bluuebunny/crossref_metadata_2025 huggingface dataset:
Signal-to-noise ratio analysis of a digital polarimeter application to thermal imaging
Authors: Lamouroux B. F. , Prade B. S.
Published: March 2003

A digital scanning polarimeter is described. It measures the local variations of the rotatory power of a thin liquid crystal target. This device is used for thermal imaging purposes. The incident scanning beam is split after traversing the target in two parts and then analyzed with two analyzers and detectors. Taking into account the photon noise, the existence of an optimal angle of the analyzer azimuth is shown. A numerical example is given.
Simple, low-cost reciprocating crystallizer for solution crystal growth
Authors: Aggarwal M. D. , Lal R. B.
Published: March 2003

A simple, low-cost reciprocating crystallizer for crystal growth from aqueous solution has been described. The main feature of this crystallizer is its simple automatic switching arrangement for reciprocating motion.
Goniometer attachment for low-speed diamond wafering saws
Authors: Hintz M. B.
Published: March 2003

The construction of a compact, two-axis goniometer that has been designed specifically for use on commonly available low-speed diamond wafering saws is described. The device can be easily attached to practically any back reflection Laue camera and is, therefore, suitable for the orientation and cutting of single crystals parallel to particular crystallographic planes or directions. It is both simple and inexpensive to construct.
Granulated metal cathode start-up surface for pulsed electric discharges
Authors: Benesch W. M. , Fraedrich D. S. , Ginter M. L.
Published: March 2003

The sustained, reliable operation of a repetitive, high-current pulsed arc discharge in a large-volume container has been found to require the use of ignition enhancing techniques to maintain adequate turn-on reproducibility. Application of a few grams of 20-mesh granulated zinc to a portion of the copper cathode surface produces a striking reduction in the rise time and turn-on reliability of pulses carrying up to 1000 A.
Fast multiscaling module with a dwell time of two nanoseconds and its application to quantum beat spectroscopy
Authors: Blaich T. , Bollen G. , Georgi K.-H. , Kluge H.-J. , Kremmling H.
Published: March 2003

A digital multiscaling module has been constructed to record time differentially in a series of single events with a time increment of 2 ns. The memory of the module consists of 1920 sequential bits which are read by a minicomputer via a CAMAC device for further data processing. The module was tested by a quantum beat experiment on the 6s6p 3P1 state of Hg.
Two-frame flash x-radiography device for the study of particle beam fusion target implosions
Authors: Fehl D. L. , Chang J.
Published: March 2003

A two-frame flash x-radiography (FXR) system has been developed for studying the implosion hydrodynamics of particle beam driven, inertial confinement fusion (ICF) targets. This system consists of two micropoint flash x-ray sources, two gated x-ray cameras, and a mechanical framework for aligning these components with respect to the target. The tungsten micropoint sources yield a bremsstrahlung spectrum with an end-point energy of 600 keV, an x-ray dose of 8 mrad at 61 cm, a spot size of ∼100 μm, and an exposure time of ∼3 ns. A geometric magnification of 4× was employed in this radiographic arrangement, with an overall system resolving power of 4 line pairs/mm. This system has been used successfully to observe relativistic electron beam (REB) driven, ablative pusher target implosions.
Infrared calorimeter for time-resolved plasma energy flux measurement
Authors: Ingraham J. C. , Miller G.
Published: March 2003

An infrared calorimeter system for measuring energy flux in a noisy electromagnetic environment has been developed. A thin (13 μ) oxidized stainless-steel foil is heated by energy flux and its temperature is determined by measuring the infrared emission from the back surface of the foil. The radiation is transported to the detector, which is located inside a double-shielded enclosure, through a nylon-tube infrared telescope. The calculated response time is 12 μs, and the measured peak-to-peak noise is equivalent to 0.4 mJ/cm2 deposited energy.
High-current ion implanter using a microwave ion source
Authors: Sakudo Noriyuki , Tokiguchi Katsumi , Koike Hidemi , Kanomata Ichiro
Published: March 2003

A new ion implanter has been designed for high-dose predeposition in a semiconductor production line. It incorporates a microwave ion source, a 90° magnetic mass separator, and a rotating disk target chamber. Mass peak variations of PH3 gas are shown as a function of the incident microwave power. The ion energy level can be varied from 10 to 50 keV. It makes 10 mA P+ implantation (maximum 15 mA) possible. After beam adjustment, implantation is automatically carried out with a microcomputer. The operation rate of the implanter is remarkably improved due to the long lifetime of the modified microwave ion source and the low gas consumption. The dose nonuniformity of a 3-in. wafer implanted with this implanter has a standard deviation (σ) of 0.5%. This small nonuniformity results in a small σ in the transistor current gain (less than 3.5%).
Hot-wall epitaxy system for the growth of multilayer IV-VI compound heterostructures
Authors: Clemens H. , Fantner E. J. , Bauer G.
Published: March 2003

A modified hot-wall epitaxy (HWE) system for the growth of multiple heterolayers is described which consists of two identical HWE furnaces. The substrate furnaces are mounted on a rotatable plate which allows the growth of heterolayers under nearly identical conditions for each individual layer. Single layers and multilayer heterostructures of the PbTe/Pb1−xSnxTe system were grown with this apparatus and typical results are presented.
Thickness measurement method for thin photoresist film on transparent material
Authors: Takami K. , Shinbo C. , Izumi A. , Tomita Y.
Published: March 2003

A photoresist-film thickness measurement method based on absorbance measurement is described. In this case, a 1-μm-thick photoresist film is coated on transparent glass, e.g., a Color Picture Tube panel having a 10–12-mm thickness and a spherical, rough surface. To measure the absorbance, which corresponds to photoresist-film thickness, the developed method employs a two-dimensional scan of a 2-mm-diam light beam spot having two wavelengths, 365 nm (measuring wavelength) and 546 nm (reference). By switching wavelengths alternately at 25 Hz, total absorbance of the photoresist film and glass is measured with a ‘‘Dynode feedback’’ circuit system, but only the film thickness is displayed through simple signal processing. As experimental results, a minimum detectable thickness change of 0.001 μm (resolution) was obtained. The only remaining thing to be considered for practical use is a zero-level discrepancy, due to different panel lots, for which the value was approximately equal to a 0.1-μm thickness change.
Monochromator–microcomputer interface for photon counting, wavelength readout, and scan control
Authors: Erickson L. E. , Monnon R. E.
Published: March 2003

The problem of monochromator–microcomputer interfacing is discussed. As an example, a 0.5M Ebert monochromator is coupled to a PET microcomputer to provide photon counting (15-MHz max), wavelength readout (0.004-nm resolution), and scan control. Detailed circuit diagrams and supporting software are presented. Suggestions for adaptation to other monochromator–computer combinations are given.
Transient hot-strip probe for measuring thermal properties of insulating solids and liquids
Authors: Gustafsson Silas E. , Karawacki Ernest
Published: March 2003

The transient hot-strip (THS) method has been developed for experimental situations with two different materials kept against the sides of the strip. Based on this development THS probes, with known or separately measured thermal properties, have been designed and used successfully in a series of reported experiments. If the thermal diffusivity of the probe is less than that of the material under study and good contact is established between the probe and the sample, the accuracy of the measurements turns out to be as good as with the ordinary transient hot-strip method.
Method for monitoring resonant frequencies of heavy structures
Authors: Schauer F. , Tamada N. , Iwasa Y.
Published: March 2003

A method is presented for measuring mechanical resonant frequencies of heavy structures. This method employs only one electromechanical transducer which alternates as driver and receiver. We present results obtained with a superconducting magnet to demonstrate the applicability of the method: The resonant frequencies of the magnet shift with current, which affects stress.
Ripple-free liquid-nitrogen level controller for long-term operation
Authors: Srinivasan K. , Altin J.
Published: March 2003

This article describes the design features, construction, and operation of a liquid-nitrogen level controller which can be used continuously over a period of several weeks. Liquid level is sensed by pairs of thermistors mounted on a dip stick. Replenishing of liquid nitrogen is achieved as a result of self-pressurization of a tank containing the cryogen. The transfer system ensures a ripple-free liquid surface during the replenishing operation. This level controller has been a part of a cryostat for diffusion measurements in liquefied inert gases.
Thermal time constants of several Allen Bradley resistors immersed in liquid helium
Authors: Van Sciver S. W. , Lottin J. C.
Published: March 2003

The thermal relaxation time constant of several Allen Bradley-type resistors used in low-temperature thermometry are reported. The results indicate that thermal diffusion within the carbon composite controls this characteristic time and that it is independent of surface heat transfer. A simple formulation based on published data shows that the proper functional form and magnitude are predictable. It is most probable that these results can be used to estimate the time constant for resistors of other dimensions. The results confirm that the most effective method for decreasing the thermal time constant of carbon composition resistors is by reducing their thickness.
Improved detection of large rare-gas cluster ions
Authors: Haberland Hellmut , Winterer Martin
Published: March 2003

An exploratory experiment is described in which large neon and argon cluster ions are detected with improved sensitivity. The cluster ion beam impinges on a CuBe converter surface, and the positive fragmented and/or sputtered secondary ions, and not the secondary electron, are used for amplification. A drastic change of the mass spectrum from a supersonic expansion is observed.
Multichannel switch triggered by saturable reactor-induced voltage pulse
Authors: Cohn D. B.
Published: March 2003

A multichannel switch is described which is triggered by a high-voltage pulse applied to a switch electrode grounded through a single-turn saturable inductor. Switch voltages up to 30 kV for trigger voltages of 20 kV were successfully tested. Performance similar to other triggering schemes was obtained, but without some attendant complications.
Collimation of a dual-anode x-ray source used for x-ray photoelectron spectroscopy (XPS)
Authors: Hawn D. D.
Published: March 2003

The performance of a dual-anode x-ray source for XPS using various uncollimated and collimated configurations is described. A novel collimator design is discussed and shown to be effective in increasing the signal-to-background ratio and reducing anode cross talk without substantial signal loss.
Apparatus for the precise measurement of the physical properties of liquids at elevated temperature and pressure
Authors: Nissen D. A. , Macmillan D. C.
Published: March 2003

This report describes an instrument designed to measure the viscosity, surface tension, and density of liquids at elevated temperature and pressure. The theoretical principles, details of construction and operation, and response of the instrument are discussed in detail. As an example of the accuracy of the data generated by this instrument, the thermophysical properties of molten NaNO3–KNO3 have been measured over the temperature range 250–400 °C and are shown to be in excellent agreement with the recommended literature values.
Digital recording on video cassette
Authors: Ebstein Steven
Published: March 2003

A system is described that records digital data onto video cassettes and writes the data to a computer tape for subsequent processing. The system is capable of recording and playing back 172 800 bytes/s. This corresponds to the maximum rate achievable with a nine-track computer tape drive writing 1600 bits per inch at 125 ips. A standard two-hour cassette has a capacity of 1.2 Gbytes. Six checkbits are written with each 16-bit word to facilitate error detection and correction. Upon playback, the data are written via DMA into a computer and then to a nine-track computer tape. Error rates of less than 1 word in 300 000 have been achieved with an off-the-shelf portable video recorder and commercially available tape. The system comprises a low-cost solution to the problem of high-volume, fast data recording at remote locations when a small error rate can be tolerated.
Photoacoustic spectroscopy
Authors: West Gary A. , Barrett Joseph J. , Siebert Donald R. , Reddy K. Virupaksha
Published: March 2003

The subject of photoacoustic spectroscopy is reviewed. The basic areas of instrumentation (excitation sources, acoustic cells, and acoustic detectors) are described, and the specific advantages of various designs and techniques are discussed. Results are presented to highlight the applicability of photoacoustic spectroscopy to a wide variety of spectroscopic measurements. Applications include: linear absorption spectroscopy (vibrational and electronic), reaction kinetics, vibrational overtone spectroscopy, trace analysis, and nonlinear spectroscopy (multiphoton and stimulated Raman scattering). Special emphasis is given to photoacoustic Raman spectroscopy (PARS) and its application to gaseous trace component analysis.
Measurements of turbulent waves by means of microwave scattering and correlation techniques
Authors: Paris P. J. , Hollenstein Ch.
Published: March 2003

The turbulence induced by a current drawn in a low-density argon plasma is investigated by microwave scattering and correlation techniques. The azimuthal 30-GHz scattering system uses a newly designed variable waveguide in order to detect the scattered signal at any angle between 0° and 90°. Both diagnostic methods show that the turbulence is dominated by low-frequency waves propagating perpendicular with respect to the current. A comparison of these two important diagnostic methods for turbulent plasma is presented.
Fast, thermostatic, Pirani gauge
Authors: Milner C. J.
Published: March 2003

The Wheatstone bridge of a Pirani gauge has been made self-balancing, and the gauge thermostatic, using a simple but novel dual op-amp circuit. The system retains the electrical and pneumatic robustness, and the atmospheric to high-vacuum pressure range, characteristic of conductance-type gauges. Without recourse to ultrathin material for the temperature-dependent resistor, response time constants (dependent on bridge setting) of <30 ms in high vacuum have been demonstrated. At total pressures <0.1 Pa, the system can detect pressure change, sustained for >0.1 s, of 2.5 mPa; or an impulse of pressure change, occurring within 50 ms, of 0.25 mPa s. The circuit described is also applicable to bolometric power measurement, where fast response is required.
Compact device for x-ray section topography with synchrotron sources
Authors: Lang A. R.
Published: March 2003

An attachment which may be fitted to a standard crystallographic goniometer head for the purpose of taking x-ray section topographs is described and its application in synchrotron x-ray topography is illustrated. A collar attached below the arcs and translation slides of the goniometer head provides a bearing for a rotatable sleeve, concentric with the goniometer axis. The sleeve carries a removable x-ray entrance slit and a removable mirror used for angular setting by optical means. The device is easily transferable between topograph cameras at conventional x-ray sources and synchrotron radiation sources. It can be rapidly aligned at either source.
Simple technique for measuring the superconducting critical temperature of small (≥10 μg) samples
Authors: Pereira Rui. F. R. , Meyer Erich , da Silveira Máximo F.
Published: March 2003

A simple technique for measuring the superconducting critical temperature of small (≥10 μg) samples is described. The apparatus is built in the form of a probe, which can be introduced directly into a liquid-He storage Dewar and permits the determination of the critical temperature, with an imprecision of ±0.05 K above 4.2 K, in about 10 min.
Gallium arsenide phosphide light-emitting diodes as general thermometers above 35 K
Authors: Cheeke J. D. N. , Néron C. , Brunelle A.
Published: March 2003

It is shown that Monsanto MV54 light-emitting diodes can be mounted in the ‘‘as received’’ condition so as to serve as cheap, sensitive, and reliable cryogenic thermometers.
Binomial smoothing filter: A way to avoid some pitfalls of least-squares polynomial smoothing
Authors: Marchand P. , Marmet L.
Published: March 2003

Some pitfalls of least-squares polynomial (LSP) smoothing (better known to analytical chemists as Savitzky–Golay smoothing) are demonstrated and discussed, as well as some remedies. For instance, smoothing by long LSP sequences leads to transmission zeros, phase reversals, and overshoots that may be objectionable in some applications. An alternative method, the binomial smoothing filter, is described and some of its properties are presented. It is shown to be preferable to LSP smoothing in many cases. It is faster, better behaved in both the data and the frequency domains for many applications, and simpler to use and to program or to implement in hardware. Finally, the action of a filter of a given order is easy to predict.
Simple ultrahigh vacuum transfer system for surface barrier detectors
Authors: Withrow S. P. , Weidley J. E. , Herrell P. S.
Published: March 2003

The design of an assembly to transfer a surface barrier detector into and out of a UHV chamber is described.
Subnanosecond high-voltage two-stage resistive divider
Authors: Lee Z. Y.
Published: March 2003

A simple, easily constructed, two-stage CuSO4 solution ‘‘tube’’ resistive divider for measuring high-voltage ns pulses has been developed. The test results for the divider showed that it was capable of maintaining pulse rise times less than 1.5 ns, and the hold-off voltage for pulses with rise times less than 5 ns was above 120 kV.
Behavior of diffused planar germanium thermometers at temperatures below 1 K
Authors: Mack G. X. , Anderson A. C. , Swinehart P. R.
Published: March 2003

The performance of diffused planar germanium thermometers is found to be reliable at temperatures T>90 mK. At lower temperatures performance can be limited by overheating caused by measuring and spurious currents. The heating is associated with a thermal impedance Z∝T−4 which is larger than that found in typical bulk germanium thermometers. Surprisingly, Z is found to be essentially independent of the size of the planar resistor.
Beam-gas collision system for excitation cross-section measurements
Authors: Madson J. M. , Theby E. A.
Published: March 2003

A beam-gas collision experiment to measure excitation cross sections for translation-to-vibration (T-V) energy-transfer collision processes that produce short-wavelength infrared radiation (SWIR) has been assembled and used to obtain the (0,0°,0 → 0,0°,1) excitation cross section for CO2 by collision with Ar. A unique modulation technique used in this system involves pulse-modulating one of the reactants, injecting the pulses into a flowing plasma carrier, supersonically expanding the pulse and carrier, and extracting a beam from the expansion while preserving the modulation of the reactant. Enhanced radiation due to thermalization of excited CO2 at sphere pressures greater than single collision conditions, has been measured and a correction factor for this effect obtained. Measurements of the argon velocity and flux in a helium beam, CO2 number density in an integrating sphere, and infrared radiation at 4.25 μm were made to determine the excitation cross section at a collision velocity of 2.3 km s−1. The average of three sets of measurements yields a value of σ*=3.7(±3)×19−19 cm2.
Fully electronic servocircuitry for wavelength-modulation spectroscopy
Authors: Stearns R. , Steele J. , Braunstein R.
Published: March 2003

Electronic circuits have been developed to replace the mechanical servos and lock-in amplifiers customarily used in a wavelength-modulated derivative spectrometer. The result is a faster response and wider range of gain while maintaining a constant photomultiplier-tube voltage.
Surface acoustic-wave device for measuring high voltages
Authors: Joshi S. G.
Published: March 2003

A surface acoustic-wave (SAW) device for measuring high voltages is described. The device consists of two SAW oscillators fabricated on a 128° rotated Y-cut LiNbO3 substrate. The voltage to be measured is applied to one of the oscillators while the other oscillator acts as the reference oscillator for temperature compensation purposes. The frequency of the perturbed oscillator varies linearly with the applied voltage. An oscillator fabricated on a 0.5-mm-thick substrate can withstand greater than 9 kV of voltage giving a fractional frequency deviation greater than 1630 parts per million. Attractive features of this technique include: (1) direct measurement of high voltages without the need for resistive or capacitive voltage dividers, (2) very high input resistance, (3) direct conversion of voltage to frequency, and (4) resolution better than 0.01% of full scale. This paper will discuss the basic operation and present experimental data on the performance of the device. A technique for obtaining improved temperature compensation in SAW sensors will also be presented.
Optimization of a clip-on SQUID current probe
Authors: Leifer Mark C. , Wikswo John P.
Published: March 2003

This paper presents details of an unusual clip-on nanoammeter. The device utilizes a toroidal magnetic flux sensor which is split to allow its placement around a continuous current carrying filament, and is coupled to a sensitive superconducting current amplifier. Optimization formulas allow the design of an instrument having the greatest possible signal-to-noise ratio consistent with the physical volume available for the sensing element. A prototype exhibited 125-nA current sensitivity at 25 Hz with a noise level of 40 nA/Hz1/2. The performance of this instrument verified the predictions of the theory. The optimization analysis for this probe demonstrated that the signal-to-noise ratio could have been doubled by a slight change in toroid dimensions. It was shown that SQUID noise is negligible for this instrument, justifying the assumption of a noiseless amplifier in the original calculation. Finally, the conditions under which an impedance matching transformer can reduce the importance of the SQUID noise relative to the Johnson noise are derived, and the required inductances are given.
Load fixture for uniform plastic deformation of single crystals
Authors: Georgeson Gary , Milstein Frederick
Published: March 2003

In conventional tensile or compressive tests of single crystals, plastic deformation by slip occurs nonuniformly owing to slip plane rotation and constraint of the specimen’s ends. To minimize these problems, a ‘‘load fixture’’ (LF) that employs an air bearing and magnetic field (to provide for free rotation of the ends of the specimen) has been designed and built. The frictionless air bearing minimizes the tendency of the system to develop internal torques during the deformation of single crystals, particularly those with low critical resolved shear stresses. The LF has been tested in tensile and compressive loading of mercuric iodide single crystals. By keeping the center of rotation on the ‘‘boundary of slip’’ (i.e., on the slip plane that separates slipped from unslipped material in the plastically deformed crystal), the line of action of the applied force is maintained coincident with the sample’s central axis. The LF is particularly useful for testing small, ductile crystals and for studying mechanical hysteresis.
Sample manipulator for operation between 20 and 2000 K in ultrahigh vacuum
Authors: Chaban E. E. , Chabal Y. J.
Published: March 2003

We present a simple design for an ultrahigh vacuum (UHV) sample manipulator which allows rapid temperature changes from 2000 to 20 K while maintaining xyz translations, rotation, and tilt capabilities. A mechanical heat switch is used between the cryogenic reservoir and the sample holder. The sample is kept electrically isolated at all times. A large thermal mass of the sample holder gives good temperature stability (1 K/h); yet temperature extremes can be obtained within a few minutes.
Mechanical scan system for microscopic applications
Authors: Marsman H. J. B. , Stricker R. , Wijnaendts van Resandt R. W. , Brakenhoff G. J. , Blom P.
Published: March 2003

A high-speed mechanical scanning stage for microscopic applications has been designed and constructed. It is especially suitable for high-resolution confocal UV microscopy. It is a feedback design using electromagnetic actuators and piezoelectric sensors with motor-driven screws for coarse adjustment. Scanning of areas up to 1 mm square at up to 300 lines per second is possible with positional resolution of better than 0.01 μm. An exceptionally stable optical system is also described.
Statistics of the atom-by-atom dissection of planes in an atom-probe field-ion microscope: The number of atoms detected per plane
Authors: Macrander Albert T. , Yamamoto Masahiko , Seidman David N. , Brenner S. S.
Published: March 2003

The statistics of the atom-by-atom dissection of planes, in the atom-probe field-ion microscope, have been investigated. Tungsten specimens oriented in the [110] direction, with the probe hole over the center of the plane, were slowly pulsed field-evaporated on a plane-by-plane basis, and statistical analyses were made on the number of tungsten atoms detected per plane; 30 separate slow dissection experiments were performed. Observed fluctuations in the number of atoms per plane are used to infer a range of allowable values for the detection efficiency. We find that, in some cases, the number of atoms per plane can be described as following a binomial distribution. From these results detection efficiencies in the range 0.11 to 0.54 were inferred. This range of efficiencies can be understood with the aid of field-ion desorption images. In addition, a value for the detection efficiency of 0.2 was obtained under the assumption that all atoms in the area projected by the probe hole, along the specimen radius, were analyzed. Thus, we find that this geometrical procedure, a first-order approach to the problem, yields a reasonable result. Also, the results of a Monte Carlo simulation of atom-by-atom field evaporation of a large number of planes are presented. The Monte Carlo simulation shows that if a binomial distribution is obtained, the uncertainty in concentrations determined by the atom-probe technique will have only a small component owing to the uncertainty in the number of solvent specimen atoms—this is subject to the caveat that there are no special problems with the field-evaporation behavior of the solvent atoms. Although the statistical analyses were applied to a specific crystallographic plane and position, the methodology is reasonably general and can be applied to other situations.
Electron temperature monitor for laser-produced plasmas
Authors: Ng A. , Fong K. , Barnard A. J. , Kwan J. , Pasini D.
Published: March 2003

We have developed a multichannel x-ray analyzer for monitoring electron temperatures in plasmas. The device consists of a step-wedge x-ray filter and a Reticon sensor array. By measuring the x-ray continuum emission from a laser-produced plasma with the device, the electron temperature can be determined to within 10%.
Charged particle ray simulator and monitor
Authors: Kisker Erhard
Published: March 2003

A new method is described for simulating charged particle rays in arbitrary electrostatic lens systems of cylindrical symmetry. The method is so efficient (<4 ms/step) that even for complex lens systems the trajectories can be computed and displayed during the lens voltage adjustment, using the same laboratory microcomputer which controls the lens voltages. The time lag between a change of a lens element voltage and the trajectory display is of the order of a few seconds for long, multielement lens systems. This also allows one to optimize the voltage combinations by performing trajectory calculations for many lens voltage settings. The performance is demonstrated by comparing with recent experimental data of Heddle and co-workers on imaging properties of a three-element tube lens. As an application of the fast computation time feature, trajectories and voltages are shown for a lens system providing an electron optically adjustable angle resolution as used in a spin polarized photoemission experiment with synchrotron radiation.
Excitation pulse-shape mimic technique for improving picosecond-laser-excited time-correlated single-photon counting deconvolutions
Authors: James Douglas R. , Demmer David R. M. , Verrall Ronald E. , Steer Ronald P.
Published: March 2003

The determination of accurate subnanosecond fluorescence lifetimes by the time-correlated single-photon counting technique is often limited by difficulties in obtaining the correct instrumental response function f(λ,t) to the excitation pulse. These difficulties are increased when a grating monochromator is used to disperse the emission due to the introduction of an additional temporal broadening of f(λ,t). A technique for determining the correct f(λ,t) at the wavelength of sample emission, λem, is described. The technique consists of using a very short-lived fluorophore to ‘‘mimic’’ the excitation pulse shape at λem, yielding the convoluted mimic decay function Cm(λem,t), and then to computationally extract f (λem,t) from Cm(λem,t). The technique is experimentally and computationally simple and yields the desired instrumental response function at λem which eliminates problems due to the sensitivity of f(λ,t) to λ (color shift artifact). The photomultiplier tube receives spatially equal illumination when both the sample decay and Cm(λem,t) are determined because both the mimic and sample emission are spectrally broad, eliminating the problem of the variation of f(λ,t) with position of incident light on the photomultiplier tube photocathode (targeting artifact). Artifacts due to monochromator temporal broadening are eliminated since both the mimic and sample emission are monitored at constant wavelength.
High-speed, low-cost laser-triggered plasma shutter
Authors: Hasselbeck M. , Huang L. , Hsu S. C. , Kwok H. S.
Published: March 2003

Design and construction of a CO2 laser-triggered plasma shutter is described. An inexpensive pyroelectric detector and a novel needle-resistor spark gap, requiring an applied voltage of less than 500 V, are employed. The total electronic delay can be made to be less than 15 ns with subnanosecond jitter. This plasma shutter finds applications in producing picosecond CO2 laser pulses and in optical isolation.
Vernier fringe-counting device for laser wavelength measurements
Authors: Kahane A. , O’Sullivan M. S. , Sanford N. M. , Stoicheff B. P.
Published: March 2003

A vernier fringe-counting circuit designed for use with a Kowalski-type wavemeter is described. Wavelength measurements made with this device have a high reproducibility of 5×10−9 (or 1/50 of a fringe) and measured accuracy of 4×10−9. The results of accuracy tests are presented along with systematic errors incurred when the wavelengths of two He–Ne lasers (632.9 nm) are compared by the vernier method.
Improved differential photocurrent method for measurement of optical-absorption coefficient and minority-carrier diffusion length in a semiconductor
Authors: Hasegawa S. , Watanabe T. , Tanaka A. , Sukegawa T.
Published: March 2003

This paper describes an improved differential photocurrent method of measurement of optical-absorption coefficient α and minority-carrier diffusion length L. A prototype instrument can detect signals of the photocurrent Ip, the differential photocurrent ΔIp, and the depletion-layer width W of sample diode, and plot automatically two linear relationships: log(ΔIp/ ΔW) vs W and Ip vs ΔIp/ ΔW. From these plots, α and L are readily obtained. Performance of the instrument is demonstrated using a Au–GaAs 0.62P0.38 Schottky-barrier photodiode.
Time-resolved photoelectron spectroscopy for the study of dynamic surface species
Authors: Steinbach Friedrich , Schütte Joachim
Published: March 2003

The principle and experimental setup of time-resolved photoelectron spectroscopy are outlined. In comparison to conventional molecular beam relaxation spectrometry a reaction channel is analyzed not only at the end but prior to the end. In at least three points time-resolved photoelectron spectroscopy is superior to photoelectron spectroscopic experiments under static and direct current adsorption conditions: (1) a general increase in detection power of transient adsorbates and contaminations; (2) the possibility to discriminate by individual relaxation time between species that cannot be resolved in their binding energy; and (3) a significant simplification of the mathematical formalism in comparison to conventional molecular beam relaxation spectrometry and a more straightforward understanding of the results, in particular the chemical identification of transient species. This is illustrated with time-resolved UV-photoelectron spectra of intermediate adsorbed carbon in the catalytic decomposition of methanol on iron and with time-resolved x-ray photoelectron spectra of intermediate adsorbed oxygen in adsorption and catalysis of methanol/oxygen mixtures on iron.
ac calorimeter for liquid including suspension of biological materials
Authors: Imaizumi Shigeo , Suzuki Koichi , Hatta Ichiro
Published: March 2003

An ac calorimeter is developed for the measurement of heat capacity in liquid including the aqueous suspension of biological materials in the temperature range between 270 and 400 K. Using this apparatus we perform the measurement of heat capacity at the main phase transition of lipid suspended in water. Additionally a new method to determine the absolute value of the heat capacity is proposed.
Conductimetric method of determining the hematocrit value of blood
Authors: Neelakantaswamy P. S. , Aspar K. F. , Rajaratnam A. , Das N. P.
Published: March 2003

A simple conductimetric method for measuring the hematocrit value of blood is described. Using a conventional electronic conductivity meter having a two-electrode cell, the conductivity between the electrodes dipped in a diluted sample of the blood is measured and related quantitatively to the strength of suspended erythrocytes (that is, to the hematocrit value) in the test suspension. The extent of diluting the sample prior to the measurement is optimally determined on the basis of theoretical considerations. The merits of this instrumentation in terms of simplicity, economy, and linearity are compared with those of conventional methods of hematocrit determination. Possibilities of improving the present method by using inductive-type conductivity meters and/or by using vhf (very high frequency) resonant circuit sensors are suggested. Relevant theoretical considerations and experimental results are presented.
Pulse technique for measuring magnetoresistance of metals in high magnetic fields
Authors: Czarnecki P. , Surma M.
Published: March 2003

A method for measuring magnetoresistance of metals and metallic alloys in a pulse magnetic field of high intensity is presented. The accuracy of the sample magnetoresistance Δ ρ/ρ0 is ±12% and ±5% for Δ ρ/ρ0 values of 10−3 and 10−1, respectively. This accuracy can be achieved for sample resistances of the order of 10−1–102 Ω.
Detonic research infrared radiometer with nanosecond response
Authors: Von Holle W. G. , McWilliams R. A.
Published: March 2003

Two infrared radiometers were constructed for use in shock wave and detonation research. Fast detectors were combined with wide-band amplifiers to achieve an overall response of about 5 ns, which was confirmed by experiments on planar shocked copper plates. Detonation experiments show the merits of a new optical technique for probing detonation wave structure and for reactive and nonreactive shock wave research.
Radon daughter carousel: An automated instrument for measuring indoor concentrations of 218Po, 214Pb, and 214Bi
Authors: Nazaroff William W.
Published: March 2003

A microprocessor-controlled instrument for measuring the concentrations of radon progeny in indoor air is described. The measurement technique is based on alpha spectroscopy and uses two counting intervals following a sampling period during which radon progeny are collected on a filter. The counting intervals are selected to provide optimal precision for measuring 222Rn progeny for fixed total measurement times ranging from 30 to 60 min: concentrations as low as 0.5 pCi/1 can be measured with less than 20% uncertainty in 45 min. The instrument can also be used to estimate the potential alpha energy concentration of 220Rn decay products. The device operates under the control of a computer or a data terminal and functions for week-long periods between filter changes. The user can specify the sampling- and counting-interval timing over a wide range and select from among several operating modes. A number of performance tests are also described indicating that for typical indoor concentrations the measurement uncertainty is dominated by counting statistics.
Drift reduction of the incident signal in time domain reflectometry
Authors: Chahine R. , Bose T. K.
Published: March 2003

Modification of a 1811A Hewlett–Packard time domain reflectometry (TDR) system is described for long-time drift reduction. Triggering methods for single-channel as well as dual-channel TDR systems are discussed. It is shown that the long-time drift of the 1024-point incident signal is reduced to less than one discrete point over a period of several hours. This modification extends the upper frequency limit of a TDR system to about 10 GHz for precision permittivity measurements.
Auger microscopy using sample modulation
Authors: Stupian Gary W. , Leung Martin S.
Published: March 2003

Although the spatial resolution of a scanning Auger microprobe is limited by its electron optics, its effectiveness for the analysis of semiconductor devices that have features of interest comparable in size to the diameter of the analyzing electron beam is enhanced by a variation in the method of signal detection. Signal detection in an Auger spectrometer is most often accomplished using phase-sensitive detection. The modulating signal required in the phase-sensitive detection process is applied to the electron energy analyzer. Instead, by applying the modulating signal directly to different electrically isolatable regions of a device, only those Auger electrons originating in a particular region are detected. By rejecting signals from regions adjacent to a modulated region, Auger spectra characteristic only of the region of interest are obtained without spurious contributions from adjacent areas inadvertently illuminated by the analyzing beam.
Grazing incidence time-resolving spectrograph for magnetic fusion plasma diagnostics
Authors: Hodge W. L. , Stratton B. C. , Moos H. W.
Published: March 2003

A time-resolving grazing incidence spectrograph based on an image intensified photodiode array detector has been constructed and has demonstrated its utility as a fusion plasma diagnostic. The total wavelength coverage is 15–360 Å with 0.7 Å resolution (line profile FWHM); portions of this range may be observed during a single plasma discharge with a bandwidth of ∼40 Å when the detector is centered at 40 Å and ∼80 Å with it centered at 200 Å. Integration times from 5.4 to 13.1 ms are available when the entire photodiode array is read out; integration times as short as 1 ms can be obtained for a few lines of interest through the readout of selected photodiodes. The spectrograph has been radiometrically calibrated over the 60- to 360-Å range at the NBS SURF II electron storage ring and is currently in operation on the Princeton Large Torus (PLT) tokamak.
Versatile double-crystal topography camera
Authors: Kuo C. L. , Emamian M. , Bilello J. C.
Published: March 2003

A versatile double-crystal topography camera is described which has provisions for both image detection and precision rocking curve analysis for a wide variety of single-crystal samples. The camera has a variable base separating the two crystals and this base is rotatable for working with a range of diffraction vectors. The accuracy of the second crystal goniometer stage is of the order of 0.2 arc s. An example of typical data taken with this camera is displayed.
Hollow-cathode magnetron ion source
Authors: Miljević V.
Published: March 2003

A new type of ion source with axial extraction, based on hollow-cathode magnetron discharge, has been developed. Constant hydrogen ion currents in excess of 1 mA with an exit source aperture of 1 mm in diameter and accelerating voltages up to 3 kV, have been extracted axially from the cylindrical hollow cathode. Similar results have been obtained with helium, argon, and nitrogen plasmas.
Cesiated porous molybdenum converter for intense negative ion sources
Authors: Alessi J. G. , Hershcovitch A. , Sluyters Th.
Published: March 2003

Maintaining the proper low work function surface in steady-state high-current-density negative ion sources is difficult, due to intense ion bombardment of the surface. Experiments were performed in which liquid cesium was forced through a porous molybdenum converter in order to obtain a low work function, while at the same time allowing the surface to be cooled. In a small steady-state hollow cathode discharge source, the H− yield from a porous molybdenum converter was five fold higher than from a solid molybdenum converter which relied on the conventional method of cesium coverage by vapor deposition.
Simple, efficient UHV manipulator
Authors: Thiel P. A. , Anderegg J. W.
Published: March 2003

A simple manipulator is described for use in ultrahigh vacuum. Unhindered rotation within vacuum is provided by a commercial differentially pumped adapter to which the entire XYZ stage is attached. The combination of movements provided by the XYZ stage, the rotating vacuum flange, and a gimbal permits alignment of the sample with any of the peripheral view ports. The resistively heated sample support, mounted through a cold finger, permits rapid variation of sample temperature from several hundred degrees Kelvin to near cryogenic. It is anticipated that this design could be easily used with many existing types of commercial vacuum systems, with the consequent advantage of increased ease and simplicity of both mechanical motion and cryogenic cooling.
Foucault pendulum with eddy-current damping of the elliptical motion
Authors: Mastner G. , Vokurka V. , Maschek M. , Vogt E. , Kaufmann H. P.
Published: March 2003

A newly designed Foucault pendulum is described in which the mechanical Charron ring, used throughout in previous designs for damping of the elliptical motion of the pendulum, is replaced by an electromagnetic eddy-current brake, consisting of a permanent magnet attached to the bottom of the bob and a metallic ring. This damping device is very efficient, as it is self-aligning, symmetrical in the damping effect, and never wears out. The permanent magnet is also used, together with a coil assembly and an electronic circuitry, for the dipole-torque drive of the pendulum as well as for accurate stabilization of the amplitude of the swing. A latched time display, controlled by Hall probes activated by the magnet, is used to visualize the Foucault rotation. The pendulum system and its associated electronic circuitry are described in detail. The optimizing of the drive mode is discussed. Measurements of deviations from theoretical value of the Foucault rotation velocity made automatically in a continuous run show a reproducible accuracy of ±1% or better in individual 360° rotations during the summer months. The quality factor of the pendulum as mechanical resonator was measured as a function of the amplitude in the presence of the eddy-current damping ring.
Simplified UV-preionized long-pulse TEA CO2-laser amplifier
Authors: Nemoto Kohshichi , Kogoshi Sumio , Noda Etsuo , Sekiguchi Tadashi , Ohhashi Hirokazu
Published: March 2003

A simplified UV-preionized long-pulse TEA CO2-laser amplifier is proposed, which is powered by a common Marx generator for both the preionization arc discharges and the main laser discharge. The measurements of small-signal gain reveal that there exists an optimum capacitance for the capacitors which are provided in the preionization circuit for the control of preionization level. The physical interpretation for this is also given. A small-signal gain higher than 3%/cm and an extraction energy of nearly 14 J/l (at the input energy level of nearly 1 J) have been achieved. It has also been demonstrated that the amplifier can amplify a long laser pulse of the order of microseconds without serious distortion of pulse waveform.
Variable-temperature x-ray powder diffraction attachment for vertical goniometers
Authors: Rivers-Bowerman A. , Dutcher J. R. , Haering R. R.
Published: March 2003

A lightweight, accurate, quick-mount, variable-temperature x-ray powder diffraction attachment for use on the vertical goniometer of a diffractometer is described. The unit is capable of producing temperatures between T=50 and 350 K at the sample position. In addition to a general description of the attachment, details of system performance are given. We have found that diffraction patterns obtained with the attachment mounted on the goniometer are of comparable quality to those obtained with the goniometer itself.
Elastic constants of plastic crystals by Schaefer-Bergmann scattering
Authors: Marx S. V. , Simmons R. O.
Published: March 2003

A Schaefer–Bergmann technique for ultrasonic sound velocity measurements on single crystals has been developed for use with substances which are either gas or liquid at room temperature. The advantages of this method for measuring elastic constants of such crystals are discussed. A method for simultaneously determining the elastic constants and the spatial orientation of the crystal from the light scattering data is presented.
Powerful single-frequency CO2 laser for plasma diagnostics
Authors: Takahashi Hidemi , Kimura Minoru , Morita Yasuyuki , Sano Reiji
Published: March 2003

A cw 240-W CO2 laser has been developed for plasma scattering measurements. The laser oscillates only on the 10P(20) transition (10.5912-μm wavelength) at a single longitudinal as well as transverse mode with linear polarization. These properties are obtained by using an adequately long cavity with a folded beam configuration. Part of the output beam was heterodyned with a local oscillator laser to confirm the single-frequency oscillation. The short-term frequency stability was 200 kHz (7×10−9) for an observation time of 1/15 s. The shift of the oscillating frequency due to the discharge current was 360 kHz/mA and the frequency shift due to the total gas pressure was 4.1 MHz/Torr. These frequency shifts are mostly attributable to the change of the refractive index of the laser gas.