bluuebunny/crossref_metadata_2025 huggingface dataset:
Simple wavelength monitor for a scanning spectrometer
Authors: Rhinewine M.
Published: March 2003

A simple technique has been devised for accurately and reliably monitoring the pass frequency of a scanning spectrometer. Deviations of the order of ±0.5 cm−1, when the radiation source wavelength is approximately 5000 Å, can be expected in commercial spectrometers. An order of magnitude improvement is obtainable with the apparatus described here that uses a laser source and a Ronchi ruling as exit slit. The technique has been used successfully for Raman scattering experiments in liquid and solid helium, where high accuracy is required for measuring frequency shifts and linewidths.
Equipment developed for static high temperature resistivity measurements
Authors: Slivinsky Sandra H.
Published: March 2003

Apparatus has been developed to accurately measure electrical resistivity as a function of temperature at high temperatures for metals and alloys. The resistivity of 0.254 mm diam tantalum wire has been measured between the temperatures 1170 and 2860 K. Temperature measurements were taken with an automatic optical pyrometer, a two-color ratio pyrometer, and a tungsten–rhenium thermocouple. The temperature observations were made under simulated blackbody conditions, in accordance with the blackbody calculations of deVos. The 2–3% agreement with the tantalum data previously published indicates that the apparatus performs satisfactorily.
Batch processing in autocorrelation function analysis
Authors: Knox A. , King T. A.
Published: March 2003

The effect of batch processing on signal recovery statistics, in the case of an exponential autocorrelation function, is investigated. It is shown that the loss of information and accuracy is small provided the interval between batches is less than the coherence time of the signal.
A uhf superconducting magnetometer utilizing a new thin film sensor
Authors: Duret D. , Bernard P. , Zenatti D.
Published: March 2003

A new type of thin film superconducting quantum interference device is described. It has many advantages compared to usual ones: higher critical temperature, readily established critical current (any value can be chosen between 0.5 μA and 1.5 μA with a ±0.1 μA accuracy), high reliability, and low cost. This SQUID works with a uhf magnetometer utilizing a 350 MHz pumping frequency. All rf circuits are perfectly matched, and the use of a particular rf detection leads to an improved signal-to-noise ratio. A sensitivity of 2×10−4 φ0/√Hz is easily obtained, with a slew rate of 2500 φ0/sec.
Aging phenomena in a low-temperature glass–ceramic capacitance thermometer
Authors: Lawless W. N.
Published: March 2003

On plunging a glass–ceramic capacitance thermometer into liquid helium or nitrogen, the capacitance decays slightly for about 30 min before stabilizing. This aging effect at 4.2 K corresponds to a drift of about 15 mK at 1 kHz measuring frequency. The effects of several parameters on this aging are investigated: encapsulation, lead-wire material, measuring frequency and voltage, bias voltage, voltage application, and dip temperature. The aging appears to be due to a slow component of relaxation of the glass matrix surrounding the precipitated SrTiO3 microcrystals. Aging effects occur whenever the glass matrix is spatially perturbed, either by thermal expansion (above 77 K), or by electrostrictive coupling to the microcrystals following a voltage pulse, or by warming or cooling across the 65 K transition temperature. An application of the Devonshire phenomenological theory of polar dielectrics satisfactorily explains the salient features of the aging effect based on this delayed relaxation component.
Intense atomic-hydrogen beam source
Authors: Koschmieder H. , Raible V.
Published: March 2003

A new design for a hydrogen atom beam source is described. A long tube is used as the source and is heated by radiation from a heater loop. Dissociation fractions of more than 80% are achieved at oven temperatures of 2500 K, with beam number densities exceeding 1010 atoms/cm3.
Portable, solid-state fluorometer for the measurement of chlorophyll fluorescence induction in plants
Authors: Schreiber Ulrich , Groberman Leslie , Vidaver William
Published: March 2003

A miniaturized Kautsky apparatus was developed for measuring chlorophyll fluorescence induction in photosynthetic plants in situ. The instrument is based on a new sensor–emitter combination of a phototransistor on the back of a light emitting diode (piggy-back arrangement). Fluorescence curves can be recorded with a time resolution of 250 μsec, illumination time is infinitely variable from 0.1 to 100 sec, and light intensity variable from 0 to 104 erg⋅cm−2sec−1. In combination with portable recorder the new instrument provides a rapid and reliable means of measuring photosynthetic activity of plants in natural environments. The piggy-back sensor–emitter combination is suggested to be of general importance as a new opto-electronic device for detecting fluorescence and reflected light. Examples of operation are given which demonstrate time resolution, sensitivity, and specificity of the new instrument.
Thermal diffusivity measurements of particulates using the differentiated line source
Authors: West Edward A. , Fountain James A.
Published: March 2003

A method is described in which thermal diffusivity measurements can be made on particulate materials using the identical instrumentation as described in previous papers for measuring thermal conductivity. The measurements for the two properties can be made simultaneously, thus eliminating the changes in conditions when they are made separately. This system has particular application for studies of simulated lunar, planetary, or asteroidal surfaces in which laboratory measurements can be correlated with astronomical observations of thermal inertia. A representative set of data is shown which gives thermal diffusivity and thermal conductivity measurements on a particulate basalt in which the values for each temperature were taken simultaneously. A value for specific heat is calculated for measurements taken at each temperature.
Variable temperature apparatus using a thermal conductivity measurement technique for the determination of superconducting ac power loss
Authors: McConnell R. D. , Critchlow P. R.
Published: March 2003

A variable temperature apparatus is described which uses a thermal conductivity measurement technique for the determination of superconducting ac power loss. The technique consists of measuring the increase in temperature of a thermally isolated sample carrying an alternating current. Accurate measurements over a relatively large temperature range are possible. Loss data on a 13 cm long, single filament NbTi superconductor are presented at various temperatures and currents.
Heterodyne interferometer to determine relative optical phase changes
Authors: Lavan M. J. , Cadwallender W. K. , Deyoung T. F.
Published: March 2003

We have constructed a visible light interferometer which measures relative phase variations continuously at rates up to 3 kHz. The sytem, which is based on the technique of optical heterodyning, may easily be extended to several channels, each recording continuous phase data.
Switching regulator emission control circuit for ion sources
Authors: Clay Forrest P. , Brock F. J. , Melfi Leonard T.
Published: March 2003

An electron emission control circuit of the switching regulator type operating at 100 kHz has been developed which maintains a constant emission current within 0.1% for a cathode power demand variation of approximately 100%. The power output stage has an efficiency of 67%, and the overall efficiency is 45% when driving a thoria-coated iridium cathode having a nominal resistance at operating temperature of 2.5 Ω. Under optimum conditions, the bus power demand is 1.75 W. The circuit is useful in controlling the electron emission current of ion sources in applications which involve a substantial variation of the cathode work function, such as oxygen partial pressure measurements over a large dynamic range.
Self-balancing, calibrated CMN thermometer with digital readout
Authors: Graebner John E.
Published: March 2003

We have developed a modification of the SQUID–CMN thermometer of Giffard, Webb, and Wheatley which has the advantages of (1) not needing recalibration against a thermometric standard at the beginning of each run, and (2) its accuracy not depending upon the absence of mechanical or electrical transients. A special current source provides a smoothly adjustable current to a field-generating solenoid around the CMN. The SQUID output can either be measured directly with a digital voltmeter for high accuracy, or it can be fed to an analog dividing circuit which converts it to temperature with 1/2% accuracy and displays it directly in mK. The thermometer apparatus is not restricted to measurements of CMN; 1 mm3 samples of other materials can easily be measured in fields of a few oersteds. The absolute uncertainty in χ is 10−5 emu/cm3, while relative changes of 2×10−7 emu/cm3 or smaller can be detected. We have observed marked deviations from a Curie law in partially dehydrated CMN below ∼0.2 K. This illustrates the danger of pumping a vacuum on CMN powder at room temperature.
DuoPIGatron II ion source
Authors: Davis R. C. , Jernigan T. C. , Morgan O. B. , Stewart L. D. , Stirling W. L.
Published: March 2003

The DuoPIGatron ion source concept at Oak Ridge has proven itself capable of providing multiampere beams at tens of kilovolts. The DuoPIGatron II operates very reliably at 6–8 A total output current in the 25–35 kV range. Impurity level is easily maintained below 0.4% and the 0.2 sec pulses show no appreciable wear on the copper accel–decel electrode system after thousands of pulses with duty cycles up to 10%. The 7 cm diam grids are 50% transparent and optimum curvature of the grids allows about 60%–65% of the current to be incident on a 9 cm diam target 100 cm from the source. Beam ion and neutral species fractions have been measured as a function of total source current. Studies of the ion source plasma show an m=1 helical instability to be present. Probe measurements show a density variation of about 25%–30% across the extraction grid. Instantaneous density variations from ± 10% to ± 40%, depending on radius, are observed to be driven by the instability at 250–400 kHz. A stabilizer has been developed which reduces the oscillation amplitude by about an order of magnitude. Studies at extraction voltages up to 10 kV show that the use of the stabilizer yields a less divergent beam and higher current output through a single aperture either on axis or 1.8 cm from the source axis.
Automated flux pump for energizing high current superconducting loads
Authors: Bernat T. P. , Blair D. G. , Hamilton W. O.
Published: March 2003

An automatic superconducting flux pump is described capable of energizing an inductive load to high currents (∼1000 A). These currents are derived from an inexpensive low current power supply and control circuits.
High resolution microwave Zeeman spectrometer
Authors: Bhattacharyya Pranab K. , Taft Harrison , Smith Nelson , Dailey Benjamin P.
Published: March 2003

The design and description of a microwave absorption cavity and a superheterodyne magic-T balanced bridge, high resolution, microwave Zeeman spectrometer, where a superconducting magnet is employed, are discussed. Accurate values of the magnetic properties of molecules such as the rotational magnetic moments and the magnetic susceptibility anisotropies may be obtained with this apparatus.
New device for generating ultra-high pressure
Authors: Kendall D. P. , Dembowski P. V. , Davidson T. E.
Published: March 2003

This paper describes a unique device for generating ultra-high pressures of the order of 300 kilobars (30 GPa). This is a variable lateral support, Bridgeman anvil device which utilizes the principle of a segmented cylinder to provide the lateral support and to apply the force to the anvils. The system has been calibrated to 212 kilobars using resistivity measurements to detect the known phase transitions in bismuth, iron, lead, and 10 and 20% cobalt alloys of iron.
Modified Soxhlet extractor for high pressure application
Authors: Cuddeback J. E. , Burg W. R.
Published: March 2003

A simple, inexpensive device for long term solvent extractions of highly reactive compounds with low boiling solvents and gases is described.
Performance evaluation of a minicomputer
Authors: Takeuchi K. , Mogel T.
Published: March 2003

With the advent of high speed computers, the digital processing of data became a common practice among many researchers. The recent trend among geophysical researchers has been to establish their own computer system by use of a minicomputer rather than time sharing of a larger system. In developing such a system, a question arises as to how reliable is the newly acquired computer system. A method of evaluating the performance of such a computer system is presented. The method consists of processing data of known characteristics and comparing the results. The quantities calculated include probability densities, higher order moments, spectra, cross spectra, and a coherency spectrum.
Low cost visualizer for mixing and stirring phenomena in some real gaseous flow reactors
Authors: Rondeau J. A. , Andre J. C.
Published: March 2003

The observation of the light emission due to the chemiluminescent gas phase oxidation of phosphorus gives information on the stirring of gaseous fluids in real flow reactors. Three types of reaction vessels have been tested.
Hot window, metal vapor tube
Authors: Altman D. E. , Barstow G. J. , Geller M. , Mooradian G. , Ingram C. , Andry G. T.
Published: March 2003

A new quartz laser tube, which can operate at 1000°C for metal vapors, has been built. The tube was operated in a three-zone oven, with the Brewster windows at a slightly higher temperature than the main laser body. Thus, a buffer gas was not necessary to prevent condensation of the metal on the windows. A technique for fusing the quartz windows to the quartz tube, without degrading the optical flatness, has been developed. Molybdenum ribbons fused into quartz cylinders provide vacuum-tight electrode connections.
New differential scanning high pressure microcalorimeter
Authors: Kamphausen M.
Published: March 2003

A high pressure microcalorimeter based on the differential scanning calorimeter (DSC) principle is described. In the present investigation this device was used for the determination of heats of transformation at pressures up to 2200 bar. The procedure for calibrating this apparatus is discussed. The temperature accuracy is considered to be ± 1 K in the range from −20 ° to +200 °C and to be about ± 5% for the determination of heats of transformation.
Large multi-feedthrough vacuum seal for low temperature applications
Authors: Derenzo S. E. , Savignano J. , Schwemin P. , Vuletich T. , Zaklad H.
Published: March 2003

An alumina-filled casting epoxy (trade name Stycast) was found to reliably seal to thin stainless steel edges and 1 mm diam stainless steel feedthrough pins. All seals retained their integrity after typically 50 cycles from −196 ° to 20 °C and 10 cycles from −196 ° to +100 °C. Several chambers were constructed using the epoxy both as a vacuum-tight wall and as an electrical insulator for a large number of multi-kV feedthroughs. The largest of these was 18 cm in diameter and contained 125 feedthrough pins. The chambers were immersed in a Freon-11 bath at −105 °C, filled with liquid xenon, and tested for the presence of electronegative impurities. After degassing, the contamination levels measured were slightly higher than those we commonly observe for chambers constructed only of glass and metal.
Technique to measure distribution of electron current density and electron trajectories in a high current relativistic electron beam
Authors: Bradley L. P.
Published: March 2003

A passive dosimetric technique was used which maps electron current density with a spatial resolution of 0.013 cm at 300 keV. Electron divergence and emittance angles are distinguished and can be mapped at any point in an intense electron beam with an accuracy of 10%. The technique applies to beams of up to 50 kA/cm2 and 100 keV–3 MeV.
Angular displacement transducer for use in a torsion pendulum
Authors: Zoller P. , Oppliger H.-R. , Casalini A.
Published: March 2003

A simple electro-optical angular displacement transducer for use in a torsion pendulum is described. It uses the changing light intensity transmitted through two polarizers, which are rotating against each other as the sample undergoes damped sinusoidal oscillations, to produce a voltage output linear in angular displacement over a range of 10 °.
Determination of secondary electron ejection coefficients for rare gas metastable atoms
Authors: Dunning F. B. , Rundel R. D. , Stebbings R. F.
Published: March 2003

Secondary electron ejection coefficients for rare gas metastable atoms striking a stainless steel surface have been determined using an improved gas cell technique. Data are presented for He(2 1S), He(2 3S), and Ne(3P0,2) atoms, and limitations of this technique are discussed. An alternative method for γ determination is described which utilizes laser induced photoionization rather than chemiionization, and results are presented for He(2 1S) and Xe(3P0).
Balloon-borne low temperature air sampler
Authors: Lueb R. A. , Ehhalt D. H. , Heidt L. E.
Published: March 2003

Design, construction, and performance of a balloon borne low temperature air sampler are described. The sampler can collect 16 samples of 10 liter STP at different stratospheric altitudes. The collected samples allow measurement of the trace gases H2, H2O, CH4, CO, CO2, and N2O. In the future, measurements will include the Freons, CCl4, SF6, CH3OH, and ΣNOx; also, the altitudes will be extended from the present 35 km to above 45 km.
Spectrometry by modulated dynamic nuclear polarization
Authors: Kokavecz B. , Kramer K. , Seiler T.
Published: March 2003

The modulation of the dynamic polarization is used to measure the longitudinal nuclear relaxation. This method is complementary to the rf pulse technique and combines the advantages of the dynamic nuclear polarization (DNP) enhancement and the high signal/noise from narrow band detection. The DNP spectrometer with microwave modulation is described and the results of its application to a fluorine–electron system are compared with those from the conventional pulse technique.
Microwave time domain Fabry–Perot emission spectrometer
Authors: Somers Ralph M. , Poehler T. O. , Wagner P. E.
Published: March 2003

A K-band time domain microwave spectrometer with a plane parallel Fabry–Perot resonator external to the gas cell is described. A time domain emission technique consisting of a two pulse sequence of a long saturating pulse followed by a short π/2 pulse is used to measure energy relaxation times, which are the Fourier transform of pressure and wall collision broadened linewidth independent of Doppler broadening. The flexible resonator configuration yields sensitivities comparable to waveguide spectrometers with various gas cells suitable for collision studies or ir-double-resonance experiments.
New type of thermally regulated coaxial conducting glass dielectric cell
Authors: Bahadur Birendra
Published: March 2003

A new type of coaxial cylindrical dielectric cell for low frequency measurements (up to 1 MHz), and for high resistance samples was designed using conducting Pyrex glass. The cell also contains a mercury regulator with a temperature control of better than ±0.02°C. The capacity of the cell is 57.03 pF, with a temperature coefficient between 20° and 120°C = − 6.5×10−3 pF/°C. The lead capacitances (fixed internal lead capacitance associated with the cell = 2.72 pF external lead capacitance of the leads joining the cell with measuring instrument = 0.79 pF) are found to be small. The cell is capable of working up to 350°C with mercury and is expected to work from 250° to 500°C with melts of high conductivity solid electrolytes (like MAg4I5, where M stands for K, Rb, Cs, and NH4, etc.). The dielectric constants of cyclohexane, chlorobenzene, bromobenzene, and carbon tetrachloride, etc., were measured with the help of this cell and the results are in very good agreement with literature values. The frequency variation of the cell has also been recorded.
Purely ionic synthesized plasma
Authors: Baribaud M. , Dolique J. M. , Monte J. , Zadworny F.
Published: March 2003

A synthesized plasma containing no electrons but only positive H+ and negative H− ions has been made from a very intense H− ion source. A rectilinear H− ion beam, extracted from a Penning-type source through a magnetic shield, crosses a gaseous target. By two-electron collisional detachment, positive ions are created which, according to the gas pressure and target depth, can balance the negative current intensity of the negative remaining ions. Precautions have been taken to avoid any pollution by electrons. Such purely ionic plasma beams have a density in the range 1012–1013 m−3, with a velocity of the order of 106 m/sec. This particular kind of plasma was first obtained in 1970 and reported in 1971.
Optimum power from rf line generators
Authors: Cheetham Andrew D. , Jones Ieuan R.
Published: March 2003

It is shown in this paper that if, as is the case in general, a lumped recurrent rf line generator is to be constructed from a given, readily available type of capacitor, then it should be designed to operate at a certain optimum frequency if the absolute maximum output power is required.
Isolating dc–dc coupler
Authors: Dandl R. A. , Wintenberg R. E.
Published: March 2003

A simple circuit is described which accurately couples a dc signal across a dc potential of several hundred volts. The method of extending the current linearity of the high-voltage transistor used to perform this function is probably useful in other applications.
Single photon fluorimetry
Authors: Chandler Dean W.
Published: March 2003

We present modifications of the phase fluorimeter previously described by Schlag et al. These modifications make the instrument more versatile and eliminate the need for custom-made components.
Novel method for measuring total pressure of fuel gas in hollow, glass Microshell pellets
Authors: Rensel W. B. , Henderson T. M. , Solomon D. E.
Published: March 2003

A sampling technique has been developed that permits direct, rapid, and accurate determination of the pressure inside gas-filled, hollow, glass Microshell pellets.
Small, low internal volume valve and a low temperature bellows-sealed needle valve
Authors: Oversluizen T.
Published: March 2003

Two valves are described: (1) a small regulating valve with an internal volume of 0.24 cm3 which uses some commercially available parts and is used in high pressure 3He gas handling systems, and (2) a high pressure bellows-sealed valve for low temperature applications, including superfluid 4He.
Measurement of high-frequency turbulent temperature
Authors: LaRue John C. , Deaton Tom , Gibson Carl H.
Published: March 2003

In many areas of turbulence research of current interest, it is of increasing importance to make reliable measurements of high frequency, small scale temperature fluctuations. Platinum wire resistance thermometers provide adequate spatial resolution, but may, after a period of time, suffer a degradation in frequency response when used in air. Relative effects of various sensor parameters on sensor performance under various flow conditions are also discussed as a guide to sensor selection. However, measurements of actual frequency response of wires in turbulent flow systems using circuits especially developed for the purpose show substantial deviations from the analytic results, as well as a dependence of the frequency response on a probe aging effect, which is possibly due to surface contamination. The measured frequency response was used to correct a temperature spectrum measured in a heated jet. The corrected spectrum agreed well with the expected shape.
Modified ’’Harvard’’ dry dust disperser
Authors: Ciliberti David F. , Lancaster Brian W.
Published: March 2003

A modified dry dust disperser has been used to produce test aerosols from very fine powders which show a tendency to agglomerate in feeders and dispersion equipment.
Rocking furnace for homogenization of melts
Authors: Mobley M. J. , Glaunsinger W. S.
Published: March 2003

A rocking furnace is described that permits variable agitation of melts prior to crystal growth. The design permits adjustment of furnace inclination, variation of oscillation frequency and amplitude, and rotation of the furnace into a vertical position. The fabrication of an explosion-proof furnace and sample-mounting procedure are also described.
Bakeable glass isolation valve for UHV systems
Authors: Sharma J. K. N. , Sharma D. C.
Published: March 2003

This note describes a bakeable (up to 450°C) isolation valve made of glass using a standard ground ball and socket joint. The valve is useful for most glass UHV systems, e.g., field-ion microscopes or gauge calibration.
Microcomputer interface for a pulsed NMR spectrometer
Authors: Kri?an M.
Published: March 2003

A relatively simple microcomputer interface for data acquisition from pulsed NMR experiments is described. The timing of the sampling of the NMR signal is performed by the interface itself, based on the pulses delivered by the spectrometer-pulse programmer. The acquired data are stored in a buffer memory and after completion of the experiment can be transferred into the computer for further processing.
Automatic Bragg angle control with simple, inexpensive electronics
Authors: Storm Arthur R.
Published: March 2003

A simple, inexpensive comparator circuit and its associated equipment providing automatic Bragg angle control (ABAC) and allowing determination of lattice curvature and film stresses with scanning x-ray topographic cameras is described.
Optical superheterodyne spectrum analyzer using an acousto-optic effect
Authors: El Badawy El-S. , Leblond J.
Published: March 2003

An optical superheterodyne analyzer, which is destined for high resolution spectral analysis in the optical domain, is described. The optical local oscillator of continuously variable frequency, the core of this analyzer, is obtained by means of an acousto-optic effect. By changing the acoustic frequency linearly, and by appropriately choosing the order of diffraction, one can scan the frequency of the local oscillator beam over a range of 2.4 GHz. This optical superheterodyne system is analogous to the one used in rf receivers. By this proposed method of optical spectral analysis, we have overcome three drawbacks existing in the classical heterodyne detection. Firstly, the analyzable domain extends to 2.4 GHz instead of 400 MHz for heterodyne detection; secondly, we use a fixed frequency tuned amplifier instead of an expensive rf spectrum analyzer. Finally, there exist no
Ultraviolet source suitable for Tokamak preionization
Authors: Smeulders P.
Published: March 2003

In order to ionize molecular deuterium a photon energy greater than 15.6 eV is required. This is created by radiation from bombardment of a thick wall by energetic electrons, as in x- tubes. A high voltage pulse extracts the electrons by field emission from the sharp pointed electrode and accelerates them to the cylindrical anode. The degree of ionization is measured with an ionization cell and has been measured at pressures from 5×10−6 up to 5×−4 Torr in D at a distance of 70 cm from the source, averaged over the volume of the chamber. This made it possible to start discharges in the T.F.R. (Tonomav de Fontenaya-Tokomak from as low as 10−5, giving an appreciable increase in the range of working pressures of the T.F.R. experiment.
Stark cell for infrared–microwave double resonance experiments
Authors: Redon M. , Fourrier M.
Published: March 2003

A parallel-plate Stark cell giving a very homogeneous electric field is described. It can be used either for Stark spectroscopy in the infrared and microwave ranges or in infrared–microwave double resonance experiments. Microwave absorption lines, 12.600 GHz frequency shifted, have been observed; it is more than 36 times as much as earlier displacements obtained with such cells. For pressures up to 30 mTorr, a suitable device keeps the breakdown voltage always above 10 kV, corresponding to an electric field of 50 kV/cm.
Laser triggered switching of a pulsed, charged, oil filled spark gap
Authors: Guenther A. H. , Zigler G. L. , Bettis J. R. , Copeland R. P.
Published: March 2003

A focused, Q-spoiled laser, aligned along the interelectrode axis of a pulse charged switch assembly, was used to initiate the conduction of an overvolted transformer oil filled gap. Laser power varied between 5 and 200 MW and the voltage pulse exhibited a risetime of 500 nsec to a voltage of 700 kV. A parametric study of the factors affecting the delay between the laser pulse arrival at the gap and conduction of the gap was accomplished, in which the effects of the focal point location, laser power, switch polarity, and voltage on the gap at laser arrival were determined. Delay times as short as 12 nsec were recorded with jitter, a measure of reproducibility, in the low nanosecond region.
Pressure-scanning mm-wave dispersion spectrometer
Authors: Liebe H. J.
Published: March 2003

A differential refraction spectrometer for measuring the absolute intensity distribution of microwave spectra in gases by means of dispersion pressure profiles is described. The instrument was applied to study the 60 GHz band spectrum of oxygen under simulated atmospheric conditions (10−3–103 Torr, 252–325 K). The detection sensitivity for dispersion was better than 1 part in 109 using two high-Q (∼4×105) resonators at 2:1 related frequencies and a sampling phase meter. Illustrative examples of data taken around 61 GHz, their reduction to spectroscopic parameters, and problems related to dynamic limitations are dealt with.
Synchronized rapid scanning vacuum uv spectrometer
Authors: Weiser C.
Published: March 2003

By the introduction of a rotating mirror near the exit slit of a Rowland circle mounting, we have designed a rapid scanning spectrometer capable of being synchronized with a short duration source of radiation. The wavelength range 1150–2000 Å is covered in 345 Å increments by setting the entrance arm at each of several predetermined angles of incidence. Spectral measurements of the vacuum ultraviolet (vuv) carbon monoxide fourth positive system are presented. The spectra have been obtained at a scan speed of 300 Å/msec, and the conversion from a time scale to a wavelength scale is shown to be linear.
Laser Doppler velocimeter signal processing using sampling spectrum analysis
Authors: Simpson R. L. , Barr P. W.
Published: March 2003

A new technique for processing laser Doppler velocimeter signals by sampling spectrum analysis is presented. A swept-filter spectrum analyzer and pulse-shaping and sample-and-hold circuits are employed. Sampling turbulence frequencies up to 4 kHz. In contrast to most tracking techniques, high dropout of signal cases and high frequency signals normally associated with directionally sensitive velocimeter systems can be processed.
Measuring the moment of inertia of irregular cross sections
Authors: Martin R. Bruce
Published: March 2003

A stereologic method for measuring any moment of an irregular plane section is described.
Time-of-flight measurements of low-energy electron energy distributions from ion–atom collisions
Authors: Toburen L. H. , Wilson W. E.
Published: March 2003

A time-of-flight technique for the measurement of the energy spectra of electrons ejected in ion–atom collisions is described. Ionization is produced by a pulsed beam of protons which are obtained by chopping the dc proton beam from a Van de Graaff accelerator with a 3.33 MHz high voltage oscillator. Electron energy and angular distributions are derived from time-of-flight spectra recorded for different emission angles. This system is capable of measurements for proton energies from 0.25 to 2.0 MeV, ejected electron energies from 0.3 eV to several hundred eV, and electron ejection angles from 30° to 150°. The advantages and limitations of this technique are illustrated.
Combination glove box–sample compartment cover for a Fourier transform ir spectrophotometer
Authors: Oertel Richard P. , Fehl Allen J.
Published: March 2003

A combination glove box–sample compartment cover has been constructed for a rapid scan Fourier transform ir spectrophotometer so that greater advantage can be taken of the speed and sensitivity of this type of instrument. While maintaining the atmospheric purge throughout the sample and optical chambers of the instrument, the cover provides routine operator access to the interior of the sample chamber and a pathway for interchanging samples.
Generation and detection of plane-polarized ultrasound with a rotatable transducer
Authors: Hsu Nelson N. , Sachse Wolfgang
Published: March 2003

The construction of a rotatable transducer for generating and detecting pulses of plane-polarized 10 MHz ultrasound is described. The usefulness of the transducer is demonstrated in attenuation measurements made along various symmetry directions on a single crystal, and in acoustical birefringence measurements made on anisotropic solids, as well as elastically deformed structural alloys. The calibration of the polarization of the transducer, and its utilization to determine the directions of principal axes of the shear waves, are also reported.
Conversion of A-60 NMR spectrometers to Fourier transform operation
Authors: Tomkiewicz M. , Horsley W. J. , Klein M. P.
Published: March 2003

A description of the instrumental modifications and additions required for the conversion of this class of field-swept, field-modulated 60-MHz NMR spectrometers is given. The rf portions are straightforward adaptations of the single-coil sample circuit to pulsed operation. The standard instrument achieves field-frequency stabilization through use of a NMR sideband oscillator employing a separate sample. While such a configuration is adequate for the normal mode of operation, it does not provide sufficient absolute stability for the pulsed Fourier mode of operation. The requisite stability was achieved by phase locking the sideband oscillation frequency to an external reference by forcing the radio frequency to change in accordance with the phase-lock error signal. Both analytical and control channels are driven by this common rf source, as is the reference signal to the analytical channel synchronous detector.
Design of a simple and inexpensive analog gate
Authors: Rosen H. , Robrish P. , de Vries G. Jan
Published: March 2003

We have designed and built a simple and inexpensive analog gate which, when used in combination with an electrometer and a high gain photomultiplier, has a sensitivity of better than 1 photoelectron/sec and a linearity of better than 10% over a dynamic range of 1000.
Pole-zero cancellation in the feedback circuit of wide-band preamplifiers to improve the baseline stability for high count rates or large signals
Authors: Kopp M. K.
Published: March 2003

Pole-zero cancellation was applied to the feedback circuit of wide-band preamplifiers to improve the baseline stability and reduce the saturation of the output for high count rates (106 counts/sec) or large output signals (≳1 V), without compromising the bias point stabilization.
Inexpensive liquid nitrogen pump
Authors: Chopra D. , Babb H.
Published: March 2003

We describe the design of a simple and inexpensive system for transferring liquid nitrogen from one container to another.
Fast, high-current, high-repetition-rate pulse generator for injection lasers
Authors: Armstrong D. R. , Katzir A. , Yariv A.
Published: March 2003

The circuit described is capable of generating high-current (2–50 A), fast-rise-time (10 nsec), square-wave pulses into a 50-Ω load. This circuit may be used for driving injection lasers at high repetition rates (up to 1.5 kHz) when connected to coaxial cables.
Stabilization of photomultipliers in liquid scintillation counters
Authors: Soini Erkki
Published: March 2003

A special stabilization system has been constructed to control the overall gain of photomultiplier tubes in a liquid scintillation counter. The system uses GaAsP light emitting diodes in the measurement chamber to produce separate reference light pulses for each photomultiplier tube. The system has provided a significant improvement in both short and long term stability and in operational reliability.
Modified airlock door for the introduction of frozen specimens into the JEM 100B electron microscope
Authors: Taylor Kenneth A. , Glaeser Robert M.
Published: March 2003

An airlock door modification for the JEM 100B electron microscope is described. This modification permits prefrozen specimens to be introduced into the microscope without frost forming on the specimen or the specimen warming excessively. The imaging of hydrated biological material using frozen specimens is demonstrated with crystalline catalase as a test specimen.
Logarithmic time base generator
Authors: Wills L. J. , Denby E. F.
Published: March 2003

A digital counting circuit is described that generates output pulses at intervals geometrically increasing at a rate proportional to the elapsed time, thus making it suitable as a logarithmic time base generator. The design procedure to deliver any number of pulses per decade of time and for any number of decades of time is discussed, and a prototype giving 37 pulses per decade of time with an accuracy of ± 0.5% of the output per decade is described. The unit is capable of starting at 1 μsec and has an analog output covering approximately seven decades with a range of (0–10) V.
Precision isoperibol calorimeter with automatic data acquisition and processing
Authors: Shin C. , Criss C. M.
Published: March 2003

A precision isoperibol calorimeter with automatic data acquisition and processing, capable of operating over a wide temperature range, has been constructed and tested. The calorimeter was designed to have a very low thermal modulus and fast equilibration time. A small vapor space above the liquid and a vapor trap make the calorimeter useful for measurements with nonaqueous solvents. Time–temperature data are automatically recorded in digital form on magnetic tape and processed on a Univac 1106 computer. A series of electrical calibrations causing a temperature rise of 0.13 K were reproducible to about 0.01%. Several determinations of the enthalpy of reaction of a standard sample of Tris (hydroxymethyl) aminomethane with 0.1 N HCl gave an average value of 29.764±0.013 kJ/mol, which agrees satisfactorily with published results.
Automated small sample calorimeter
Authors: Schwall R. E. , Howard R. E. , Stewart G. R.
Published: March 2003

We describe an automated calorimetry system for measuring heat capacity in the range 1–35 K. The system employs an on-line computer for signal averaging and data reduction and is capable of performing rapid, accurate specific heat measurements on very small (1–100 mg) samples.
Quadrupole electrodes with flat faces
Authors: Sakudo Noriyuki , Hayashi Tomonao
Published: March 2003

A method to analyze multipole fields formed with flat-face electrodes by using conformal mapping is described. Quadrupole fields of various parameter values which define the electrode shape are analyzed by this method, and the optimum parameter values for making distortion components of the field minimum are obtained. This result is also useful in designing the shapes of magnetic quadrupoles.
Microwave discharge atom source for chemical lasers
Authors: McFarlane R. A.
Published: March 2003

A high-power, cw microwave magnetron is used to produce a discharge in a gas column flowing at high velocity. The large atom production rate obtained makes this a valuable atom source for chemical laser application.
Pressure gauge employing ultrasonic liquid level detection
Authors: Corsaro R. D.
Published: March 2003

A pressure gauge is described which accurately measures high static pressures. It features continuous digital readout, simple construction, and freedom from aging and hysteresis effects. While this device is thoroughly tested over the pressure range 170–1000 bar, its characteristics can be reliably extrapolated to 7000 bar. As tested, the maximum pressure uncertainty is typically 0.1%, and substantial improvement is anticipated with minor design modification. This gauge is shown to be a practical alternative to the commonly used manganin cell at pressures less than 7000 bar. It uses the well-established principle of the acoustic dilatometer: A compressible fluid (n-hexane) is contained in a closed volume by a piston of mercury, and the height of the free mercury surface is accurately monitored using a sound-ranging (ultrasonic echo time) technique. Pressure changes cause the compressible fluid to expand or contract. This in turn changes the height of the mercury surface and hence also the ultrasonic echo time. Thus, a measurement of ultrasonic echo time provides an indication of the pressure on the system.
Low-impedance, high-pressure feedthrough for nanosecond-pulsed high electric field investigations
Authors: Jones R. E. , Keeler W. J.
Published: March 2003

A low-impedance coaxial feedthrough has been developed for nanosecond-pulsed high electric field investigations to 20 kilobar. This feedthrough is compatible with stripline conductors and has been used at low and room temperatures.
One-dimensional focusing x-ray telescope for stellar x-ray astronomy
Authors: Helava H. , Mitchell D. , Novick R. , Weisskopf M. C. , Wolff R. S.
Published: March 2003

A one-dimensional x-ray telescope of the Kirkpatrick–Baez design is described. The instrument consists of a grazing-incidence x-ray telescope and a multiwire proportional counter. The optics were provided with a gold reflecting surface to yield an energy response from below 0.25 to above 4.0 keV. The angular resolution of the system is 6′×9.5° over a 1.1°×9.5° field of view.
Linearity of capacitance displacement transducers
Authors: Gladwin Michael T. , Wolfe Joseph
Published: March 2003

The calibration and in particular the linearity of a three-plate capacitance displacement transducer of range 1 mm and sensitivity 0.1 nm is measured with reference to a He–Ne laser standard using a Fabry–Perot etalon. The magnitude of the nonlinearity over the operational range is compared with estimates obtained from calculations of fringing fields. The most important contribution to nonlinearity is found to be inaccuracy in machining the capacitor plates, but this can readily be restricted to less than 1 nm over a central range of 0.3 mm (i.e., 3 parts in 106).
Optimization of toroidal electrostatic analyzers for measurements of low energy particles in space
Authors: Decreau P. , Prange R. , Berthelier J. J.
Published: March 2003

After having used an analytical expression in the form of a power series expansion to calculate the interelectrode electrostatic field in the general case of a toroidal electrostatic analyzer, we derive approximate analytical expressions for the most interesting response functions (geometrical factor, angular aperture, energy resolution, etc.). Results of a study of the dependence of these quantities with respect to the geometrical parameters of the analyzers are given in the form of grids of curves. By using such grids one is able to determine the optimal parameters to obtain any particular solution. Examples of such a choise are given in the case of measurements of low energy particles in space (10 eV to 50 keV).
New high-temperature noble-metal thermocouple pairing
Authors: Glawe George E.
Published: March 2003

A new thermocouple pairing was formed by combining thermocouple elements from two existing commercially available thermocouples to form a new combination (Ir–40 Rh/Pt–40 Rh) thermocouple. The output of this new pairing is nearly linear with temperature, and approximately equal to the output of one of the originating pairs (Ir–40 Rh/Ir), and more than double that of the other pair (Pt–40 Rh/Pt–20 Rh). This new pairing was evolved during a search for a noble-metal thermocouple combination which could operate above the temperature limit of a Pt–13 Rh/Pt thermocouple and have a higher oxidation resistance than an Ir–40 Rh/Ir thermocouple.
High precision laser machining circuit generator
Authors: Moran J. M. , Saunders T. E.
Published: March 2003

An accuracy of ±0.25 μ has been achieved in the generation of patterns with features of 3.0 μ and gaps of 2.8 μ in metallic thin films on glass. Patterns are generated by using a raster scan motion in combination with a laser beam for machining. The positioning system consists of a stepping table capable of 0.5±0.1 μ steps over a 2 cm range in the y direction and a shuttle table capable of 0.5 m/sec constant velocity over a distance of 10 cm in the x direction. The position of the stepping table depends on the accuracy of a ball lead screw, and the position of the shuttle table is monitored by a laser interferometer whose information is used to control the laser modulation. The stepping table carries the focusing lens for the laser beam and the shuttle table carries the substrate. Laser machined spots 2 μ diam are made using a highly stable Nd-YAG cavity dump laser operating at 0.5 MHz in the TEM00 mode. The address structure for the pattern is 0.95 μ in the x direction and 1.0 μ in the y direction. A computer control system will make it possible to process up to four 1 cm × 1 cm substrates simultaneously, with a total machining time of 36 min. At present, patterns are generated using a control system comprised of a 32-bit programmable word generator for the x direction and a 63-bit counter for the y direction.
Low-temperature x-ray attachment
Authors: Davis G. T. , Eby R. K.
Published: March 2003

A commercial high-temperature, high-vacuum diffractometer attachment, which was originally designed for heating samples from ambient temperatures to 2600 K using metal ribbon heaters, has been modified for low-temperature use. This has been accomplished simply by the construction of a new sample holder and a change of the port used for evacuation. With these modifications, controlled temperatures down to 100 K can be achieved easily.
Production of small fiducial marks by means of the scanning electron microscope
Authors: Bunnell L. R.
Published: March 2003

The scanning electron microscope can be used to precisely position and apply some rather small (0.3 μ) carbon deposits which can be used as fiducial marks. These marks are quite durable and can be applied to metals and ceramics. An example of their production on graphite fibers is shown.
Interferometric electropolisher for controlled surface removal
Authors: Sprague J. A.
Published: March 2003

An apparatus is described which allows the preparation of transmission electron microscopy specimens at specified depths of the order of 1 μ below the initial surface of the specimen. The instrument is designed for electropolishing of the surface with in situ measurements by optical interference of the depth of material removed. The depth of the electropolish may be determined to an accuracy of approximately ±500 Å, and high-quality specimens may be easily prepared.