bluuebunny/crossref_metadata_2025 huggingface dataset:
Toroidal sample coil for nuclear quadrupole resonance experiments at high pressure
Authors: Zussman A. , Oron M. , Rapoport E.
Published: March 2003

Use of toroidal sample coils for 14N NQR experiments at high pressure was found to improve the sensitivity of detection of the NQR signal in pressure cells constructed of steel. NQR measurements, in particular spin-lattice relaxation time T1 in solids, can therefore be performed in steel cells with the same sensitivity but to higher pressures than are possible in beryllium–copper pressure vessels.
Measurement of shear stress near a stagnation point
Authors: Baines W. Douglas , Keffer James F.
Published: March 2003

Wall shear stress in the stagnation region of an impinging air jet was measured for stationary and moving surfaces, using a flush-mounted, hot-film probe. The response for the dynamic case proved inadequate and an alternative technique was developed which used a hot-wire probe displaced slightly from the wall. A Hiemenz flow analysis was employed to correct for the separation effect.
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u fracture device for Auger electron spectroscopy
Authors: Moorhead R. Dale
Published: March 2003

An in situ fracture device for Auger spectroscopy is described. The device is designed to handle small tensile specimens or small double-cantilever beam specimens and is fully instrumented with load and displacement transducers so that quantitative stress–strain measurements can be made directly. Some initial test results for specimens made from 4130 and 1020 steel are presented. Results indicate that impurity segregation at interfaces other than grain boundary may play a significant role in the mechanism of ductile fracture.
Electron gun for generation of subnanosecond electron packets at very high repetition rate
Authors: Weinfeld Michel , Bouchoule André
Published: March 2003

In order to create and study trapped particle modes in a plasma column, we have designed an electron gun which delivers packets with a duration shorter than 1 nsec at energies of about 100 eV, and with a repetition frequency of several hundred megahertz. This gun is made with parts of a classical disk-sealed microwave triode. This paper describes the gun itself and the pulse generator used to modulate it. Some results concerning trapped particle modes are shown in conclusion.
Zero-crossing signal averaging system for Fabry–Perot interferometry
Authors: Lao Q. H. , Schoen P. E. , Chu B.
Published: March 2003

The detailed design and performance of a zero-crossing signal averaging scheme for Fabry–Perot (FP) interferometry, which has been successfully applied to the study of Rayleigh–Brillouin scattering of gases, are presented. The system, which locks the start of each scan of a multichannel scaler (MCS) to the laser frequency, and assigns a definite frequency to each channel of the MCS, can be adapted to any piezoelectrically scanned FP interferometer. It has a variable scan rate permitting magnification of the spectrum over regions of interest and also provides sample pulses for synchronously advancing the memory address of standard multichannel scalers with the scanning FP interferometer. The principal features of our design are simplicity, adaptability, and low cost.
Efficient energy coupler for electrodeless lamps
Authors: Gabriel Fred C.
Published: March 2003

A new energy coupler of high electrical efficiency has been developed for the excitation of electrodeless lamps. The coupler can be located remotely from the source of rf energy and provides an automatic high-voltage field for lamp starting. Details are given of the construction of a coupler designed for operation at 27.12 MHz as a light source for atomic absorption spectrophotometry.
Parallelism controller for a scanning Fabry–Perot
Authors: Bechtle Daniel
Published: March 2003

A controlling unit has been developed to bring the plates of a piezoelectrically scanned Fabry–Perot into parallelism, and keep them parallel for long periods. Using feedback from the transmitted signal with repeated scans stored in a multichannel analyzer, spectra of several hours duration may be obtained. The controller is directly compatible with a commercial ramp generator and has a total materials cost of $300.
Determination of the stress in optical fibers by means of a polariscope
Authors: Saunders M. J.
Published: March 2003

A polariscope has been built for studies of the stresses in optical fibers. The stress optic coefficient has been determined for five different fibers and for one of the preforms from which one of the fibers was drawn. It was found that the coefficient of the preform was larger than that of the fiber from which it was drawn. Calculations based on measurements on a Corning B fiber indicate that the residual stress in the cladding is compressive. The polariscope has also been used in conjunction with a fiber-drawing machine and a diameter-measuring instrument to determine the relationship between the tension of a Vycor-clad quartz fiber, as it is being drawn, and the diameter of the fiber.
Improved microwave-discharge source for uv photoemission
Authors: Vorburger T. V. , Waclawski B. J. , Sandstrom D. R.
Published: March 2003

A microwave-discharge uv light source has been improved to yield significant photon fluxes at 26.9 and 40.81 eV. In order to optimize the 26.9-eV (NeII) and 40.81-eV (HeII) radiation, the discharge was operated at ∼2.5 Pa (0.019 Torr) in an external constant magnetic field of ∼0.070 T (700 G), which, together with the oscillating electric field of the cavity, produces electron cyclotron resonance. When the discharge conditions were optimized for production of 40.81-eV photons, features near the Fermi energy in the photoemission distribution from W(100) for 40.81-eV photons are approximately 6% as intense as the corresponding features in the distribution for 21.22-eV photons. We estimate that under these conditions the flux of 40.81-eV photons is roughly 50% of the flux of 21.22-eV photons. Photoemission energy distributions with hν=16.85, 21.22, 26.9, and 40.81 eV have been measured for saturated exposures of CO on W(100) at a temperature of ∼80 K. The variation in these data with photon energy is important for making orbital assignments to the energy levels of adsorbed molecular CO.
Method permitting continuous measurement of pulse height variations
Authors: Yamashita Mikio
Published: March 2003

A method is described which provides a dc voltage corresponding to the average pulse height of input pulses with a Gaussian pulse height distribution and thereby permits accurate and successive measurements of pulse height variations by the use of a digital voltmeter and associated equipment.
Constant current ballast
Authors: Rosenthal Louis A.
Published: March 2003

When placed in series with a voltage source of 5 V or more, the constant current ballast will pass a preset constant current independent of voltage or resistance variations. Performance and characteristics for a system capable of delivering up to 0.6 A are described.
Performance characteristics of an electronically tunable acousto-optic filter for fast scanning spectrophotometry
Authors: Shipp William S. , Biggins John , Wade Charles W.
Published: March 2003

A commercially available CaMoO4 tunable acousto-optic filter has been evaluated for use as a monochromator and modulator for incorporation into a rapid scanning spectrophotometer for the wavelength range 450–750 nm. The construction of a suitable rf driver is described. The bandwidth of light transmitted by the filter was found to be between 2 and 6 Å, permitting excellent spectral resolution. The contrast ratio was greater than 1400 over the major portion of the tuning range, and the skirt rejection was 35–40 dB for 1-nm-wide bands 10–100 nm distant from the center wavelength. The transmission of the filter can be switched in 20 μsec, and modulation frequencies up to 25 kHz are attainable without appreciable loss of transmission. With a conventional light source the output intensity of monochromatic light is comparable to grating monochromators. Stray light can be effectively compensated for by transmission modulation and phase-sensitive detection of the output. We show that the use of the filter as a monochromator is in many respects superior to the other devices which have been used previously for rapid scanning. The filter may also be used as a light modulator or multiple-beam spectrophotometer and, by virture of its electronic control and ease of interfacing with digital computers, can be considered to be a programmable light source.
Measurement of optical autocorrelation functions using a signal averager
Authors: Crooker P. P. , Hoover J. A.
Published: March 2003

We show that the autocorrelation function of an optical signal may be simply obtained using a signal averager and a weighted signal-averaging technique. The method applies to the measurement of either intensity fluctuations or photocount fluctuations, and we present expressions for the weighted signal average and its error for each case. Finally we test the results experimentally and compare the data with the corresponding theoretical expressions.
Fast electrometer amplifier for astronomical photometry
Authors: Oliver J. P.
Published: March 2003

A compact, inexpensive, and reliable electrometer which will respond to frequencies from dc to a few kilohertz is described. The high megohm feedback resistors are shared with a built-in calibration and zero suppression current source, resulting in substantial savings in space and money.
A multichannel ion mass spectrometer in laser-produced plasma studies
Authors: Goforth R. R.
Published: March 2003

The theory and operation of a time-of-flight mass spectrometer employing a multichannel electrostatic analyzer are discussed with emphasis placed on laser-produced plasma studies. It is shown that the finite length of the analyzer leads to enhanced mass resolution. A method of in situ calibration of the analyzer channels is described, and measurements of the resolution and beam divergence are presented. Use of the mass spectrometer to calibrate ion-collecting probes for mass and kinetic energy measurements is also considered.
Variable beam attenuator for 10.6 μm
Authors: Leeb Walter R.
Published: March 2003

A double-prism variable-beam attenuator for 10.6 μm, which is based on frustrated total internal reflection, has been built. The attenuation can be varied between 2 dB and more than 105 dB, and the transmitted power is independent of the beam polarization. For high attenuations, the phase behavior is that of a quarter-wave plate. With the aid of a visible laser beam, the prism gap can be monitored interferometrically.
Computer-controlled Auger spectrometer
Authors: Chou N. J. , Hammer R. , Bednowitz A.
Published: March 2003

The present paper describes the system configuration of a computerized Auger electron spectrometer, which incorporates various schemes of complicated process control as well as automatic data acquisition, reduction, and retrieval. Central to the system is a sensor-based computer which controls the spectrometer and interfaces with a host computer where large-scale computations can be performed. With a graphic terminal as its operator’s station, the system can operate in either automatic or interactive modes. Examples of the process control implemented for the system are given, accompanied by the circuit adaptations necessary for hardware interfacing. Spectral data obtained by the system indicate that the rate of data acquisition has increased by two orders of magnitude with a signal reproducibility of better than 0.5%. Experiments with controlled surface contamination suggest that the spectrometer sensitivity can be doubled by time averaging a number of spectra measured under identical conditions.
Sample heating and simultaneous temperature measurement in inelastic electron tunneling spectroscopy
Authors: Bowser W. M. , Weinberg W. H.
Published: March 2003

A method is described whereby the oxide surface in inelastic electron tunneling spectroscopy (IETS) experiments may be heated resistively with its temperature measured simultaneously via a four-point probe scheme. The utility of the method insofar as surface chemistry experimentation is concerned is demonstrated by following the dehydroxylation of the Al2O3 barrier in an Al–Al2O3–Pb tunnel junction as the preparation temperature is increased from 20 to 250 °C.
Saturable absorber for iodine laser radiation
Authors: Ishii S. , Fong K. , Ahlborn B.
Published: March 2003

An absorbing medium for 1.315-μm radiation was produced by pulsing an electrical discharge through CF3I gas or molecular iodine vapor. The absorption varies as a function of time and reaches 100% within a measuring accuracy of 1% for a period of about 2 μsec.
Electronic speed control for the analytical ultracentrifuge
Authors: Van Es W. L.
Published: March 2003

An electronic speed control for the Spinco model E analytical ultracentrifuge is described. An accuracy of better than 1:104 is obtained, using digital circuits and a crystal-controlled reference oscillator. Acceleration is automatic and the circuitry is provided with several safety devices.
Floating input, optically isolated, high-voltage measurement probe
Authors: Bleys C. A.
Published: March 2003

A simple, floating input, high-voltage measurement probe is described. The divider is purely capacitive and is completely isolated from earth. Optical fibers are used to transmit information to the recording instruments which can be operated at earth potential. The probe can easily be constructed in a laboratory and is adaptable to a wide range of voltages up to 1 MV. The unit built has a risetime of 80 nsec and exhibits good linearity and accuracy.
All-silica cell for pulse radiolysis studies of liquid crystals with low-energy (600 keV) electrons
Authors: Saito E. , Belloni J.
Published: March 2003

A cell for pulse radiolysis of liquids, having a silica window 0.2 mm thick for entrance of the electron beam, is described.
Improved technique for shaping long fragile alkali halide crystals
Authors: Kim K. Y. , Terry R. E. , Ruoff A. L.
Published: March 2003

An improved method of chemically shaping very fragile long crystals into cylindrical shape by the chemical lathe has been developed and successfully applied for shaping meter-long LiF and NaCl single crystals. The variation of the diameter of the finished cross section is less than 0.1 mm.
Simple masking technique for shaping magnetic epitaxial garnet films for ferromagnetic resonance
Authors: Stakelon T. S. , Gerhardstein A. C.
Published: March 2003

A simple and inexpensive technique is described by which disks of magnetic epitaxial garnet films may be chemically shaped. Using silicone rubber adhesive as a mask, disks of film as small as 0.05-cm diameter, suitable for ferromagnetic resonance studies, may be easily produced.
Portable high-temperature catalytic reactor: Application to air pollution monitoring instrumentation
Authors: Stetter J. R. , Blurton K. F.
Published: March 2003

A portable, battery operated microcatalytic reactor capable of safe controlled temperature operation from ambient to 800 °C is described. This system was designed to interface with a carbon monoxide air pollution monitoring instrument to provide a method for the continuous selective filtration of air pollutants. It permits a wide range of operating conditions (nature of catalyst, temperature, gas/catalyst contact time) to be fully utilized and significantly increases the application of many present day air pollution detection and monitoring techniques which utilize high-temperature furnaces by allowing portability.
Use of resistance wires for atmospheric turbulence measurements in the marine environment
Authors: Schacher Gordon , Fairall C. W.
Published: March 2003

The dc calibration parameters of hot wires used for wind speed measurements and cold wires used for air temperature measurements have been investigated for wires used in the marine environment. Tungsten hot wires and platinum temperature wires have been calibrated both before, during, and after their use at sea. A scanning electron microscope has been used to determine the surface condition of the wires and the amount of sea salt that is deposited on them. The results show that sea salt is quickly deposited on the wires when they are used at sea but that the deposits are rarely of sufficient thickness to affect the dc calibration of the wires.
New technique in the processing and handling of laser velocimeter burst data
Authors: Kalb H. T. , Cline V. A.
Published: March 2003

A newly developed signal processing and data handling system for use in laser velocimetry is described. The system provides for entry into lower signal-to-noise ratio environments for capture of data from smaller particles than was formerly practical. Experimental data from a two-component Bragg cell directional velocimeter is used in comparing the system with a conventional counter-type processor. Dramatic improvement in the ’’particle lag problem’’ is seen.
Contactless method of measuring resistivity
Authors: Crowley J. D. , Rabson T. A.
Published: March 2003

A method is described for measuring the conductivity of materials without having to make electrical contact with the material. Currents which are magnetically induced in the conducting sample are measured by means of the magnetic fields they produce. Although induction techniques have been used in the past for this type of measurement, the configuration presented here makes it possible to perform absolute measurements of resistivity over a wide range of values for relatively small samples. The theory of the technique, the results of measurements made with it, and a comparison of the technique with other methods are presented.
Automatic ultrasonic absorption spectrometer
Authors: Farrow Michael M. , Olsen Steven L. , Purdie Neil , Eyring Edward M.
Published: March 2003

A completely automatic ultrasonic absorption spectrometer covering the frequency range from 5 MHz to in excess of 250 MHz has been developed. The instrument utilizes Debye–Sears and Bragg reflection of light to modulate the output of a cw argon-ion laser and is interfaced to a minicomputer that interactively controls experimental parameters and accumulates data.
Acoustic measurement system for use in phase transition experiments
Authors: Alexander E. M. , Friedman G. E.
Published: March 2003

An electronic system has been developed whereby the relative velocity and attenuation of an acoustic wave can be measured simply, dynamically, automatically, and simultaneously. The best application for this system is in certain phase transition experiments where acoustic quantities undergo large changes, i.e., the attenuation changes by several dB and the velocity by a factor of two or more. The unique feature of this system is that the output pulse signal is fed into gates that track the changing position of the signal with time. Attenuation is determined from the integral of the signal in one of the gates while velocity information is determined from the time positioning of one of the gate edges.
High-repetition-rate closed-cycle rare gas electrical discharge laser
Authors: Olson Robert A. , Grosjean Dennis , Sarka Benjamin , Garscadden Alan , Bletzinger Peter
Published: March 2003

The recently developed technology of high-pressure molecular lasers has been combined with ultrahigh-vacuum technology to develop a fast-flow high-pressure laser system capable of long-duration closed-cycle operation with rare gases. The system’s economy, reliability, and capability for long-time operation at a high repetition rate make it suitable for avionics, space, and isotope separation applications. High-repetition-rate laser performance has been demonstrated in He–Xe, Ne–Xe, Ar–Xe, and Kr–Xe. Experimental results for high-pressure He–Xe mixtures are given.
Calibrated source of atomic cesium beams
Authors: Yasunaga Hitoshi
Published: March 2003

A demountable cesium source was designed to be useful for surface studies. Atomic cesium beams were emitted by effusion through a capillary bore 0.8 mm in diameter and 6 mm in length. The beam intensity was obtained by measuring the calibrated Auger peak height of cesium on the (100) surface of a tungsten single crystal. Beam intensities from 7×1014 to 1.3×1015 sec−1sr−1 were calibrated as a function of the temperature of the source from 77 to 127 °C. The observed angular distribution exhibits a half-width angle of 9°. The results are compared with available theories.
Tokamak with high-voltage theta-pinch
Authors: Inoue N. , Nihei H. , Yamazaki K. , Ichimura M. , Matsuda T. , Morikawa J. , Uchida T.
Published: March 2003

An experimental device is described which is a combination of Tokamak and a high-voltage theta-pinch. Eight Blumlein lines charged to a maximum of 100 kV are connected to the Tokamak shell which plays the role of a theta-pinch coil, besides stabilizing the plasma. A magnetic pulse with a maximum amplitude of 2.1 kG and a duration of 0.75 μsec is provided by discharging the Blumlein lines simultaneously. Heating of ions by the magnetic pulse is observed.
Inexpensive high-speed dentist drill light chopper and its use in rejecting luminescence background from Raman spectra
Authors: Nemanich R. J. , Solin S. A. , Doehler J.
Published: March 2003

An inexpensive dentist drill laser beam chopper is described. The chopper, which can be tuned for a chopping frequency from 100 Hz to 400 kHz, is compact, stable, and easily constructed. The usefulness of the dentist drill laser beam chopper is demonstrated in a technique for the suppression of luminescence background in Raman spectra. The technique is shown to be capable of almost complete suppression of luminescence with decay lifetimes greater than 10−6 sec.
High-speed light chopper wheel for modulation spectroscopy
Authors: Selzer P. M. , Yen W. M.
Published: March 2003

The construction and use of a high-speed mechanical chopper wheel, compatible with the frequency ranges of most lock-in detectors, is described. The chopper, consisting of an air turbine handpiece and multihole disk, can span the region from 500 Hz to 300 kHz with a single blade change. This device is particularly suited to modulated laser spectroscopy.
Precision high-impedance source for small currents
Authors: Edwall G. , Bengtsson L. G.
Published: March 2003

A constant current source has been designed for use in connection with calibration and constancy checks of instruments measuring current or charge. The current is generated by electrons from a beta-ray source in an evacuated container. With a 270 mCi 90Sr, a current of about 445 pA was obtained with a day-to-day standard deviation in a single measurement of about 0.02%. The standard deviation of measurements in immediate sequence is 0.001%, and the full range of variation of current during a 7-mo period is 0.4%. The source impedance is about 1013 Ω.
Short focus paraboloid
Authors: Arnold B. W. , Offenberger A. A.
Published: March 2003

A method is presented of producing approximately paraboloidal mirror substrates of short focal lengths. The substrate, of aluminum, is machined to a rough spheroid, bent in a strong jig, and then optically finished to a spheroid while bent. When removed from the jig the substrate relaxes and assumes an approximate paraboloidal curve.
Ultrahigh vacuum lock
Authors: Tauber G. , Viefhaus H.
Published: March 2003

An UHV lock is described that makes it possible to change samples, keeping the pressure in the UHV system at 10−9– 10−10 Torr. The samples are mounted on a sample holder that can be heated up to about 1000 DC.
Experimental methods at high pressures. II. A simple internal stirring system for very high pressures
Authors: Lohmüller Reiner E. , Tiltscher Helmut
Published: March 2003

This note describes a magnetic stirring system, which can be installed inside high-pressure autoclaves. Pressures up to 4 kilobar are possible and gaseous or liquid pressurizing media can be used. The stirrer moves a magnetic stirring bar inside the sample cell in a vertical direction. Owing to its simple and efficient design, thermal side effects are very small. The effectiveness of the stirrer is demonstrated by following the rate of solution of PbCl2 in water at various pressures.
In situ demountable, UHV-compatible HeI filter for photoelectron spectroscopy
Authors: Norton P. R. , Tapping R. L. , Goodale J. W.
Published: March 2003

Parylene N, which is UHV compatible, is also shown to be an excellent filter material for selectively removing the 21.2-eV line produced by a helium resonance lamp. A simple modification to a Vacuum Generators ESCA-3 spectrometer allows in situ movement of the filter.
Parallel movement piezoelectric transducer
Authors: Tuma W. , van der Hoeven C. J.
Published: March 2003

This note describes a compact mechanical device that eliminates tilting of a piezoelectrically driven platform.
Gain-insensitive technique for predetection flutter noise cancellation in FM tape recorders
Authors: Cox D. C.
Published: March 2003

A predetection technique for cancelling flutter noise in FM multichannel magnetic analog tape recorders is described. Cancellation of all correlated flutter noise components is done automatically in the phase-frequency domain so the technique is insensitive to amplitude variations and does not depend on any gain adjustments in the system.
Two-axis sample positioning mechanism
Authors: Chaban E. E. , Hagstrum H. D.
Published: March 2003

The design of a sample positioning mechanism for use in a multiexperiment ultrahigh vacuum apparatus is described. It permits positioning of a solid sample for surface studies at four points on a 7.6-cm circle and the independent rotation of the sample about an axis through it at any one of these positions.
Remotely controlled mirror of variable geometry for small-angle x-ray diffraction with synchrotron radiation
Authors: Webb N. G. , Samson S. , Stroud R. M. , Gamble R. C. , Baldeschwieler J. D.
Published: March 2003

A total-reflecting mirror of 120-cm length was designed and built to focus synchrotron radiation emanating from the electron–positron storage ring at the Stanford Linear Accelerator Center (SPEAR). The reflecting surface is of unpolished float glass. The bending and tilt mechanism allows very fine control of the curvature and selectability of the critical angle for wavelengths ranging from 0.5 to 3.0 Å. Elliptical curvature is used to minimize aberrations. The mirror is placed asymmetrically onto the ellipse so as to achieve a tenfold demagnification of the source. The bending mechanism reduces nonelastic deformation (flow) and minimizes strains and stresses in the glass despite its length. Special design features assure stability of the focused image. The mirror reduces the intensity of shorter wavelength harmonics by a factor of approximately 100.
Fast-response apparatus for 11-decade logarithmic current–voltage measurements
Authors: Grimbergen C. A. , Köhnke G. H. P.
Published: March 2003

A measuring setup is described, which is being used for the recording of the logarithmic current–voltage characteristics of semiconductor devices. The logarithmic current to voltage conversion is accomplished by a transistor, connected as a diode, operating as a feedback element avoiding stability problems. The response time at low current is minimized by a compensation of the capacitance of the feedback element. The high current range is extended by a current division which is switched on automatically when the current exceeds 10−3 A. The importance of the quality of the insulating materials, especially that of the logarithmic element, is discussed. Finally the performance of the measuring setup is demonstrated.
High precision four-terminal resistance bridge utilizing a SQUID null-detector
Authors: Rowlands J. A. , Woods S. B.
Published: March 2003

A practical method which may be used to measure small four-terminal resistances at liquid helium temperatures with a precision of 0.1 ppm is described. Sensitivity sufficient to do this with a measuring current of 30 mA in a 500-μΩ resistor is achieved by the use of a SQUID null-detector in a circuit with a high precision MacMartin–Kusters type direct current comparator. A major problem is the production of suitable comparison resistors to use as standards at low temperatures. The choice of material and construction is discussed for a pair of resistors with which it was possible to obtain noise voltages in liquid helium at 4.2 K that were near the Johnson noise in value, and to obtain resistance ratio measurements that were independent of current from 30 to 80 mA within 0.1 ppm. The method may be extended to resistances from 1 mΩ to 10 μΩ in value and even lower if thermoelectric voltages can be suitably reduced.
New, compact instrument for pulse-echo-overlap measurements of ultrasonic wave transit times
Authors: Papadakis Emmanuel P.
Published: March 2003

A new instrument is described which permits the travel time of ultrasonic waves to be measured accurately and conveniently by the pulse-echo-overlap method (PEO). The accuracy and versatility of the PEO method are reviewed, and optimal methods of preparing and interrogating samples are presented. Extensive data on a large blank of fused silica are presented. Longitudinal and shear wave velocities were calculated from the wave travel times through measured thicknesses, and the elastic moduli were subsequently calculated from the velocities and the measured density. Error analysis shows that the measurement of travel time contributed less than 20 ppm to the total error of about 400 ppm in the calculated moduli.
Generation of a fast atomic hydrogen beam
Authors: Van Zyl B. , Utterback N. G. , Amme R. C.
Published: March 2003

Apparatus has been developed for producing a beam of fast hydrogen atoms having energies between 10 and 3000 eV. The procedure involves generation of a beam of hydrogen ions (H−), appropriate ion acceleration and trajectory definition, and ion neutralization by a photodetachment process. The magnitude of the resulting neutral atom flux can be determined to within an uncertainty of less than ±3% by a technique described. An atom beam intensity in excess of 1011 atoms/sec at 1000 eV is readily obtainable, with the intensities at other energies scaling approximately inversely with the primary ion velocity. The advantages of the method over other neutral beam formation procedures are discussed, and techniques allowing considerable enhancement of the beam intensity over that presently achieved are suggested.
Polarization analyzer for vacuum uv and x radiation
Authors: Samson James A. R.
Published: March 2003

A simple analyzer is described for the determination of the degree of polarization of vacuum uv and x rays. The analyzer uses solar blind detectors and, thus, is ideal for use in circumstances where visible and near-uv radiation is present in addition to the radiation under investigation.
Variable-temperature accessory for use with a four-circle x-ray diffractometer
Authors: Strouse Charles E.
Published: March 2003

A nitrogen-stream, low-temperature accessory has been constructed for a four-circle x-ray diffractometer. This device features a glass transfer line with swivel joints that allow the nitrogen stream to follow the motion of the goniometer-head axis during data collection. These joints are of simple construction and immune to ice formation even under conditions of high ambient humidity.
Automatic frequency control system for ultrasonic pulse superposition measurements
Authors: Litov Eliyahu
Published: March 2003

A system for automatic measurements of changes in ultrasonic velocity in solids is presented, using McSkimin’s pulse superposition method.
Improvements in dc-ion milling of semiconductor devices with small dimensions
Authors: Engemann J.
Published: March 2003

Direct current- or radio frequency-ion milling is often used to define submicron patterns of semiconductor devices. One of the main problems therewith is the pattern distortion during etching. Because of charging effects the distortion of insulating patterns (e.g., photoresist) in the dc process can be almost completely suppressed. Therefore in some cases dc-ion etching is preferable. Problems arising with electrical field inhomogeneities (causing uncontrolled etch attacks) on the actual wafer surface are discussed and a method for avoiding these undesired effects is proposed.
Simple, high-power Zeeman modulator for nuclear quadrupole resonance spectroscopy
Authors: Nakamura Nobuo
Published: March 2003

A simple, direct-coupled Zeeman modulator for nuclear quadrupole resonance spectroscopy is described. It provides an antisymmetric square-wave current into a Helmholtz coil in which a magnetic field on the order of 100 G can be generated.
Elimination of errors due to sample polishing in refractive index profile measurements by interferometry
Authors: Stone J. , Derosier R. M.
Published: March 2003

The surface contouring caused by routine polishing of fibers and preforms in preparation for measurement of the refractive index profile has been studied. By observation of the surface interference fringes the effect of polishing on doped preforms is visualized. It is found that composition-dependent thickness variations occur which can cause a sizable error in the refractive index variation deduced by interference measurements in performs (several percent) and in fibers (∼50%). The difficulty is eliminated by several minutes of additional polishing on a hard lap.
Interface for a hand calculator and a digital power supply
Authors: Hummer Charles R. , Burns Donal J.
Published: March 2003

An interface using a simple calculator is described. The calculator display is encoded in BCD and drives the input of a programmable power supply, thus providing a versatile control. This gives the capability of producing a variable step ramp controlled by external clock pulses.
Optical characteristics of the thin-film scintillator detector
Authors: Muga Luis , Burnsed David
Published: March 2003

A study of the thin-film detector (TFD) was made in which various light guide and scintillator film support configurations were tested for efficiency of light coupling. Masking of selected portions of the photomultiplier (PM) tube face revealed the extent to which emitted light was received at the exposed PM surfaces. By blocking off selected areas of the scintillator film surface from direct view of the PM tube faces, a measure of the light-guiding efficiency of the film and its support could be estimated. The picture that emerges is that, as the light which is initially trapped in the thin film spreads radially outward from the ion entrance/exit point, it is scattered out of the film by minute imperfections. Optimum signals were obtained by a configuration in which the thin scintillator film was supported on a thin rectangular Celluloid frame inserted within a highly polished metal cylindrical sleeve.
Optical thickness monitor for sputtered films
Authors: Walsh D. A. , Pukite G. U. , Fenter J. R.
Published: March 2003

A modification to a commercial sputtering apparatus to provide real-time monitoring of the optical thickness of sputtered films is described. The design utilizes a small vacuum window in the center of the targets, permitting the passage of a helium–neon laser beam. Modulation of the beam reflectance by the growing sputtered layer permits in situ thickness measurement.
Elastic moduli of NaCl by Brillouin scattering at high pressure in a diamond anvil cell
Authors: Whitfield Charles H. , Brody Edward M. , Bassett William A.
Published: March 2003

Instrumentation has been developed to conduct Brillouin scattering measurements on small (0.15 mm) transparent single crystals at hydrostatic pressures up to 35 kilobars in a gasketed diamond anvil cell. Phonon velocities obtained this way can be used to calculate elastic moduli as a function of pressure. Results of measurements made on NaCl yield zero-pressure values of c11=4.82×1011 dyn cm−2, c12=1.28×1011 dyn cm−2, and c44=1.27×1011 dyn cm−2. The plots of the elastic moduli versus pressure are fitted with straight lines with the following slopes: ∂c11/∂P=11.62, ∂c12/∂P=3.05, and ∂c44/∂P=0.759.
Apparatus for measuring pressure–volume–temperature relationships of polymers to 350 °C and 2200 kg/cm2
Authors: Zoller P. , Bolli P. , Pahud V. , Ackermann H.
Published: March 2003

An apparatus for determining the specific volume of solid and liquid polymers as a function of pressure (to 2200 kg/cm2) and temperature (30–350 °C) has been constructed. It is based on Bridgman’s bellows method and makes use of a linear variable differential transformer (LVDT) mounted outside the pressure vessel to measure the length changes of the bellows. The off-null output of the LVDT drives a digital indicator, displaying length changes with an accuracy of 0.01 mm, corresponding to a volume change of 10−3 cm3. Typical samples weigh about 2 g. Volume changes of the sample are calculated from the bellows displacement using the pvT properties of the confining mercury, and by using a calibration function determined in a separate experiment. This apparatus is capable of measuring specific volume changes of polymers with an accuracy of 0.001–0.002 cm3/g. Results for a commercial polystyrene in the glassy and liquid states are given.
Nuclear polarization measurements of oriented 3He gas by ’’frequency jump’’ spectrometry
Authors: Timsit R. S. , Daniels J. M.
Published: March 2003

An NMR technique capable of yielding measurements of polarization of highly oriented 3He gas without appreciably disturbing the state of nuclear orientation is described. The nuclear polarization is determined through a measurement of dispersive shifts in the frequency of the NMR oscillator as the magnetic field is swept through resonance, rather than from the magnitude of NMR signals.
Apparatus to demonstrate the piezoelectric effect in crystalline powders
Authors: Battaglia A. , Della Croce U.
Published: March 2003

An electric instrument for testing the piezoelectric properties of crystalline powders is described. The instrument consists of a rf oscillator, frequency modulated at the rate of 150 Hz with deviation of about 2 kHz. The sample is contained in a capacitor of the oscillator tuning circuit. The oscillator frequency is slowly and continuously shifted in a wide range of frequencies. When one of the resonant frequencies of the microcrystal powder belongs to the range of frequencies swept by the oscillator, the sudden fall of the impedance of the tank circuit appears as an amplitude modulation of the rf carrier. This modulation signal detects the piezoelectricity of the sample.
Aluminosilicate sources of positive ions for use in collision experiments
Authors: Feeney R. K. , Sayle William E. , Hooper J. W.
Published: March 2003

Filament sources of all alkali metal and thallium ions have been made using 90% Pt–10% Rh gauze coated with natural or synthetic aluminosilicate materials. Details of the material preparation and emitter fabrication techniques are discussed. The various ion emitters are examined as to total emission, impurity emission, and lifetime. A composite emitter capable of simultaneously producing the several ions is presented.
Absorber cell for Mössbauer spectroscopy of heterogeneous catalysts at reaction conditions
Authors: Delgass W. Nicholas , Chen Ling-Yuan , Vogel Gilbert
Published: March 2003

A stainless steel cell with external heaters, a Cu gasket seal, vacuum brazed Be windows, and a path length of 80 mm allows in situ collection of Mössbauer spectra for absorber wafers at temperatures up to 800 K and reacting or adsorbing gas pressures up to 1.4×105 Pa (1.4 atm).
Solid state surface charge sensor
Authors: Vosburgh K. G. , Schenck J. F.
Published: March 2003

Measurements with a novel solid state sensor show the ability to detect surface charge densities smaller than 0.1 nC/cm2 with an inherent spatial resolution of less than 50 μ. Surface contact is not required, and the sensing process is nondestructive. These devices may be constructed in arrays using present day semiconductor processing technology.
Microwave coupler for EPR cavities at 1.3 K
Authors: Isaacson R. A.
Published: March 2003

This note describes improvements in the commonly used Gordon coupler used in reflection-type EPR spectrometers. The improvements permit stable, low noise operation in liquid helium at very low modulation frequencies. At microwave powers as high as 10−2 W, the superheterodyne spectrometer noise at 2 Hz is only 2 or 3 times worse than at 100 kHz.
Diffraction effects on angular response of x-ray collimators
Authors: Blake R. L. , Barrus D. M. , Fenimore E.
Published: March 2003

Angular responses have been measured for x-ray collimators with half-widths ranging from minutes of arc down to 10 arcsec. In the seconds-of-arc range, diffraction peaks at off-axis angles can masquerade as side lobes of the collimator angular response. Measurements and qualitative physical arguments lead to a rule of thumb for collimator design; namely, the angle of first minimum in the Fraunhofer single-slit diffraction pattern should be less than one-fourth of the collimator geometrical full-width at half-maximum intensity.
Automatic conductimetric instrument for kinetic studies of photochemical ionization reactions in solution
Authors: Ballard S. Gwyn
Published: March 2003

This paper describes an instrument for conductimetric detection of charged species formed in solution-phase photochemical reactions in the time region 1 μsec to 100 msec. A low-voltage pulsed dc polarization technique is employed, and electrochemical complications minimized by pulse reversal. By using state-of-the-art operational amplifiers it is possible to study ion transients as short as 10 nsec, but the present instrument is set up for a 1% settling time of 400 nsec, giving sufficient sensitivity to detect ions in nanomolar concentration and sufficient speed to follow encounter-limited reactions at millimolar reactant concentrations. The instrument is dc coupled throughout, but employs an automatic zeroing system to refer photoconductance transients to a zero baseline and provide continuous readout of the static conductance.
Michelson interferometer for deformation measurements in an UHV system at elevated temperatures
Authors: Röll Klaus , Hoffmann Horst
Published: March 2003

An interferometric device is described, which permits deformation measurements and observation of small changes of shape in samples under UHV conditions and in the temperature range 20–400 °C. Adjustment during operation can be made by a simple mechanism with the use of only one single flexible UHV connection (stainless steel bellows). The interferometer was used to investigate the origin of stresses in thin Ni films and the stress relaxation during annealing by means of the ’’bending-plate method.’’
Microspecular reflectance apparatus for use with Cary 14 or 17 series spectrophotometers
Authors: Dessent Thomas A. , Palmer Richard Alan
Published: March 2003

The design of an attachment for the Cary Instruments model 14 or 17 series spectrophotometers for the measurement of the polarized specular reflectance spectra of microsamples in the near uv, visible, and near ir is described. The attachment is easily interchangeable with standard sample handling accessories in the extended cell compartment of the instrument. When aligned, the apparatus focuses the beam on the sample at nominally normal incidence by means of Cassegrain optics. The reflected beam is passed by a series of mirrors to the standard Cary detector. The spectrophotometer is operated in the double beam absorbance mode. Comparison of the sample reflectance with that of a calibrated mirror measured under the same conditions allows the calculation of the absolute reflectivity of the sample, which can then be used to derive the absorptivity via a Kramers–Kronig relationship. The use of the apparatus to obtain polarized spectra of highly absorbing single crystals is discussed.
Production of a quiescent plasma by a rf discharge
Authors: Bitter M. , Hollenstein Ch. , Paris P. J.
Published: March 2003

Quiescent argon plasmas of densities of 109–1011 electrons/cm3 with a symmetric radial density profile and a Maxwellian electron velocity distribution (Te≃5 eV) have been produced by a rf discharge for neutral gas pressures of 1×10−4 to 2×10−3 mm Hg and magnetic fields in the range 0.2–0.5 kG. The main sources of density inhomogeneities and noise, which can arise from the formation of a plasma in regions of strong rf field inhomogeneities, have been eliminated by appropriate construction of the rf wave structure. The rms density fluctuation level δn/n is in the range 2×10−3 to 5×10−2, and decreases with increasing neutral gas pressure.
Simple, high-resolution laser mirror mount
Authors: Pace Paul W. , Atkinson J. B.
Published: March 2003

A simple, inexpensive, high-resolution angular orientation device for use with interference filters, Fabry–Perot etalons, and laser mirrors is described.
CMOS diffusion-pump monitor
Authors: Miller Alan R.
Published: March 2003

A battery-powered CMOS circuit for monitoring the coolant temperature and power line voltage of a diffusion pump is described. The two sensing functions are independent, so that the system will automatically restart after a short-term power failure (e.g., one caused by lightning), but not after a longer-term power failure or if the cooling system failed.
Liquid filters for the ultraviolet
Authors: Passner A. , McCall S. L. , Leventhal M.
Published: March 2003

Some liquid transmission filters suitable for use in the ultraviolet are described.
Flow device to measure γ radioactivity and size of microparticles
Authors: Annis M. , Cobb C. M. , Bjorkholm P. J. , Frederick E. E. , Ramsey A. T. , Frisch D. H.
Published: March 2003

A description is given of the design and performance of an instrument which measures particle size and radioactivity of individual microparticles after uptake of a γ-emitting radioactive tracer. A flow system allows the activated particles to be measured quickly and individually, giving statistically significant frequency distributions in a short time. The purpose of the flow device is to measure some property of particles of a given type, provided this property is correlated with the uptake of the tracer. The instrument sizes particles in the 5–150-μm-diam range, and detects γ rays of E≳30 keV.
Arc-heated high-intensity source of hydrogen atoms
Authors: Way Kermit R. , Yang Sze-Cheng , Stwalley William C.
Published: March 2003

A very intense source of hydrogen atoms for atomic and molecular beam experiments has been obtained using pure hydrogen gas. In this work, a source head heated by a dc arc, very similar to the unit described by Knuth’s group [Rev. Sci. Instrum. 40, 1346 (1969)] was used. Fluxes of at least 4×1017 hydrogen atoms/sr sec with energies of about 5 eV have been repeatedly attained.
New technique for measuring extremely high heat transfer rates to surfaces
Authors: Smith J. L. , Pfender E.
Published: March 2003

A simple method for determining very high local heat fluxes (in the order of 106 W/cm2) to surfaces is based on a comparison of calculated and measured temperature–time histories of the surface.
Automatic concentric shaft reflectometer for use in the vacuum uv
Authors: Emerson L. C. , Cox J. T. , Ostrom G. L. , Painter L. R. , Cunningham G. H.
Published: March 2003

A vacuum uv reflectometer is described which makes use of a highly reproducible stepping motor drive system. The concentric shaft design eliminates many alignment problems common to other systems and makes possible a single flange mounting. The pulsed drive system is particularly well suited to automation, both from the standpoint of sample position control and the application of signal averaging techniques to improve the precision of reflectance measurements. Examples of both manual and automatic control systems are presented.