bluuebunny/crossref_metadata_2025 huggingface dataset:
High-voltage linear pulse amplifier
Authors: Ekstrom P. A. , Crosby D. A. , MacAdam K. B.
Published: March 2003

This linear amplifier employs moderate-voltage power supplies and components to generate high-voltage pulses of arbitrary shape on a μs time scale. A linear version of the Marx generator, it is limited to a small duty fraction, but can deliver a large multiple of its supply voltage. Its initial application was generation of specially shaped field–ionization pulses in studies of Rydberg atoms.
Circuit for the measurement of surface potential changes by the static capacitor method
Authors: Pasco R. W. , Ficalora P. J.
Published: March 2003

Circuitry is presented for the measurement of surface potential changes upon adsorption of gases on a metal foil or film by the static capacitor method. The circuit operates in the usual manner applying a backing off potential which opposes the flow of current from the cell comprised of the foil or film and a reference surface. The advantages of the present circuit include simplicity, low cost, fast response time, no moving parts, and the requirement of only one low voltage, dual-polarity power supply.
Economical replacement for gold O-ring type gaskets in metal vacuum systems
Authors: Beaver Edward M.
Published: March 2003

A technique for fabricating O-ring type gaskets from electrical utility wire is described, including criteria for successful welds using facilities readily available in the average laboratory.
Experimental facility to produce and measure compression and shear waves in impacted solids
Authors: Gupta Y. M. , Keough D. D. , Walter D. F. , Dao K. C. , Henley D. , Urweider A.
Published: March 2003

An impact facility has been designed and constructed to produce and measure large amplitude one-dimensional compression and shear waves in solids. Design considerations and experimental details to produce the necessary impact configuration and to measure the particle velocity profiles resulting from compression and shear waves are described. Experimental results are presented to show that the impact facility was satisfactorily constructed. After a brief discussion of shear wave measurements, the experimental measurements made under compression and shear loading in polymethyl methacrylate and polycrystalline aluminum oxide are presented. These results are expected to provide new information on material response at high strain rates.
On the possibility to measure volumes of small gas bubbles and the bubble producing gas flow rates acoustically
Authors: Oosterwegel G. G. , de Groot H. J.
Published: March 2003

Using the pulsation properties of gas bubbles it is possible to measure acoustically volumes c.q. equivalent diameters of gas bubbles in the range of 1.8–2.1 mm, produced at low frequencies at capillary tubes in a silent environment. Hence it is possible to measure very low gas flow rates (from 4 up to 100 mm3/s). During formation of bubbles at capillary tubes phenomena of repeated coalescence can occur between a just released bubble and the following bubbles under formation. This occurrence depends on the speed of rise, the bubble volume and the formation frequency. There is experimental evidence that this swallowing-up gives cause to a swinging-up of the amplitude of the pulsation signal. This coalescence process is the main physical limitation of the claimed method to low frequencies. There is also some experimental evidence by laser pulse synchronization between acoustics and bubble photographs that the often reported neck during bubble formation actually is an effect caused by this swallowing-up process.
Elmo Bumpy Torus heavy ion probe
Authors: Bieniosek F. M. , Colestock P. L. , Connor K. A. , Hickok R. L. , Kuo S. P. , Dandl R. A.
Published: March 2003

A diagnostic system based on the heavy ion beam probe technique has been developed for the Elmo Bumpy Torus. A variety of singly charged alkali metal ions have been used in the probing beam; detection of multiply charged reaction products allows a continuous spatially resolved monitor of the plasma space potential. Typical spatial resolution is 1 cm−3; time resolution is on the order of 1 s. The potential measurement is direct and properly referenced to the plasma ground. An investigation into possible sources of error in the measurement points to the conclusion that the uncertainty is an order of magnitude less than the experimentally measured potentials.
Development of a high-repetition-rate mini-TEA CO2 laser
Authors: Menyuk N. , Moulton P. F.
Published: March 2003

A 1.8 cm3 active volume gas-recirculating mini-TEA CO2 laser of relatively simple design is described. The laser is capable of operating at 500 Hz with an average output of 10 W. The device is line tunable over ∼50 CO2 laser frequencies, has operated with up to 34 J/l output density and has a nearly diffraction-limited output.
Precision two-compartment bomb calorimeter for combustion in fluorine
Authors: Lenski H. , Böhler D.
Published: March 2003

An isothermally jacketed liquid calorimeter permitting thermochemical studies on spontaneous combustion in fluorine has been built and tested. The fluorine storage tank was located outside the calorimeter vessel, thus lowering the heat capacity of the system and its thermal inertia. Particular attention was paid to the method and rate of liquid circulation since it largely determines the experimental accuracy. The system can be calibrated electrically. The possible experimental errors are discussed, and their analysis shows that calibration is feasible with an accuracy of ≳99.98%. A series of measurements involving a temperature rise of about 0.9 K showed a standard deviation of 0.02%.
Automated, simultaneous measurement of electrical properties of pyroelectric materials
Authors: Dougherty J. P. , Seymour R. J.
Published: March 2003

An automated system for measuring the pyroelectric properties of materials is described. This system can simultaneously measure pyroelectric coefficients and permittivities eliminating errors introduced in the figures of merit by temperature uncertainties. Results on deuterated triglycine fluoroberyllate (DTGFB) are presented.
Stable CO2 and N2O laser design
Authors: Thomas J. E. , Kelly M. J. , Monchalin J.-P. , Kurnit N. A. , Javan A.
Published: March 2003

A complete working design for highly stable grating controlled N2O and CO2 lasers is presented. The lasers are suitable for general high resolution spectroscopy, frequency mixing and clock applications.
Apparatus to measure the viscosity of strongly oxygen reactant amalgam
Authors: Masera M. Bosco
Published: March 2003

A new apparatus for the preparation and preservations of amalgams in absence of oxygen is described. It has some advantages over the preparation in presence of chemicals: (1) there is no reaction with the amalgam; (2) no extraneous material remains in the crucible, which contains the amalgam. For the viscosity measurements, the amalgam is contained into a free-oscillating viscometer, which was described by Gallina et al. This paper shows the reproducibility of the viscosity measurements in the temperature range from −20 ° to 50 °C, and compares his values to a literature value.
Precision low cost V block for heavy loads
Authors: Deutsch Moshe , Vago Eli
Published: March 2003

A new type of V block is described. It is constructed from separate elements and is suitable for use with heavy loads. Its accuracy is the same as conventional monolithic V blocks while its cost is much lower than that of commercial precision V blocks.
Wheatstone bridge fed from a bilateral constant current source
Authors: Velayudhan C. , Oommen Daniel
Published: March 2003

A simple inexpensive scheme of an electronic amplifier for Wheatstone bridge application is presented. The bridge is excited from a bilateral constant current square wave source. The advantage of constant current drive is presented.
Small tritium filling and monitoring apparatus for particle beam inertial confinement fusion targets
Authors: Chang J. , Leeper R. J. , Martinez C. , McMurtry W. M.
Published: March 2003

A small gas filling apparatus has been developed to fill a particle beam ICF target with D–T gas mixture seconds before the target is irradiated. Included in the filling apparatus is a novel miniature pressure monitor which determines quantitatively the fill pressure by counting the rate of Beta particles emitted by the decaying tritium atoms.
A fully stabilized Brillouin spectrometer with high contrast and high resolution
Authors: Vacher R. , Sussner H. , Schickfus M. v.
Published: March 2003

Using a triple-pass plane and a confocal Fabry–Pérot interferometers in tandem, we have constructed a Brillouin spectrometer with a frequency resolution of 108 and a contrast of more than 1010. Our system is controlled and fully stabilized by a desktop calculator, allowing efficient data collection for very long integration times.
Thickness measurement of a thin oxide layer by secondary electron emission
Authors: Okamoto K.
Published: March 2003

A method for measuring the thickness of a very thin oxide layer by secondary electron emission is described. The secondary electron signals are measured for an oxide-covered silicon surface and a reference surface by using the line mode of scanning electron microscope. Then, their ratio correlates well with the thickness of oxide layer, and it is demonstrated that the thickness of an oxide layer can be obtained by measuring the ratio γ. At the beam energy of 2 keV, the measurable thickness lies within the range of 15–150 Å. The lower limit is due to the natural oxide remaining on the reference-silicon surface and the upper limit to charging effects of oxide layers. A remarkable feature of this method is that an oxide thickness localized in a very small area is measurable, and the measurement is carried out for an oxide deposided in 0.1-mm-wide ditches.
Stabilized flow in capillary-type closed viscometer
Authors: Kobayashi Hiroshi
Published: March 2003

Small periodic variations in a main gas flow through a capillary are reduced from 1% to 0.1% in peak-to-peak width by a feedback circuit between a pressure gauge and a motor of a pump. The variations in flow result from nonlinear transmission of a worm mechanism in a capillary-type closed viscometer, Dynamical properties of the system are discussed by the Laplace transform method, and it has been shown that low pressure, a long guide tube, and high gain of the amplifier are responsible for the flow instability.
Proportional step size tracking analog-to-digital converter
Authors: Last Thomas A.
Published: March 2003

A new type of tracking analog-to-digital converter, which is capable of responding quickly to step changes in the input voltage, has been developed. The device produces an error signal which indicates the difference between the converter’s state and the input signal level. This error signal is used to modify the converter’s slew rate in such a way as to optimize convergence back to the tracking condition (i.e., the condition at which the converter’s state accurately tracks the input signal). This error signal is also used to generate an accuracy code which indicates if the converter is accurately tracking the input signal, or if the converter is out of track, how many bits of the encoded data are actually significant. An eight-bit transient recorder was developed using the converter described above. The instrument was found to be capable of recording data at rates up to 106 points/s, and was observed to respond to step voltage changes within eight datum points.
A magnetic-reluctance thickness gauge for high conductivity, ferromagnetic films
Authors: Ryan S. R. , Ryan A. R.
Published: March 2003

A magnetic comparator for measuring the thickness of high conductivity, ferromagnetic films is described. The instrument compares the reluctance of a standard sample to that of a film of unknown thickness at the same value of magnetic field intensity to insure that the permeability is the same for both. The comparator utilizes an ac Hartshorn, mutual-inductance bridge configuration and is designed to operate at low frequency and low magnetic field intensity to maximize the skin depth δ and thus the measurable film thickness. The output of the comparator is linear in thickness for films less than δ/2 and is capable of measuring films of thickness greater than δ with some reduction in accuracy. The effects of the skin depth and magnetic properties of the film on the accuracy of the comparator are discussed.
High efficiency melting furnace
Authors: Riveros H. G. , Cory W. K. , Toca R. , Cabrera E.
Published: March 2003

With a hot plate and a spherical mirror, a highly efficient crucible heating furnace was theoretically calculated and constructed. The upper part of the crucible provides free access to the melt, as is needed in the Czochralski crystal growth technique. For the design, the heat radiation flow between the hot plate, a cylindrical crucible, and the enclosing ellipsoidal mirror was computed. The calculated temperature profiles on the crucible, for different values of the crucible diameter and the eccentricity of the ellipsoid are shown and a comparison is made with the constructed oven. Using a cylindrical crucible (od=5 cm, height=5 cm), the power consumption is 720 W during the growth of NaCl (≈800 °C).
High pressure apparatus for PVT measurements of liquids and plastic crystals at low temperatures
Authors: Landau R. , Würflinger A.
Published: March 2003

A high pressure apparatus for determining PVT data of liquids and plastic crystals and volume changes which might accompany phase transitions is described. In the present investigation the PVT data of acetonitrile have been determined from +40° to −50 °C and up to 3000 bar, including the volume changes due to the melting and to a solid–solid transition. The procedure for calibrating this apparatus is discussed. The accuracy of the PVT data is supposed to be better than 0.1%, both for the liquid and the solid state.
Broad beam ion source operation with four common gases
Authors: Pak S. , Sites J. R.
Published: March 2003

A Kaufman-type broad beam ion source, used for sputtering and etching purposes, has been operated with Ar, Kr, O2 and N2 gas inputs over a wide range of beam energies (200–1200 eV) and gas flow rates (1–10 sccm). The maximum ion beam current density for each gas saturates at about 2.5 mA/cm2 as gas flow is increased. The discharge threshold voltage necessary to produce a beam and the beam efficiency (beam current/molecular current), however, varied considerably. Kr had the lowest threshold and highest efficiency, Ar next, then N2 and O2. The ion beam current varied only weakly with beam energy for low gas flow rates, but showed a factor of two increase when the gas flow was higher.
Sensor for the measurement of the level and volume of conductive liquids
Authors: Walton Kenneth R.
Published: March 2003

A sensor for the measurement of the level and volume of liquids is described. The device employs an array of point sensors, each of which is sensitive to the large changes in impedance between a conductive liquid and the gas above it. The device, in principle, will function in any liquid medium that can conduct an electric current without significantly perturbing that medium. It has in fact been successfully tested in aqueous solutions with conductivity ranging from 9.0×10−7 Ω−1 cm−1 to 0.38 Ω−1 cm−1. The sensor is activated with either AC or DC applied voltage and used with electronic circuits having linear outputs. The sensor’s output is solution independent and a function of the number of conducting electrodes. The precision of the sensor is controlled by the spacing of its electrode array. The linear output of the sensor has been correlated linearly to solution volume regardless of the shape of the solution tank by the use of unequal spacing between the array electrodes. Several designs of sensors with fixed and adjustable precision are described.
Electromechanical polishing of metal spheres
Authors: Miller N. E. , Engelhaupt D. E.
Published: March 2003

Equipment has been developed to electromechanically polish metal spheres. Mechanical polishing is accomplished by the action of three cup-shaped laps which rotate against the sphere. An abrasive slurry containing an electrolyte is continuously applied to the sphere and laps. Electrochemical etching is accomplished by applying a positive potential to two of the laps and a negative potential to the third.
Cell poker: An apparatus for stress-strain measurements on living cells
Authors: McConnaughey William B. , Petersen Nils O.
Published: March 2003

An apparatus is described which can make force vs. displacement measurements on regions of a living cell. A force on the order of 10−3 dyne is applied by a stylus to an area of about 10 μm2 on the upper side of a cell growing on a culture dish. The resulting deformation is deduced from a solution conductance measurement with a sensitivity of 0.1 μm. The technique is compatible with optical microscopy and electrophysiological recording.
High sensitivity vibrating reed magnetometer
Authors: Roos W. , Hempel K. A. , Voigt C. , Dederichs H. , Schippan R.
Published: March 2003

A high sensitivity vibrating reed magnetometer useful for measurements on very small ferromagnetic particles is described. The reed is made of gold wire (18 μm in diameter, 10 mm long). The mechanical vibrations of the reed are converted directly to an ac voltage by a piezoelectric ceramic. Using a lock-in amplifier magnetic moments as small as 10−9 Acm2 can be detected.
Parametric study of an acoustic levitation system
Authors: Oran W. A. , Berge L. H. , Parker H. W.
Published: March 2003

The fields and forces along the axis of an acoustic levitation device were measured and characterized. The device consisted of a St. Clair generator and reflector arranged in a single-axis configuration. A significant (i.e., factor of four) enhancement in the levitation forces was obtained by using concave surfaces for the driver and reflector. For bodies of various sizes and geometries, the acoustic levitation force is roughly proportional to body volume until the characteristic ’’diameter’’ reaches ∼λ/2(λ=wavelength). In addition, the behavior of materials when in the liquid state was studied. Liquid drops were found to deform and generally rupture when a characteristic size was reached. The characteristic radius appears to depend on material parameters and is from 0.2–0.5 cm for most materials on the ground.
Astronomical spectrometer using a Charge Coupled Device detector
Authors: Meyer Stephan S.
Published: March 2003

This paper describes a low light level, low resolution astronomical CCD (Charge Coupled Device) spectrometer useful in the spectral range 5000–9000 Å. The instrument has a second CCD channel for direct broad-band photometry of the region around the entrance slit. Both applications benefit from the high quantum efficiency, stability, dynamic range and linearity intrinsic to CCD’s. The detectors are cooled to 130 K which eliminates dark current and permits exposure times long enough to overcome the readout noise of ±30 electrons. At low spectral resolution the instrument has a signal-to-noise ratio which approaches the photon counting noise limit. The overall average quantum efficiency during observations is 1.3% between 5500 and 9000 Å.
Design and performance of a small CS2/O2/additive flame laser
Authors: Babarogić Z. , Konjević N. , Trtica M.
Published: March 2003

The design and performance of a small cw CO flame laser with a total power output of 5 W is presented. The influence of the flow rates of the reactants and additives to the spectral composition of the laser power output has been studied in detail.
High temperature Electron Paramagnetic Resonance Cavity for easily oxidized samples
Authors: Evora C.
Published: March 2003

We describe an EPR cavity for doing measurements on readily oxidized samples—fluorides—at the molten state. The use of hydrogen fluoride at high temperatures, as a reducing atmosphere, sets stringent requirements on the materials used for making crucibles and oven.
New technique of surface flow visualization based on oxygen quenching of fluorescence
Authors: Peterson John I. , Fitzgerald Raphael V.
Published: March 2003

A surface pattern flow visualization technique is demonstrated based on the principle of oxygen quenching of dye fluorescence. The technique uses visible light excitation and streams of oxygen or nitrogen, which are inexpensive and nontoxic. A sensitive material can be spray coated on shapes of interest to study flow at surfaces.
Simple parallel interface between an optical multichannel analyser detector controller and a microprocessor
Authors: Bialkowski Stephen E.
Published: March 2003

A simple circuit is given which will allow data transfer from a LSI-11 DRV11 parallel interface unit to a PARC 1216 Optical Multichannel Detector Controller. The Circuit for OMA to LSI-11 data transfer is slightly more complicated. Data buffering is used so that data transfer can occur without time-out loss due to the dynamic memory refresh cycle of the LSI-11. The circuit may be constructed and mounted within the PARC 1216 unit with only minor, noncritical, modifications to the controller unit. The unit is able to transmit data from the 1216 controller running at dwell times as short as 40 μs/channel.
Convenient thermal/vapor barrier for constant temperature water bath
Authors: Huang John S. , Kim Mahn Won
Published: March 2003

We report a simple scheme to install an effective thermal/vapor barrier for precision temperature baths. We have found that by floating on the water surface, a pile of common packing material such as styrofoam pellets fused together by a solvent spray, a ten-fold reduction in the bath temperature fluctuation can be achieved.
Simple interferometric instrument for evaluating the dynamic stress-optical coefficients and the ratio Poisson’s ratio to modulus of elasticity
Authors: Raftopoulos Demetrios D. , Kartalopoulos Stamatios V.
Published: March 2003

A simple prototype opto-electronic-mechanical instrument has been designed and constructed in order to measure optical and mechanical properties of transparent materials.
Comments on ’’Determination and optimization of frequency response of constant temperature hot-wire anemometers in supersonic flows’’
Authors: Freymuth P.
Published: March 2003

A practical limit for the value of low overheat is given.
Quasi–dc extraction of 70 keV, 5 A ion beam
Authors: Okumura Y. , Matsuda S. , Mizutani Y. , Ohara Y. , Ohga T.
Published: March 2003

An ion source that produces a high energy ion beam in quasi-dc mode has been fabricated and tested. The significant features of the source are effectively cooled accelerator grids with properly shaped apertures and a carefully cooled douPIGatron plasma generator. To opeate the source quasi-continuously, the heats dissipated in the accelerator grids and in the back plate of the plasma generator were suppressed below permissible values by attaining low pressure in the arc chamber. Under such condition, a 70 keV, 5 A, 10 s ion beam was obtained repeatedly without any deleterious problems. The measurement by photo beam monitor indicates no change of beam divergence during 10 s. The pressure change in the beam drift region during the pulse has also been investigated.
Double probe circuit used in pulsed plasma diagnostics
Authors: Hoegger B. A. , Bulliard A.
Published: March 2003

The construction of a new double probe circuit using wide band optically isolated electronic elements is described. The circuit is adaptable to measuring plasma characteristics generted by pulsed discharges. The entire system is powered by a high performance dc/dc converter. The probe and ramp generator circuits are at floating potential and possess an over-all capacity relative to ground <50 pF. The bandwidth of the probe circuit is better than 250 kHz.
Technique for measuring cooling patterns in ion source grids by infrared scanning
Authors: Grisham L. R. , Eubank H. P. , Kugel H. W.
Published: March 2003

Many plasma souces designed for neutral beam injection heating of plasmas now employ copper beam acceleration grids which are water cooled by small capillary tubes fed from one or more headers. To prevent thermally-induced warpage of these grids it is essential that one be able to detect inhomogeneities in the cooling. Due to the very strong thermal coupling between adjacent cooling lines and the concomitant rapid equilibration times, it is not practical to make such measurements in a direct manner with a contact thermometer. We have developed a technique whereby we send a burst of hot water through an initially cool grid, followed by a burst of cool water, and record the transient thermal behavior using an infrared television camera. This technique, which would be useful for any system with cooling paths that are strongly coupled thermally, has been applied to a number of sources built for the PLT and PDX tokamaks, and has proven highly effective in locating cooling deficiencies and blocked capillary tubes.
Optimized linear variable differential transformer displacement transducer for cryogenic use
Authors: Sponagle N. C. , Atherton D. L.
Published: March 2003

A simple procedure is given for optimizing the performance and coil dimensions of an Ellis and Walstrom type moving coil, linear variable differential transformer displacement transducer as well as a method of compensating for changes in calibration at different operating temperatures. The resulting transducer has been used successfully in liquid He and ambient magnetic fields up to 3 T but may also be used at any temperature up to 300 K without recalibration.
Time dependence of rate-dependent photomultiplier gain and its implications
Authors: Yamashita Mikio
Published: March 2003

Time dependences of rate-dependent photomultiplier gain were measured precisely in two particular tubes for various count rate changes. Most of the measured time dependences are shown to be well described by three exponential components. While the corresponding time constants remain unchanged for different count rate changes except the one of the first component, the relative population of each component varies considerably according to duration of the measurement immediately before the count rate change. Since the time dependence is considered to reflect the charge buildup on the dynode, a charge buildup model based on electron and hole trapping is proposed to explain the measured time dependences. An abrupt rise or fall in gain, which is clearly seen immediately after a count rate change, is interpreted as a manifestation of a large difference in value between the detrapping constants for trapped electrons and holes. It is shown that in order to be consistent with the measured time dependences the observed tendency of trapped holes to settle into deeper levels at larger times should be attributed to physical processes similar to those of polaron hopping. The proposed charge buildup model should not only indicate possible factors affecting the time dependence, but also give an insight into the physical mechanism involved in charge buildup on thin oxide films.
Pseudorandom digital cross correlator for impulse response measurements
Authors: Bassi Davide
Published: March 2003

A μ processor based pseudorandom digital correlator has been developed to perform near real time impulse reponse measurements in linear, time-invariant systems. It operates with a time base of up to 2 μs, signals up to 104 counts/s and with 255 channels resolution.
Use of nonlinear least mean squares fitting to achieve compensated electrical filters
Authors: Sanders Ann H. , Cannell David S.
Published: March 2003

The results of using nonlinear least-mean-squares fitting procedures to compensate passive electrical filters for the effects of frequency-dependent losses in the inductors by changes in the other components are reported. This technique, when applied to third- and fifth-order low-pass Chebysheff filters, resulted in actual transfer functions which were essentially identical to the ideal transfer functions. Filters having cutoff frequencies ranging from 300 Hz to 3 MHz were constructed and tested.
A 5-m grating spectrograph for studying molecular x-ray fluorescence spectra
Authors: Andermann G. , Bergknut L. , Karras M. , Griesehaber G. , Smith J.
Published: March 2003

A variable grazing incidence 5-m focal length grating spectrograph has been assembled and fitted with a thin window Henke x-ray tube. With a closely coupled sample to anode arrangement the speed of the instrument at 0 K emission at equivalent instrumental resolution is approximately on par with a 2-m spectrometer’s response which uses the DORIS storate ring at DESY as a source.
A new probe for three-dimensional flow measurements
Authors: Soundranayagam S. , Ramarajan V.
Published: March 2003

A new four-hole cylindrical cantilever probe is described which could be used for three-dimensional flow surveys. The probe is more compact than the usual cylindrical type allowing for closer approach to a boundary. The probe is robust and gives good reproducibility. It can be used for a wide range of pitch angle.
Capacitance cell for liquids
Authors: Jacobs D. T. , Greer S. C.
Published: March 2003

We present a simple and chemically inert, guarded cylindrical capacitance cell for liquids in the temperature range 170 to 370 K and at pressures near atmospheric. A precision in the dielectric constant of 2 ppm is realizable with this cell.
Use of standard broadcast signals to measure time intervals
Authors: Saull V. A. , Arcuri J. , Lapierre D. P.
Published: March 2003

Broadcast band radio transmissions can be recorded along with data signals and used to time-correlate data events, and thus to measure the time intervals between these events.
Optimization of the trochoidal electron monochromator
Authors: McMillan Michael R. , Moore John H.
Published: March 2003

The trochoidal electron monochromator employs an axial magnetic field and a transverse electric field. Many aspects of its performance can be described by electron trajectory equations which include the voltage drop across the entrance aperture. A beam shear is predicted, which is a function of a parameter tanϑ. Optimum performance is achieved by matching the exit aperture to the sheared beam. tanϑ establishes a relationship between the field magnitudes and the dimensions of the monochromator. Estimates of appropriate values for these parameters can be made, with the final optimum values being determined by a combination of practical and empirical considerations. Finally, the use of the instrument as an energy analyzer is described.
An amplitude modulated active method for plasma density measurements
Authors: Moore William F. , Robertson Harry S.
Published: March 2003

An active system for plasma density measurement using an amplitude modulated microwave carrier signal is described. For plasmas of higher density, IR or visible carrier signals may be used. Adjacent-mode competition is avoided by choosing the wavelength of the modulating signal to be comparable to the active delay-line oscillator’s feedback path length. Although the technique described is intended for use with plasma, it can be applied to measurements of other dielectrics.
Graphite–halogens as temperature calibration standards for transmission electron microscopy
Authors: Chung D. D. L.
Published: March 2003

Graphite–halogen (Br2, ICl) residue compounds have been found to be convenient temperature calibration standards for transmission electron microscopy in the medium temperature range. Due to the order–disorder transformation associated with the intralayer intercalate ordering in these intercalation compounds, the observation of the disappearance of the superlattice diffraction spots as the sample temperature is raised serves to calibrate the temperature. The transformation occurs at 100±1 °C in graphite–Br2 and 41±1 °C in graphite–ICl. The simplicity of specimen preparation gives added attraction to the use of graphite–halogens as temperature calibration standards.
A time-of-flight spectrometer for the measurement of angular distributions of scattered slow positrons and electrons
Authors: Coleman P. G. , McNutt J. D. , Hutton J. T. , Diana L. M. , Fry J. L.
Published: March 2003

A technique for measuring directly the angular distributions, and consequently the absolute differential cross sections, for positron- and electron-atom elastic scattering is described. By exploiting time-of-flight spectrometry, simultaneous measurement over a wide range of forward angles is achieved. The structure and performance of the components of the experimental system are described in detail, and the reliability of the apparatus in the measurement of positron-atom cross sections is tested by using the same spectrometer to study electron scattering. Results are presented for elastic electron-argon scattering at energies between 5 and 20 eV which are in reasonable agreement with other recent results. Systematic effects on the measurements are discussed.
A goniometer for cutting single crystals
Authors: Price G. L.
Published: March 2003

A simple, compact and robust goniometer is described which is suitable for aligning and cutting metal single crystals with a slow speed saw.
Determination and storage of space potential in a fast changing plasma
Authors: Chakravarti P. K. , Basu J.
Published: March 2003

A new method for determination and storage of the space potential in a plasma is described. The analog storage device employed in the method is automatic and suitable for recording of the variable space potential in a fast changing plasma.
High current source of He− ions
Authors: Hooper E. B. , Pincosy P. A. , Poulsen P. , Burrell C. F. , Grisham L. R. , Post D. E.
Published: March 2003

A negative helium ion beam of 70 mA at 10.5 kV has been produced by charge exchange in sodium. The production is studied as a function of sodium line density, beam energy and background helium gas density. The characteristics of this high current He− source are analyzed to determine the design requirements for He− beam generation in the range of tens to hundred of milliamperes.
A wide range high sensitivity film balance
Authors: Abraham Bernard M. , Miyano Kenjiro , Buzard Kurt , Ketterson John B.
Published: March 2003

A film balance has been constructed that features a wide range (∼80 dynes/cm) and high sensitivity (∼10−3 dyne/cm). The device is rugged, simple to operate and can be repeatedly assembled/disassembled in cycles (for cleanings) without affecting its mechanical parameters (nullpoint and sensitivity).
Simple analytic method for microwave cavity Q determination
Authors: Frait Zdenek , Patton Carl E.
Published: March 2003

A simple method for the accurate determination of the quality factor, Q, of a reflection microwave cavity is described.
A parallel-plate electrostatic size classifier for aerosol particles
Authors: Schowengerdt F. D. , Brown J. T.
Published: March 2003

A parallel-plate electrostatic aerosol size classifier has been constructed, analyzed, and tested. The instrument can produce sub-micron aerosols with high output, good resolution in the size distribution, and of either single or mixed charge polarities. Performance tests were conducted on latex aerosols and on coal dust, and the instrument was used to calibrate a laser particle size analyzer on coal dust. Calculated and measured output sizes agree to about 7%. A size resolution of approximately 13% for monodisperse aerosols and 17% for a polydisperse coal dust aerosol was obtained.
High pressure stopped-flow apparatus for the rapid mixing and subsequent study of two fluids under high hydrostatic pressures
Authors: Karan Daniel M. , Macey Robert I.
Published: March 2003

A stopped-flow apparatus is described for the rapid mixing and subsequent study of two dissimilar fluids under pressures up to 1200 bar. The device consists of two identical pressure chambers which contain the two fluids, a third pressure chamber which contains gas to maintain the pressure in the system, an optical port for photometric observation, and various connections. The device has been used to measure reaction times on the order of a hundred milliseconds to tens of seconds, using a maximum of 2 ml of each reagent per experimental determination. The dead time is found to be 5–25 ms with minium average flow velocities of 2.0 m/s. The construction and operation of the device are described and examples of water transport data in red blood cells and the bromophenolblue indicated chemical reaction of NaHCO3 and HCl under pressure are presented.
A direct reading linear dichroism apparatus for extended wavelength ranges
Authors: Goode D. H. , Buchanan M.
Published: March 2003

We describe how a commercially available photoelastic modulator can be used in a direct reading apparatus to measure linear dichroism over large wavelength ranges without external adjustments.
Stimulated raman scattering cell
Authors: Hamm W. , Taboada J.
Published: March 2003

Construction of an apertured Dewar cell designed for transforming the 1.06 μm Q-switched pulses of a Nd+3 glass laser by stimulated Raman scattering in liquid N2 or O2 is described. Performance data for the 1.06 μm to 1.4 μm conversion in N2 are given.
Simple electron beam guiding system including automatic capture circuitry
Authors: Stein W. , Schulenburg M. , Freund F.
Published: March 2003

The spatial stability of the point of impact of an electron beam is a stringent requirement in some experiments such as soft x-ray spectroscopy using a focussing curved crystal spectrometer. The occasinally poor design of moderately priced electron guns, thermal instabilities, electromagnetic stray fields and so on, make spot stabilization an arduous task. The problem can be solved to some extent by a simple electron beam guiding system: a small fraction of the electron beam is captured by a metal wire mounted in the vicinity of the target. The beam position is fixed, if this fraction is controlled by a feedback loop via the deflection plates of the gun.
Vibrating mirror drive circuit
Authors: Hawthorne Alan R.
Published: March 2003

A self-starting, stable, and symmetric driving circuit is described for use with a taut-band optical modulator such as a Bulova L50 or L51. The astable multivibrator consists of a capacitor, two resistors, three adjustment potentiometers, two diodes, and a dual operational amplifier. The circuit is particularly useful in applications requiring a small modulation amplitude that cannot be obtained from the factory-supplied driver.
A deep level transient spectroscopy system using single-gated signal averager
Authors: Atanasov R. D.
Published: March 2003

A mode of operation of a single-gated boxcar averager performing the function of a dual-gated boxcar averager in deep level transient spectroscopy (DLTS) measurements is described.
Power transmission characteristics of a two-stage multiaperture neutral beam source
Authors: Menon M. M. , Tsai C. C. , Schechter D. E. , Ryan P. M. , Barber G. C. , Davis R. C. , Gardner W. L. , Kim J. , Haselton H. H. , Ponte N. S. , Whealton J. H. , Wright R. E.
Published: March 2003

Beam power transmission and grid loading characteristics of a two-stage neutral beam source are presented. The dependence of power deposition on the target, the grids, and the gas cell was studied over a wide range of extraction perveance values with the accel-to-extraction gap field ratio as the other parameter. The results show that the power transmission improves remarkably with increasing field ratio. For sufficiently large field ratios (≈2.5), more than 80% of the input IV power was collected on a target located 4 m downstream and subtending 2 ° half angle to the source. The sum of the grid loading is approximately double that of single-stage accelerators; the plasma grid loading is the highest, followed by ground grid, accel grid, and extraction grid in that order.
Microcomputer-based laser Doppler velocimeter in marine biology
Authors: Paul Mark , Nicoli D. F.
Published: March 2003

A laser doppler velocimeter (LDV) has been designed and constructed for use in measuring ocean water flow velocity in the immediate vicinity of marine organisms anchored inside a water tunnel. The principal innovation reported here is the use of a microprocessor to produce an ’’intelligent’’ instrument which automatically calculates and displays the flow velocity. The resulting electronics design represents a considerable simplification over existing instruments which generally require the use of a separate autocorrelator and/or multi-channel analyzer (MCA) plus an external minicomputer. The LDV configuration employed is a crossed-beam design using a 2-mW He–Ne laser and inexpensive optics. A 48-channel 1-bit clipped autocorrelation function is implemented using a modified TTL design reported previously by Chen and co-workers. A Motorola 6800 micromodule updates the contents of each channel by direct memory access and displays the resulting correlogram on a CRT monitor. The velocity is periodically calculated (±5%) and displayed by LED digits.
Laser doppler blood flow meter and optical plethysmograph
Authors: Wunderlich R. W. , Folger R. L. , Giddon D. B. , Ware B. R.
Published: March 2003

An apparatus is described which combines laser Doppler velocimetry and optical plethysmography for a rapid, multi-parameter characterization of blood flow in cutaneous tissues. The Doppler parameter is determined by analog computation of the square root of the normalized second moment of the photodiode detector output during illumination by laser light scattered from the illuminated tissue. Incident and scattered light are transmitted by fiber optics to permit convenient sampling of local tissue regions. The instrument is compact, portable, and inexpensive. Data are presented which illustrate the utility of this device, and potential applications are discussed.
Microcomputer-based gas chromatograph with IEEE-488 interface
Authors: Ashworth Harry A. , Augustine Robert L.
Published: March 2003

A gas–chromatograph system controlled by a PET microcomputer is described. The system features twelve-bit resolution, automatic sensitivity selection, and interfaces to a general purpose instrument bus commonly called the IEEE-488 bus. The hardware of the interface is described in detail and uses only a few common integrated circuits. A sample chromatograph with retention times and peak areas is presented.
Microprocessor control of a superconducting magnet for adiabatic demagnetization
Authors: Bartolac T. J. , Gardner D. S. , Bozler H. M.
Published: March 2003

We present a microprocessor-based magnet control system used in our laboratory to generate the complicated sequences of magnetic field ramps required to operate a nuclear demagnetization cryostat. Considerations of high reliability, complete isolation, and overall simplicity have led to this stand-alone design.
Controlled humidity gas circulators
Authors: Gruner Sol M.
Published: March 2003

A programmable circulator capable of regulating the humidity of a gas stream over a wide range of humidity is described. An optical dew-point hygrometer is used as a feedback element to control the addition or removal of water vapor. Typical regulation of the gas is to a dew-point temperature of ±0.2 °C and to an accuracy limited by the dew-point hygrometer.
Flow viscometer for solutions that make a glass wall water repellent
Authors: Los J. M. , Out D. J. P. , Letzer W. M.
Published: March 2003

A constant-level viscometer has been designed especially for solutions that make glass water repellent. The lower meniscus remains at a constant level (±0.02 mm) during the flow period. Lower and upper meniscus corrections and the drainage error are discussed. It is shown that the performance of the viscometer is at least as good as that of the suspended-level type for solutions that completely wet the glass wall, as KCl in water. For tetraethyl and tetrabutylammonium bromide solutions in water, this performance is free of the inaccuracies described in the literature. For Bu4NBr the relative viscosities measured at twelve concentrations in the range 10−4 to 160×10−4 M at 25°C, show a standard deviation of 0.01% about the best fit to the extended Jones–Dole equation. From these data the corresponding A coefficient has been determined, and found to agree with the value from theory.
Pulsed molecular beam source
Authors: Bassi D. , Iannotta S. , Niccolini S.
Published: March 2003

A pulsed molecular beam source has been developed using a conventional car fuel injector and an especially designed vacuum chamber. Beam pulses of about 150 μs duration (FWHM) and peak intensity better than 1020 mol sr−1 s−1 have been achieved for nitrogen. A simple model explaining the behavior and features of this source is proposed and a comparison with experimental data is presented.
Fast-closing vacuum valve for high-current particle accelerators
Authors: Hanson C. L. , Clark J. C.
Published: March 2003

A fast-closing vacuum valve for a high-current particle accelerator was fabricated and tested. The 51 mm (2 in) ball valve is located in the accelerator beamline and closes within 5 ms if a vacuum loss is detected in the beamline. The valve is activated by a pressure-rise detector that initiates a capacitor bank to discharge its current through two solenoids. The impulse force closes the valve and activates an air-powered, cam-type mechanism. This mechanism forces a diaphragm equipped with an O-ring housing against the ball valve to produce a high-vacuum seal in the beamline. The valve functions reliably and is simple to reset after each firing. Only the metal energy absorbers, which are deformed during valve closure, require replacement. Another desirable feature of this valve is that its inner body contour is essentially symmetrical to the beamline. Thus, the magnetic field produced by the large return current is symmetrical and does not deflect the particle beam.
Automatic curve digitizer
Authors: Blackburn James A. , Smith H. J. T.
Published: March 2003

The construction of an automated curve digitizer using a desktop computer, digital plotter, and an optical reflective sensor is demonstrated. The equipment is useful for digitizing continuous line graphs.
Impedance measurement as a diagnostic for plasma reactors
Authors: Ilić Dragan B.
Published: March 2003

A simple and noninvasive technique is demonstrated for measuring the plasma electrical impedance for a class of reactors commonly used in fabricating integrated circuits. These reactors have an adjustable electrical matching network for optimizing the power transfer into the plasma. A procedure for determining in the matching network the needed values of components, which are normally difficult to measure directly, is also developed and illustrated. This dynamic measurement of plasma impedance, when combined with an electrical model of the plasma, is shown to be useful for monitoring the electron density and the electron-neutral collision frequency in the process plasma.
Effect of a magnetic filter on hydrogen ion species in a multicusp ion source
Authors: Ehlers K. W. , Leung K. N.
Published: March 2003

Hydrogen ion species and discharge characteristics have been compared for two different magnet geometries in a multicusp ion source. One magnet configuration indicated that the H2+ ion percentage in the extracted beam could be reduced by eliminating the high energy ionizing electrons near the ion extraction region. To accomplish this and maintain the desired features of both magnet geometries, a magnetic filter was installed near the source exit. With this combined arrangement, we found that the H+ ion percentage and discharge condition were much improved and a more uniform density profile across the extraction plane was achieved. The atomic species fraction can then be further enhanced by the addition of low-energy (∼16 eV) primary electrons into the source plasma chamber.