bluuebunny/crossref_metadata_2025 huggingface dataset:
The Soft Particle Spectrometer in the ISIS-I Satellite
Authors: Heikkila W. J. , Smith J. B. , Tarstrup J. , Winningham J. D.
Published: February 2004

The soft particle spectrometer uses electrostatic deflection for simultaneous measurement of the differential energy spectra of electrons and protons. The energy range is from 10 eV to 10 keV per unit charge with ±40% energy spread. Twelve stage BeCu electron multipliers are used as detectors in the counting mode over a five decade dynamic range. A swept mode of energy selection provides a spectrum in 0.5 sec for high fluxes, while a stepped mode suitable for lower fluxes takes 40 sec. A typical electron spectrogram for a transpolar pass is included as an example of the data reduction procedure used.
An Internal Heating Arrangement for the Teflon Hydrostatic Pressure Cell
Authors: Maines R. G.
Published: February 2004

An internal heater arrangement for hydrostatic pressure experiments (Teflon cell technique) at elevated temperatures is described. With fluid pressure media such as silicone oil, Nujol, etc., temperatures in the range of 350°C at pressures up to 30 kilobars have been achieved. Since direct current is employed for heating, pickup problems associated with very sensitive electronic detection techniques are eliminated.
Shock Tube Studies Using Image Orthicon Spectroscopy
Authors: Hewitt E. W. , Bott J. F. , Jacobs T. A.
Published: February 2004

An image orthicon detection and recording system has been adapted for making spectroscopic measurements in shock tube emission studies. The system provides greater sensitivity than film and permits electronic control of both the timing and duration of the exposure. The linear response with light intensity and immediate recording of output on an oscilloscope trace makes the system a convenient diagnostic tool. A description of the system as well as quantitative spectroscopic data obtained with it is presented.
Semiautomatic Acquisition of Extreme Ultraviolet Reflectance Data for Calculating Optical Constants
Authors: Hunter W. R.
Published: February 2004

A data acquisition system is described that obtains reflected intensity measurements in digital form directly on punched cards. The cards can then be fed directly to a computer to calculate reflectances, thus eliminating the time consuming process of reducing strip chart recordings to reflectances. In addition, the precision with which the reflectances can be calculated is improved, which is important if they are to be used to calculate optical constants.
Wide Bore Helical Inductively Pumped Argon Laser
Authors: Ling H. , Colombo J. , Fisher C. L.
Published: February 2004

Commercial available argon lasers are narrow bored, which can support only a limited number of modes. In order to suit the scan laser operation, a wide bore multimode laser is designed. This communication discusses the design procedure, technique, and apparatus setup for a helical inductively pumped wide bore argon laser. The experimental result and further improvement are also discussed.
Oscillatory Flow Measurements with a Directionally Sensitive Laser Velocimeter
Authors: Denison E. B. , Stevenson W. H.
Published: February 2004

The concept, design, and construction of a directionally sensitive laser velocimeter for unsteady flow measurements are presented. Oscillatory flow measurements are compared with theoretical predictions.
An Absolute Detector for Short Duration Bursts of Ions
Authors: Zwally H. Jay
Published: February 2004

Nonrepetitive bursts of ions, several microseconds in duration, with intensities less than 105 ions per burst were measured by a linear signal from the ninth PM dynode in a Daly-type secondary emission detector. The signal height was proportional to the number of ions and was calibrated for various ion species to an estimated absolute accuracy of ±15% and relative accuracy of ±5% between identical detectors.
Transient Method of Measuring Very Low Conductivities without Contacting Electrodes
Authors: Chatain Daniel , Gautier Pierre , Lacabanne Colette
Published: February 2004

An experimental procedure is proposed, which amounts to Fourier transforming the frequency depending torque in the Ogawa's torsion pendulum method. This reduces by a factor of the order 100 the fairly long times needed for measuring the very low conductivities of insulating materials.
A Semiautomatic Integrating Densitometer with Digital Readout for One Dimensional X-Ray Diffraction Films
Authors: Keefe W. E. , Williams R. C. , Ham W. T. , Stewart J. M.
Published: February 2004

A technique is described whereby the density of diffraction spots on unidimensional x-ray film is measured by means of a microdensitometer and recorded on a strip chart recorder; simultaneously, the area under the curve is integrated electronically and the results are displayed on a digital counting device. The data for one structure which has been completed gave a final R value of 0.064.
Aminco-Bowman Spectrophotofluorometer Modification-II
Authors: Mode V. Alan , Thomas Richard A. , Sisson David H.
Published: February 2004

We have modified a standard Aminco-Bowman spectrophotofluorometer to allow collection of spectral data on punched paper tape. Using this tape, we have obtained high quality corrected spectra by postprocessing techniques on a digital computer. We have examined the errors associated with changes in the energy distribution of the excitation source.
A Photoconductive Self-Balancing Circuit
Authors: Ben-Yaakov S.
Published: February 2004

An ac self-balancing potentiometric photoconductive circuit has been developed and employed to measure resistive ratios. It includes a cadmium sulfide photoconductive cell and an incadescent lamp in an ac negative feedback configuration. The tested ratio is measured by incorporating the photocell in a dc circuit and monitoring the resulting current which is proportional to the tested ratio. Two specific examples are described, one of which is a precision circuit that was used to construct an inductive conductivity meter for oceanographic applications. By properly selecting the photocell type and increasing the open loop gain, a 0.1% accuracy (of full scale) may be obtained with a relatively simple circuit. The circuit is applicable for signal conditioning of resistive transducers such as platinum thermometers and strain gauges. It may be particularly useful in cases where a dc output signal is preferred while the resistive device must be driven by an ac signal.
The Characteristic of Gold and Aquadag Contacts with Single Crystal Nickel Oxide Surfaces
Authors: Anderson W. , Martinez J. , Madjid A. H.
Published: February 2004

The electrical characteristic of gold and Aquadag contact with single crystal nickel oxide surfaces is determined within a moderate temperature range around 273 K. The current-voltage characteristic of these contacts is linear, but the contact resistance is found not to be negligible when compared to the resistance of NiO samples of ordinary size.
A Transducer for Measuring High Heat Transfer Rates
Authors: Schulte E. H. , Kohl R. F.
Published: February 2004

A quasi-steady-state, water cooled heat flux transducer has been developed for the measurement of heat fluxes exceeding 1000 W/cm2. The transducer utilizes single crystal germanium materials as the sensing elements and the design allows the transducer to be calibrated by direct conduction. Utilizing this technique, a transducer has been calibrated to 1000 W/cm2 and the calibration has been verified by radiation techniques up to 455 W/cm2. Transducers only 1.1 cm in diameter have been tested. The transducers exhibit an output greater than 15 mV at 1000 W/cm2, a nearly linear output vs heat flux, and a response time on the order of 100 msec.
A Digital rf Pulse Burst Generator for NMR Relaxation Experiments
Authors: Radeka V. , Chase R. L. , Petrinovic M. , Glasel J. A.
Published: February 2004

This paper describes a pulse burst generator designed to provide coherent rf pulse sequences with lengths applicable to NMR relaxation experiments. The burst generator is based on a principle which provides an inherently high on/off ratio. The frequency of interest is generated by mixing two higher frequencies. Bursts of arbitrary length are generated by gating these two higher frequencies so that in the off intervals there is no signal at the frequency of interest in the entire generator system. Burst lengths are determined digitally to within one cycle by a preset counter. A number of different burst lengths can be selected by several sets of switches to generate a Carr-Purcell sequence of bursts. Bursts with 90° rf phase shift can be generated in this sequence as is required for the Meiboom-Gill method. Phase and frequency relations in the generator are determined digitally, so that no tuning adjustments are required for operation of the generator over the whole frequency range. The described generator employs MECL II integrated circuits which restrict the highest output frequency of the generator to about 10 MHz.
A Soft X-Ray Appearance Potential Spectrometer for the Analysis of Solid Surfaces
Authors: Park Robert L. , Houston J. E. , Schreiner D. G.
Published: February 2004

A simple, nondispersive spectrometer has been designed which allows the binding energies of core electrons to be determined for atoms at a solid surface. The spectrometer consists of a photomultiplier which measures the total soft x-ray fluorescence of the anode surface of a vacuum diode. The derivative of the multiplier current as a function of the anode potential rises abruptly at the appearance potentials of characteristic x rays. The derivative is taken by superimposing a small oscillation on the anode potential and synchronously detecting the variation in multiplier current. The information obtained is comparable to that usually derived from absorption spectroscopy but is much more sensitive to the surface region. Thus, in addition to determining the elemental composition of the surface, chemical shifts in the binding energies of core electrons are readily observed.
A Timer and Event Accumulator for the FIM Atom Probe
Authors: Johnson Charles A.
Published: February 2004

The field ion microscope atom probe makes possible the chemical identification of individual atoms field desorbed from a sharp metal tip by time of flight along a drift tube. An instrument to control the rate at which desorption pulses are applied and to record the resulting data is described. Rates of a few hundred pulses per second are readily achieved, and the instrument can be programmed to terminate either after a present number of cycles or in response to the acquisition of the first piece of data. This latter mode of operation is particularly convenient for establishing the best field desorption conditions. Resolution of adjacent mass numbers depends on the time resolution of the instrument; the best time resolution achieved is 40 nsec, resulting in a mass resolution of about 1% for typical ion travel times.
Lloyd Mirror Laser Interferometer for Diffusion Layer Studies
Authors: Watkins Laurence S. , Tvarusko Aladar
Published: February 2004

A Lloyd mirror laser interferometer is described which determines the refractive index gradient in a diffusion layer. The interference fringe movement is detected by an array of n-p-n planar silicon photodevices the output of which is recorded by oscillographs. Various modes of measurement are discussed which are suitable for transparent or opaque electrodes. The presently used measuring mode is based on the determination of the reflected ray's optical path length change at various angles of incidence. The refractive index gradient is obtained by an iterative solution of the derived equation for the optical path length change on a digital computer. The time dependence of the fringe movement during electrodeposition from CuSO4 solutions is discussed in addition to the effect of incidence angle and cathode displacement. The use of this interferometer is not limited to electrochemical processes and it can be used for the study of refractive index gradients in heat and other mass transfer boundary layers at solids.
A New LEPR Spectrometer
Authors: Wells J. S. , Evenson K. M.
Published: February 2004

A new spectrometer for conducting laser electron paramagnetic resonance experiments on gases is described. This spectrometer yields at least an order of magnitude better sensitivity than the first spectrometer used in this type of investigation.
A Control System for Superimposed High Speed Photographic Records
Authors: Curzon F. L. , Dimoff K.
Published: February 2004

A control system has been designed for high speed photographic diagnostics based on the action of a rotating mirror. Built from simple circuitry and readily available standard delay units, it can operate independently of the mechanism driving the mirror. The system displays an over-all jitter of less than 0.05%. It has been used successfully in the accurate superposition of repetitive pulsed discharge images on film.
Thickness Monitor for Transparent Thin Film Deposition
Authors: Roberts J. F. , Clark C. A. , Dumbri A. C.
Published: February 2004

A technique is described for monitoring the thickness of transparent thin films growing on heated polished substrates (as in chemical vapor deposition). Thermal energy, radiated by a substrate and transmitted by a growing film, undergoes optical interference as a result of multiple reflections between the substrate-film and film-ambient interfaces. A narrow bandpass detector is used to measure the transmitted intensity and film thickness is correlated with the maxima and minima of the detector output. Using a 1P21 photomultiplier tube and a 6000 Å interference filter (90 Å half-width) this technique has been applied for substrate temperatures as low as 800°C and thickness in the range of 1000–6000 Å with an accuracy of ± 100 Å. A special comparison technique is described which operates by sampling, storing, and subtracting signal intensities obtained from two substrates. Using this technique it is possible to terminate deposition of the outer film of a duplex combination (500 Å of Al2O3 on SiO2, for example) within 25 Å of the chosen thickness.
A Laser Interferometer for Highly Transient Plasma Diagnostics
Authors: Rowley Paul D.
Published: February 2004

A description is given of a modified Michelson interferometer that is particularly useful for locally probing highly transient plasmas such as occur behind incident shock waves in high performance shock tubes. The interferometer has the following features: (a) It is of a modified Michelson form with spherical mirrors to minimize effects of spatial variations in the index of refraction normal to the beam, (b) the light source is a cw laser that provides a very narrow coherent beam to allow high spatial and temporal resolution of the probe, and (c) it is operated in a single fringe mode over the narrow beam (constant phase difference between the two interfering beams over the illuminated field) and fringe shifts are observed through the time response of single channel detectors. Because photon transit time is negligible in shock tube diagnostics, the response time of the interferometer is determined solely by detection capabilities. Rapid response is achieved because nearly the entire laser energy is available for detection and high contrast interference takes place, allowing high signal-to-noise ratios at wide bandwidths. The spatial resolution can be diffraction limited. Thus, one-dimensional observations can be made of temporally and spatially varying events with a combined temporal and spatial resolution exceeding that available with other current interferometric techniques. Index of refraction profiles behind strong shock waves have been observed at two wavelengths simultaneously and verify the usefulness of the design. A further design modification is discussed which removes the uncertainty in the sign of the temporal gradient of index of refraction and would allow accurate fractional fringe interferometry.
A Flexible Simple Thermostat for Small Objects and the Range of 100 to 400 K
Authors: Bilger H. R. , Nicolet M-A.
Published: February 2004

A flexible, inexpensive thermostat for the temperature range 100 to 400 K is described. Liquid nitrogen is the coolant and a gas serves as transfer medium. The temperature can be set to better than 1 K and is held there within ½ K by an electronic control system. The relatively small working volume of the order of 10 cm3 allows quick changes of temperature, a desirable feature in typical semiconductor experiments.
Vertical Temperature Gradients in a Liquid Helium I Bath
Authors: Kerrisk Jerry F.
Published: February 2004

Vertical temperature gradients in a helium I bath have been measured with a movable probe, using a carbon resistor as the sensor. The bath temperature was controlled so that the temperature at the bottom of the bath was fixed. The measured temperature gradients were in substantial agreement with those predicted from the change of the vapor pressure of the bath with height.
A Fast Acting All-Metal Gas Valve for Plasma Research
Authors: Novak B. , Pekarek S.
Published: February 2004

A fast acting, all-metal valve has been developed for injecting pulses of neutral gases into a high vacuum. The theoretical motion of the piston is analyzed and compared with its actual dynamic and electrical operating characteristics. The design of the valve makes it possible to change the length of time the valve is open and thus vary the number of atoms admitted. Preliminary measurements of the pressure in the gas pulses have been made with fast stabilized ionization gauges. Reproducibility of measurement of the operating times of valve and gas pressure pulses was better than 95%. The gases used were hydrogen, helium, argon, and nitrogen.
A Small Strain Tension-Torsion Extensometer
Authors: Brown Graham M.
Published: February 2004

The design and error analysis of a high accuracy, high sensitivity, low interaction tension-torsion extensometer for use on thin wall tubes is presented. Direct current differential transformers are used as position transducers and the extensometer outputs are independent of any symmetric specimen bending that may occur, although it is possible to combine the outputs to measure bending in two perpendicular directions through the specimen axis in order to check specimen alignment. Usable accuracies are of the order of 10−4% for both modes, the interaction of the two modes is less than 0.2%, and over-all linearity is better than 0.5%, all percentages being relative to full scale. The total strain range is 5% in tension and 1.25% in torsion.
A Soft X-Ray Spectrometer with Improved Drive
Authors: Cuthill J. R.
Published: February 2004

The spectrometer described is a grazing incidence grating instrument with an improved drive system for moving the electronic detector around the Rowland circle. In this system the lead screw driving the detector always lies along a chord of the Rowland circle joining the grating and the detector. With this design there is less chance of error due to flexure of the components than in previous designs, and the resolution of the spectrometer is constant in wavelength.
Beam Switching Cassegrain Feed System and Its Applications to Microwave and Millimeterwave Radioastronomical Observations
Authors: Slobin S. D. , Rusch W. V. T. , Stelzried C. T. , Sato T.
Published: February 2004

A beam switching Cassegrain antenna configuration was developed for the purpose of making radioastronomical measurements at a wavelength of 3.33 mm. The subreflector periodically switches the antenna beam between the astronomical source and the adjacent sky reference position. The tilting subdish system is used in conjunction with a synchronous detection radiometer, and a complete description of both the rf and electronic systems is given. A discussion of the mechanical and electronic considerations associated with the development of this particular subdish system is made; and a discussion of low frequency switching problems in general is carried out, based upon a series of radiometer noise and gain change measurements made as a function of subdish switching frequency. A method of signal calibration is discussed, with primary emphasis on radioastronomical applications. The use of the tilting subdish system in the investigation of lunar temperature changes during a total lunar eclipse indicates that the system can be used for sensitive radioastronomical measurements.
Biasing Circuitry for Tunnel Junctions
Authors: Longacre Andrew
Published: February 2004

A method of generating bias has been developed which greatly facilitates studying the voltage-current characteristics of tunnel junctions. A triangle wave to sweep the bias, a dc level for offset, and a small amplitude sine wave used for taking derivatives are all summed in a dc amplifier. The junction is biased by the attenuated output of this amplifier with either a high or low impedance load line. The two transistor circuits which largely comprise this bias supply are compact and battery powered, minimizing grounding problems.
A Simplified Pulsed Bridge for Use in Low Temperature Resistance Thermometry
Authors: MacDonald Douglas B. , Kornreich Philipp G.
Published: February 2004

We present a comprehensive description of an inexpensive bridge circuit suitable for use with low temperature resistance thermometers. The bridge is energized by a pulse source with a duty cycle of 8.33×10−5. Average power dissipation of 10−8 W in the resistance thermometer is achieved by means of the pulsed operation. An oscilloscope is used as a detector. The ``range gate'' effect of the oscilloscope serves as an effective noise filter. A precision of four significant figures is obtained with this system.
Use of EPR to Measure the Termination Rates of Photochemically Produced Organic Free Radicals in Solution
Authors: Hamilton Edwin J. , Wood David E. , Hammond George S.
Published: February 2004

A general method for the measurement of absolute rate constants for the termination of photochemically produced organic free radicals in solution has been developed. Radicals are generated in the cavity of an EPR spectrometer by high intensity uv irradiation of a sample; the disappearance of EPR signal due to intermediate radicals is followed after irradiation is abruptly stopped. This technique permits determination of rate constants as fast as diffusion controlled.
Pyrolytic Graphite in the Design of a Compact Inert Heater of a Lanthanum Hexaboride Cathode
Authors: Vogel S. F.
Published: February 2004

Pyrolytic graphite serves two functions in a new type of LaB6 cathode; it supports and heats the LaB6 emitter. The high anisotropic resistivity of pyrolytic graphite allows a compact heater-emitter design a few millimeters in size, and the chemical compatibility of graphite with LaB6 at the operating temperature of about 1500°C prevents any lifetime reducing chemical reactions between the two materials. Typical heating power inputs have been measured to be 15 W at a heating current of about 3 A. One of these LaB6 cathodes has been tested in a demountable vacuum system at an average emission current density of 1.6 A/2cm for over 900 h without signs of impending failure.
Simple Versatile Techniques for Qualitative and Quantitative Evaluation of Spark Source Mass Spectrographic Plates
Authors: Owens Edward B.
Published: February 2004

Qualitative analysis is performed by comparing unknown spark source spectra with reference spectra made from mixtures of metal oxides and salts with graphite. Quantitative evaluation is accomplished with a densitometer and added equipment that allows the analyst to choose any one of six methods of data treatment. The maximum blackening of the spectral line can be determined in terms of %T, 1−T, or I (ion density); or the line can be scanned while the blackening is integrated in terms of ∫%T, ∫(1−T), or ∫I. All measurements are read out in digital form. A method of internal system check, correction, and adjustment is described.
A Lithium Ion Source Using the Surface Ionization Process
Authors: Remy M. , Haug R.
Published: February 2004

We have constructed a capillary ion source using the surface ionization of lithium on rhenium. Currents of 400 μA during 300 h, or 100 μA during 1000 h, can be obtained; the life span of the source is only limited by the capacity of the lithium reservoir.
Improved System of Methane Synthesis for Radiocarbon Dating
Authors: Buddemeier R. W. , Young A. Y. , Fairhall A. W. , Young J. A.
Published: February 2004

An improved design for a catalytic hydrogenation converter which can convert up to 5 liters·atm of CO2 to methane with negligible losses is described. A palladium alloy hydrogen diffusion cell is used for selective removal of excess hydrogen after completion of the reaction. This innovation in purification technique permits quantitative methane recovery over a wide range of sample sizes and significantly reduces the number of man-hours required to process a sample.
Optical Transformation of Field Ion Micrographs
Authors: Rendulic Klaus D. , Müller Erwin W.
Published: February 2004

A field ion micrograph approximately resembles a stereographic projection of a hemispherical tip. By a second imaging through an objective with a strong barrel type distortion (fish eye lens) one can obtain orthographic and gnomonic projections as well as perspective images of the hemispherical metal crystal. The method can be extended to generate stereoscopic pictures of the tip surface for 3-D viewing.
Apparatus for Magneto-Optical Studies of Magnetic Structures at Low Temperatures
Authors: Huebener R. P. , Kampwirth R. T. , Rowe V. A.
Published: February 2004

A magneto-optical apparatus is described which is used for studies of magnetic structures at liquid helium temperatures. The system employs the high specific Faraday rotation of a mixture of EuS and EuF2. A resolution of about 20 μ has been obtained.
Energy Resolution of the Conventional Time-of-Flight Mass Spectrometer
Authors: Sanzone George
Published: February 2004

The resolutions of time-of-flight (TOF) mass spectrometers using multiple acceleration are compared with respect to their ability to compensate for initial ion velocities while operating in the space focusing mode. A theorem is proved which demonstrates that the Wiley-McLaren two-step TOF has the theoretical limit for energy resolution of a large class of spectrometers and has the practical limit for all other conventional TOF's which employ time independent fields. An alternate explanation is given for the increased resolution obtained by Studier.
Dissection Methods for Measuring the Characteristics of Expanding Clouds
Authors: Swift H. F. , Preonas D. D. , Turpin W. C.
Published: February 2004

Dissection techniques were developed to measure dynamic parameters of debris clouds from energetic events such as explosions or impacts. Various configurations of plates and grids were designed for selectively interrupting expanding clouds to generate discrete and identifiable debris segments. Variations of the basic technique were used to obtain dynamic data pertaining to (1) debris distribution, (2) velocity profiles, (3) segment trajectories, (4) departure sequences from the region of original impact, and (5) impulse profiles. Extensive technique evaluation indicated that no artificial alterations of dynamic parameters were produced by the dissection process.
High-Sensitivity Linear Dichroism Measurement with a Modified Commercial Spectropolarimeter
Authors: Mandel R. , Holzwarth G.
Published: February 2004

An electro-optic device is described which permits the measurement of polarized absorption spectra (linear dichroism) to high sensitivity between 1850 and 5000 Å in a commercial spectropolarimeter. For polarimeters with the standard electro-optic circular dichroism attachment, or for any instrument measuring circular dichroism by the electro-optic technique, the new device consists merely of a simple electronic power supply and a quartz depolarizer. Sensitivities on the order of 10−4 absorbance units are easily attainable.
A Versatile Molecular Beam Scattering Apparatus Utilizing Electron Bombardment Detection
Authors: Bickes R. W. , Bernstein R. B.
Published: February 2004

A versatile crossed molecular beam apparatus has been designed, fabricated, and tested. The instrument consists of a large cylindrical stainless steel ``scattering chamber'' which contains differentially pumped nozzle-skimmer and detector chambers. The crossed beams intersect at the cylinder axis. The detector assembly can be rotated about the scattering center from −43 to +133° with respect to the primary beam direction. The scattered intensity is measured using a modified Weiss electron bombardment ionizer with quadrupole mass filter. Over-all detection efficiency of the system for a thermal argon beam is 0.25%. Background discrimination is effected by means of double modulation (synchronous chopping of both crossed beams with beat frequency lock-in detection). The apparatus has been employed in studies of the rainbow scattering of Ar by various gases.
Junction Field Effect Transistors at 4.2 K
Authors: Wagner R. R. , Anderson P. T. , Bertman B.
Published: February 2004

We report the behavior of 24 different types of junction field effect transistors at 4.2 K, giving the characteristics (gain, bandwidth, and noise) of the six different types which make satisfactory amplifiers.
Rotating Polarizer Technique for Measuring the Coherent Relaxation Rates of Excited Atomic States
Authors: Saloman E. B. , Baghdadi A. , Halpern J. B.
Published: February 2004

A new technique for studying the relaxation rates of excited atomic states, using a rotating linear detection polarizer, is described. Theoretical expressions for the resultant signals are obtained and a procedure for adjusting the various experimental parameters is explained. This method separates the various coherent signals and provides a large signal intensity with much more convenience and stability than methods previously used.
An Instrument for Automatic Correction from the Background Due to Uncorrelated Events in Nuclear Pulse Spectrometry
Authors: Cova S. , Bertolaccini M.
Published: February 2004

For measurements of the statistical distribution of parameters of pulses (peak amplitude, etc.), a technique is introduced to measure accurately the background due to pulses not correlated in time to the events of interest. This technique is applicable when an event marker signal, correlated in time to the events of interest, is available, i.e., always in time measurements and often in other cases. The basic principle is to make cycles of two successive measurements, in which the probability of measuring a background pulse is the same for both, while the one of measuring an event pulse is much higher in the first measurement; the results of the two measurements must be treated differently. The technique and its applications to amplitude and time measurements are considered in detail. The instrument developed is presented together with some experimental results.
Rotating Cylinder Apparatus for Rarefied Gas Flow Studies
Authors: Alofs Darryl J. , Springer George S.
Published: February 2004

A rotating cylinder type apparatus is described, suitable for determining drag in cylindrical Couette flow of rarefied gases, and for evaluating tangential momentum accommodation coefficients at gas-solid boundaries. The apparatus is equipped with a damping device using diffusion pump oil for eliminating undesirable oscillations in the system. Tangential momentum accommodation coefficients of argon on aluminum were determined with an accuracy of ±2.5%. The results obtained indicate that the apparatus may be used over a wide pressure range, corresponding to free molecule and continuum flow conditions.
An Automated Atomic Absorption Spectrophotometer for the Acquisition of Thermodynamic Data
Authors: Rapperport E. J. , Pemsler J. P. , Adler E.
Published: February 2004

An atomic absorption spectrophotometer has been constructed to provide automated measurement of elemental vapor pressure changes with temperature. Three alloy-containing absorption cells and a blank reference cell are fixed in a furnace which is automatically moved to position each cell sequentially on the spectrophotometer optic axis, while the furnace independently follows a predetermined time-temperature profile. Measurements of spectral intensities and thermocouple outputs are recorded at selected intervals and are printed and punched on paper tape. Subsequent computer processing of the punched data yields values of thermodynamic activities and partial molar enthalpies and entropies of the alloy constituents.
A High Speed Spectrograph Shutter
Authors: Wood S. M. , Miller M. H.
Published: February 2004

An event triggered spectrograph shutter with a speed of 70 m·sec−1 has been constructed and used to study shock tube plasmas. The shutter can simultaneously serve two high aperture spectrographs. Several sequential exposures of 8–150 μsec can be obtained over a period of 300 μsec. Jitter in opening and exposure times is 6–8%. Delay times can be varied mechanically in a simple and predetermined way.
Synthesis of Diffraction Line Profiles from Continuous Scanning Data
Authors: Gangulee A.
Published: February 2004

Two methods have been developed for synthesizing diffraction line profiles from continuous scanning data. The first method uses numerical analysis where segments of profiles are approximated by one or more polynomials. The second method employs Fourier analysis to obtain the Fourier coefficients of the diffraction profile from continuous scanning data. Examples of application are discussed.
A System for Determining the Mass and Energy of Particles Incident on a Substrate in a Planar Diode Sputtering System
Authors: Coburn J. W.
Published: February 2004

A bakable ultrahigh vacuum system has been constructed to sample the particle flux incident on the substrate of a planar diode sputtering system. A beam of particles from the discharge is extracted into a long mean free path environment where it passes through a 90° deflection electrostatic analyzer into a quadrupole residual gas analyzer. The mass spectra of positive ions incident on a substrate during dc sputtering of copper and aluminum bronze are shown and the influence of hydrogen contamination is illustrated. The energy distribution of the Ar+ ions is presented for several values of the substrate bias.
Electron Multiplier Efficiency for Hydrogen Atom Detection
Authors: McKnight R. H. , Crandall D. H. , Jaecks D. H.
Published: February 2004

The efficiency of an electron multiplier for detecting fast hydrogen atoms has been measured by a coincidence technique employing Lyman α photons from the induced decay of metastable hydrogen atoms. Results reported are for the energy range 3–20 keV.
Application of Frequency Locking and Control to an Autodyne Oscillating NMR Detector
Authors: Brandwein Leonard , Lipsicas Max
Published: February 2004

The use of an autodyne oscillating NMR detector is discussed with particular reference to experimental situations where signal averaging or magnet field locking are involved. A frequency locking scheme which has proved very useful in this connection is described. Some additional circuits used in this locking scheme are discussed as applied to a Robinson circuit.
A Hot Wire Method for Low Velocity with Large Fluctuations
Authors: Sadeh W. Z. , Maeder P. F. , Sutera S. P.
Published: February 2004

The theory of the hot wire anemometer is reviewed with emphasis on low velocity flow with relatively high turbulence intensity. A constant temperature linearized method is developed specifically for such measurements. Results for turbulence intensity as high as 90% are presented.
An Automatic Zero Suppression Circuit
Authors: Trigg D.
Published: February 2004

A practical technique is described for high sensitivity recording of input signals having a large dynamic range. The circuit senses when the input signal exceeds preset limits and applies a precise and stable baseline shift in the correct sense to maintain the output within these limits. The circuit may be regarded as a black box to be inserted between an analog signal source and a recording device and requiring no alteration to either. A system is presented in detail which permits recording of signals within the range −5.4 to +6.1 V on a recorder at 1.0 V full scale sensitivity. The drift introduced by this system is maintained at less than 1 mV/°C over a wide ambient temperature range. A discussion of the sources of error is presented and techniques for reducing these errors are described.
A Microwave Frequency Marginal Oscillator for Electron Spin Resonance
Authors: Walsh W. M. , Rupp L. W.
Published: February 2004

A compact, inexpensive, and surprisingly sensitive microwave frequency ESR spectrometer has been developed. A Gunn diode placed directly in the sample cavity and operated near the threshold of oscillation is the central feature of the unit.
Improvements in an Electron Microscope for Clean, Quiet, Vibrationless Operation
Authors: Marcus R. B. , Calbick C. J. , Sheng T. T.
Published: February 2004

A new vacuum system has been designed and constructed for a Siemens Elmiskop I electron microscope in order to provide a cleaner environment about the specimen during normal use of the instrument, and to prepare the instrument for the addition of an ultrahigh vacuum specimen chamber for in situ film growth studies. Liquid nitrogen sorption pumps are used on the upper and lower parts of the microscope column, and an Orb-Ion pump is used to pump differentially on the large Siemens specimen chamber (with airlock). An impedance tube at the top and an impedance aperture at the bottom of the specimen chamber restrict the gas flow rate into the chamber to 7.04×10−3 liter/sec. Under operating conditions the pressure in the upper and lower parts of the microscope is <2×10−5 Torr, the (large Siemens) specimen chamber pressure is <2×10−6 Torr, the hydrocarbon contamination rate is ∼0.7 Å/min, the specimen changing time is 2 min, and the plate changing time is 4 min. The corresponding figures in the original unmodified microscope are ∼2×10−4 Torr, ∼2×10−4 Torr,∼ 500 Å/min, 1 min, and 4 min. Further advantages are noiseless and vibrationless operation.
Continuously Operating 4He Evaporation Refrigerator
Authors: DeLong L. E. , Symko O. G. , Wheatley J. C.
Published: February 2004

A simple and compact device was developed to provide continuous, self-regulating refrigeration at approximately 1.3 K. The temperature of the device remains nearly constant, independent of external power, up to a critical power. For a molar flow rate of 10−4 moles/sec, the refrigerator can absorb 4.5 mW. Such a refrigerator should be suitable for condensing 3He in a 3He–4He dilution refrigerator.
A Faraday Type Magnetometer with an Adjustable Field Independent Gradient
Authors: Lewis R. T.
Published: February 2004

The design and performance of a set of coils for providing the field gradient in a Faraday type magnetometer are described. In contrast to systems which employ special pole caps for this purpose, these coils produce a gradient which is field independent, maintaining the high sensitivity of the Faraday technique at all fields. The facility of being able to adjust the gradient electronically is also shown to have several advantages. The coils described can produce a gradient as large as 485 Oe/cm in a region 3 mm high in which the gradient varies by less than ±0.1%. The magnetometer can detect absolute magnetic moments as small as 10−6–10−7 emu.
A Pyroelectric Energy Meter
Authors: Lachambre Jean-Louis
Published: February 2004

The energy measurement of high peak power CO2 laser pulses is generally accompanied by permanent damage to the surface of the detecting element. The use of appropriate optics simultaneously reducing the field density and enlarging the detection area appears to be a successful mean to bypass this difficulty. The instrument described in this paper combines diverging optics with a large sensing sheet made of pyroelectric material in order to provide fast response. The device is capable of detecting a 10 J, 10 MW peak power pulse at a repetition rate of 10 pulses/sec. Its spectral response is flat from 0.36 to 12 μ.
Improving the Field Stability of a Commercial Electromagnet for High Resolution EPR
Authors: Foulger P. H. , Harvey J. S. M. , Munnings R. H.
Published: February 2004

High resolution electron paramagnetic resonance spectroscopy often requires a magnetic field stability of 1 ppm. A simple NMR field regulation circuit is described which improves the stability of a Harvey-Wells L-128, HS-1365B current regulated electromagnet system by better than one order of magnitude to meet this requirement.
An Electronic Particle Counting and Dispensing Device for Use in Animal Injection Experiments
Authors: Mullaney P. F. , Coulter J. R.
Published: February 2004

An electrical resistance counter of the Coulter type has been designed to count particles intended for animal injections and to dispense them into a package (a length of polyethylene medical tubing). The packaged particles are used for injections at a later date. In a typical application, two thousand 10 μ spheres can be counted and loaded into a 61 cm length of PE-50 tubing (total volume 0.25 ml) in about 5 sec. The accuracy of the count has been determined by an independent method.
Space Focusing of Polar Diatomic Molecules Using Electrostatic Hexapole Fields
Authors: English Thomas C.
Published: February 2004

Space focusing of polar diatomic molecules using an electrostatic hexapole field is discussed, and it is shown that focused molecular trajectories in this type of field are properly described by a Jacobian elliptic function. Although a detailed mathematical treatment is given, emphasis is placed upon the physical nature of the trajectories. These results are applied to the design of a molecular beam resonance apparatus using hexapole fields, and it is shown that, in practice, several simplifying approximations (with little loss in accuracy) may be made which allow design calculations to be carried out using only a slide rule.
Small Coaxial Gun for Plasma Injection Studies
Authors: de la Fuente H. , Forsen H. K.
Published: February 2004

Properties of plasmas produced by a 1.5 cm diam coaxial gun are investigated. Gas is provided from the center electrode material which is interchangeable. Materials such as lithium, titanium with occluded hydrogen, and carbon are used as the plasma source. Typically, a lithium plasma is produced which has equal ion and electron energies of 25 eV and 1017−1018 particles/pulse.
Magnetic Densimeter-Viscometer
Authors: Hodgins M. G. , Beams J. W.
Published: February 2004

A combination magnetic densimeter and viscometer, which essentially simultaneously measures the density and viscosity on 0.3 ml specimens of fluids, is described. A small cylindrical buoy is freely suspended magnetically and coaxially with a larger surrounding cylindrical glass tube which contains the fluid in which the buoy is completely immersed. After calibration, the electrical current in the air core solenoids which magnetically support the buoy measures the density of the fluid while the period of revolution at constant power input determines the viscosity. The density can be measured to the order of magnitude of one part in 106 and the viscosity to one part in 104.
Far Ultraviolet Spectroscopy of Solids in the Range 6–36 eV Using Synchrotron Radiation from an Electron Storage Ring
Authors: Rubloff G. W. , Fritzsche H. , Gerhardt U. , Freeouf J.
Published: February 2004

The 240 MeV electron storage ring at the University of Wisconsin Physical Science Laboratory provides an intense polarized continuum light source in the far ultraviolet. Experimental equipment is described which allows the measurement of optical reflectivity and absorption of solids in the photon energy range 6–36 eV at temperatures between 90 and 500 K with this source. A discussion of the experimental procedures and the performance of the system is presented.
Optical Pyrometer with Microsecond Resolution Time
Authors: Korneff T.
Published: February 2004

A three color, fast response optical pyrometer utilizing the double-ratio method is described. The temperature of a rapidly heated source is displayed on a cathode ray oscilloscope as a function of time. Direct current sources can also be observed. The basic approach involves a beam splitter, a three-channel logarithmic photometer, and a summing amplifier. For proper choice of wavelength, the measurement is independent of the emissivity of the source. Results are shown for an exploding wire.
A Miniature Vacuum Furnace for Mössbauer Spectroscopy
Authors: Sundaram V. S. , Gupta V. P. , Subbarao E. C.
Published: February 2004

The complete geometry and operation of a simple miniature furnace designed for heating the sample up to 1000°C for Mössbauer spectroscopy are reported. Cooling coils over the entire body of the furnace protect the source and counter from heating. Maintenance of constant temperature (±1°C) for several hours, temperature uniformity (±1°C) across the sample, and flexible use of vacuum, ambient, or inert atmosphere constitute the special features.
On-Line Digital Spectral Analysis
Authors: Calvert W. , Greenwald R. A. , Geissler K. H.
Published: February 2004

The paper describes a straightforward spectral analysis system using the fast Fourier transform algorithm and an on-line digital computer in the laboratory. The technique is backed by a sound mathematical foundation and yields directly both components of the cross spectrum for a process measured at two points as well as the power spectrum at either point. For a potential user, certain of the details of implementing the system are included. A specific example, that of correlating density fluctuations in a plasma, demonstrates the sensitivity of such a system.
Sulfurization Technique for Stabilizing Germanium Surfaces
Authors: Janssen H. , De Bock A.
Published: February 2004

Most surface states on germanium single crystals are quite sensitive to changes in the local environmental conditions. One of the methods of stabilization is to cover the surface with a GeS layer by the process of chemisorption and migration of sulfur atoms at elevated temperatures. A complete recipe of the sulfurizing technique is given and the results of a structural analysis of the reaction product are presented. No crystalline structure of the layer is detected for films a few microns thick.
Windowless Photoelectron Spectrometer for High Resolution Studies of Solids and Surfaces
Authors: Cashion J. K. , Mees J. L. , Eastman D. E. , Simpson J. A. , Kuyatt C. E.
Published: February 2004

An ultrahigh vacuum photoelectron spectrometer capable of measuring electron energy distributions for solids and chemisorbed gases at photon energies of 16.8, 21.2, 26.9, and 40.8 eV is described.
Fast Rejuvenation of Copper-Beryllium Multipliers Used with Mass Spectrometers
Authors: Märk Tilmann D. , Oskam H. J.
Published: February 2004

A simple procedure for restoring the signal-to-noise (S/N) ratio of electron multipliers is described. The method consists of removing the surface contamination on the dynodes by chemical etching and cleaning.
A New Tuning Method for Dye Lasers
Authors: Sousa John A. , Roach Joseph F.
Published: February 2004

An instrument is described that allows extraction of various wavelengths of monochromatic coherent light from a variety of dye solutions. Since no external optics are required, problems of optical cavity degradation are minimized.
A High Resolution, High Sensitivity Channel Plate Image Intensifier for Use in Particle Spectrographs
Authors: Galanti M. , Gott R. , Renaud J. F.
Published: February 2004

Details are presented of an image intensifier for electrons using a channel plate, scintillator, and fiber optics combination, which gives a reduction in exposure time of several thousand compared to a photographic plate. During the course of the investigation, measurements were made on the characteristics of the channel plate for various electron energies and angles of incidence.