bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymmetric crystal topographic camera
Authors: Boettinger William J. , Burdette Harold E. , Kuriyama Masao , Green Robert E.
Published: March 2003

The practical aspects of asymmetric crystal topography are described. In this technique, asymmetric Bragg diffraction is utilized to obtain a monochromatic and well collimated x-ray beam large enough to cover the entire area of sample crystals. Thus, the recording of diffracted beams from a sample crystal provides topographic images of the entire sample crystal. Advantages of this technique are simplicity (no scanning device), excellent sensitivity to crystal imperfections (strain fields), and versatility. Information is given on the general alignment of the camera, magnification of the x-ray beam width, preparation of the first crystal, and divergence of the beam due to the first crystal. The practical aspects of this topographic system are demonstrated using thick Cu and Ni crystals of various degrees of perfection. An inexpensive image intensifier is also described, which is used routinely to aid in the alignment of sample crystals.
Pirani manometer with linearized response
Authors: Hidber H. R. , Süss G.
Published: March 2003

A fast-reading Pirani manometer with an electronically linearized response for gas pressures between 3×10−4 and 0.5 Torr is described. The time constant of the manometer is 20 msec. Two NTC resistors are used, one for the sensor in the vacuum system and one for the reference at constant pressure. The pressure in the vacuum system is measured by analog computation of the power needed to stabilize the two resistors to equal temperature. By a relatively simple compensation circuit, changes in room temperature within ±10 °C can be eliminated to less than 1 per mille per degree. The manometer is built from inexpensive standard electronic components.
Picosecond resolution, real-time linear detection system for 10-μm radiation
Authors: Walker A. C. , Alcock A. J.
Published: March 2003

A 10-μm detection system based on up-conversion in proustite has been developed for the measurement of subnanosecond pulses of CO2 laser radiation. This has involved the development of a ’’stretched-pulse’’ Q-switched Nd:YAG oscillator which can be synchronized with the output of a transverse discharge CO2 laser. The 1.06-μm radiation generated by this oscillator and the incoming 10-μm radiation pass collinearly through a 0.6-cm-long proustite crystal which is oriented for type II phase matching. An investigation of the bandwidth of the up-conversion process has shown that it should be possible to resolve 10-μm pulses with durations of ∼5 psec. Using an image converter streak camera to record the 0.96-μm sum frequency, the overall performance of the system has been investigated with the aid of a mode-locked CO2 laser operating at a pressure of 12 atm. The results have demonstrated that mode-locked CO2 pulses as short as ∼75 psec can be generated and that the temporal resolution of the complete detection system corresponds to that of the streak camera.
Automated resonance-bar damping measurement system
Authors: Klimasara A. , Fiore N. F. , Kuczynski G. C. , Schutt D. W.
Published: March 2003

This paper describes an automated internal friction measurement system which allows continuous resonant-frequency tracking and continuous recording of damping and resonant frequency during resonance-bar internal friction experiments. A phase-locked loop based on a phase detector maintains the system at resonant frequency although the frequency may change during the course of an experiment. A modified White cathode follower is used to overcome capacitive loading effects in coaxial cables between the damping system and electronic controlling–recording components. In this manner, monitoring and recording components may be located at distances of tens of meters from the drive-detector-specimen damping system, which may in turn be located in some hostile environment of interest. The automated system may be used with damping measurement systems which employ piezoelectric, electromagnetic, or electrostatic drive-detection transducers.
Simple surface ionization detector with field reversal for absolute ionization coefficient and ionic and neutral desorption measurements
Authors: Holmlid Leif , Olsson Jim O.
Published: March 2003

Recent absolute reactive scattering experiments have demonstrated the need for and usefulness of absolute flux measuring molecular beam detectors. A field reversal detector of the type described here can conveniently and accurately (<±3%) measure the absolute flux of molecular beams of easily ionizable substances, without external calibrations or surface condition or surface temperature changes. The detector is mechanically very similar to the common surface ionization detector and uses uncomplicated electronics. With such a detector the neutral and ionic desorption rates may also be accurately determined separately. Thus the values of the true desorption parameters may be measured; such values have usually not been produced by previous methods for desorption rate measurements.
Dependence of gaseous diffusion measurements on cell geometry
Authors: Staker G. R. , Dunlop Peter J.
Published: March 2003

A comparison is made of the composition dependences of the mutual diffusion coefficient 𝒟12 for the helium–nitrogen binary gas system at 300 K and 1 atm pressure in two different types of diffusion cells. In the first group of cells 𝒟12 is markedly dependent upon their geometry, whereas there is no geometry dependence in the second group.
Precise determination of very low dielectric losses at frequencies of 9 and 29 GHz
Authors: Stumper Ulrich , Frentrup Klaus-Peter
Published: March 2003

For the special case of determining the dielectric loss factor of liquids of very low loss (tanδ about 10−4) at centimeter wavelengths, an improved interferometer method using standard waveguide components has been developed. One interferometer operating at frequencies of about 9 GHz is described in detail. The influence of multiple reflections and of wall losses on the accuracy of measurement is investigated. The uncertainty in tanδ is less than 1.2×10−5. Measurements by a second interferometer at 29 GHz coincide well with values obtained by known cavity resonator methods.
Simple microwave interferometer for measuring small phase shifts with high spatial resolution
Authors: Bacon M. E. , Goodhead D. T. , Wantenaar G. H. J.
Published: March 2003

A simple X-band microwave interferometer is described. Spatial resolution to ∼0.2 cm was obtained by using a simple Lecher wire system to transmit the microwaves through the test region. Power levels were such (∼1 mW) that in the vicinity of the balance point the crystal detectors operated in their linear region. Under these conditions the output from the phase-sensitive detector varied linearly with phase over ±10° to better than 1%. The sensitivity in the region of the balance point was about 18 mV per degree of phase shift with a noise level of <0.1 mV. This gave a resolution above noise to better than 0.01°. The performance of the interferometer was evaluated using 2 cm diameter simulators made of cardboard. Line-of-sight phase shifts were determined as a function of distance from the simulator center and the Abel transform of the data taken to yield local values of refractive index. The agreement between the experimental and theoretical local values of refractive index was better than 10% using a simulator giving a maximum phase shift of 0.42°. The system should be useful in determining local values of electron density in small diameter (2–5 cm), low density (109–1010 electrons/cm3), cold plasmas, as well as other media in which small phase shifts are to be measured.
Check on the linearity of a capacitance diaphragm manometer between 10−4 and 10−1 Torr
Authors: Van Zyl B.
Published: March 2003

A procedure is outlined whereby the pressure measurement linearity of a certain class of capacitance diaphragm manometers can be evaluated. Data are presented to illustrate the technique as applied to the 10−4–10−1 Torr pressure range.
Digital interface for remote control of a Cary 14 spectrophotometer
Authors: Reiser Christopher , Evans James S.
Published: March 2003

A general purpose interface has been employed to digitize data from a Cary 14 spectrophotometer, transmit data to a PDP-11/20 laboratory computer, and operate the spectrophotometer remotely under program control. A powered bidirectional bus approximately 50 m in length connects the two instruments for communication of data and commands.
Design, development, and performance of a fiber optics refractometer: Application to HPLC
Authors: David D. J. , Shaw D. , Tucker H. , Unterleitner F. C.
Published: March 2003

A fiber optics refractometer has been developed based on a simple low-volume cell (5–7 μl) which confines the liquid to be measured around a waveguide whose multiple reflections can enhance the contrast at the critical angle. The electromechanical and electrooptical design allows the fiber optics refractometer to measure absolute refractive index with manual or automatic readout, and differential operation with automatic tracking that permits its use as a universal detector for gradient elution chromatography. Present sensitivity is approximately 1×10−5 refractive index units in the static mode and 7×10−5 refractive index units in the scanning beam mode. These sensitivities can probably be improved by a factor of 5 by appropriate system changes.
High-speed automatic ellipsometer for industrial uses
Authors: Kasai T.
Published: March 2003

An automatic high-speed ellipsometer and its practical use are described. The instrument can measure the thickness and optical constants of thin films on materials in 0.03 sec with an accuracy of 0.1°. It has been in use in a factory for about three years and can be used for in situ ellipsometry of evaporated thin films on glass, metal, etc.
Reduction of the pulse duration from a Febetron 707
Authors: Lesigne B. , Sauneuf R.
Published: March 2003

This paper describes the use of a deflecting magnetic field to reduce the duration of an electron pulse from a Febetron 707 (normally 90 nsec at the base, Imax=4000 A) to 12 nsec (6–7 nsec half-width) with Imax =450 A. Under these conditions a dose of about 300 kilorad is delivered in a circular area 2 cm in diameter.
Constant temperature thermostat for electronic noise measurements at frequencies above 1 μHz.
Authors: Boehm T. J. , Bilger H. R.
Published: March 2003

A thermostat at a temperature of 33.50 °C was constructed for noise measurements on electronic devices for periods of days. A stabilization factor with respect to room temperature fluctuations of over 4×104 is achieved. Upper limits are determined for stray magnetic field fluctuations as ‖Ḃ‖⩽0.3 μT/sec, and for electric fields as ‖E‖⩽8 μV/m, measured in the frequency range 10−4 Hz <f<100 Hz. Long-term drifts of temperature are estimated as ‖δT/δt‖<100 μ°C/day. We consider this instrument a medium stable, thermally, electrically, and magnetically quiet thermostat suitable for long-term investigations of basic fluctuations in device properties.
Photon counting system for subnanosecond fluorescence lifetime measurements
Authors: Leskovar Branko , Lo C. C. , Hartig Paul R. , Sauer Kenneth
Published: March 2003

A new photon counting system has been developed for subnanosecond fluorescence lifetime measurements. The system incorporates a nanosecond light pulser, a dual counter unit, and a constant-fraction discriminator. The operating conditions of the light pulser have been adjusted to minimize the spread of the light pulse waveshape. The discriminator has upper and lower level adjustments and a time walk of no more than ±35 psec over a 50-mV to 5-V input pulse amplitude variation. The measuring system has a total system time resolution, expressed as the FWHM of the light pulse, of 800 and 1480 psec using photomultipliers 8850 and 8852, respectively, with full photocathode illumination and optimized operating conditions. The system will measure both single and multiple decay components, and it is designed and optimized for experiments involving measurements of decay time constants as short as 90 psec.
Simple grazing incidence far ultraviolet monochromator for differentially pumped discharge lamps
Authors: Shevchik N. J.
Published: March 2003

A simple, compact, grazing incidence monochromator designed for isolating the strongest photon lines of He, Ne, and Ar produced in a differentially pumped discharge lamp is described. The light intensity loss of photons with energies hν∼40 eV due to monochromatization is less than a factor of 10, allowing electron count rates to be obtained on a commercial electron spectrometer comparable to those obtained with synchrotron sources. Photoelectron energy distributions of ZnTe and SnTe taken with monochromatized He I and II, and Ne I and II photons demonstrate the usefulness of the discharge-lamp monochromator source for valence band and core level studies.
Construction and performance of a scanning, photon-counting spectrofluorometer
Authors: Jameson D. M. , Spencer R. D. , Weber G.
Published: March 2003

A photon-counting spectrofluorometer interfaced to a Nuclear Data ND 812 computer was constructed to facilitate acquisition of emission spectra at very low signal-to-noise ratios. The photon-counting technique combined with repetitive scanning permits the detection and quantitation of emission from strong fluorophors near the picomolar level. The computer performs a variety of digital manipulations such as subtraction of background, normalization of spectra, corrections for instrument response, and polarization calculations. Special attention needs to be given to handling of cuvets and solvents to minimize background signals.
Cable-driven large-angle rotator used in a superconducting solenoid
Authors: Alles H. G. , Chang Y. K. , Higgins R. J. , Nosler J.
Published: March 2003

A rotator with two independent cable drives plus one shaft drive was constructed to provide smooth and large-angle rotation of a sample in an arbitrary crystallographic plane in a superconducting solenoid.
Pulsed reference source for photon-counting systems
Authors: Hagen E. C. , Eklund P. C.
Published: March 2003

A simple design for a pulsed light source consisting of an LED and temperature-compensating current pump has been built and tested. The source stability has been found to depend primarily on ambient temperature change. The temperature stability of the emitted number of photons (γ?670 nm) in a 200-nsec-wide pulse has been measured to be 0.05%/°C. Thus in normal laboratory environments it will provide a stable reference which can be used in monitoring and calibrating inevitable gain shifts observed in photon-counting systems. Its application to the scintillation detection of γ radiation is discussed.
Possibility of particle acceleration by laser beams along crystal channel axis
Authors: Kanofsky Alvin
Published: March 2003

The possibility of particle acceleration along crystal channel axis is discussed. Rough estimates of the output beam intensity are made using two different methods.
Rapid measurement of liquid thermal conductivity by the transient hot-wire method
Authors: Trump Walter N. , Luebke Harold W. , Fowler Lewis , Emery Edward M.
Published: March 2003

A modification of the transient hot-wire method of measuring liquid thermal conductivities provides simplified operation through direct plotting of wire resistance as a function of logarithm of time, following application of a constant heating current. An electronic transient recorder operating from a logarithmic time base stores resistance readings at equal increments of log time for subsequent plotting by a servo recorder on linear coordinates. Multiplication of the inverse slope of the resulting curve by an instrumental constant gives the thermal conductivity. Designed for obtaining engineering data of moderate precision and accuracy, the method was tested on water, methanol, carbon tetrachloride, and toluene. The results obtained were 0.4–4.4% lower than recent literature values for these liquids. The relative standard deviation of repeated measurements was 0.5–1.0%.
Pi-meson range shifter for clinical therapy
Authors: Liska D. J.
Published: March 2003

An energy-absorbing instrument, designed for use with a linear accelerator producing a high-intensity beam of negative pions, is described. The system makes use of a variable column of energy-absorbing fluid with depth controlled by a hydraulic servomechanism to conform to theoretically or experimentally derived sweep curves in the form of histograms or continuous functions. The dose-vs-depth curves which result from the vertical sweep of the instrument show excellent flattening over the stroke. The details of construction and control of this ’’range shifter’’ are described, as well as a unique method for command-function storage and interrupt control using programmable memories and microprocessor techniques.
Frequency response of hot wires used for atmospheric turbulence measurements in the marine environment
Authors: Fairall C. W. , Schacher Gordon
Published: March 2003

We have examined the frequency response of hot wire anemometers using 4.5-μ tungsten wires with laboratory-produced salt layers. The salt layers are produced by exposure of the heated wire to a NaCl–water aerosol and are intended to simulate salt layers produced on wires used in the marine environment. The frequency dependence was determined by measuring the response of the wires to a sinusoidal velocity field generated in a sound chamber. The relaxation frequency (or rolloff frequency) was found to vary as t−2, where t is the thickness of the salt layer, in agreement with the theory presented in this paper. In addition, the dc calibration parameters for thick coatings were investigated and compared with theory.
Measuring small changes in calorimetric properties using a ’’direct difference’’ technique
Authors: Lechevet Jon , Neighbor J. E. , Padamsee H. , Shiffman C. A.
Published: March 2003

A simple method is described for determining small changes in calorimetric properties when an external field is applied, without the use of curve fitting or other interpolation schemes. This is illustrated using recent data for strong-coupling superconductors, in which the changes in the electronic specific heat, entropy, and free energy between the normal and superconducting states are to a large extent obscured by the common lattice contribution. In the same context, errors introduced by thermometer magnetoresistance at low fields are discussed, and a new technique for determining the magnetoresistance correction is presented.
Detection efficiency of a ceramic channel electron multiplier in the vacuum ultraviolet
Authors: Masuoka Toshio
Published: March 2003

Detection efficiencies and other performance characteristics of ceramic channel electron multipliers (named Ceratron) were examined in the vacuum ultraviolet region. Detection efficiencies of magnetic electron multipliers (Bendix M306) and quantum efficiencies of tungsten and nesa glass were also measured for comparison with those of the Ceratron. The results indicate that the efficiency of the Ceratron is similar to that of the Bendix M306, and about an order of magnitude smaller than that of tungsten.
Synchronous marker for measuring phase in the presence of noise
Authors: Robertson Baldwin , Potzick James E.
Published: March 2003

A circuit has been constructed to mark the phase of a sinusoidal signal even when it is obscured by noise. The time jitter of the marker signal due to the noise can be reduced as much as desired in trade for slowed response time of the circuit. A theoretical description of the performance of the circuit and an error analysis are presented. Results of tests on the circuit agree approximately with the theoretical description.
Laser–ion coaxial beams spectrometer
Authors: Huber B. A. , Miller T. M. , Cosby P. C. , Zeman H. D. , Leon R. L. , Moseley J. T. , Peterson J. R.
Published: March 2003

An apparatus has been constructed to provide laser excitation of ion beams in both coaxial and crossed configurations. The coaxial geometry provides very high sensitivity and nearly Doppler-free wavelength resolution for spectroscopic measurements, and allows the use of the Doppler shift to ’’tune’’ the wavelength. A novel transverse quadrupole electric field arrangement is used to deflect the ion beam into and out of the laser beam axis. The ion beam is highly collimated and a high-resolution 180° electrostatic analyzer is used for photofragment energy analysis. The apparatus has demonstrated a resolution of better than 10 meV for normal photofragment spectroscopy and 0.001 meV for coaxial beams photofragment spectroscopy using a single-mode laser. While providing these high resolutions the apparatus has an overall sensitivity several orders of magnitude greater than conventional ones.
Interferometric technique for the simultaneous measurement of passive membrane transport coefficients
Authors: Meyer R. A. , Friedman M. H.
Published: March 2003

A novel membrane transport cell is described which enables the simultaneous measurement of the hydraulic conductivity, reflection coefficient, and effective permeability of a membrane. Laser interferometry is used to measure the solute concentration difference across the membrane in an unsteady experiment. Results for sucrose transport across a Cuprophan-150 PM membrane are reported.
Surface potential probe operated at 77 K with nanosecond response
Authors: van Welzenis R. G. , de Zeeuw W. C.
Published: March 2003

We describe the design, construction, and performance of an instrument for time-resolved surface potential distribution measurements on fragile specimens of small dimensions, e.g., semiconductor bars or wafers. The instrument can operate at 77 K and is easily adapted to computer control. Spatial resolution is about 10 μm in two dimensions. On low-resistivity material a time resolution of 1 ns can be achieved.
Performance analysis of transformer–rectifier flux pumps
Authors: Bernard S. P. , Atherton David L.
Published: March 2003

The operation of transformer–rectifier flux pump power supplies is described and analyzed. Two cases, based on the mode of current commutation between cryotron gate switches, are considered, and expressions for power output, losses, and efficiency are developed. Results of tests on a prototype flux pump are in good agreement with theoretical predictions.
High-efficiency flux pump power supply using inductive current transfer
Authors: Bernard S. P. , Atherton David L.
Published: March 2003

A superconducting flux pump power supply of the transformer–rectifier type is described. Load current commutation between gates is by transformer primary current control. A simple, inexpensive system of generating the required control waveforms is outlined. Results of load magnet charging tests to currents of 500 A are given and are consistent with calculated performance.
Transient experiment using a multiple-pulse laser light source
Authors: Oertel Fritz H.
Published: March 2003

We applied a technique of passively Q switching a ruby laser to photograph transient development of an unsteady, underexpanded jet. In this technique, a bleachable absorber was used to generate multiple laser pulses which backlighted a Mach-Zehnder optical interferometer used to observe the jet flow; instantaneous images of the laser-illuminated event were swept onto a fixed film drum by a mirror rotating at ∼75 000 rpm for a film writing speed of ∼16 mm/μs. Our success ratio, which was good, was achieved despite the fact that control of pulse separation, number of pulses, duration of lasing action, and pulse-to-pulse intensity were not precise. We had more success with the passive technique than we did with an electronic, high-voltage technique—described in the paper—for multiple Q switching of a Pockels cell.
Surface multipole guide field for plasma injection
Authors: Breun R. A. , Rael B. H. , Wong A. Y.
Published: March 2003

Described here is a surface guide field system which is useful for injection of plasmas into confinement devices. Experimental results are given for 5–25-eV hydrogen plasmas produced by a coaxial discharge (Marshall) gun. It is found that better than 90% of the plasma produced by the gun is delivered to the end of the guide 180 cm away, while the neutral component falls by more than an order of magnitude. For these results the rod current providing the magnetic field had to be large enough to provide at least 1.5-ion gyroradii from the center of the guide to the surface of the inner rod.
Transmission properties of a cylindrical mirror analyzer viewed in energy-angle space
Authors: Eagen C. F. , Sickafus E. N.
Published: March 2003

In this paper we present a general method for calculating the transfer and transmission functions of a cylindrical mirror analyzer (CMA) which employs the exact, albeit numerical, solutions of the particle equations of motion. The analysis incorporates emission from extended sources and easily lends itself for use with elements which preretard the particle’s kinetic energy. Our approach leads directly to a convenient display of the analyzer transmission in energy-angle space which provides a vantage point for assessing the role of each CMA aperture in the transmission process and for assessing the influence of the angular distribution of the emitted particles on the energy transfer function. The general method can be extended to include any dispersive analyzer for which the particle equations of motion are solvable.
Multichannel grating spectrometer for millimeter waves
Authors: Pasour J. A. , Schlesinger S. P.
Published: March 2003

A multichannel grating spectrometer for use with high-power (∼1 MW), short-duration (≲5 ns) pulses of millimeter-wavelength radiation is described.
Low-frequency function generator/controller using an X–Y recorder
Authors: Myers John H. , Frost Charles F.
Published: March 2003

An electrical circuit is described which allows an X–Y recorder to be used as a function generator or process controller. A small optical sensor placed in the pen position is used to track a black–white curve edge used in place of the normal graph paper on the recorder. As the sensor tracks the edge, the associated circuit gives an electrical voltage proportional to the curve height. The device has proven useful in the generation of nonanalytical or unusual functions for analog computation and can also be used in control applications.
A modified heat pulse method for determining heat capacities at low temperatures
Authors: Fagaly R. L. , Bohn R. G.
Published: March 2003

A heat pulse method is described which can be used to determine the low-temperature heat capacity of a sample that is linked thermally to a heat sink. This method may be used with samples that have internally generated sources of heat, such as radioactive isotopes. The analysis makes use of a characteristic time constant τ and the actual temperature of the sample before and after the heat pulse. Specific results are shown for samples with effective internal sources of heat.
Calorimeters for measurement of ions, x rays, and scattered radiation in laser-fusion experiments
Authors: Gunn Stuart R. , Rupert Viviane C.
Published: March 2003

Several types of calorimeters have been developed for measuring ions, x rays, and scattered radiation produced by fusion experiment targets imploded by laser pulses. One version for ions and x rays uses metal absorbers in a differential arrangement to compensate for the small fraction of scattered laser radiation that is also absorbed; the other version uses a glass absorber which transmits most of the scattered laser radiation. The scattered-radiation calorimeters use a transparent glass shield to remove ions and x rays and colored glass to absorb the radiation.
Pulsed high-density source of cesium atoms
Authors: Anderson David K. , Jones Douglas W. , McCullen J. D.
Published: March 2003

A new source of high-density cesium vapor is described. Flash evaporation of a thin cesium layer by means of a xenon flash tube yields atom densities in excess of 1016/cm3 for pulse durations of about 20 μsec. Data are presented for a range of operating parameters.
Pressure distribution in the diamond anvil press and the shear strenght of fayalite
Authors: Sung Chien-Min , Goetze Christopher , Mao Ho-Kwang
Published: March 2003

High-pressure cells, using opposed diamond anvils, have become an increasingly sophisticated tool for high-pressure research as the high-pressure environment within th cell becomes more quantitatively established. We have used the ruby fluorescence technique for measuring pressure to obtain the radial distribution of pressure between the diamond anvils for samples of fayalite (Fe2SiO4). Precompacted specimens appeared to be in a conditon of extrusion, limited by the plastic strength of the fayalite aggregate formed. Specimens which were not precompacted were too thin to show this condition.
Test of flux conservation using a radially resolving diamagnetic loop
Authors: Gerber K. A. , Spector D. N. , Sethian J. D.
Published: March 2003

A high radial resolution, triple diamagnetic loop is employed to test the validity of magnetic flux conservation in the vacuum chamber of the SEEBIE electron beam–neutral gas interaction experiment.
Linear optics theory of ion beamlet steering
Authors: Whealton J. H.
Published: March 2003

Based on the paraxial approximation, a linear optics theory which accounts for steering effects in multibeamlet ion sources is presented. For a triode accelerating structure, the steering is independent of the accel potential and is in the opposite direction to the electrode displacement. For a tetrode, the steering is dependent on the potential distribution and may be in either direction relative to the displacement. With arrangements used for best optics, in tetrodes, the beam steering may be in the opposite direction to that of triodes.
Characteristics of a 600-W convective flow CO laser
Authors: Lim D. G. , Mendoza P. J. , Cohn D. B.
Published: March 2003

Operating characteristics of a moderate power, convective flow, longitudinal discharge CO laser are presented. Incorporation of a novel electrode geometry has resulted in a highly stable and reliable device, useful as a laboratory tool.
Device for optically exciting XeF and other rare gas excited complexes
Authors: Mandl A. , Ewing J. J.
Published: March 2003

A device is described in which Xe is optically pumped (147 nm) and reacted with NF3 to form XeF. The same apparatus can be used to pump Kr and Ar and thereby form excited rare gas halides, oxides, and sulphides. The device is small, allowing repetitive pulsing and signal averaging techniques to be used.
Two-photon spectrometer based on flashlamp-pumped dye lasers
Authors: SethuRaman V. , Small G. J. , Yeung E. S.
Published: March 2003

We describe here a two-photon spectrometer that utilizes two independently tuned, flashlamp-pumped dye lasers, and the associated detection electronics for the determination of the temporal profile of the two lasers (FWHM≈200 ns) and the fluorescence pulse following two-photon excitation. This spectrometer allows for proper normalization of the observed signal to the laser power. Procedure for the extraction of relative cross sections for two-photon absorption is described, and a spectrum obtained for a solution of naphthalene in benzene is presented.
Barrier technique for separate measurement of radon isotopes
Authors: Ward W. J. , Fleischer R. L. , Mogro-Campero A.
Published: March 2003

Longer-lived radioactive isotopes of elements can be separated from a mixture of isotopes in passing from one volume to a second by the use of an appropriate intervening barrier so that the shorter-lived isotopes decay before reaching the detector. The separation can most effectively be created by use of a membrane; a purely diffusional barrier is also effective. The techniques are demonstrated in experiments with 3.8-day 222Rn and 56-s 220Rn.
Measurement of subnanosecond fluorescence decays by sampled single-photon detection
Authors: Harris J. M. , Lytle F. E.
Published: March 2003

A new method of single-photon timing and its application to measuring fast fluorescence decays is discussed. The detector-signal processor, having a transient response of 0.77 nsec FWHM, is designed around an inexpensive, two-channel sampling oscilloscope. Using a mode-locked, pulse-picked argon ion laser as an excitation source, the system performance in measuring fast fluorescence decays was evaluated. An uncertainty for lifetimes measured in the range of 4 nsec to 50 psec was found to be ±6% or ±10 psec, whichever is greater.
Induction-heated oven for laser spectroscopy of atomic uranium
Authors: Erez G. , Kerman A. , Kimhi D. , Levin L. A. , Miron E.
Published: March 2003

A simple compact oven was built for spectroscopy of atomic uranium. The oven is especially suitable for laser induced fluorescence spectroscopy.
Resistors for recording currents in the microsecond region
Authors: Nanduri Vidyardhi
Published: March 2003

A circumferential slit design for a coaxial current shunt and a resistor stack construction are described for recording current waveforms in the microsecond region.
Rotating ball generator
Authors: Kunhardt E. , Dollinger R.
Published: March 2003

A generator which uses a stainless steel ball to transfer a charge between two electrodes has been designed and tested. The generator, known as the RBG, produces very high amplitude, narrow (⩽1-nsec wide) baseband pulses with variable repetition rate into a 50-Ω line.
High-resolution pulsed electron beam time-of-flight spectrometer
Authors: Kennerly R. E.
Published: March 2003

A time-of-flight electron spectrometer employing a microchannel plate detector has been developed for measuring the spectra of electrons ejected from gaseous targets by electron impact. A time-resolving capability of 240 psec is achieved, allowing energy resolution comparable to the best obtained with electrostatic dispersion analyzers for energies of several eV and below. Examples from the ejected electron spectra of He, Ar, and N2 are presented, demonstrating the intensity, accuracy, and energy resolution. In addition, the relative efficiency of the microchannel plate detector for single electron detection has been measured.
Effects of A/D converter resolution in signal averaging
Authors: Diebold Gerald J.
Published: March 2003

Signal averaging is investigated for the case of a sample-and-sum averager where errors are introduced by the finite amplitude and resolution capabilities of the analog-to-digital (A/D) converter. This is a refinement of a previous treatment [R. R. Ernst, Rev. Sci. Instrum. 36, 1689 (1965)] where the summed signal is an integrated average over the width of each channel. It is shown that when the noise amplitude is much larger than the least significant digit of the A/D converter the original signal is given back after averaging along with two error voltages—one depending on the resolution, and the other on the maximum allowable input to the A/D converter. The expressions given for the magnitudes of the error voltages show that under most laboratory situations the signal can be recovered with high precision—much greater than the resolution of the A/D converter. Also, a general expression for noise in the time averaged output is derived and evaluated for the case of bandwidth-limited white noise. The result shows that the signal averaged noise is small for a low resolution A/D converter and approaches a limiting value for a high resolution converter. Finally, these results are applied to the operation of a high resolution digital voltmeter.
Directional rf probe for measurement of conductivity of flowing plasmas
Authors: Jayakumar R. , Chakravarthy D. P. , Rohatgi V. K.
Published: March 2003

An electrodeless immersible rf probe for measurement of plasma conductivity in the range 0.01 to 100 mho/m has been designed and fabricated. The probe, with an overall diameter of 11 mm, employs unidirectional electromagnetic field lines which reduce the inaccuracies caused by insertion of the probe in a flowing plasma. In the range studied the probe output shows a linear relationship with the conductivity of the medium. Such probes are of interest in the study of MHD and reentry plasmas.
Shock isolator for diode laser operation on a closed-cycle refrigerator
Authors: Jennings D. E. , Hillman J. J.
Published: March 2003

Impact shocks occurring during the expansion phase of a closed-cycle refrigerator cause large excursions in the output frequency of a diode laser. We have characterized these frequency instabilities by observing their effects on spectra, and have reduced these effects to less than observable (corresponding to frequency deviations <5 MHz).
Improvements on the measurements of dielectric constant and dissipation factor in a wide frequency range
Authors: Kakimoto A. , Ogawa I. , Matsushita T.
Published: March 2003

This paper describes an improved micrometer electrode system for the measurements of dielectric constant, dissipation factor, and mean thickness of sheet specimens in a wide frequency range and its appplication to a series of measuring methods. The influence of the edge capacitance and the residual impedance of this electrode system has been decreased to a negligibly small amount by the adoption of a shield ring and improvements in construction of the electrode system. The characteristics of the system are easily examined by using its electrode gap fine adjustment mechanism, which is developed for a series of measuring methods. In case the varying gap immersion method is adopted, the imperfect contact between the electrodes and the specimen and the residual impedance of the system do not affect the results, even at the highest frequency. Furthermore, the measurements are limited to only the gap variations and the resonance voltage ratio, and are freed from those of the electrode gap length, the electrode area, and the specimen thickness. Therefore, the measuring and calculating processes are so simplified that they take only a few minutes for each specimen, and in a series of methods, the best results are obtained without any correction in a wide frequency range from 1 to 200 MHz. The resolution is limited by the sensitivity and stability of the adopted apparatus such as a Q meter. The accuracy reaches ±0.2% for dielectric constant and ±2% or 3 μrad for dissipation factor, respectively, even at the highest frequency of 200 MHz.
Double-pulse laser flashlamp pumping and a new method of flashlamp triggering
Authors: Mroczkowski J. A. , Milburn R. H.
Published: March 2003

The design of a flashlamp triggering and driving circuit is described for the short pulse pumping of a Nd3+ YAlO crystal suitable for Q-switched operation. The special features of this system were a prepulse circuit for pulsing the flashlamp immediately before the main pulse, and a new method of flashlamp triggering based upon a saturable choke. An increase in laser efficiency and pulse reproducibility was obtained when the prepulse mode of operation was used.
Energy measurements on fast-pulsed near-relativistic electron beams using bremsstrahlung absorption spectroscopy
Authors: Smith A. C. , Swannack C. E. , Fleischmann H. H. , Schrandt R. G. , Thompson W. L.
Published: March 2003

The paper describes a technique for measuring the average energy—and its temporal changes—of intense electron beams on timescales down to a few nanoseconds using 3-channel absorption spectroscopy of the bremsstrahlung from a thin target. The technique appears useful for reasonably monoenergetic electron beams in the energy range of 200–800 keV.
Novel Faraday cup for the simultaneous observation and measurement of ion-beam currents
Authors: Wei Ching-Yeu , Seidman David N.
Published: March 2003

A novel Faraday cup is described which allows the simultaneous observation and measurement of ion-beam currents. The Faraday cup is constructed around a Galileo channel electron multiplier array (CEMA), which serves as the basis of an internal image intensification system (a gain of ≳104) for the observation of the ion beam; the CEMA also acts as a collector for the ion current which is measured by a Keithley 602 electrometer. The ion current is integrated by a simple and inexpensive dosimeter; the electronic circuit for the dosimeter is described. The application of the Faraday cup to the observation and measurement of a 30-keV Ar+ ion beam is presented as an illustrative example. We have also employed this Faraday cup to observe and measure 30-keV Cr+, Mo+, or W+, and 18-keV Au+ ion beams employed for the in situ irradiation of field-ion microscope specimens.
Measurement of nanosecond HV transients with the Kerr effect
Authors: Bergmann Ernest E. , Kolleogy Gary P.
Published: March 2003

A technique for measuring the high-voltage transients associated with low inductance, pulsed gas discharges is described. Measurements are made directly at the 10-kV level with a transmission line Kerr cell and narrow-width, pulsed dye laser, synchronized with the test discharge. The data indicates a temporal resolution of 2 ns.
New instrument for circular dichroism measurements in the vacuum ultraviolet
Authors: Gedanken Aharon , Levy Miriam
Published: March 2003

A new instrument is described for measurements of circular dichrosim (CD) in the vacuum ultraviolet region. A reflecting biotite plate is used as a linear polarizer and enables us to extend the CD measurements to about 1300Å. The CD spectra of d-camphor and of 3-methyl cyclopentene are presented.
Rapid-scan spectrophotometer for the study of turbid systems
Authors: Ogan Kenneth , Essig Alvin , Beach Kirk W. , Caplan S. Roy
Published: March 2003

We have constructed a type of rapid-scan spectrophotometer which can be used in several modes. The scanning element is a mirror mounted on the rotor of a galvanometer, which is under closed-loop control, forcing the mirror orientation to follow the input drive signal rapidly and accurately. Consequently, the wavelength scan pattern closely reflects the input waveform, imparting considerable versatility in the use of this controlled-scan spectrophotometer (CSS). We have operated the CSS as a dual-wavelength spectrophotometer, utilizing a square wave as the mirror drive waveform. In another application, we have used a periodic ramp mirror drive signal and a signal averager in the operation of the CSS as a sensitive (0.0003 A) differential spectrophotometer which incorporates correction for light scattering changes.
Condensation of hydrogen isotopes in laser fusion targets
Authors: Grilly E. R.
Published: March 2003

In the development of laser fusion targets, glass microballoons (∼100 μm diam) containing D2, T2, or DT were cooled through four types of heat transfer: radiation, solid conduction, exchange gas, and a cold He stream. Observations of condensate temperature of formation, volume, and distribution roughly agreed with calculations. A thermal gradient set up by the cold He stream from above was useful in counteracting gravity, and the resulting condensate formed a fairly uniform spherical shell, the desired form for the fuel.
Measuring plasma turbulence with a spectrum analyzer
Authors: Ilić D. B.
Published: March 2003

A simple combination of a wide-band differential amplifier and a spectrum analyzer is shown to be equivalent to a frequency-swept interferometer, which can yield phase information on wide-band random signals. Measurements of plasma wave dispersion, and correlation times and lengths are presented for ion acoustic turbulence in the positive column.
Application of photon counting techniques to measurement of the risetime of chromium (III) phosphorescence in the near infrared
Authors: Stuart D. C. , Kirk A. D.
Published: March 2003

An extremely sensitive system for luminescence decay lifetime measurements based on multichannel delayed coincidence photon counting is described. The stop channel photomultiplier is an RCA C31034 gallium arsenide photocathode type, resulting an in system capable of measurements on emissions with lifetimes in the range nanoseconds to tens of microseconds, and spanning the wavelength range 300 nm to at least 900 nm. The system has been used to seek a risetime of phosphorescence from chromium (III) complexes in room temperature and cooled solutions. No risetime could be observed. An upper limit of 10 nsec can therefore be placed on the risetime for the compounds studied except for [Cr(en)3]3+, where an upper limit of 1 nsec has been established.
Carousel stage for multisample microanalysis by scanning electron microscopy/energy dispersive x-ray spectrophotometry
Authors: Mroz E. J. , Taylor M. E.
Published: March 2003

Multielement microanalyses of multiple samples by scanning electron microscopy coupled with energy dispersive x-ray spectrophotometry is facilitated by the construction of a carousel stage that allows multiple samples and standards to be accessible to the electron beam.
Space charge effects in ionization type particulate detectors
Authors: Simon Frank N. , Axmark Roger E.
Published: March 2003

The response to particulates of an ionization chamber with adjacent unipolar and bipolar zones is analyzed. Values of reduced ion mobility from particulate charging in the unipolar zone and the resulting increase in surface recombination in the bipolar zone are determined from experimental data. A solution of the general field equation as a function of distance in parallel plate geometry is plotted. The current–voltage characteristic from the general equation is compared with that from the simpler vacuum field approximation for bipolar volumes. The close agreement warrants general use of the vacuum field in ionization chambers for the small operating current densities employed in these detectors.
Melting point of gallium as a temperature calibration standard
Authors: Sostman Henry E.
Published: March 2003

Enzyme reaction rates and other biomedical parameters depend critically upon temperature, and require accurate temperature measurement. A variety of thermometers are available, but these require reference to and calibration against a standard. The melting temperatures of pure metals are constants of nature, and during phase transition provide stable temperature environments for thermometer calibration. Pure gallium melts at 29.770 °C (IPTS68) and is shown to be a suitable standard for the calibration of thermometers in the biomedical range.
Design of a three-stage alkali beam source
Authors: Lambropoulos Melissa , Moody S. E.
Published: March 2003

A three-stage effusive alkali beam source is described in detail. Among the advantages of this device over ordinary effusive ovens are greatly increased intervals between refillings, and the production of beams with significantly reduced alkali dimer densities.
Homogeneous rf field delay line probe for pulsed nuclear magnetic resonance
Authors: Lowe I. J. , Whitson D. W.
Published: March 2003

The analysis of delay line coils for use in pulsed nuclear magnetic resonance, as carried out by Lowe and Engelsberg, is extended to include magnetic coupling between coil sections. The predicted cutoff frequency for the delay line is found to be considerably extended, and this is experimentally verified. The rf magnetic field distribution is theoretically analyzed for the case of a wide flat coil. The conclusion is that the field should be relatively homogeneous as long as the coil thickness is much smaller than the wavelength of the electromagnetic wave traveling down the coil axis. Several different flat coil designs using distributed capacitance are then described, along with operating characteristics of constructed models. The most successful model had a time delay of 20 nsec and a measured inhomogeneity of 4% at 60 MHz.
Interferometric laser technique for accurate velocity measurement in shock wave physics
Authors: Durand M. , Laharrague P. , Lalle P. , Le Bihan A. , Morvan J. , Pujols H.
Published: March 2003

An interferometric system for continuously measuring specimen velocity is described. The Döppler shift of a laser beam reflected from the specimen’s free surface is transformed into a variation of the diameter of Fabry–Perot interference rings, and the evolution of the diameter versus time is continuously recorded by a streak camera. Two examples of the use of this system for study of shock waves are given to show the accuracy of this device.