bluuebunny/crossref_metadata_2025 huggingface dataset:
Construction and alignment of a high performance multipass vernier tandem Fabry–Perot interferometer
Authors: Lindsay S. M. , Anderson M. W. , Sandercock J. R.
Published: March 2003

A multipass vernier tandem Fabry–Perot interferometer is easily constructed and aligned when the two scanning mirrors are mounted on a common scanning stage. Using such a system we obtain an ultimate resolution of 10−3cm−1 and a maximum scanning range, free of overlapping orders, of ≳50 cm−1. Using a 5 plus 4 pass arrangement a contrast ≫10 is obtained which, together with a high overall luminosity, permits simultaneous resolution of both weak spectral features near zero energy shift and low-frequency Raman bands. In addition to constructional details of this system we discuss the alignment procedure for uniform transmission in tandem operation, and demonstrate how the alignment requirments ultimately limit the performance of any tandem system to an ’’effective finesse’’ of <1000. Spectra showing surface waves in silicon and shear waves in polystyrene illustrate the power of this technique.
Palladium–silver–oxygen–cesium photocathode
Authors: Hou X. , Sibbett W. , Weekley B.
Published: March 2003

A low surface resistivity, semitransparent photocathode consisting of a palladium–silver–oxygen–cesium layer has been developed. It has been shown to have near infrared (NIR) response which extends to cut-off wavelengths ∼1.5 μm. The processing scheme and its effect on the photoemission characteristics of this photocathode are described.
Application of dynamic emittance matching to secondary ion mass spectrometry
Authors: Campana J. E. , DeCorpo J. J. , Wyatt J. R.
Published: March 2003

The implementation of the dynamic emittance matching (DEM) concept into our secondary ion mass spectrometer is described. The importance of this feature is presented in terms of increased ion transmission when operating at low primary ion beam fluxes, that is, the static secondary ion mass spectrometry (SIMS) or molecular SIMS mode. A discussion of the principle and the design of the DEM electronics in the system is given. Experimental comparisons are presented and discussed which contrast DEM and conventional results with respect to viewing area, ion transmission, and imaging capability.
New device for determining small changes in length
Authors: Grössinger R. , Müller H.
Published: March 2003

A versatile system for measuring the thermal expansion and the magnetostriction of spherical samples has been developed. A diaphragm sensor was constructed for measuring changes in strain (Δl/l0) in the range 10−3–10−6. A strain gauge technique is used where the change in length of the sample is determined by measuring the deformation of a membrane. A linear correlation between the change of length and the output signal of the sensor is shown. The temperature dependent calibration function is determined by a data processing system. The device is calibrated by using the known thermal expansion of Ni and Al in the temperature range 80–300 K. The correct operation of this technique is verified by measuring the thermal expansion of Cu and Nb. In addition the thermal expansion of Tb, Dy, TbCo2, and DyCo2 have been obtained and the results are in good agreement with published data.
Coaxial flashlamp design for high temperature operation
Authors: Drummond David
Published: March 2003

A design for a high temperature coaxial flashlamp is presented. This device has proved very useful in optical pumping studies of high temperature metal vapors. It is easily constructed, and provides high power ultraviolet irradiation of samples at up to 950° C. 5000 pulses of 2 μs length and 500 J of energy have been produced without apparent degradation of the lamp.
Automatic method for fabricating a three-dimensional plastic model with photo-hardening polymer
Authors: Kodama Hideo
Published: March 2003

A new method for automatic fabrication of a three-dimensional plastic model is presented. A solid model is fabricated by exposing liquid photo-hardening polymer to ultraviolet rays, and stacking the cross-sectional solidified layers. Three types of equipment were constructed, their operational conditions were investigated, and some solid models were fabricated. A transparent plastic model whose internal structure was visible from the outside of the model was obtained. The operations are simple and can be easily automated. The present method is useful in displaying three-dimensional shapes.
Observation of a cylindrical mirror analyzer artifact
Authors: Bargeron C. B. , Nall B. H.
Published: March 2003

Using a cylindrical mirror analyzer (CMA) to perform electron energy loss spectroscopy, a small surface-independent peak has been observed in the energy spectrum at an apparent energy above that of the primary elastic peak. The position of this peak varies linearly with the primary beam energy. Calculations using the parameters of the CMA indicate that this peak is due to elastically scattered electrons passing through the analyzer along a secondary path.
Bismuth magnetoresistive thermometry for transient temperature measurements in liquid helium
Authors: Brodie L. C. , Sinha Dipen N. , Sanford C. E. , Semura J. S.
Published: March 2003

We have developed a thermometric technique adapted from our work on the galvanomagnetic effects in bismuth at liquid helium temperatures. We find that a single crystal of bismuth can be used effectively as a thermometer for transient temperature measurements at these low temperatures. The thermometric property which is exploited is the strongly temperature-dependent magnetoresistance exhibited by these crystals at liquid helium temperatures. The bismuth thermometer is characterized by a fast thermal response, good sensitivity, low Kapitza resistance, and ease of electrical resistance adjustment, and it is particularly well suited to the situation in which the thermometer is itself used as a heater. In earlier work we successfully used these properties to study transient heat transfer from bismuth into liquid helium I and to measure the homogeneous nucleation temperature of liquid helium I.
Rare gas recovery systems for rare gas halide lasers
Authors: Kutschke K. O. , Hackett P. A. , Willis C.
Published: March 2003

A system is described for the recovery of xenon from XeCl lasers and variants for other rare gas halide (RGH) combinations are presented. The batch recovery systems discussed are simple and cost effective and lead to no degradation of laser performance. The added cost associated with continuous gas processing seems difficult to justify at the present time for a system of this size.
General purpose microcomputer-based data acquisition and laser control circuitry for use in one-photon and two-photon laser spectroscopy
Authors: Alameda George K. , Bennett James A. , Birge Robert R.
Published: March 2003

Four general purpose circuits are described which facilitate computer control and synchronization of laser firing, analog-to-digital conversion, and digital-to-digital multiplexing. These circuits retain generality by using only the 16 input and output lines of the computer interface without utilization of handshaking or data request lines. Accordingly, these circuits can be used with any 16-bit TTL interface that provides latched output lines. The generality is obtained at the expense of data transfer and control speed and with a loss of interrupt capability. An analog-to-digital converter circuit is described which provides eight computer selected input channels, 12-bit resolution, and a total cycle time for each input reading of ≈60 μs. Each input channel can be independently set to generate a full scale reading for 0.1, 1, or 10 V inputs. A pulse conditioning trigger circuit is described which generates an output pulse of selected delay (50 ns–2 ms), pulse width (30 ns–2.5 ms), and magnitude (up to 10 V) in response to a computer-generated positive going TTL pulse. Applications of the above circuits in controlling and acquiring data from a two-photon laser spectrometer are discussed. A 28-bit to 16-bit digital multiplexer circuit is described which can be used to input data using a 16-bit computer interface from instruments with data words up to and including 28 bits. The EG&G Princeton Applied Research (PAR) model 4202 transient signal averager and the PAR model 1205A optical multichannel analyzer are discussed as examples. Finally, a laser firing circuit specifically designed to provide one-shot triggering of the Chromatix CMX-4 flashlamp-pumped tunable dye laser is described. The unique external triggering requirements of the CMX-4 require a 10-V pulse of 8.34±0.01 ms duration to generate reliable triggering.
Subnanosecond fluorescence waveforms measurements with a dual time-scale microprocessor-controlled averager
Authors: Docchio F. , Longoni A. , Zaraga F.
Published: March 2003

This paper presents a microprocessor-controlled apparatus for the measurement of fast fluorescence waveforms. This apparatus features a dual-time scale for the analysis of multiexponential decays. A sampling oscilloscope is used as the sampling device. The sampling time is externally controlled by means of a staircase reference voltage. The dual-time scale is obtained by enhancing the density of sampled points in a time window corresponding to the faster portion of the waveform. The slow vertical output of the sampling oscilloscope is digitized, and numerical averaging is performed in order to improve the signal-to-noise ratio. An on-line display of the measured waveform and a connection with a host computer for further data processing are also provided. Details of the hardware and software structure are given, together with applicable examples.
Energy dispersive x-ray diffraction from high pressure polycrystalline specimens using synchrotron radiation
Authors: Baublitz Millard A. , Arnold Volker , Ruoff Arthur L.
Published: March 2003

Energy dispersive diffraction from high-pressure specimens with a synchrotron radiation source is described. A remote-controlled diffraction stage which has greatly facilitated alignment of the high-pressure sample in the radiation beam is discussed. An experimental diffraction pattern and theoretical relative intensities are compared.
Wedge absorption remote sensor
Authors: Watkins Wendell R. , White Kenneth O.
Published: March 2003

Remote detection of gases, especially methane, is important in several fields including coal mining, natural gas storage, and pollution monitoring. Near real-time remote sensing of atmospheric gases can already be performed by using differential absorption lidar or transmission techniques. A new system called the wedge absorption remote sensor has been developed which improves integrated path detection of atmospheric gases. The wedge absorption remote sensor utilizes an emission spike train of short-time duration as is found in the long-pulse output mode of a solid-state laser to define the on- and off-line absorption of an atmospheric gas and, hence, its concentration. The wedge absorption remote sensor has performed well as a remote sensor of methane concentrations with an erbium:ytterbium–aluminum–garnet laser as the source.
Multinuclear nuclear magnetic resonance observations of η-cyclopentadienyldicarbonylrhodium (I) including heteronuclear double and triple irradiation
Authors: Dykstra Robert W. , Harrison Arnold M. , Dombek B. Duane
Published: March 2003

A rhodium heteronuclear spin decoupler has been designed and built; the decoupler and probe modifications now permit multiple irradiation experiments on our Varian XL-100 nuclear magnetic resonance (NMR) Spectrometer, including 13C–{1H, 103Rh}, 170–{103Rh}, and 1H–{103Rh}. These capabilites and 103Rh–{1H} capability (using a modified Varian FT-80A NMR spectrometer) are demonstrated using η-cyclopentadienyldicarbonylrhodium (I) samples.
National Bureau of Standards line-heat-source guarded-hot-plate apparatus
Authors: Siu M. C. I. , Bulik C.
Published: March 2003

A description is given of a line-heat-source guarded-hot-plate apparatus for determining the effective thermal conductivity of insulation materials in the temperature range from 250 to 400 K. Measurements made on fibrous glass boards are in good agreement with results obtained from the guarded-hot-plate apparatus used for over 40 years by the National Bureau of Standards for calibration purposes.
Method for determining the thermal diffusivity of liquids at elevated temperatures
Authors: Etter D. E.
Published: March 2003

A technique was developed for the determination of the thermal diffusivity of transparent, translucent, and opaque liquids at ambient and elevated temperatures. The inherent vaporization characteristics of the liquid under investigation dictate the temperature limitations of the technique. The method uses modifications of the laser flash technique previously established for measurement of the thermal diffusivity of solids. The accuracy of the technique is estimated to be ±8.
Titration microcalorimeter using nanomolar quantities of reactants
Authors: Spokane R. B. , Gill S. J.
Published: March 2003

A microcalorimeter has been developed for measuring the heat produced from small (10 μl) injections of 10 nanomoles of titrant into a 1-ml glass cell containing 100 nanomoles of sample. Typical heat measurements range from 30 to 300 μcal with reproducibility of 4 μcal. The small sample size is especially useful in studies of previous biological materials. The high sensitivity permits the use of low titrant concentrations (1 mM). The device is computer controlled allowing for automatic titration of preset injections. Heat compensation response times (half life) of 30 s are achieved with electronic feedback heater control. Both exothermic and endothermic titrations can be performed. Heat effects of single titration steps are given as computer output.
Precision expansion cloud chamber for homogeneous nucleation studies
Authors: Schmitt John L.
Published: March 2003

The author describes an expansion cloud chamber for the study of the nucleation of a single component vapor (homogeneous nucleation). The design draws on the many years of experience in this Center in construction of chambers for homogeneous nucleation of water. Design features of the chamber are: exact control of temperature (±0.03 ° C), pressure (±0.5 mm Hg), and automatic control of cycling. Construction features are: all construction materials are stainless steel, glass, or fluorocarbon plastics; the piston seal is a very flexible welded stainless steel bellows; the chamber can be made very clean by heating under vacuum and it is compatible with many substances, e.g., ethanol, nonane, and toluene. Performance features are: excellent repeatability of the expansion cycle over a temperature range of 45° to —15 °C and in day to day operation. Safety features are: automatic detection and warning and inerting against fire and explosion from combustible vapor in the chamber enclosure. The determination of the gas temperature at the maximum expansion is discussed as well as the importance of the ’’fast’’ pulse technique for the measurement of high nucleation rates.
High-temperature vacuum ultraviolet reflectometer
Authors: Blum J. B. , Coble R. L. , Kearney P. A.
Published: March 2003

A system is described which has been used to measure the near-normal vacuum ultraviolet reflectivity of Al2O3 up to 450 °C. The system consists of a commercially available lamp and monochromator, and a specially designed reflectometer chamber with an internal electrical furnace and heat shields.
Simple, reproducible, acoustically transparent pressure transducer with an 18-ns rise time
Authors: Migliori A. , Hofler T. J.
Published: March 2003

We describe an inexpensive, unbacked, solid dielectric capacitance-like pressure transducer and preamplifier. The device has an adjustable sensitivity of about 0.5 μV/Pa into a 50-Ω load, a geometry-determined rise time of about 12 ns, and a flat frequency response from a few kHz to its resonant frequency of about 40 MHz. The geometry and method of construction make it simple to calculate response characteristics and it is usable at pressures from 103 Pa to at least 107 Pa.
Heating technique for investigating trace element distribution in grains
Authors: Sörensen J. , Wegmüller F. , Krähenbühl U.
Published: March 2003

A heating technique is described which permits investigation of small samples (10–100 mg) of material originating from natural or technical processes. The distribution of trace elements throughout mineralogical samples was measured. It is demonstrated that mechanisms leading to surface coatings can be studied. This apparatus was developed for the investigation of small lunar samples.
Improved method of phase measurement by using an interferometer having a filamentary spatial filter
Authors: Mori Sadahiko
Published: March 2003

The method for phase measurement by an interferometer having a filamentary spatial filter, (IFSF), [reported in Rev. Sci. Instrum. 50, 685 (1979) by the author] is much simplified and combined with the multipass interference method. The same accuracy, 2π/100, as the previous experiment is kept through measurements of multiplied phases up to the fifth order. The advantage in the principle of the improved method in comparison with conventional methods is distinctly discussed.
Time-resolving extreme ultraviolet spectrograph for fusion diagnostics
Authors: Bell R. E. , Finkenthal M. , Moos H. W.
Published: March 2003

A time-resolving spectrograph for the simultaneous measurement of emissions at extreme ultraviolet wavelengths (300–2200 Å) is described. The spectrograph is a 400-mm normal incidence f/30 system with seven gratings. Together two of the gratings cover the entire wavelength range at low resolution. The other five gratings have higher dispersion and cover adjacent intervals of the spectrum. The spectral resolution varies between 0.7–4 Å. The detector consists of a windowless microchannel plate/phosphor screen image intensifier, coupled by fiber optics to a 1024-element self-scanning integrated photodiode array. The output from the array is digitized and stored by a small desktop computer which has sufficient memory to record up to 80 spectra during a single plasma discharge.
Role of the anode area in the behavior of magnetic multipole discharges
Authors: Holmes A. J. T.
Published: March 2003

A theoretical model and experimental measurements are presented for a hydrogen discharge in a magnetic multipole (bucket) plasma source where the plasma potential is negative with respect to the anode. This plasma potential depends critically on the anode cusp field, and the measurements show clearly that electrostatic ion confinement is obtained when the anode field is strong (1400 G), which leads to a high electrical efficiency for useful ion production. However, when the anode field is reduced, the plasma potential reverts to its normal positive value with respect to the anode with a consequent reduction in electrical efficiency.
Optimum dc current resolution for high-source resistances with a dc transformer matched rf SQUID
Authors: Xue S. Q. , Gutmann P. , Kose V.
Published: March 2003

By using a cryogenic current comparator with a ferromagnetic core, optimum matching for high-source resistances of up to about 400 kΩ for a commercially available rf SQUID is achieved. This extends the use of SQUID instruments considerably, especially for applications where the source resistance exceeds 10−1 Ω.
Low-friction, anhydrous, low- to high-temperature furnace sample assembly for piston-cylinder apparatus
Authors: Boettcher A. L. , Windom K. E. , Bohlen S. R. , Luth R. W.
Published: March 2003

A newly designed furnace assembly for piston-cylinder, high-pressure apparatus uses NaCl or KBr rather than hydrous materials such as talc or pyrophyllite. Unlike previous designs, our cell can be used hundreds of degrees above the melting temperatures of the salts. This cell requires little or no pressure correction and provides conditions that are free of H2 and H2O. The electrical power requirements are only about 60% of that for talc furnace assemblies, resulting in cooler operation and longer life for the steel and carbide in the pistons and pressure vessels.
Computer-assisted system for measuring capacitance and conductance of a diode using a phase sensitive technique
Authors: Ketelsen L. J. P. , Serway R. A.
Published: March 2003

This paper describes a system for making accurate and reliable ac measurements of capacitance as a function of frequency, bias voltage, and temperature. The experimental apparatus consists of the basic capacitance measuring circuit and an information gathering device. The basic circuit includes a constant ac voltage source in series with the cell, a dc source for biasing the cell, an ac current amplifier in series with the cell for monitoring the current, and a lock-in amplifier to measure the ac current. The capacitance device is interfaced with a microcomputer to facilitate handling large quantities of data in a short time. The computer is also used to increment the bias voltage for C–V measurements. The system has the capability of measuring capacitance to an accuracy of about 5 digits. We have used this system to study deep impurity levels in thin-film, polycrystalline CdS/CuxS solar cells. The deep traps appear as anomalies in the otherwise linear l/C2 versus V plots. These levels play an important role in determining cell characteristics and may also influence the cell’s efficiency. The advantages of the capacitance–conductance system described in this paper are: (1) simple construction; (2) accurate calibration procedure; (3) ability to take data with 4 1/2 stable digits; (4) the admittance can be measured as a function of bias voltage, frequency, and temperature; (5) automation, i.e., computer controlled, and (6) the ability to accurately provide information on unstable samples.
Computer-assisted magnet shimming
Authors: West David H.
Published: March 2003

An iron electromagnet with a gap width of 23.5 cm and diameter of 30 cm was shimmed so that the field was uniform within ±4.2 parts in 104 over the central 19 cm of the axis. A description is given of the shim configuration used, and of the algorithm by which the measured field changes (produced by perturbing a shim) are used to predict an improved set of shim dimensions. The method is not limited to any specific geometry of either the shims or the region over which field homogeneity is desired.
High performance multihole SQUID sensor
Authors: Zarembiński Stefan , Jarmul Bartl/omiej
Published: March 2003

The design of a mechanically stable, thermal shock resistant, and vacuum-sealed multihole SQUID sensor is described in detail. The relevant technological process involving diffusion welding is outlined.
Low temperature specific heat and thermal conductivity of a commercial pyrolytic boron nitride
Authors: Hsieh T.-C. , Anderson A. C.
Published: March 2003

The specific heat and thermal conductivity of commercial pyrolytic boron nitride have been measured at temperatures down to 0.1 K.
Simple fast transient digitizer
Authors: Crosby D. A. , MacAdam K. B.
Published: March 2003

The design and operation of a simple transient digitizer are described, capable of digitizing repetitive analog–transient signals with 30 ns, 8 bit resolution, at repetition rates of at least 300 Hz. The 2 μs maximum transient width (64 samples at 30 ns intervals per transient) can easily be extended. The digitizer connects directly to a single 8-bit TTL-compatible microcomputer I/O port. The circuit uses only commercially available integrated circuits, and the total parts cost is low. Both circuitry and software are described.
High-speed rotary-motion feedthrough suitable for UHV applications
Authors: Engel T.
Published: March 2003

A rotary-motion feedthrough suitable for use in UHV at frequencies between 1200–15,000 rpm is described. The outgassing rate in operation is less than 2×10−8 torr l/s.
Laser drilling small holes for x-ray pinhole cameras
Authors: Rizzo J. E.
Published: March 2003

Holes of 4 μm diameter for x-ray pinhole camera use have been drilled in 12 μm thick platinum foils using a series of single pulses of 80 ps duration and energies of 10 mJ.
High-performance ac preamplifier
Authors: Kumar Umesh
Published: March 2003

A simple bandpass amplifier is presented which exhibits a very high gain, selectivity, and input impedance. The amplifier has a very narrow bandwidth and a high Q factor.
Metal mirrors for far-infrared wavelengths
Authors: Dionne Gerald F.
Published: March 2003

A simple machining procedure has been used successfully to produce low f-number (f/2) metal mirrors suitable for far-infrared wavelengths.
Simplified technique for measuring specific heat and thermal conductivity of a liquid under pressure
Authors: Allen P. C. , Paulson D. N. , Wheatley J. C.
Published: March 2003

A technique for simultaneously measuring the specific heat and the thermal conductivity of a liquid over a broad range of pressure is described. The technique uses a system in which the liquid circulates in a pulsating manner through a counter-current heat exchanger, or regenerator, made of parallel plates and thereby achieves the advantage of a continuous flow method where parasitic heat losses may be readily identified and eliminated. Typical results for water at 28 bar and propylene at 34.5 bar are presented.
Output performance of the coaxial-type Marx generator consisting of BaTiO3 series ceramic capacitors
Authors: Ogura Tokihiko , Kannari Fumihiko , Obara Minoru , Fujioka Tomoo , Toyoda Koichi , Nanba Susumu
Published: March 2003

We have theoretically analyzed the output performance of the coaxial-type Marx generator consisting of BaTiO3 series ceramic capacitors. In this analysis, the capacitance of the BaTiO3 series ceramic capacitor has been considered to be variable with applied voltage. The results were compared with experimental results, and fairly good agreement was obtained. As a result of this analysis, it was clarified that the BaTiO3 series ceramic capacitor was not able to store efficiently the electrical energy when charged at high voltages. On the other hand, the SrTiO3 series ceramic capacitor has an almost constant capacitance against applied voltages, so that stored energy may be extracted efficiently. We have quantitatively revealed the superiority of SrTiO3 series ceramic capacitors over BaTiO3 series capacitors.
Shielded thermionic diode detector for precision spectroscopy
Authors: Harvey K. C.
Published: March 2003

A thermionic diode with a shielded auxiliary compartment has been constructed to detect Doppler-free two-photon absorption. The shielded compartment prevents Zeeman and Stark broadening from external fields. The detector’s construction and mode of operation are discussed.
Photoelectron microscope for x-ray microscopy and microanalysis
Authors: Polack F. , Lowenthal S.
Published: March 2003

Synchrotron radiation has recently contributed to the development of high-resolution x-ray microscopy either for biological investigations or for chemical microanalysis. Contact microscopy for this end appears to be particularly useful, but is mainly limited by the detectors that are used. In order to overcome these limitations—i.e., to obtain real time imaging and quantitative information—a study of a photoelectron x-ray microscope is made. Contact configuration is used, but the usual detector is replaced by a thin photocathode. The emitted secondary photoelectrons are then imaged by a suitable emission electron microscope. Problems of photoemission, resolution, and D.Q.E. limitation are discussed. The particular nature of electron lens aberrations, due to photoemission characteristics, is taken into account. The conclusions are that resolutions down to 500 Å can be obtained in certain conditions. A preliminary low- magnification experiment is described and results are shown.
Pulsed plasma guns for intense ion beam injectors
Authors: Humphries S. , Anderson R. J. M. , Freeman J. R. , Greenly J.
Published: March 2003

Plasma guns designed to provide high-pulsed fluxes of ions for intense ion beam injectors are described. The guns use pulsed radial magnetic fields to accelerate ions longitudinally into magnetically insulated extraction gaps. Plasma was supplied using both spark sources and pulsed gas injection. In typical operation, a 1-Ω pulse of nitrogen ions with an ion flux equivalent to 50 A/cm2 was produced. A variety of ions ranging in mass from protons to argon was investigated.
Beam steering in tetrode extraction systems
Authors: Holmes A. J. T. , Thompson E.
Published: March 2003

A model of beam steering and beam collimation in tetrode extraction systems is presented which includes the effects of space charge in the interelectrode gaps. This model is compared with experiment in several geometries and shows that the inclusion of space charge allows better agreement to be obtained than in earlier theories.
Spherical hydrogen pellet generator for magnetic confinement fusion research
Authors: Gilliard R. P. , Kim K. , Turnbull R. J.
Published: March 2003

The design and operation of a cryogenic pellet generator is described. The device is capable of producing spherical solid hydrogen pellets of sufficient size and repetition rate to meet prospective refueling requirements of near term tokamak fusion machines. It accelerates pellets to speeds in excess of 102 m/s by gas dynamic drag techniques and has achieved initial injection into the APEX tokamak at Argonne National Laboratory. A discussion of gas dynamic drag acceleration techniques is presented with an evaluation of their significance to pellet acceleration technology.
Evaluation of nanosecond pulse–fluorometry measurements—no need for the excitation function
Authors: Ricka J.
Published: March 2003

The standard method of evaluating pulse–fluorometry measurements is to deconvolute the data using an experimentally determined excitation function. However, it is known that its determination may be inaccurate, because the instrumental response and the form of the exciting light pulse do vary with the wavelength. This may limit the accuracy of deconvolution and the confidence in its results. Therefore, in this paper an alternative evaluation method is suggested. The excitation function is not needed, if two independent measurements differing in the kinetics of the involved decays, but not in the excitation and emission wavelengths, can be performed. Those two measurements are sufficient to obtain the parameters of both decays.
Data calibration in electron tunneling spectroscopy
Authors: Magno R. , Adler J. G.
Published: March 2003

Practical problems which arise in obtaining calibrated electron tunneling spectra using harmonic detection techniques combined with a resistive bridge are examined. The instrumentation uses a computer-controlled data acquisition system along with the necessary software. The effect of neglecting various calibration details is shown using real tunneling data. This paper shows the steps which are essential to obtaining good calibrated tunneling spectra even where weak structure is involved. Results are shown to demonstrate the effect which harmonic distortion has on the data, and various calibration schemes are examined to determine which give sufficiently good results to reproduce accurate line shapes. Finally numerical differentiation techniques are examined for obtaining tunneling spectra, but these methods are found lacking in the case of weak structure unless complex smoothing algorithms are used to avoid digitizing errors.
Twin-wire resistance probe manometer
Authors: Liu C. Y. , Poo A. N.
Published: March 2003

This note describes a new type of water manometer which is designed especially to measure a very low-pressure difference with low cost. When a comparison over the range from 0.025–10 mm H2O was made with a commercial electronic manometer, almost identical results were obtained.
Development of a fast ion mass spectrometer for space research
Authors: Hahn S. F. , Burch J. L. , Feldman W. C.
Published: March 2003

An ion mass spectrometer with a cylindrical Ē×B̄ analyzer and either a cylindrical or a spherical electrostatic analyzer is described in this paper. The instrument features two nested channels and a postacceleration between the electrostatic and Ē×B̄ analyzers for wide ranges of energy and mass responses. The dual-channel construction not only doubles the data acquisition rate, but also makes it possible to reverse the electrostatic field orientation in the inner channel (radially outward, as opposed to radially inward in the outer channel) for lighter ions. The outer channel is then optimized for ions of medium to high mass numbers resulting in enhanced mass resolution for such heavy ions. A 90 °-deflection angle spherical electrostatic analyzer in combination with a cylindrical Ē×B̄ analyzer provides an extremely wide viewing angle. The angular distribution of ions can be obtained from such geometry if a position-sensitive resistive anode or a detector array is used at the exit aperture. Details on the principles of operation, the instrument design, and calibration are given in this paper.
Methods for the grinding and polishing of sphere samples
Authors: Paranto Joseph N. , Patton Carl E.
Published: March 2003

Three preparation methods for the production of sphere samples 0.5–5 mm in diameter have been refined and improved. The methods are: (1) a rotating horizontal surface technique in which the sample bounces randomly on a rotating surface, (2) a two-pipe lapidary method in which the sample is held between two pipes during grinding, and (3) a cage-held sample polishing procedure in which the sample is contained in a plastic cage while two oppositely rotating horizontal surfaces make contact with the exposed sample surface. The basic methods are described and the current improvements presented.
Audio frequency pulse code modulation data link using an optical fiber
Authors: Blackburn James A.
Published: March 2003

A design is presented for an asynchronous digital data link using pulse code modulation and a fiber optic cable. It is suitable for audio and instrumentation applications where a bandwidth of dc–10 kHz is adequate. Notable features are simplicity, economy, and the noise immunity of the fiber optic transmission line.
Voltage-controlled phase shifter for measuring transfer function in the presence of noise
Authors: Potzick James E. , Robertson Baldwin
Published: March 2003

A linear voltage-controlled phase shifter has been constructed for use in a feedback loop to measure the amplitude and phase of a signal buried in noise. The feedback circuit has a phase marker output with an accuracy of 0.0025 rad while automatically following an arbitrarily large phase shift. In addition it has one output voltage proportional to the amplitude of the signal and another proportional to its phase with automatic translation in increments of π. A voltage-controlled oscillator is also described whose frequency and amplitude are proportional to their respective control voltages. The frequency control voltage for this oscillator is also used by the phase shifter circuit to make the proportionality constants for the outputs of the feedback circuit independent of frequency. Thus the circuits described make possible the highly accurate measurement of the transfer function of a two-port system that outputs more noise than signal.
Multiple sampling digital boxcar integrator, an efficient signal averager
Authors: Suzuki R. , Umezu K. , Takuma H. , Shimizu F.
Published: March 2003

A digital boxcar integrator of multiple sampling type which has a maximum sampling rate of 10 MByte/s has been developed. The efficiency, which is defined as the ratio of the number of sampling pulses applied during each cycle of a signal waveform to the total number of sampling points needed to cover a cycle of signal waveform, has been improved to 25% for a sampling time duration of 25 ns. The accumulation of a sampled signal at such a high rate has been accomplished by the parallel operation of 16 newly developed memory circuit blocks, each having arithmetic capability. As a demonstration, the present system was applied in optical coherent transient spectroscopy and shown to be far more efficient than a conventional boxcar integrator.
Interactive interfacing of an optical multichannel analyzer using CAMAC
Authors: Weinfeld M.
Published: March 2003

An optical multichannel analyzer is used to make spectroscopic measurements when studying nonlinear effects occurring during the interaction of intense laser pulses focused onto solid targets. The interactive interfacing of this apparatus to a CAMAC based real time minicomputer acquisition and processing system is described, and also some experimental results.
High-temperature proportional counter and its application to resonance–electron Mössbauer spectroscopy
Authors: Isozumi Yasuhito , Kurakado Masahiko , Katano Rintaro
Published: March 2003

The operation of a proportional counter designed for resonance–electron Mössbauer spectroscopy measurement at high temperatures up to 900 °C has been investigated. In order to avoid insulation difficulties due to electric leakage on the surfaces of heated insulators, the counter is carefully constructed so that the sensitive volume of the counter can be warmed up while keeping the insulators at room temperature; all insulating materials between the anode and cathodes are located outside the electric furnace in the counter system. The counter operation is influenced by thermal electrons emitted from the cathode material; the maximum working temperature is about 800 °C when an a-Fe foil is mounted as a cathode while operation at 900 °C is possible without the sample. 57Fe Mössbauer spectra for surface layers (∼1000 Å) have been sucessfully obtained for samples of Fe3C, Fe2O3, and a Fe. Chemical changes of the sample surfaces have been observed at temperatures greater than 600 °C by the measurements. The high-temperature counter provides us with a new method to observe directly surface phenomena at high temperatures. Some features of the counter system are described.
Absolute measurements of fluorescence polarization at high pressures
Authors: Paladini Alejandro A. , Weber Gregorio
Published: March 2003

The measurement of polarization of the fluorescence of solutions under high pressure is rendered uncertain by the photoelastic birefringency of the windows, and needs a correction dependent upon the fraction of the light emerging from a window with polarization normal to that of the incident light (scrambling coefficient). This correction, which increases rapidly with applied pressure, differs according to whether the method of measurement employs rotation of the excitation polarizer (T format) or the emission polarizer (L format), and the latter is shown to involve the more reliable and the smaller correction. A four window pressure bomb housing a 1 ml volume cuvette that permits absorption and fluorescence measurements up to 4 kbar is described. The polarization correction up to 2.5 kbar was determined. Its reliability was demonstrated by measurements of the fluorescence polarization spectra of fluorophores in solvents of high viscosity at all pressures and by comparison of isopiestic and isothermal measurements of a fluorophore in isobutanol, a fluid solvent with viscosity that changes rapidly with pressure or temperature.
Temperature-stabilized wide-band ultrasonic delay line
Authors: Kasahara Yukio , Inaba Ritsuo
Published: March 2003

The low ultrasonic attenuation of fused quartz in the very high frequency range makes it attractive for an ultrasonic delay line. However, the temperature instability restricts its application. A method of stabilizing the delay time based on the properties of a positive temperature coefficient resistor that is used simultaneously as a temperature sensor and a regulator is discussed. This new type of temperature regulator improves the temperature coefficient of the delay time from 85 ppm/°C to 8 ppm/°C. A temperature-stabilized wide-band delay line has been fabricated for high definition television. A wide-band frequency response is obtained by using LiNbO3 transducers and new type bonding adhesion which is stiffened by irradiation of ultraviolet rays. The design of the delay line, which has a midband frequency of 45 MHz, a band width of 50 MHz, and a delay time of 29.55 ms, is presented and experimental results are also presented.
Diagnostic system of the Lawrence Livermore National Laboratory two-stage light-gas gun
Authors: Mitchell A. C. , Nellis W. J.
Published: March 2003

A two-stage light-gas gun is used for a variety of dynamic physical-property measurements at 100 GPa (1 Mbar) pressures. The diagnostic system described here consists of a flash x-ray system to measure impactor velocity, detectors and electronics to measure shock-wave velocities with subnanosecond resolution, and data–analysis techniques that permit us to measure the tilt and distortion of the impactor and of the resulting shock front. We describe our methods for safely purging hydrogen gas from the system after each shot.
Plasma production by staged laser irradiation of mm-size deuterium pellets
Authors: Pechacek R. E. , Greig J. R. , Raleigh M. , DeSilva A. W. , Koopman D. W.
Published: March 2003

A fully ionized plasma consisting of 2×1019 D+ ions with an average energy of 50 eV is produced by irradiating a free-falling solid D2 pellet with a sequence of two laser pulses. An Nd–glass laser pulse first evaporates the pellet and a CO2 laser pulse ionizes and heats the resulting D2 cloud. This staged laser process couples about 2/3 of the energy of the 70 ns CO2 laser spike into the plasma. The techniques for making, dropping, and irradiating the pellet are discussed in detail. The properties of the resulting plasma are described, and a brief account is given of the cusp containment experiment for which this plasma production method was developed.
Plasma probe system with automatic sweep adjustment
Authors: Holmes J. C. , Szuszczewicz E. P.
Published: March 2003

The capabilities of the pulsed Langmuir probe technique have been expanded to operate in charged particle environments having spatial and temporal variations in plasma or reference–electrode potentials. This practice is implemented by logic circuitry which tracks local floating potentials and adjusts automatically the sweep center voltage to guarantee a complete current–voltage characteristic with minimum sweep voltage excursion.
High-performance cryogenic pulsed NMR spectrometer
Authors: Wood B. M. , Code R. F.
Published: March 2003

A pulsed NMR spectrometer for cryogenic use is described. It includes an improved coupling scheme which is suitable for installation in most cryostats. An rf preamplifier has been developed which offers wide bandwidth, high gain, low noise and fast recovery (⩽2 μs). While the spectrometer was designed for a resonance frequency of 27 MHz, extension from 4–100 MHz is discussed. At 27 MHz the bandwidth of the free-induction decay is 1 MHz, and the dead time, after the end of the rf pulse, is 3.6 ms. Techniques are presented for reducing the dead time, the noise, and the amplitude of ground loops as well as extending the signal bandwidth and dynamic range.
Simple, fast recovery, low-noise receiver amplifier for pulsed NMR experiments
Authors: Stoll M. E.
Published: March 2003

A fast recovery, low-noise receiver designed for use in pulsed NMR, especially high-resolution multiple-pulse NMR, is described. This receiver is easy to build from commercially available parts. Passive (but biased) voltage limiters placed before each amplifier in the cascade prevent any of the amplifiers from saturating, so it is only the limiters that ever saturate. Recovery times of 850 ns and 2.35 ms are measured with a 50-W load and a high Q (Q = 141) resonant sample probe in the circuit, respectively. The receiver has a measured overall noise figure of 6.5 dB, including crossed diodes and filter on the input. An example of the use of the receiver to measure a short proton free-induction decay at 186.5 MHz is also shown.
Instrument design for pulse voltammetry with microvoltammetric electrodes
Authors: Ewing Andrew G. , Withnell Ronald , Wightman R. Mark
Published: March 2003

The current measured during the back step of a double potential step chronoamperometry experiment at microvoltammetric electrodes is primarily nonfaradaic and can be used for residual current correction. An instrument has been designed which provides direct readout of the corrected current. This instrument also provides differential output and adjustable delay and step times which can be important for the unusual conditions of in vivo voltammetric experiments. All of these features are tailor made for use with microvoltammetric electrodes and are unavailable in commercial instrumentation. Experimental results indicate that potential step times as short as 100 ms can be used with back step correction with a faradaic accuracy of better than 5%. Pulse scans are compared to conventional cyclic voltammetry in the reduction of 5×10−5 M potassium ferricyanide.
Aluminum shielded room for biomagnetic measurements
Authors: Stroink G. , Blackford B. , Brown B. , Horacek M.
Published: March 2003

We have constructed an eddy current shielded room from high-conductivity aluminum sheets, 1.88 cm thick. A series of measurements designed to test the performance of the room has been carried out. The results of the measurements have been compared with theoretical predictions and also with the results from similar rooms reported in the literature. In some respects the agreement is good while in other respects considerable discrepancy exists. The response time of the room to a uniform field was found to be in good agreement with theory, whereas the response to a nonuniform field was found to be much worse. We also found that the room does not shield the vertical field component as well as the horizontal components. We give the reason for this and suggest a possible solution.
Device for direct transfers of filtered liquids to volumetric flasks
Authors: Shinn David W. , De Carlo Eric H. , Zeitlin Harry
Published: March 2003

A solid–liquid separation filter has been adapted to transfer a filtered liquid directly to a volumetric flask. Time savings of approximately 50%, as compared to the conventional method, can be achieved.
Numerical procedure for determining the dynamic conductance of an electronic device
Authors: Smith H. J. T.
Published: March 2003

A numerical procedure for differentiating current/voltage data of electronic devices is discussed within the framework of an example that uses a Pb–PbO–Pb superconducting tunnel junction. The derivative is obtained from measured values of current and voltage by a combination of numerical integration and digital filtering. Advantages are that the data can be acquired rapidly and the filtering time constant can be adjusted during the analysis, which is not performed in real time.
Low thermal conductance rigidizer for reducing torsional oscillations in cryogenic dewars
Authors: Harper D. A. , Moseley S. H.
Published: March 2003

We describe a new type of rigidizer designed to eliminate torsional oscillations in cryogenic Dewars.
Spark point light source
Authors: Edgerton Harold E. , MacRoberts Vernon E.
Published: March 2003

A mechanically-improved spark gap, in an open groove along a glass or quartz rod, is described in this paper. The output is about 0.5 cps with a flash duration of less than a microsecond. The effective source size is limited by a 1.6-mm diam. hole in an aperture plate. Ease of assembly and replacement of faulty components is the important improvement over earlier spark gaps. Mach apparently was the first to study bullets and shock waves in air with illumination from an open spark gap. A bibliography of the history of spark discharges can be found in books by Edgerton and Frungel.
Temperature-controlled cell for laser-induced fluorescence and absorption studies
Authors: Shelton R. N. , Rice W. W. , Wampler F. B. , Tiee J. J.
Published: March 2003

A temperature-controlled cell has been constructed for laser-induced fluorescence studies of UF6 and other corrosive gases. The temperature stability achieved in our UF6 fluorescence investigation was ±0.1 °C from −30° to 0 °C and ±0.05 °C from 0° to 80 °C. The cell has also been used in UF6 absorption measurements at temperatures as high as 100 °C with comparable stability.