with 4He film-flow suppression
Authors: Pratt W. P.
Published: March 2003

A still for a 3He–4He dilution refrigerator has been constructed which suppresses the 4He superfluid film flow and attains 3He/4He ratios as large as 600. This design has the novel feature that all the heaters are attached to the outside of the still.
Cryostat for single-crystal absorption spectrophotometry
Authors: Barclay A. , Binks J. H. , Cameron N. D.
Published: March 2003

A simple and robust cryostat is described for the investigation of single-crystal absorption spectra. The specimen, mounted on a small nickel aperture, is cooled by means of conduction along a copper rod which fits closely into a copper cylinder containing liquid nitrogen. The rod is easily removed in order to mount and align the specimen, and is enclosed in a vacuum tight, brass sleeve to prevent condensation of water vapor on the specimen. The cryostat is easily constructed with a minimum of workshop equipment.
Thin-film thickness monitor range extender
Authors: Wilson F. C. , Sandstrom D. B. , Serreze H. B.
Published: March 2003

A simple thin-film thickness monitor mechanical range extender is described which permits rapid in vacuo switching from reduced to full deposition rate sensitivity.
Magnetic probe for use in intense electron beam environment
Authors: Gerber K. A. , Hammer D. A. , Dove W. F.
Published: March 2003

A quartz housed, liquid dielectric insulated, magnetic probe capable of withstanding electron beam current densities exceeding 3.5 kA/cm2 is described as it is employed on the ’’Triton’’ electron beam–plasma interaction experiment.
Glow discharge source of H− ions
Authors: Rhodes II R. A. , Block W. F. , Wallace B. G.
Published: March 2003

A simple glow discharge source of H− ions has been built that has the advantages but not the disadvantages of the hot cathode type. The maximum stable current produced by this source was 8.8×10−9 A. The source was also found to produce stable currents of H+, H2+, and H3+ at the same order of magnitude as that of the H− ions.
Two-dimensional photon-counting detector arrays based on microchannel array plates
Authors: Timothy J. G. , Bybee R. L.
Published: March 2003

The production of simple and rugged photon-counting detector arrays has been made possible by recent improvements in the performance of the microchannel array plate (MCP) and by the parallel development of compatible electronic readout systems. The construction of proximity-focused MCP arrays of novel design in which photometric information from (n×m) picture elements is read out with a total of (n+m) amplifier and discriminator circuits is described. Results obtained with a breadboard (32×32) -element array employing 64 charge-sensitive amplifiers are presented, and the application of systems of this type in spectrometers and cameras for use with ground-based telescopes and on orbiting spacecraft discussed.
Interferometer for measuring fast changes of refractive index and temperature in transparent liquids
Authors: Miller A. , Hussmann E. K. , McLaughlin W. L.
Published: March 2003

A double-beam interferometer has been designed for detecting changes of refractive index in transparent liquids associated with the absorption of ionizing radiation energy, due to short electron beam pulses from an accelerator. The response time of the interferometer is less than 0.2 μsec, and refractive index changes of the order of 10−7 can be measured, corresponding to a temperature change of ∼10−3 °C and an absorbed dose in water of ∼350 rad. The interferometer can be used as either a real-time or integrating radiation dosimeter, if the temperature coefficient of the refractive index (dn/dT) is known for the irradiated liquid in the temperature region of interest.
Ultrahigh vacuum low temperature stage for i
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i
t
u film deposition and characterization
Authors: Miller D. L. , Arns T. , Hrabak G.
Published: March 2003

An apparatus which combines a liquid 4He Dewar with an ultrahigh vacuum system used for LEED or AES surface analysis and ultrathin film deposition is described. A linear motion bellows seal allows the substrate for film deposition to be moved out of the radition shields, which makes ion bombardment cleaning possible. A He gas heat exchanger between the substrate holder and He reservoir provides a wide variation of temperatures. In situ measurements of superconducting transition temperatures below 2 K have been made with this apparatus.
Digitally programmable ratio transformer bridge
Authors: Magerlein J. H. , Sanders T. M.
Published: March 2003

We describe a digitally programmable impedance bridge, used here for low-temperature resistance thermometry, and a compatible digital programming and data logging interface. The bridge employs a commercial programmable ratio transformer to achieve high resolution with minimum circuit complexity. We measure the ratio of the resistances of a carbon thermometer and a fixed reference resistor, both near 2 K, with a resolution limited by Johnson noise in the resistors. The bridge circuit described here is suitable for a variety of programmable or self-balancing impedance measurements.
Sources for seeded beams of K and KF
Authors: Lübbert A. , Rotzoll G. , Viard R. , Schügerl K.
Published: March 2003

Double chamber ovens having an additional gas feed line which allows generation of seeded K and KF beams with a variety of gases are described. The seed species partial pressure is kept at ?1 Torr, and the total pressure is varied up to 800 Torr. The beams are skimmed with heated nickel skimmers. The velocity and speed ratio of the beams and their dependence on seeding gas identity and pressure are presented.
Digital trigger circuit with excellent noise suppression
Authors: Van Driessche W. , Gullentops C.
Published: March 2003

The digital trigger circuit described in this paper allowed us to trigger digital data acquisition equipment accurately. Its main feature is a noise suppression circuit which introduces only a small phase shift and permits us to reject noise very close to the frequency range of the measured signal. The level of the rejected noise signal as well as the trigger level are adjustable with thumbwheel switches. The performance of the trigger circuit is demonstrated with a disturbed sine wave as input signal. An analog equivalent circuit with noise rejection characteristics similar to those of the pseudo-filter is described.
Calorimetry automation in the 0.4–3 K range: Use of the NBS superconductive fixed point device and the specific heat of copper
Authors: Martin Douglas L.
Published: March 2003

Operation of an automatic data acquisition system, with an on-line minicomputer, in the 0.4–3 K temperature range is described and illustrated by results obtained on pure copper. The temperature scale was set up using both 3He vapor pressure thermometry and the NBS superconductive fixed point device. On the basis of specific heat measurements on pure Cu and Cu alloys, it appears that the temperatures assigned by the NBS to the superconducting transition temperatures of cadmium and zinc are too close. The required adjustment is within their assigned uncertainty limits.
Compression–expansion technique for wide dynamic range recording
Authors: Vanderkooy J.
Published: March 2003

A simple circuit is presented which allows a signal with over 100 dB of dynamic range to be recorded on a modest tape recorder. No pilot track is necessary, and the same curcuit in a different mode is used on replay to reproduce the original dynamic range. There is no spectral distortion of the recorded signal, and calibration of reference levels is unnecessary.
New method for very sensitive dielectric difference measurements on high-loss liquids at microwave frequencies
Authors: Hallenga K.
Published: March 2003

A microwave system for very sensitive dielectric measurements on high-loss liquids over the frequency range 8–26.5 GHz is described which depends on the cavity resonance perturbation method. Equations for the resonance perturbation by a thin capillary in cylindrical as well as in rectangular cavities are derived, demonstrating the dependence of the real and imaginary part of ε on both the resonance frequency shift and the change in resonance width of the cavity. The microwave generator with high frequency stability (1 part in 108) is frequency modulated at one or two frequencies. The use of phase sensitive detection allows ε measurements on water to within 1%, as well as dielectric difference measurements on aqueous solutions to within 0.005 in Δε′ and Δε″ (1 part in 104 or better). Details of cavity constructions are given and some measurements on water and on dilute aqueous solutions are reported.
Water spark gap for a nitrogen laser
Authors: Saikan Seishiro , Shimizu Fujio
Published: March 2003

Satisfactory operation of the Blumlein type nitrogen laser was obtained by using a water-filled spark gap. The water-filled spark gap uses flowing water, and the Blumlein circuit is charged by a Marx-bank driver.
Automatic Bragg angle control comparator modification for the General Electric SPG-3 ratemeter
Authors: Storm A. R.
Published: March 2003

A modification to a previously described automatic Bragg angle control (ABAC) comparator circuit is described that makes it compatible with a General Electric SPG-3 ratemeter.
Application of minicomputers in high resolution electron tunneling
Authors: Adler J. G. , Straus J.
Published: March 2003

A minicomputer−based system for obtaining ’’absolute values’’ of tunnel conductance σ to one part in 105 and simultaneous measurement and ’’calibration’’ of its rate of change dσ/dV is described. The analog, digital, and interface hardware along with the necessary software are discussed in detail and typical results are shown for the system used. The system is capable of presenting the calibrated results in only a few minutes after each sweep is completed, yet requires less than 8 k of core memory, provided a mass storage device such as magnetic tape is available.
A gain−stabilizing detector for use in radio astronomy
Authors: Yerbury M. J.
Published: March 2003

Excess noise in total−power radiometers, its origin, and its effect on continuum radio astronomy measurements during data reduction are discussed. The theory of a new type of noise−adding radiometer is presented, and the resulting practical application of the theory in the form of a gain−stabilizing detector is described. It is shown that the performance of this type of noise−adding radiometer can be optimized, quite simply, to yield an effective system temperature which is less than that of an ideal Dicke system.
Reliability of a capacitance manometer in the range 2×10−4−5×10−6 Torr
Authors: Loriot G. , Moran T.
Published: March 2003

A capacitance manometer has been tested and compared to the method of volumetric pressure division using helium as a working gas in the range 2×10−4−5×10−6 Torr. The results show that the unit tested was linear to the lowest pressures utilized, and the two methods were in agreement to about 0.6% plus 4×10−7 Torr, in addition to the errors introduced by the least count of the capacitance manometer’s digital readout. Argon and air gave similar results.
Instrument for automatic kilovolt pulsed measurement of electronic properties
Authors: Domingo George , Holm−Kennedy James W. , Daud Taher
Published: March 2003

A new instrument which electrically characterizes devices and materials at high voltages applied for short duration at low repetition rates is described. The instrument automatically measures and plots I−V or J−E sample and device characteristics up to very high voltage levels under pulsed dc conditions. In addition, the system measures and plots resistance, conductance, resistivity, and conductivity versus voltage, current, or electric field. Minor modifications in the analog computing circuit will extend the usefulness of the system to other types of pulsed data acquisition. The system was tested with resistive samples ranging from 60 Ω to 125 kΩ, using pulsed voltages from 0 to 8000 V, maintaining measurement error well below 1%. The system is particularly useful in characterizing semiconductor materials at high electric fields (warm and hot electron effects) and electronic devices under pulsed conditions (power transistors, IMPATTS, TRAPATTS, Gunn oscillators, PIN diodes, etc.). The design, operation, and performance of the instrument is described.
Time domain difference amplifier
Authors: Hidaka Takehiko
Published: March 2003

This paper describes a new electronic circuit, the time domain difference amplifier, used to reduce strong drifts which bury weak repetitive signals. The principle is that the input, with signal and drift, is sampled at signal on and signal off states, and subtracted from each other. The random drift is reduced by integrating the subtracted values. Drift suppression is about 35 dB for 3.0 Hz ac drift and 100 repeatings for integration.
Hot−wire anemometry in moderately heated flow
Authors: Ali S. Firasat
Published: March 2003

Hot−wire probes have been calibrated in air flow at different velocities and air temperatures. The Reynolds number range was 0.5−2.5 at air temperatures of 20−100°C. The empirical heat loss equation was found to be significantly different from the often quoted one by Collis and Williams [J. Fluid. Mech. 6, 357 (1959)]. A two−wire probe followed by an electronic analog circuit was devised in order to provide simultaneous velocity and temperature signals in turbulent air flow. This circuit is appreciably simpler than the one reported by Chevray and Tutu [Rev. Sci. Instrum. 43, 1417 (1972)] and for a given probe configuration only minor circuit adjustments are needed before operation.
Simple cryostat for measuring rf susceptibility from 4.2 to 300 K
Authors: Habbal F. , Watson G. E. , Elliston P. R.
Published: March 2003

We describe a cryostat for measuring the rf (100 kHz) susceptibility of insulators in the temperature range from 300 to 4.2 K. The sample is connected by a tube to room temperature and is moved in and out of the coil of a tunnel diode oscillator located at a constant low temperature. The change in frequency of the oscillator is measured with a digital frequency counter. The oscillator is stable to ±2 Hz over periods of several hours. The counter resolution and the attainable filling factor limit the resolution χ/Δχ to about 2×104. The susceptibility of anhydrous NiCl2 powder was measured to evaluate the apparatus and determine the filling factor
A simple reliable current−voltage power supply for superconductive solenoids
Authors: Sullivan N. S. , Vaissiere J. , Mauc C.
Published: March 2003

We describe a relatively simple circuit for the charging and discharging of superconductive solenoids using inexpensive integrated circuit components. The circuit consists of a regulated voltage−regulated current power supply with an automatic voltage−current crossover and includes protection for the solenoid in the event of a quench.
Mechanically operated thermal switches for use at ultralow temperatures
Authors: Roach Pat R. , Ketterson J. B. , Abraham B. M. , Roach Paul D. , Monson J.
Published: March 2003

Some thermal switch designs are discussed in which a 4He actuated bellows is used to make or break mechanical contact between two sections containing metallic surfaces. Techniques are discussed which permit the switch sections to make thermal contact to liquid 3He by employing a large liquid−solid surface area. Designs are presented for a Pomeranchuk cell and an adiabatic demagnetization cell, which incorporate the bellows−actuated mechanical switch concept.
A dynamic admittance meter based on a voltage controlled oscillator IC
Authors: Budding R. W. , Strackee L.
Published: March 2003

A simple and versatile admittance meter is described, wich is built around a commercially available voltage controlled oscillator (VCO). The instrument measures the real and imaginary part of an unknown admittance separately in the frequency range from 1 kHz up to 1 MHz. A compensating admittance can be inserted in order to improve the precision of the measurement. The accuracy of the instrument is estimated as better than 3%.
The ESRO 4 gas analyzer
Authors: Trinks H. , von Zahn U.
Published: March 2003

On 22 November 1972 a gas analyzer was launched into earth orbit on board the satellite ESRO 4. This mass spectrometer for the investigation of the upper atmosphere composition and density employs a spherical antechamber connected to an electron impact ion source, an analyzing field of the monopole type, and a threefold detector system including one multiplier operated in the analog mode. The instrument measures neutral constituent number densities within the mass range 1−44 amu. The sampling frequency is one mass scan per 9 sec using a total bit rate of 90 bps. The laboratory calibration of the instrument sensitivities was performed using a gas flow method.
New compact molecular beam velocity selector
Authors: Este G. O. , Hilko B. , Sawyer D. , Scoles G.
Published: March 2003

A new, compact, molecular beam velocity selector is described. It utilizes the same principle as the slotted disks velocity selectors but consists only of one disk incorporating a series of multichannel collimators. Advantages: simplicity, short length, light weight. Disadvantages: limited resolution and limited maximum speed selected.
Extrusion of indium wire for vacuum seals
Authors: Bernat T. P. , Blair D. G. , Hymel B.
Published: March 2003

Indium wire for making demountable vacuum seals has been easily extruded from used indium at virtually no cost. Apparatus and procedure are described.
High stability pulsed oscillator with coherent starting
Authors: Lawless Phil A.
Published: March 2003

A pulsed oscillator for ultrasonic work was built having phase coherence with the gating pulse. It was based on an integrated circuit gated amplifier and a quarter−wave resonant line. The stability of the frequency is one part in 105 and is due to the quarter−wave line. The frequency can be changed easily be means of a mechanical sliding short circuit or by an electronic method. The range of operation is from 10 to over 35 MHz.
High pressure optical cell for biochemical studies
Authors: Williams Richard Kenneth
Published: March 2003

The adaptation of a commercially available high pressure optical cell to monitor changes in absorbance in aqueous solutions by use of a fused quartz cuvette, and a high pressure seal, inert to n−hexane, is described. Measurements of percent transmittance to an accuracy of ±0.2% have been obtained. Contact of the sample solution with the metal surface of the optical cell is avoided, and the cell is, therefore, suitable for studies of biochemical reactions.
Study of the behaviour of mirror electrostatic analyzers in the case of energetic particles
Authors: Prange R.
Published: March 2003

We study three models of electrostatic mirror analyzers and show that these kinds of instruments are inadequate to analyze energetic particles because they require too high retarding voltages compared to the mean energy of the particles analyzed.
ESR cavity cryostat system for investigations of single crystals under uniaxial stress
Authors: Assmus W. , Silber D.
Published: March 2003

We describe a cavity−cryostat system for ESR investigations of uniaxial stress effects on single crystals. We are able to eliminate two problems which often arise in such investigations: I. Our system allows a homogeneous high intensity irradiation of the crystals at low temperatures inside the cavity. II. A reference crystal system enables a reliable determination of small stress effects. Two typical examples show the range of application of the setup.
High power CO2 laser energy detector
Authors: Offenberger A. A. , Smy P. R. , Burnett N. H.
Published: March 2003

A CO2 laser energy detector is described which uses the pressure rise generated in a vaccum cell by gaseous infrared absorption to provide linear energy detection over many decades, good responsivity, wide aperture, and in−line beam monitoring. Nonadiabatic pressure measurements resulting when the beam size is less than the cell aperture are discussed.
Conversion of a commercial CO2 laser to CO operation at 5.6 μ
Authors: Davis J. A.
Published: March 2003

Modifications on a commercial room temperature CO2 laser to create a CO laser are discussed. Powers of 1 W were easily obtained in the 5.4−5.6 μ wavelength region.
A simple, fast, side−looking current transformer
Authors: Avinor M. , Hasson A.
Published: March 2003

A very simple current transformer is made by using a loop of shorted coaxial cable. The measured current passes near the loop and not through it. Decay constants between 10 and 100 μsec are readily obtained. The rise time is limited only by the quality of the coaxial cable.
’’Triodization’’ of transistor replacement for the pass tubes in a Varian V−2100 B magnet power supply
Authors: Tschudin Rolf , Resing H. A.
Published: March 2003

A feedback resistor suffices to make the transistor pass bank of Pearson [Rev. Sci. Instrum. 42, 713 (1971)] equivalent in terms of current−voltage characteristic to the pass tubes they replace in the V−2100 B supply. The tendency of the Pearson circuit to oscillate, a difficulty in its locking to superstabilizer control, and the necessity of constructing a switched resistor bank are thereby overcome.
Pulse shaper
Authors: Heydemann P.
Published: March 2003

The rounding of pulses is a convenient way to suppress transients when rf signals are switched with balanced mixers or semiconductor switches. The use of a serial−in, parallel−out shift register for shaping the leading and trailing edges of pulses is described. The original pulse is clocked through a shift register and the outputs of the register are weighted and added to form a new pulse. The maximum rise time is equal to the clock period times the bit−capacity of the register.
Helical channel multiplier package design for space instrumentation
Authors: Hoshiko H. H.
Published: March 2003

A design for packaging helical channel multipliers with large input cones is discussed. This design utilizes silicon rubber to bond the channel multiplier into its housing and also provides magnetic shielding up to 150 G. Detector modules built from this design have been qualified to fly on the Apollo−Soyuz Test Project over the temperature range from −35 to +80°C and with up to 100 g of vibrational loading. These detectors have also been operated successfully under vacuum in their appropriate instruments.
Laser beam waist determination by means of multiphoton ionization
Authors: Granneman E. H. A. , van der Wiel M. J.
Published: March 2003

The two−photon ionization process in Cs at λ = 4545 Å is used as a tool for accurate measurement of an Ar−ion laser beam waist. The method is based on the variation of the relative multiphoton ionization yield with the position of a lens between laser and ionization region; it does not require knowledge of any parameter other than the type of intensity profile of the laser beam and the wavelength of the light.
Simple cable delay multiplexer for displaying multiple nanosecond signals on a single oscilloscope channel
Authors: Boller J. R. , Cooperstein G.
Published: March 2003

A simple multiplexer circuit is described which allows the displaying of two or more coincident wide band pulse−type signals on a single horizontal oscilloscope sweep by means of appropriately clamping, delaying, and mixing the input signals.
High resolution system for photoresponse mapping of semiconductor devices
Authors: Kasprzak L. A.
Published: March 2003

A system has been built which employs a cw 6328 Å laser beam to excite the photoresponse of a semiconductor device. The excitation is achieved by focusing the laser beam to a 1 μ spot on the surface of the device under investigation. Heretofore 5−10 μ resolution has been reported in the literature. Further, the optical path of the system is such that the device surface and spot are simultaneously in focus. A Pockel’s cell is used to amplitude modulate the laser beam intensity. The result is a photoresponse at the characteristic amplitude modulation frequency of the Pockel’s cell. A lock−in amplifier, with a reference input at the characteristic amplitude modulation frequency, is used to amplify the photoresponse to the desired level. The result is a versatile, high−resolution system for the study of light−sensitive devices and phenomena. Programmed area scans have given qualitative and quantitative information about semiconductor diode and transistor junction properties near the semiconductor surface. Specifically, areas of surface inversion have been located on transistor structures. Finally, by comparing the device (p−n junction) output to the amplitude modulation (square wave), an effective minority carrier lifetime was measured in the vicinity of a p−n junction.
Production of single liquid drops of controlled size and velocity
Authors: Cheng Lung , Cross Warren G.
Published: March 2003

A technique for producing single drops of preselected size and velocity is described. The present apparatus produces water drops ranging in diameter from 300 to larger than 600 μ with velocities ranging from 800 to 2000 cm/sec, but the ranges of these values can be extended by changing apparatus parameters. Particular attention has been given to the effect of apparatus parameters on drop velocity.
Fast single channel analyzer with integrated circuits
Authors: Martiens C.
Published: March 2003

A fast SCA has been implemented using integrated circuits. A 20 nsec resolution time is obtained. The anticoincidence gate is pulse shape independent.
High performance, far-infrared bolometer working directly in a helium bath
Authors: Coron N. , Dambier G. , Leblanc J. , Moalic J-P.
Published: March 2003

This paper describes the mounting of a high performance, far-infrared, three-part bolometer designed to permit its use directly in a helium bath. It can be matched with low loss to any optical system or to a waveguide. Optimal performance and constant characteristics have been obtained; D (at 4 K and 20 Hz) = 1.4×1012 W−1⋅cm⋅Hz(1/2) and more than 30 cooling cycles have been made without the seals leaking.
Fast electrical discharge tube for time dependent spectoscopy
Authors: Binur Y. , Shuker R. , Szoke A.
Published: March 2003

An improved transverse discharge tube for time resolved spectroscopy is described. Current densities of 1000 A/cm2 with risetime of less than 5×10−9 sec and total pulse length of 3×10−8 sec were achieved in pressures up to 500 Torr of noble gas mixtures. This improved performance, compared with the Tanaka longitudinal tube, is essential for observation of fast energy transfer processes originating at highly excited atomic and molecular levels.
Improving light beating experiments by dust discrimination
Authors: Alon Yosef , Hochberg Amiram
Published: March 2003

A method for reducing the unwanted effect of dust in fluid samples used in light scattering experiments is described. An on-line minicomputer is employed to reject data accumulated during the presence of dust particles in the light beam, using a digital autocorrelator and a homodyne or heterodyne detection setup. The effectivity of the method is demonstrated by comparing
Large area extreme ultraviolet focusing collector
Authors: Henry Patrick , Cruddace Raymond , Paresce Francesco , Lampton Michael , Bowyer Stuart
Published: March 2003

A grazing incidence one-dimensional focusing collector for use in the extreme ultraviolet is described. The collector has a field of view of 1×50°, a focal length of 3015 cm, and a total unobstructed area of 224 cm2. The instrument employs an interchangeable detector package of either channel-electron multipliers or proportional counters which yield a limiting sensitivity of 1.0 photons/cm2 sec Å at 170 Å and 0.05 photons/cm2 sec Å at 90 Å, respectively, for one second integrations. The design and calibration of the instrument are described in detail. Data obtained by this instrument during recent rocket flights are presented.
Digital data acquisition for laser scattering spectroscopy using the scattered-to-incident light intensity ratio
Authors: Schwiesow R. L. , Post M. J.
Published: March 2003

We describe a digital data acquisition system for laser scattering spectroscopy, which measures the ratio of the scattered signal to either the incident laser power on the sample cell or the total signal incident at the spectrometer entrance aperture. The incident reference that is not used to form the ratio is used to check stability of the scattering sample. This report outlines the philosophy of the technique and gives components and circuit diagrams for its implementation. Digital measurement of light
Modified rf interferometer for relative phase measurements
Authors: Starke T. P. , Malmberg J. H. , Vidmar P. J.
Published: March 2003

A modified rf interferometer which produces a direct measurement of the phase difference between a test wave signal and a reference wave signal is described. With this instrument the relative phase change can be continuously observed as some other experimental parameter is varied. The instrument is capable of measuring a total phase change of 240 rad. We have used this interferometer to measure small variations in the wavelength of a nonlinear electron plasma wave.
Specific heat and thermal conductivity measurements on thin films with a pulse method
Authors: Filler R. L. , Lindenfeld P. , Deutscher G.
Published: March 2003

Heat pulses propagating along one dimension are used for measurements of the heat capacity, the diffusivity, and hence the thermal conductivity of thin films on glass substrates. The method is illustrated with results on a film of granular aluminum.
Stratospheric Aitken nuclei counter
Authors: Haberl J. B.
Published: March 2003

An aircraft mounted system is described which permits the measurement of concentrations of Aitken nuclei in the stratosphere at altitudes up to 20 km. An automatic cycling cloud chamber, with a dark field optical system and photomultiplier detector, is used to analyze 2.5 samples/sec. A pressurization system is incorporated which standardizes ambient air samples to approximately 1 atm absolute pressure and 298 K temperature before analysis. Seven successful data flights have been accomplished in the period March–May 1974.