bluuebunny/crossref_metadata_2025 huggingface dataset:
High-resolution low-energy diffractometer
Authors: Wendelken J. F. , Propst F. M.
Published: March 2003

A high-resolution low-energy electron diffractometer is described. Motivation for its design features is provided and data obtained in several operating modes using an Al(100) target surface are displayed. These modes of operation include LEED, ILEED, AES, and ELS (electron loss spectroscopy). Angular dependence and temperature dependence may be examined in each of these modes. An interband transition is observed at 1.6 eV and a vibrational energy of 102 meV for oxygen on aluminum is reported. The influence of phonon scattering is displayed via temperature-dependent angular profiles.
50 picosecond detector laser pulse monitor
Authors: Green Samuel I.
Published: March 2003

A conventional Shottky barrier-switching diode is shown to be photosensitive and to have exceptionally high speed of response. Rise-times less than 50 psec have been observed in response to mode-locked lasers. The detector operates equally well at 532 and 1064 nm. The design of a high-speed detector mount is described.
Growth of large single crystals. Nd(C2H5SO4)3⋅9H2O (NES)
Authors: Fisher R. A.
Published: March 2003

A method for growing large, well-defined, visually flawless, oriented, single crystals (cylindrical boules at least 42 mm diam ×45 mm long) of neodymium ethyl sulfate 9 hydrate [Nd(C2H5SO4)3⋅9H2O (NES)] is described. A discussion of NES synthesis and solution stability is given. The single crystals were grown in Teflon-lined Pyrex containers in thermostats (held at 8 or 28°C) using H2SO4 (98 wt.%) to remove H2O. At 28 °C,the growth rate was 0.72 or 0.95 g NES/day; at 8 °C it was 0.40 g NES/day. The only detected impurity in the crystals was Na at ∼1500 at. ppm relative to Nd. One of the crystals was shaped into a sphere and used in a low temperature magnetothermodynamic investigation with fields along the c crystal axis. This study showed the stoichiometry to be off (possibly due to small solution inclusions) by −0.28±0.08% (confirmed by chemical analysis) in terms of moles of Nd resulting from a given crystal weight. Small translucent regions in the crystals grown at 28 °C were absent in the crystal grown at 8 °C, which was visually flawless and completely transparent.
Apparatus for the crossed-beam measurement of reactive scattering using short-lived radioactivity
Authors: Grover J. R. , Iden C. R. , Lilenfeld H. V. , Kiely F. M. , Lebowitz E.
Published: March 2003

A new method is described for crossed molecular beam measurements of differential cross sections. One of the reagent beams is labeled with a short-lived radioactive isotope, and detection utilizes counting of radioactive disintegrations. It is shown theoretically that for optimal sensitivity in crossed-beam scattering measurements, nuclides with half lives in the range 10−5–10−1 sec should be chosen for labeling. The usefulness of the new method was demonstrated by making measurements of differential cross sections for reactive scattering. The labeling nuclide chosen for development and testing was 0.032-sec 217At, and the chemical reactions used were Cl+HAt→HCl+At and Br+HAt→HBr+At. For the latter reaction, the total reaction cross section is only 1.5 Å2 under the conditions of the experiment. Background levels are sufficiently small that differential cross sections as small as 10−2 Å2 sr−1 could be measured at a resolution of 0.05 sr, if the primary beam intensity could be made large enough. One of the most useful features of this technique is that the measurement of absolute differential cross sections is readily carried out. Methods are described for making the requisite calibrations for the beam monitor and detector. In the prototype apparatus described here, the labeling nuclide was continuously generated by the radioactive decay of only 1–2 mCi of a long-lived precursor, 10-day 225Ac. However, it is calculated that on-line use of a nuclear accelerator to generate the short-lived nuclide will permit labeled beams 105 times more intense than those used in this demonstration experiment. Consequently, it should be possible to measure differential cross sections for reactions having total reaction cross sections significantly smaller than 1 Å2, and further development of this technique is therefore justified.
Active-recording x-ray crystal spectrometer for laser-induced plasmas
Authors: Koppel Louis N.
Published: March 2003

An active-recording x-ray crystal spectrometer has been built to recover spectral data from laser-fusion experiments. The spectrometer uses an x-ray-sensitive spatially resolving solid-state detector to monitor the spectra of line radiation of highly ionized silicon emitted by laser targets. A digital data system is described that expedites the recovery of data from the spectrometer.
Derivative measurement by frequency mixing
Authors: Paoli Thomas L. , Svacek Joseph F.
Published: March 2003

A dual-frequency technique for electronically measuring high-order derivatives by frequency mixing is described. The technique utilizes an ac modulation at two distinct but synchronous frequencies to produce a derivative signal at a useful difference frequency which is unique to the order of the derivative being measured. By appropriate selection of the frequencies, significant experimental advantages are obtained compared to the conventional method in which derivatives are sensed at harmonics of a single frequency. The technique is illustrated with a practical measurement of the second derivative of the electrical characteristic of a silicon rectifier diode.
Frequency-agile millimeter-wave phase lock system
Authors: Henry P. S.
Published: March 2003

A frequency-agile phase lock system for millimeter-wave klystrons is described. The system locks the klystron to a crystal-controlled reference signal derived from a frequency synthesizer. By programming the synthesizer, the klystron can be stepped through any sequence of frequencies lying within a band roughly 200 MHz wide. Acquisition of phase lock typically requires 1 msec. The 200-MHz pull-in range is achieved through the use of combined frequency and phase feedback; there is no ’’search’’ mode. The measured linewidth of an 82-GHz phase-locked klystron is ?10 Hz.
Metastable hydrogen atom detector suitable for time-of-flight studies
Authors: Czuchlewski S. , Ryan S. R. , Wing W. H.
Published: March 2003

A selective detection scheme for atoms in the metastable 2s state of hydrogen that provides the high spatial resolution (0.1 cm) necessary for time-of-flight atomic-beam studies is described. The scheme utilizes the Lyman α photon emitted when the metastable is de-excited in an electric field via the Stark effect. Details of construction and operation are discussed.
Measurement of very short fluorescence lifetimes by single-photon counting
Authors: Hartig Paul R. , Sauer Kenneth , Lo C. C. , Leskovar Branko
Published: March 2003

Measurement of very short fluorescence lifetimes by the single-photon technique is made possible by an improved fluorescence lifetime system. Fluorescence lifetimes of 4.94±0.07 nsec for anthracene in cyclohexane, 640±30 psec for diphenyl butadiene in cyclohexane, and 90±30 psec for erythrosin in water were determined. The use of a small wavelength shift between excitation and emission minimizes the effect of the wavelength dependence of the photomultiplier response and light pulser emission. The effects of deaeration of solutions and time averaging of the excitation profile are presented. We investigated the origin of small-amplitude early and late artifactual peaks in the light pulser and fluorescence profiles. Complications in the analysis of lifetime data introduced by intrinsic fluorescence and phosphorescence processes in commonly used absorption filters are discussed. Certain ’’blind spots’’ are found in the electronic pulse pileup rejection schemes most commonly used in photon counting.
Closed system gas circulating pump
Authors: Torre F. J. , Eshelman D. M. , Lee M. W. , Neufeld P. , Watson W.
Published: March 2003

A closed system gas circulating pump, which has a dynamic range 10−6–105 Torr and circulation rates 0–20 cm3/min, has been designed, constructed, and tested. The welded stainless steel pump is divided into two compartments separated by a welded stainless steel bellows, which has a magnet on the top surface and is driven by an external magnet. Through an appropriate arrangement of three-way solenoid valves, which are actuated by the external magnet drive, a unidirectional, continuous circulation of gas with respect to the external gas circuit is achieved in both the expansion and compression cycles of the bellows. The pressure drop across the bellows is solely that encountered in the gas circulation line. 363
Annular-cathode electron gun for in-line injection in a racetrack microtron
Authors: Manca J. J. , Edmonds D. S. , Froelich H. R.
Published: March 2003

A compact annular-cathode electron gun which allows direct, efficient injection into the accelerating structure of a racetrack microtron has been designed, built, and tested. The gun operates under pulsed conditions with applied high voltages of 40 kV or more and delivers an output current in excess of 1 A. Design and construction details are presented for both a basic gun and a gun with built-in output current monitor. Gun performance in a test chamber and in the multicavity racetrack microtron at the University of Western Ontario is described.
Pseudo real-time coded aperture imaging system with intensified vidicon cameras
Authors: Han K. S. , Berzins G. J.
Published: March 2003

A coded image displayed on a TV monitor was used to directly reconstruct a decoded image. Both the coded and the decoded images were viewed with intensified vidicon cameras. The coded aperture was a 15-element nonredundant pinhole array. The coding and decoding were accomplished simultaneously during the scanning of a single 16-msec TV frame.
Simplified magnetic suspension densimeter for absolute density measurements
Authors: Haynes W. M.
Published: March 2003

A magnetic suspension densimeter, incorporating three support coils, has been reduced to a system using only one coil. This simplifies considerably the design of the apparatus and the procedures involved in the measurements. This instrument can be used for absolute density measurements; i.e., it does not have to be calibrated with reference fluids of known density.
Mechanical analysis of internal friction measurement apparatus for sheet steel
Authors: Otabe Soji , Ohmura Taizo
Published: March 2003

Measurements of internal friction peaks for solute carbon and nitrogen in sheet steel specimens have been obtained with apparatus based on the original design of G. Collette et al. A mechanical analysis of the original design has been made and mechanical and theoretical discrepancies have been discovered. These are discussed in this report. Initial test results show that specimen size had a large effect on the internal friction values. It was observed that the change in behavior involved the coupling of the sheet specimen and certain parts of the apparatus, resulting in force-induced oscillations of the coupled system.
Supersonic atomic and molecular halogen nozzle beam source
Authors: Valentini James J. , Coggiola Michael J. , Lee Yuan T.
Published: March 2003

A reliable, resistance heated nozzle beam source is described which is capable of producing high-intensity supersonic atomic and molecular beams of chlorine, bromine, and iodine. The use of a high-density graphite nozzle eliminates corrosion and allows for operation up to 2300 K. The performance of this source is reported using seeded halogen gas mixtures which extend the accessible kinetic energy region to several eV.
Fabrication and calibration of ultrafine capillaries having diameters between 0.5 and 60 μ
Authors: Hedley W. H. , Olt R. G. , DuFour H. R. , Wurstner A. L.
Published: March 2003

Micro-openings having diameters from 0.5 to 60 μ, lengths from 100 to 4000 times the diameter, and regular cylindrical geometry were needed for studies of flows of gases and liquids. Comparison of predicted flow rates with those measured through these openings would serve as a basis for the prediction of leakage rates of toxic materials through small holes in container walls. A literature search uncovered numerous methods for making small holes in materials, but none of these seemed to be capable of covering the entire dimensional range of interest or especially for producing the smaller-diameter micro-openings. Two new methods of producing micro-openings having diameters spanning the required range and meeting requirements for regular cylindrical geometry were therefore developed. The first, called the cylindrical mount method, involved drawing quartz tubing to the desired diameter, filling the tubing with a low-melting metal alloy, casting the microtubing in epoxy resin, slicing the specimens of the cast material with a cutoff wheel, polishing the ends, and removing the metal alloy. The second, called the disk mount method, consisted of drawing quartz tubing to the desired diameter, drilling a hole in a thin metal disk, inserting the microtubing in the hole, cementing it in place, and then breaking off the ends of the microtubing to the approximate desired length. The cylindrical mount method successfully produced micro-openings with regular cylindrical geometry from 5 to 60 μ in diameter. The disk mount method produced micro-openings of the same quality in the diameter range from 0.5 to 5 μ.
Slotted tube resonator: A new NMR probe head at high observing frequencies
Authors: Schneider Hans Jürgen , Dullenkopf Peter
Published: March 2003

Superconducting magnetic systems permit increasing observing frequencies for NMR experiments. The sensitivity and range of application of the single-layer detection system is evaluated. High measuring frequencies demand new detection systems because the conventional detection systems lose their good features above about 100 MHz. In this paper a new detection system is presented. The slotted tube resonator (STR) is suitable for all intensities of magnetic field which will be produced in the near future. The characteristic parameters of the STR are calculated and the construction is described in detail. Theoretical sensitivity considerations are compared with practical measurements.
Tailored waveform modulation calculation for integral Auger spectra
Authors: Springer R. W. , Pocker D. J.
Published: March 2003

Basic lock-in amplifier principles and instrument response function formalism are reviewed to provide a mathematical model for potential modulation signal detection in Auger electron spectroscopy. The effect of sinusoidal modulation on a Gaussian peak is calculated exactly as a function of modulation amplitude. The result illustrates the degree of distortion and linearity of signal strength as a function of modulation. Nonsinusoidal modulations are considered and when proper waveforms are utilized can provide EN (E) and I (E) =ℱE′N (E′) dE′ measurements directly from the lock-in amplifier. The removal of troublesome background effects is also accomplished to second- and third-order terms depending upon the modulation used. Results of the application of the various tailored modulation waveforms on Auger spectra are presented.
Measurement of charge distribution in electrets
Authors: Collins R. E.
Published: March 2003

A new nondestructive technique is described which provides information about the distribution of charges in nonpolar electrets. Changes in the equivalent electret voltage are measured during and after the absorption of a short pulse of heat on one side of an otherwise well thermally isolated electret. The total electret charge and its mean position are obtained directly with this technique. The main features of the charge distribution can also be resolved using a deconvolution technique, although it is not yet possible to determine fine details uniquely.
Intense flowing hollow cathode lamp
Authors: Rambow F. H. K. , Schearer L. D.
Published: March 2003

An inexpensive, simple, and versatile hollow cathode lamp has been developed which produces intense ion resonance radiation of about 1 mW into 4π/25 sr. The lamp employs flowing helium gas to sustain the discharge. The construction permits a variety of cathode seed materials to be easily interchanged. The same lamp has been used as a source of ion resonance radiation for Ca, Ba, Zn, Mg, Sr, Yb, and Eu.
Thermal conductance of indium solder joints at low temperatures
Authors: Radebaugh Ray
Published: March 2003

The thermal conductances of two indium solder joints were measured between 2 and 130 K. One joint was between two copper pieces and the other joint between beryllium and copper. Both joints gave nearly the same results even though beryllium is much more difficult to wet with indium. The thermal conductances of the joints at 4 K were considerably higher than those of joints using alloy solders such as lead–tin. The maximum conductance per unit area was about 100 W/cm2 K, which occurred at about 20 K.
Exposure time of a pulsed channel plate
Authors: Nahrath B. , Blanz W. E. , Decker G.
Published: March 2003

By means of a N2 laser with about 0.5-nsec pulse duration it was possible to determine the exposure times, realized by pulsing operation, of a two-stage channel plate (3 nsec) and an image converter planar diode (3 nsec).
Full synchronization of an optical multichannel analyzer for picosecond spectroscopy
Authors: Ostertag E.
Published: March 2003

A continuous or slowly varying optical spectrum can be recorded electronically by means of an optical multichannel analyzer (PAR). However, this instrument is not very well suited for pulsed operation, especially at low repetition rates, as is the case with mode-locked lasers. The interface described here converts this analyzer into a true pulse-operated system, fully synchronized, and having a pulse selection capability. This interface provides an additional feature, ’’on line’’ background substraction, which corrects automatically for long range drifts of the dark current of the television picture tube.
NMR probe for combined homonuclear multiple pulse decoupling and magic angle spinning
Authors: Pembleton R. G. , Ryan L. M. , Gerstein B. C.
Published: March 2003

An NMR probe is described which is capable of use in combined multiple pulse–magic angle spinning experiments for removal of homonuclear dipolar broadening and chemical shift anisotropies in randomly oriented samples. Two examples are included to illustrate the utility of the technique.
Medium speed gating of ISIT tubes
Authors: Simpson R. W. , Talmi Y.
Published: March 2003

Image intensified silicon vidicon tubes (SITs) and doubly intensified vidicon tubes (ISITs) are useful in time-resolved spectroscopy studies, when gated by a kilovolt pulse applied to the tube gate or photocathode electrode. An ISIT detector, used in conjunction with the Princeton Applied Research Corporation (PARC) optical multichannel analyzer (OMA), has been gated by HV pulses as short as 30–50 ns. A simple modification of that ISIT reduced the minimum gate pulse width of the ISIT to 5 ns. The time and spatial resolution are primarily limited by the pulse distortion introduced by the various stray reactances in the gate coupling circuitry, regardless of the conductivity of the photocathode.
Correction of secondary ion intensity by a new total ion monitoring method
Authors: Kobayashi H. , Suzuki K. , Yukawa K. , Tamura H. , Ishitani T.
Published: March 2003

A new total ion monitoring (TIM) method is developed for the correction of secondary ion intensity changes. These changes depend on the primary ion beam current fluctuations, surface topography, and surface state of the specimens to be analyzed. The total ions detection sensitivity of this new TIM is 103 times better than that of the conventional method using the absorbed primary current. It is possible to obtain the true concentration image of a specific element for the specimen surface by dividing the specific ions (mass analyzed) by the total emitted ions (without mass analysis) at a certain solid angle. This process eliminates the influence of primary ion beam current fluctuations, surface topography, and surface state. In this paper, the new TIM method is described. In addition, its applications to low alloy steel fracture surfaces, a color television shadow mask, and Quenched and Tempered steel fracture surfaces are investigated. The obtained results indicate good agreement with the true concentration.
Automated ’’float’’ method for determination of densities of molten salts
Authors: Andreasen Helge A. , Bjerrum Niels J. , Foverskov Carl Erik
Published: March 2003

A new system for measuring densities of molten salt systems is described. The system consists of an accurate metal block furnace, the temperature of which can be changed linearly in time, a fused quartz tube containing quartz floats loaded with a ferromagnetic material, a differential transformer wound with platinum wire, an amplifier, a digital voltmeter, an interface, a paper tape punch, and a recorder. The advantages of the system are its ease of operation compared to other ’’float’’ methods, and the possibility of looking at highly colored melts and also melts having a high vapor pressure.
Determination of electron energy distribution in a plasma
Authors: Chakravarti P. K. , Gupta S. N. Sen
Published: March 2003

A simple method of direct display of electron energy distribution in a gaseous plasma is presented. The apparatus is an analog computer used on line with a Langmuir probe. The new features of this work are (1) an analysis of the time response of a filter input differentiating operational amplifier, (2) a procedure for noise eliminating differentiation that is also capable of taking account of the higher derivatives of the input signal, and (3) a simple determination of the plasma potential with a phase comparator. The method is being used in the analysis of electron energies in a positive column plasma. The results so far found show that the distribution has a single peak sharper than the Maxwellian at pressures of about 0.1 Torr and it changes into a two-peak distribution at lower pressures (∼0.01 Torr). The second peak also found in similar studies by other investigators (Alexeff and Howell, Rezacova et al.) is possibly due to the presence of accelerated electrons from the hot cathode of the discharge.
Noise discrimination method for pulse counting applications
Authors: Arnow M.
Published: March 2003

A method is shown which distinguishes noise bursts from Poisson time distributed pulses on a real time basis. A gate is described which will pass only the Poisson distributed pulses.
Determination of slopes of microscopic surface features by Nomarski polarization interferometry
Authors: Dowell Michael B. , Hultman Carl A. , Rosenblatt Gerd M.
Published: March 2003

The two images produced by each feature in a Nomarski polarization interferogram are in general not equivalent. In the case of an etch pit or other isolated, sloped feature, the angle ϑ between the feature and the flat background surface can be computed from the fringe spacing l in the feature by the relationship sin[ϑapp−(ε/2) cosα] =λ/2l. The angle ε/2 is calculated from the background fringe spacing l0 and the relation sin(ε/2) =λ/2l0. The angle α is the orientation of the feature with respect to the background interference fringes on the flat surface. An additional correction is necessary to calculate ϑ from ϑapp because of the distortion of the fringe spacings which occurs in microinterferometers when using microscope objectives of large numerical aperture. Empirical observation shows that this obliquity correction can be calculated accurately by a formula first derived by Ingelstam. The method of determining slopes from fringe spacings in Nomarski polarization interferometry is described in detail. This description may be of interest to investigators who study crystal surfaces or changes in their topography during chemical reactions, because the Nomarski microinterferometer is suitable for continuous observation of surface changes which accompany reactions in a controlled-atmosphere heating stage.
Superleaktight Teflon gasket seals for use at low temperatures
Authors: Gylling R. , Manninen M. , Veuro M. , Zimmermann W.
Published: March 2003

A commercial expanded Teflon gasket material (Gore-Tex) in the form of 1-mm-diam cord has been found useful in making 4He superleaktight seals between metal parts at low temperatures.
Improved method for heating large tungsten cathodes
Authors: Laul V. , Rynn N. , Böhmer H.
Published: March 2003

A modification of a previously described method for heating large cathodes is described. Self-sustaining ac electron bombardment of two tungsten electrodes is replaced by dc electron bombardment of the main cathode using a LaB6 coated auxiliary electrode.
Demand-type gas supply system for rocket borne thin-window proportional counters
Authors: Acton L. W. , Caravalho R. , Catura R. C. , Joki E. G.
Published: March 2003

A simple closed loop control system has been developed to maintain the gas pressure in thin-window proportional counters during rocket flights. This system permits convenient external control of detector pressure and system flushing rate. The control system is activated at launch with the sealing of a reference volume at the existing system pressure. Inflight control to ±2 Torr at a working pressure of 760 Torr has been achieved on six rocket flights.
Inexpensive high performance dichrograph control unit
Authors: Krausz Elmars , Cohen Geoffery
Published: March 2003

A simple inexpensive circuit is described which, when combined with a high efficiency photomultiplier, a low-grade high-voltage supply, and a phase-sensitive detector, provides the electronic basis of a versatile high performance dichrograph.
Simple moiré technique for measuring normal anisotropy
Authors: Sang H. , Kenny L. D.
Published: March 2003

An apparatus for measuring the normal mechanical anisotropy of a tensile specimen using a moiré fringe technique is described. Measurement of R values by the method specified was found to be a quick and reproducible procedure.
Automatic internal friction and modulus measurement apparatus utilizing a phase-locked loop
Authors: Simpson H. M. , Sosin A.
Published: March 2003

An inexpensive apparatus for the continuous and automatic measurement of internal friction and elastic modulus is described. This apparatus is regenerative, maintaining a specimen in resonance at constant amplitude, unless interrupted by the experimenter. A vital component of this system, generally absent in such devices, is a phase-locked loop.
Impulse response of curved microchannel plate photomultipliers
Authors: Boutot J. P. , Delmotte J. C. , Miehé J. A. , Sipp B.
Published: March 2003

The temporal characteristics of microchannel plate photodetectors are discussed in the pulse-saturation and the linear-amplification modes of the electron multiplier.
Method for recording the three-dimensional trajectory of a luminous pointlike object
Authors: Indebetouw G. , Tschudi T.
Published: March 2003

A simple method to record the three-dimensional, time-resolved trajectory of a luminous pointlike object moving in space is presented. The trajectory can easily be calculated from a single photographic record of two superposed images of the moving object formed by two optical systems viewing the object space from different angles. The method could find applications in the field of mechanics (machine control), medicine, or dentistry (design of prostheses).
Resolution of a spectrum analyzer under dynamic operating conditions
Authors: Tsakiris George D.
Published: March 2003

The effect of high frequency sweep rate on the resolution bandwidth of a spectrum analyzer is discussed. An analytical treatment of the problem is presented and the cases of a noncausal and a causal resolution filter are compared. The case of a cascaded synchronous single-tuned amplifier is also examined. The analysis shows that under certain circumstances, the dynamic resolution bandwidth can be used instead of the static one. In this case, the changes introduced by the high frequency sweep rate in the resonance curve of the resolution filter must be taken into consideration.
Microcomputer-based controller for temperature programming the direct inlet probe of a high-resolution mass spectrometer
Authors: Pomernacki Charles L.
Published: March 2003

A microcomputer-based temperature controller has been developed which uses the high-level language basic. The controller dynamically programs the temperature profile of the direct-inlet probe in a high-resolution mass spectrometer. Temperature sensing is accomplished using a probe-mounted thermocouple which feeds a digital thermometer. A microprocessor, executing a digital proportional-plus-integral-plus-derivative (PID) feedback-control algorithm in interpretive basic, reads the probe temperature once every second and computes a control action. This action determines a power-level setting for the probe heater, thus completing the feedback path. The controller has been used for linear-ramp pyrolysis experiments on the mass spectrometer. Performance curves for the ramp response, as well as for step responses, are exhibited. A steady-state precision of ±0.1°C is attained. The microcomputer approach is open-ended in that more complex temperature profiles and control algorithms are achievable by changing the software program. The generality of implementation is sufficient enough to allow its application to other pyrolysis experiments.
Interface between a Biomation 8100 and a remote computer for data acquisition in TEA-CO2 laser-induced photochemistry
Authors: Bialkowski S. , Guillory W. A.
Published: March 2003

The experimental setup for data acquisition in infrared photolysis experiments is described. The data was obtained with a Biomation model 8100 transient recorder interfaced to a remote computer via a serial line. The interface was built from inexpensive parts and the circuit is described in detail. The described method of data acquisition may be used where high rf noise renders conventional multichannel analyzer techniques impractical.
Technique for measuring the differential ion flux vector
Authors: Stone Nobie H.
Published: March 2003

A diagnostic technique is discussed which gives the angle of incidence of a plasma stream, the energy corresponding to the mean velocity of the ions, and the distribution of the ion thermal motion superimposed on the drift. The technique is shown to be operable for low-energy plasma streams (5–60 eV) and in the presence of multiple plasma streams differing in direction and/or energy. Resolution is better than 3.5° with ∼1% energy spread in the streams. The instrument samples the plasma at a single region in space, independent of the number of plasma streams or their characteristics. The technique was developed to investigate plasma flow interactions in the laboratory. Its capabilities are demonstrated by some preliminary data taken for the case of a long cylindrical body inmersed in a drifting, collisionless plasma.
Use of the thin dielectric track detector as particle discriminator
Authors: Pai H. L. , Phillips C. R.
Published: March 2003

Thin dielectric track detectors are applied as particle discriminators, with special reference to practical applications such as alpha dosimetry. The thin detector is defined as a detector in which the particle range is greater than the film thickness.
Technique for measuring very high surface velocities
Authors: Maron Y.
Published: March 2003

A new interferometric technique for measuring displacements of surfaces moving at velocities in the range of a few millimeters per microsecond is presented. The technique is also capable of recording large and rapid velocity variations which are very difficult to measure by known methods. It is based upon monitoring the signal resulting from the interference between two beams reflected from the surface at different incidence angles. Measurement systems for specularly as well as diffusely reflecting surfaces are described. A light source with very modest temporal coherence delivering about 100 mW power is required. The accuracy of the technique is discussed.
Inexpensive portable Cu2S–CdS radiometer
Authors: Windawi H. M.
Published: March 2003

A portable radiometer employing a large area Cu2S–Cds solar cell as the sensing element has been used for the measurements of solar radiation intensity. Its characteristics and calibration are discussed.
Using a pulse height analyzer as an X
Y recorder: Application to Auger spectroscopy
Authors: Dwyer Daniel J. , Rodgers Robert S.
Published: March 2003

The circuit described provides a simple, novel, and inexpensive (about $50) method of using a multichannel pulse height analyzer to digitize and record an Auger spectrum and to read it out in computer-compatible form for subsequent data analysis. Other potential uses might include the digitization of ESCA or ESR spectra. The technique is applicable to the recording of any experimental data provided that the experiment response signal is to be recorded against an excitation signal which is changed linearly with time.
Magnetic float densimeter for wide range density measurements
Authors: Barman Bhajendra Narayan , Rahim Zillur
Published: March 2003

A magnetic float densimeter capable of measuring density over a wide range of values to within 5 ppm is described. The solenoid of the system consists of a few thousand turns of fine copper wire and the float has been provided with a quickfit joint to change its weight by the addition or subtraction of mercury from inside. There is a micrometer syringe assembly to vary the concentration of the solution. The whole densimetric assembly is placed in a thermostatic air bath. A fixed temperature of the air bath is maintained by a sensitive relay system and the exact temperature of the experimental liquid at the time of measurements can be checked and monitored with the help of a specially designed thermistor probe.
On the use of screw-fastened joints for thermal contact at low temperatures
Authors: Manninen M. , Zimmermann W.
Published: March 2003

Electrical resistance measurements at 4.2 K on a simple screw-fastened joint between two pieces of copper indicate the usefulness of such joints for thermal contact down to millikelvin temperatures.
Thermal conductivity of an electrically conducting epoxy below 3 K
Authors: Reynolds C. L. , Anderson A. C.
Published: March 2003

Electronic conduction enhances the thermal conductivity of a commerical silver-filled epoxy below 0.5 K. When used as a bonding agent between two metals, this epoxy provides improved thermal contact; however, when one or both of the materials to be joined is a dielectric, no advantage is obtained over a pure epoxy joint due to the presence of the thermal boundary resistance.
Active thermal compensator for diode laser stabilization on closed-cycle refrigerators
Authors: Jennings Donald E. , Hillman John J.
Published: March 2003

Cycling of a closed-cycle refrigerator produces temperature oscillations at the cold-tip which may be 0.5 K peak-to-peak. An active diode heater is described which compensates for the varying temperature and reduces the oscillations at the sample to about 0.003 K peak-to-peak at 9.5 K.
Bakeable, ultrahigh-vacuum compatible, retractable contacting mechanism for i
n s
i
t
u thin film resistance and superconductivity measurements
Authors: Miller D. L.
Published: March 2003

A bakeable, ultrahigh-vacuum compatible, retractable four-point resistance probe has been constructed to make in situ measurements of superconductivity in ultrathin films. A bellows actuation mechanism allows the very compact contacting mechanism to be withdrawn from the substrate area for cleaning and characterization of the substrate surface, then returned for film resistance measurements. The device has been used to make contact to Pb films less than 10 Å thick deposited on high-resistivity Si substrates, which require a cleaning step that would be destructive to permanent or predeposited contacts.
Optical alignment procedure for an unstable resonator high-power laser
Authors: Ackenhusen John G. , Steel Duncan G.
Published: March 2003

A method for aligning the optics of a pulsed high-power positive branch unstable resonator is described. The procedure relies on the distribution of the output beam and is thus independent of a separate alignment laser, allowing systematic and rapid adjustment.
Cold probe semiconductor type tester
Authors: Dhar S.
Published: March 2003

A simple three-probe setup is described for the nondestructive testing of the type of high resistivity semiconductors. The apparatus does not require heating of one of the probes and is more reliable and sensitive compared to the instruments already in use.
Photon correlation in the nanosecond range and its applications to the evaluation of RCA C31034 photomultiplier tubes
Authors: Gulari Erdogan , Chu B.
Published: March 2003

Photon correlation in the nanosecond delay time range by arrival times of photoelectric pulses can be achieved using a computer-controlled digital counter. We have demonstrated the dynamic range of such a photon-counting system by determining the linewidths of light scattered from concentration fluctuations in a noncritical binary fluid mixture and in an aqueous suspension of polystyrene latex spheres. The system can be used to measure linewidths from about a few hundred hertz to the tens of megahertz. The RCA C31034 and C31034-A photomultiplier tubes with gallium arsenide photocathodes have been assessed for application in experiments related to photon-correlation spectroscopy. Pulse height distributions, overall quantum-counting efficiencies, time-dependent statistical correlations, and dark count properties have been investigated. Our results show that both tubes are superior to the previously tested photomultiplier tubes in terms of overall quantum-counting efficiencies, after-pulsing characteristics, and dead time. They match with existing fast amplifiers and discriminators which permit photon-correlation measurements in the nanosecond delay time range.
Double-crystal, vacuum x-ray diffractometer
Authors: Kikuta S. , Takahashi T. , Tuzi Y. , Fukudome R.
Published: March 2003

An x-ray double-crystal diffractometer installed in a high-vacuum chamber is designed and constructed for the study of photoelectron emission accompanying x-ray dynamical diffraction. The rotation mechanism of the second crystal, based on torsion of a cylinder, provides an accuracy of 0.1 s of arc.
Magnetoflyer method for measuring gas-gun projectile velocities
Authors: Kondo Ken-ichi , Sawaoka Akira , Saito Shinroku
Published: March 2003

The magnetoflyer method has been developed as a convenient and fiducial technique for measuring projectile velocities from propellent and gas guns. The velocity is estimated from the time interval between two electromotive force signals when the projectile, which includes a small ferrite magnet, passes through two pick-up coils. It was confirmed that the method was available up to 5 mm/μs.
Optical stress-wave measurement in hammer drilling rods
Authors: Borg Lars
Published: March 2003

A new method of optically measuring the state of stress in a drilling rod is described. Using a position-sensitive Schottky photodiode (PSD) and a laser beam, the displacement of the surface of the rod was measured during stress-wave passage. The results are described. The accuracy was 3%, at a surface displacement of 2 mm. The rise time of the detector was better than 60 μs in an area with linear signal response. It may be altered to get higher speed.
New technique for improved low-temperature SQUID NMR measurements
Authors: Webb R. A.
Published: March 2003

A description of the technique used for performing a variety of SQUID NMR measurements in fields varying from 3.7 to 309 G is presented. Pulsed NMR, cw NMR, adiabatic fast passage, and static susceptibility measurements have been made on liquid 3He, using the same detection system, in the temperature range 1.2K–2mK. The spin-lattice relaxation times varied from 100 s at 1 K to as fast as 0.26 ms at 2 mK. The spin–spin relaxation times varied from 3×10−5 s in 309 G to nearly 3×10−3 s in 3.7 G.
Convectively mixed humidity chamber
Authors: Ashworth T. , DeVries J. L. , Smith David R.
Published: March 2003

A humidity chamber is described, based on the principle of thermodynamically regulated (vapor pressure) control, in which the attainment of thermodynamic equilibrium is enhanced by gentle convective stirring. It may be used as a chamber which maintains constant dew point while allowing variation of the temperature of the test section, or the test section may be kept at constant temperature while the dew point temperature is varied. Dew point temperatures may be produced with a certainty of 0.3 and 0.1 °C at −20 °C and +30 °C, respectively; calculated relative humidities have an uncertainty of 0.1%–0.6% relative humidity for low to high humidities, which correspond to errors of 4% and 1%, respectively. The chamber has been operated down to -200 °C.
Measuring system for high-precision voltage measurements from high-impedance sources
Authors: Edwall G.
Published: March 2003

A high-impedance voltage measuring system is described. The system is intended for long-term, high-resolution, high-accuracy measurements from high-impedance sources or sources which are easily polarized. For input voltages of 1-V magnitude, the overall accuracy is better than 0.1 mV and the resolution is 30 μV (noise limited). The input impedance is above 2×1014 Ω and the input bias current is 14 fA. A flexible scanning channel selector allows measurements from up to eight signal sources in parallel, a low-cost calculator provides on-line analytical processing of measurement data, and a dynamic variable zero suppression unit makes long-term recording of signal variations down to the resolution level possible.
Measurement and analysis of fluorescence decay curves
Authors: Wild Urs P. , Holzwarth Alfred R. , Good Hans P.
Published: March 2003

A fluorescence lifetime apparatus using a mode-locked argon ion laser as excitation source and single photon counting detection is described. The high repetition rate and intensity of the excitation source allows twofold discrimination in the stop channel, giving excellent time resolution. The data analysis is based on statistical concepts. The standard deviations of the Fourier transforms of the deconvolved decay curves are discussed and the advantages of performing a curve fit in the Fourier space are outlined.
Nondestructive technique for the measurement of fast diffusion
Authors: Kim K. K. , Mundy J. N. , Puri S. M.
Published: March 2003

A nondestructive technique is described that measures diffusivity of fast-diffusing atoms to an accuracy of 1%. The technique utilizes coincidence counting of γ rays emitted in opposite directions when a positron annihilates with an electron. The application of the method is discussed.
Linearization of thermistor resistance-temperature characteristics using active circuitry
Authors: Chakravarty R. K. , Slater K. , Fischer C. W.
Published: March 2003

A linear relationship is obtained between the temperature of a thermistor and the voltage output from an electronic circuit into which the thermistor is incorporated. The circuit is basically a combination of a logarithmic amplifier and an analog divider. It is capable of producing a linear voltage output with temperature for virtually all commercially used thermistors having resistance in the range of 3 MΩ–500 Ω.
New apparatus for accurate diffusion measurements in fluids
Authors: Codastefano P. , Di Russo A. , Zanza V.
Published: March 2003

A new apparatus for the diffusion measurement of radioactive tracers in fluids is reported. This apparatus allows measurements of the diffusion coefficient with an error less than 0.3% in a temperature range from 70 to 350 K and up to a pressure of 50 bars.
Standing wave high gradient accelerator structure
Authors: Vaguine Victor A.
Published: March 2003

A novel type of standing wave linear accelerator structure has been developed at Varian Associates, Inc. This accelerator is an interlaced combination of two side-cavity-coupled standing wave substructures. An S-band prototype accelerator guide with two identical substructures and total accelerating length of 10 cm has been built and successfully tested with a 2-MW magnetron. Significant improvement in maximum permissible accelerating gradient was achieved. Output electron beam energy of 4 MeV and corresponding accelerating gradient of 40 MeV/m were experimentally demonstrated. The stunt impedance of the structure corresponds to 83 MΩ/m.
EPR techniques for studying defects in silicon
Authors: Brower K. L.
Published: March 2003

Due to long spin-lattice relaxation times and low defect concentrations, the EPR study of defects in irradiated silicon requires special experimental capabilities. The superheterodyne spectrometer described in this paper, which has been used in numerous defect studies, can detect 1010 spins/Oe linewidth. This spectrometer employs superstabilized, phase-locked klystrons, can be tuned to either the absorption or the dispersion mode, utilizes phase-sensitive detection, and can operate at either X or K band. The microwave probe and cryogenic system allow us to produce defects in situ at low temperatures and to probe these defects with light, stress, and annealing. For these measurements the cavity and sample can be stabilized to ±0.01 K between 4 and 300 K.
Ammonia-pellet generation system for the Baseball II-T target plasma experiment
Authors: Goodman Ronald K. , Hunt Angus L.
Published: March 2003

The irradiation of a small pellet by a pulsed laser is one method of producing a startup target plasma for plasma experiments employing neutral-beam injection. A system for generating charged, uniformly sized, solid-ammonia, 150-μm-diam, spherical pellets having a charge-to-mass ratio of 10−4 C/kg is described. These pellets are electrostatically guided at a speed of 32 m/sec (over a distance of several meters) to a laser focal zone. This complete system (pellet generation and pellet guidance) has been successfully operated on a 3-m test stand where 250-μm-diam pellets were regularly irradiated by a pulsed, 30-J CO2 laser. The system is now installed on the Baseball II-T experiment; in preliminary tests, several 150-μm-diam pellets were irradiated with the pulsed 300-J CO2 laser.
Addition of an electron multiplier to the Varian movable Faraday cup assembly for measurement of angular resolved photoemission
Authors: Weeks S. P. , Ehrlich C. D. , Plummer E. W.
Published: March 2003

The movable Faraday cup assembly of the varian LEED optics system has been modified by the addition of a channel electron multiplier. Signal-to-noise was increased by several orders of magnitude, rendering the assembly suitable for the measurement of energy distributions of photoelectrons with an angular resolution as small as ±2°.
ac calorimetry at high pressure
Authors: Baloga J. D. , Garland C. W.
Published: March 2003

The ac calorimetry technique has been adapted for use at hydrostatic gas pressures up to 3 kilobar. The theory of this method has been extended to take into account high gas densities and low sample thermal conductivities, and the resulting equations have been tested on samples of Invar and ammonium chloride. The method is especially attractive for studying heat capacity variations in samples that undergo second- or higher order phase transitions at high pressures.
Dialable ampere current source with ovenless construction and ppm/h stability
Authors: Norris C. B. , Stuart D. T.
Published: March 2003

This paper describes the design and construction of a highly stable, dialable current source developed for use with an electron beam transport system. The current regulator is ovenless and employs thermal feedback to cancel effects of ambient temperature variation and self-heating in the current-sensing resistor. The regulator is of modular design and incorporates remote control features to facilitate use in applications requiring many current channels. The output current can be modulated to permit Monte Carlo beam optimization. The output stability is better than ±1 ppm/h at an output current of 1 A, in an environment subject to ±1 °C temperature variation, measured using instrumentation having a nominal stability of ±1.5 ppm/h.