bluuebunny/crossref_metadata_2025 huggingface dataset:
Broadband directional couplers for microwave-microwave double resonance
Authors: Ekkers J. , Bauder A. , Günthard Hs. H.
Published: February 2004

An improved type of broadband directional couplers specially suitable for microwave-microwave double-resonance experiments is described. It allows coupling of microwave power between different waveguide bands with almost constant coupling ratio over a full waveguide band. Constructional details and performance of two models are given, one for coupling power between 18 and 26.5 GHz into an X-band guide, the other for coupling power between 12.4 and 18 GHz into an X-band guide.
Simple pulse generator for pulsing xenon arcs with high repetition rate
Authors: Beck G.
Published: February 2004

The pulse generator described is capable of delivering up to 1500 A in a pulse of 150 μsec halfwidth at 16 pps to increase the brightness of an Osram 450 W xenon lamp.
Static elimination by corona discharge
Authors: Nicholson P. W.
Published: February 2004

A simple device for eliminating static electricity on small objects is described. It should be useful in situations where it is necessary to avoid the more usual type of device employing radioisotopes.
Cylindrical flow reactor for the study of heterogeneous reactions of possible importance in polluted atmospheres
Authors: Hedgpeth H. , Siegel S. , Stewart T. , Judeikis H. S.
Published: February 2004

This paper discusses the construction of a cylinder flow reactor used for studying heterogeneous reactions, with particular reference to reactions involving NOx. This system incorporates methods of gas analysis such as optical absorption (NO2), chemiluminescent (NO or O3), gas chromatography (N2 or O2) and mass spectrometry (SO2, etc). The system was constructed such that experimental conditions could be varied over a large pressure range from 1 to 700 Torr with a relative humidity variation of 0–90%.
Suppression of odd harmonic components in a cyclotron beam pick-up signal by means of sampling
Authors: Marchand J. F. P. , Schutte F. , Hagedoorn H. L.
Published: February 2004

The current and the phase angle of the internal beam with respect to the accelerating voltage of the Eindhoven University of Technology AVF cyclotron are measured using a number of electrostatic induction pick-up probes. Data handling is by means of sampling, correlating, and a CAMAC system. On the hf signal is superimposed a very strong first (fundamental) harmonic signal induced by the accelerating voltage. Therefore, the second harmonic component of the probe signal is used. Furthermore, all odd harmonic components of the signal are suppressed by using a special sampling technique. For the first harmonic component the suppression is about 60 dB.
Single photon phase fluorimetry with nanosecond time resolution
Authors: Schlag E. W. , Selzle H. L. , Schneider S. , Larsen J. G.
Published: February 2004

A multipoint correlation technique is described for the measurement of the fluorescence decay from a sample excited with modulated light, where the modulation and the response can be arbitrarily complex. In the case of weak fluorescence, individual photons are resolved which are so correlated. The apparatus has a high dynamic range at extremely low photon densities, or very high photon rates, only limited by the single pulse resolution time of fast photomultipliers and counters.
The calibration and use of a conical hot film anemometer probe in recirculating water flow
Authors: Stenhouse Michael H. , Stoy Robert L.
Published: February 2004

A calibration for directional sensitivity of a conical hot film anemometer probe is described. It is usually assumed that the conical probe is insensitive to the velocity vector direction but, in fact, this is not so because deviations of ±60% of the mean velocity can occur at low water speeds. In this study, the probe is aligned at right angles to the velocity vector but the trend of the results applies to probes aligned along the velocity vector. An application of the conical probe to velocity measurements in a vortical water flow for speeds from 0.06 to 3 m/sec is discussed.
A slow-scan TV-camera for the analysis of fluctuating illumination patterns
Authors: Arrigucci A. , Pandolfini P. , Stefanutti L. , Vanni R.
Published: February 2004

A versatile TV-camera system is proposed for the analysis of fluctuating illumination patterns. The system consists of a pulsed slow-scan TV camera followed by a wideband analog recorder and an electronic computer. The system is described in detail. The results of preliminary tests carried out on a prototype built in our Institute are reported and discussed.
Automated constant pressure reactor for measuring solubilities of gases in aqueous solutions
Authors: Moudgil B. M. , Somasundaran P. , Lin I. J.
Published: February 2004

An automated constant pressure reactor for measuring the solubilities of slightly soluble gases in aqueous solution is described. The apparatus can also be used for kinetic studies of aqueous reactions involving a gaseous reactant or product. The system can be operated unattended and therefore can be used for prolonged experimentation. Results obtained using the apparatus for solubilities of methane and butane in triple distilled water at atmospheric pressure and 25°C are compared with those reported in the literature.
A dual image adaptor for 16 mm cine cameras
Authors: McCarthy M. J. , Molloy N. A.
Published: February 2004

A device is described which facilitates the convenient photographic recording of two separate images on 16 mm cine film. Two examples are given of the use of the device in conjunction with hot wire and hot film anemometers, in experimental studies of an unsteady fluid flow system.
A data acquisition system for electrostatic energy analyzers
Authors: Bray A. V. , Eriksen F. J. , Fernandez S. M. , Pollack E.
Published: February 2004

An interface system has been developed which enables rapid acquisition of data from an electrostatic energy analyzer by a multichannel analyzer. Sample data from inelastic ion-molecule collisions demonstrate its capabilities.
High thermal conductivity bearing for rotating devices at liquid helium temperatures
Authors: Wyatt C. L. , Haycock R. H.
Published: February 2004

A ball bearing of high thermal conductivity has been developed to provide conductive cooling for rotating optical devices at 2 rps. The bearings are made of pure copper which is silver coated. The bearing and hub are spring loaded to provide constant contact pressure even under changing temperature conditions. The bearing can cool a 310 g circular variable optical filter to 10K within 83 min. The bearing was utilized in a helium-cooled spectrometer which was launched on a Black Brant VC rocket at Poker Flat, Alaska, on 22 March 1973, during a condition of post auroral breakup. Spectra were obtained form 185 km to about 40 km. Some 630 spectral scans covering the range of 6.75 to 23.3 μ were telemetered. The special bearing performed well through all portions of the rocket trajectory.
A synchronization device for nanosecond range coaxial spark lamp
Authors: Benci S. , Manfredi M. , Benedetti P. A.
Published: February 2004

A method is described for decreasing to 2% the jitter in firing of free running discharge tubes by applying synchronizing current pulses.
A computer controlled system for timing the Crab pulsar
Authors: Groth Edward J. , Nelson Mark Radford
Published: February 2004

A computer system which controls optical timing observations of the Crab pulsar is described.
A method for determining the location of internal partial discharges in dielectrics
Authors: Johnson R. G. , Tibbetts S. J.
Published: February 2004

The site of a partial discharge within a dielectric can be determined by the use of localized fields. An example is given of the technique using a new graphic corona display method.
A new capacitive probe for the measurement of high-field domains in Gunn-effect devices
Authors: Riginos Vasilis E.
Published: February 2004

A new capacitive probe for Gunn-effect domain measurements is reported. The probe was constructed by a vacuum deposition technique rather than the use of thin foils. This results in greatly improved resolution and easier construction.
Novel electroexplosive device firing method
Authors: Rosenthal Louis A.
Published: February 2004

By charging capacitors in parallel and discharging them in series into an electroexplosive device, improved performance is obtained. The concept is particularly useful in limited voltage systems. Certain circuit variations are presented.
Simple instrumentation for rise and decay time measurement of cathodoluminescence in an electron microprobe
Authors: Lebiedzik J. , White E. W. , Bhalla R. J. R. S. B.
Published: February 2004

A pulsed voltage generator has been built for an electron microprobe for measuring rise and decay characteristics of cathodoluminescence from micron size sample areas. The pulsed voltage operation has an advantage in that excessive heating of the sample can be avoided by keeping the electron beam on the sample surface only for the duration necessary to get the full trace. Both the pulsing frequency and the pulse duration are variable continuously over wide ranges.
A microwave cavity for circularly polarized radiation
Authors: Diaz J. , Haraldson S. , Smith U. , Pettersson L.
Published: February 2004

A relatively simple X-band cavity resonator for circularly polarized microwaves is described. The cavity has a square cross section and the two orthogonal modes TE102 and TE201 are used to obtain circular polarization.
SIMS with a standard quadrupole residual gas analyzer
Authors: Thomas G. E. , de Kluizenaar E. E.
Published: February 2004

A standard quadrupole residual gas analyzer can be used to measure secondary ion mass spectra (SIMS) if, between the sample and the entrance to the quadrupole rod system, the energy of the sputtered ions is modulated so as to produce an intensity modulation of only the low energy ions and the signal is recorded using a tuned ac amplifier.
Measurement of electron density in a plasma using cavity perturbations in a single laser
Authors: Eylon Shmuel
Published: February 2004

A method is described for the measurement of electron density in a plasma using cavity perturbations in a single cavity, inexpensive commercial laser. The method is based on auto-interference of the sensing laser light at a given delay. A lower limit of 1013 electrons/cm3 sec in the measurement of the rate of change in plasma density is expected in a practical system.
Simple anticoincidence gates for S-C pulse height selectors
Authors: Sabol Josef
Published: February 2004

Improved anticoincidence gates for S-C analyzers designed exclusively with TTL integrated circuits are presented.
Device used with charged pin technique for precision gas gun projectile velocity measurements
Authors: Mock W. , Holt W. H.
Published: February 2004

A device for determining velocity pin spacings in a gas gun to within 0.002 mm is described, yielding projectile velocities to within 0.1%.
Time-resolved position measurements—A new application for position-sensitive detectors
Authors: Dolce S. R.
Published: February 2004

It is suggested that position-sensitive detectors may be used to observe the time history of sample motion, such as that which takes place when impulse is imparted to a material sample during blowoff. In this application a laser beam is reflected from the rear surface of the sample or from a mirror attached to the sample, and the detector reproduces the time history of the position of the reflection. In this work the response of this type of detector to a rapidly moving laser beam has been studied. It has been found that detectors selected from those presently available can reliably locate the centroid of a laser beam that moves at least as fast as 0.19 cm/μsec. It is suggested that a reasonable criterion for determining the maximum velocity with which a detector may be used is ν≤ΔX/0.5RdC, where ΔX is the desired position resolution and Rd and C are the distributed resistance and capacitance of the detector, respectively.
Solar x-ray photography with multiplex pin-hole camera
Authors: Blake R. L. , Burek A. J. , Fenimore E. , Puetter R.
Published: February 2004

A scatter-hole x-ray camera has been designed and flown in a rocket to measure solar x radiation. Its distinguishing feature is that many single pin-hole images are allowed to overlap—a multiplexing approach that saves space, gives practical signal-to-fog ratio, and requires special object reconstruction techniques. It was possible to reconstruct the appearance of the dominant source of solar emission on the day of rocket flight with better than one arc minute resolution. The coronal x-ray region had the same general shape and intensity distribution as the associated calcium K-line region
Multifringe electro-optic phase modulator
Authors: Gribble R. F. , Kristal R.
Published: February 2004

An electro-optic phase modulator has been constructed for use in time-resolved laser interferometry. A set of lithium niobate crystals in tandem, driven by a fast sawtooth generator, provides a reference phase modulation of up to four fringes per microsecond at 3.39 μ wavelength.
A new approach to high resolution measurements of structure in superconducting tunneling currents
Authors: Hebard A. F. , Shumate P. W.
Published: February 2004

The design of electronic circuitry is described that has the capability of measuring independently the bias dependence of the first derivatives dI/dV (dynamic conductance) and dV/dI (dynamic resistance) and the second derivatives d2I/dV2 and d2V/dI2 of a tunneling current-voltage (I-V) characteristic over a wide range of junction impedances (less than 1 Ω to greater than 104 Ω). Connections to the sample are four terminal so that problems with lead resistance are eliminated. Resolution in the measurement of the first derivatives is better than one part in 104, and problems with long-term drift are obviated by the use of feedback. Modulation levels at the sample junction, both at constant current and constant voltage, are conveniently monitored with a calibrated lock-in amplifier and can be easily changed. The circuitry has been operated successfully with voltage modulation levels across the junction ranging from 1.0 μV to 2.5 mV rms. Data are presented on Al–I–Pb and Al–I–AuPb3 tunnel-junction samples to illustrate the capabilities of the system.
Measurement of spiraling in a magnetically confined electron beam for use in collision studies
Authors: Taylor P. O. , Dolder K. T. , Kauppila W. E. , Dunn G. H.
Published: February 2004

A method is described to directly measure mean spiral diameter in a magnetically confined electron beam. In collision experiments, spiraling affects polarization measurements and effective path length assessment; and in experiments using colliding beams, the collision energy or energy spread can be significantly altered. The technique described here allows experimental correction for these effects. Magnitudes of transverse velocities from various causes leading to spiraling are estimated on the basis of models. A gun designed for use in crossed beam electron-ion excitation experiments is described, and results of tests on spiraling and space charge effects for this gun are given. The tests generally indicate the modeling to be correct. Judicious choice of operating conditions led to path length corrections as small as 4±2% at 3 eV, decreasing to 0.25±0.2% at 200 eV.
Sensitive detection system for soft x-ray appearance potential spectroscopy
Authors: Chamberlain M. B. , Baun W. L.
Published: February 2004

A sensitive x-ray detection system has been used in the recording of soft x-ray appearance potential spectra with an electron excitation current of a few microamperes covering a sample area of 1 cm2. The system included a 6μ thick aluminum foil, a cesium iodide photocathode, a continuous-channel electron multiplier, and conventional pulse-counting electronics. The aluminum foil was placed over the entrance window of the detector in order to filter out the ultraviolet and extreme-soft x-ray emissions from the sample prior to detection of the soft x rays that passed through the foil. The transmitted soft x rays were incident on a cesium iodide photocathode and the resulting photoelectron events were individually detected with a high-gain electron multiplier whose output pulses were processed with pulse-counting electronics.
Thermal relaxation calorimetry below 1 K
Authors: Schutz R. J.
Published: February 2004

The thermal relaxation method is used to measure heat capacities of small samples from 0.060 to 1.2 K. The calorimeter incorporates a low heat capacity holder, and is designed to be used in conjunction with a 3He–4He dilution refrigerator. The accuracy was checked by measuring a 2 g copper sample. A least squares fit of the copper data yields a γ value of 0.688 mJ (K2g at.)−1 which agrees to 1.0% with published values of γ for copper. The data exhibit a standard deviation of 5.6% around the fit.
A TV-scanning method for recording time-resolved optical spectra of transients produced by a single pulse of electrons
Authors: Gordon S. , Schmidt K. H. , Martin J. E.
Published: February 2004

A new method to record the time dependence of a transient absorption or emission spectrum produced by a single pulse of radiation is described. The time-resolved spectrum is produced by an image converter camera with streak capability. The streak image is scanned by a TV camera, the output of which is transferred to a computer. Apart from its time-saving aspect, the method is particularly useful for experiments with rare or radioactive chemicals.
Use of matrices to represent electron lenses. Matrices for the two-tube electrostatic lens
Authors: DiChio D. , Natali S. V. , Kuyatt C. E. , Galejs A.
Published: February 2004

The use of matrices to represent electron lenses is discussed. It is shown that it is more convenient and natural to represent a lens by a matrix and that the matrix elements show a more regular behavior than do the focal properties. Thus matrices are more convenient to use in computer programs. Matrix elements for the two-tube electrostatic lens are presented and their properties discussed. A simple analytical form for the matrix elements of lenses with near-unity voltage ratios is given.
Plasma source for producing a large diameter plasma column in a magnetic field
Authors: Yatsu K. , Uehara K. , Hagiwara S. , Kojima S.
Published: February 2004

A new discharge-type plasma source with an average minimum B magnetic field has been developed. The plasma source produces a fairly quiescent plasma column of about 4 cm diam with almost flat topped density distribution.
Generalized attenuation correction factor for scattering from cylindrical targets
Authors: Mildner D. F. R. , Carpenter J. M. , Pelizzari C. A.
Published: February 2004

The attenuation correction factor is developed for scattering from a cylinder. The result applies for the case in which the attenuation coefficients Σ differ for incident and scattered radiation and for that in which radiation is incident or scattered obliquely from the cylinder axis. The result is related to one generated earlier for the case of scattering perpendicular to the axis and uses an improved approximation useful for slant thicknesses ΣR/cosβ 2.0 z.
A supersonic molecular beam metastable atom source initiated by direct discharge
Authors: Searcy J. Q.
Published: February 2004

A novel combination of corona discharge with a sonic nozzle has been explored as a molecular beam source of excited helium atoms. Time-of-flight velocity distributions for the excited species have been determined as a function of discharge current. The device has the advantage of simple construction along with the other desirable characteristics of nozzle sources.
Nanosecond pulsed electron source with double pulse control
Authors: Yamamoto Takayoshi , Takeda Seishi , Kawanishi Masaharu
Published: February 2004

A nanosecond pulsed electron beam is obtained by controlling the grid of the electron gun with sequential positive and negative pulses. Two mercury-wetted switches are operated to generate the double pulses. The source can deliver a 100 keV pulsed beam of the order of 1 A with 1 nsec time duration.
Preparation of MoO3 films by anodization
Authors: Padmanabhan K. R.
Published: February 2004

A method for the preparation of thin films of MoO3 by anodization on dc sputtered Mo films is described. The method uses Sodium tartrate as the electrolyte.
A multiple coaxial wire for pressure calibration
Authors: Alm O. , Andersson P. , Bäckström G.
Published: February 2004

A single wire containing several metals suitable for pressure calibration has been produced by extrusion. Coaxial combinations of Ce–Bi–Tl and Ce–Bi–Ba have been prepared by the procedure described.
An improved insertion-type liquid-helium Dewar for X-band ESR spectroscopy
Authors: Matsumura Zenjiro , Chikira Makoto , Kubota Shozo , Isobe Taro
Published: February 2004

A liquid-helium Dewar in conjunction with the X-band room-temperature cavity is reported. The Dewar consists of a fourfold silvered Pyrex glass tube graded to fourfold unsilvered clear fused quartz fingers. A full charge (250 ml) of liquid helium has given about 10 h of operation.
Generation of a square wave xenon flash
Authors: Fünfschilling J. , Zschokke-Gränacher I.
Published: February 2004

A combination of a rotating disk chopper with a xenon flashlamp is described that yields an intense, rectangular lightpulse of 2msec duration and with 5μsec rise and decay time.
Measuring the average ion mass in a gas-discharge with a simple Langmuir probe
Authors: Geissler K. H.
Published: February 2004

The orbital theory of current-collection of a cylindrical Langmuir probes is applied to determine the average ion mass in a discharge. The analytical derivations are supplemented by experimental results. Applications are discussed.
Whole-rock uranium analysis by fission track activation
Authors: Weiss James R. , Haines Eldon L.
Published: February 2004

We report a whole-rock uranium method in which the polished sample and track detector are separated in a vacuum chamber. Irradiation with thermal neutrons induces uranium fission in the sample, and the detector records the integrated fission track density. Detection efficiency and geometric factors are calculated and compared with calibration experiments.
Nonlinear scattering dipole for electromagnetic field measurements in plasmas
Authors: Stenzel Reiner L.
Published: February 2004

Absolute electric field measurements of a 2 GHz electromagnetic wave in a nonuniform plasma are described. A remote measurement technique with minimum perturbations is used in which the information is obtained at the launching antenna from the backscattered signal of a small movable dipole in the radiation field. The weak scattering signal of the test dipole is discriminated against reflections from metallic walls and the plasma cutoff layer by introducing a small frequency shift (Δω/ω≃10−3) at the dipole. The dipole contains a passive nonlinear reactive element (varactor diode) which generates multiple sidebands when irradiated with two frequencies. The nonlinear behavior of the sidebands is used to obtain an absolute calibration for the electric field strength at the dipole. Mismatch effects due to the density dependent dipole radiation resistance are minimized by terminating the dipole with a high impedance.
A fast recovery pulsed nuclear magnetic resonance sample probe using a delay line
Authors: Lowe I. J. , Engelsberg M.
Published: February 2004

A sample probe for pulsed nuclear magnetic resonance that replaces the normal resonant circuit by a lumped parameter delay line is described. Theoretical analysis shows that the delay line probe has a signal-to-noise ratio and conversion efficiency of power into rotating magnetic field equivalent to a resonant circuit of Q =(2π) (delay time) (Larmor frequency). However, the delay line probe has a much wider bandwidth, much shorter transient decay time, and faster recovery from the rf excitation pulse. Experimental results are included that demonstrate submicrosecond recovery times for the observation of the signal.
Apparatus for neutron diffraction at high pressure
Authors: McWhan D. B. , Bloch D. , Parisot G.
Published: February 2004

Powder neutron diffraction data have been obtained on cesium metal above the two transitions at 42.5 and 43 kilobar using a piston cylinder apparatus. A Lucalox cylinder (high density Al2O3) (35.4 mm o.d., 6.35 mm i.d.) is radially supported by compressing two steel plates with a hydraulic ram leaving a neutron window between the plates ∼6 mm high. A 17° included angle was used between the cylinder and support plates. A tungsten carbide piston, driven by a second hydraulic ram, raised the pressure on the sample at three times the rate of increase of the support pressure.
Velocity measurement by self-tracking correlator
Authors: Tompkins W. R. , Monti R. , Intaglietta M.
Published: February 2004

A continuously variable time delay correlator was designed for the purpose of measuring velocity. The inverse transit time (velocity) between upstream and downstream detectors is continuously adjusted by a feedback loop which maintains constant the level of cross correlation at two equal intervals from the peak correlation. Variable delay is achieved by changing the clock frequency which controls a digital shift register delay line. The output of the system is linear and identical to that calculated with parallel logic cross correlation computers.
A 400 rad flash x-ray system for pulse radiolysis
Authors: Hinsch H. , Scheel H. E. , Niemann E.-G.
Published: February 2004

Design and working principle of a flash x-ray system is described. A two-stage Marx generator is used, the charging voltage is 150 kV, the stored energy 1125 J. Anode and cathode are arranged coaxially. The anode consists of a tungsten coated aluminium tube of 20 mm i.d. into which the substances to be irradiated are placed. Measurements of electrical and radiation parameters are described. The x-ray dose per pulse is 400 rad, the half-width of the pulse is 0.2 μsec and the mean quantum energy 44 keV. An example for the application of the system in microsecond pulse radiolysis is presented.
Pulsed-discharge infrared OH laser
Authors: Wauchop T. S. , Schiff H. I. , Welge K. H.
Published: February 2004

The laser emission of vibrationally excited OH in the electronic ground state, produced in pulsed electric discharges through O3–H2 gas mixtures, has been studied using two transverse discharge systems. Discharges were produced in two electrode and multipin transverse configurations. Stimulated emission between the ν = 3→ν = 2 and ν = 2→ν = 1 levels was observed in the 3 μ wavelength region. The output has been investigated as a function of composition and pressure of O3–H2 mixtures, addition of foreign gases, and discharge energy. Output intensities were compared to that of the HF laser emission produced from H2–SF6 in the same discharge system. The two discharge configurations gave similar intensities; this OH laser was shown to have approximately 10−2 times the power of the HF† laser.
Design of a fast voltage clamp for biological membranes, using discontinuous feedback
Authors: Brennecke R. , Lindemann B.
Published: February 2004

The construction of a voltage clamp with discontinuous feedback is described. Its main feature is a pulsed membrane current with an amplitude proportional to the voltage error, which is determined by integration in the pulse intervals. A current pulse of 8 μsec length repeating every 24 μsec is used. Gain switching assures a fast response to large errors, as well as high steady state accuracy. Membrane voltage changes by 150 mV in 8 μsec to 1% of the final value. 50 μsec after such a step, a change of resistive membrane current can be read reliably. Performance is demonstrated with equivalent networks of biological membranes and with applications to black lipid membranes and epithelial membranes.
A photoionization source of monoenergetic electrons
Authors: Gallagher A. C. , York G.
Published: February 2004

A photoionization source of monoenergetic electrons is described and design criteria for such sources are discussed. The present design produces a beam of ≃10−12–10−13 A by photoionization of a metastable (1D2) barium beam inside the cavity of a He–Cd laser operating at 3250 Å. The photoelectrons are produced with 17 meV kinetic energy and a calculated energy spread of <1 meV. Energy analysis is provided by measuring the width of the 11.08 eV argon resonance. The observed width of this resonance has, to date, been limited to ∼6 meV, but tests are reported which indicate that this width is largely due to Doppler spreading in the target atomic beam and potential gradients across the collision volume.
An apparatus for observing relatively rapid hydrogen-deuterium exchange in biopolymers
Authors: Suda Nobuhiro , Nakanishi Mamoru , Tsuboi Masamichi
Published: February 2004

A simple apparatus is described for bringing a protein or a nucleic acid molecule abruptly from an H2O medium into a D2O medium and at the same time to introduce the resultant D2O solution rapidly in a sealed cell for an infrared absorption measurement. It has a small Sephadex column and three magnet valves, and biopolymer molecules are forced to pass the column and pushed into the infrared cell with D2O by means of an external pressure of nitrogen gas. By the use of this apparatus an infrared absorption measurement can be started at 10 sec from the ``zero-time,'' when the biopolymer molecules are brought into contact with the D2O molecules.
Doppler-tuned x-ray spectrometer
Authors: Schmieder Robert W.
Published: February 2004

A novel spectrometer designed especially for a fast foil-excited beam source has been studied and tested. The spectrometer makes use of a large Doppler shift to bring the emission spectrum into coincidence with known features of the absorption spectrum of a suitable filter material. Tuning is accomplished by varying the angle between the beam and the detector, with the filter material between the source foil and the detector. Knowledge of the beam velocity, angle, and the absorption spectrum of the filter is sufficient to determine the emission spectrum from the beam. The resolving power easily exceeds 103 and probably can exceed 105 with some effort, making this spectrometer competitive with conventional crystal diffraction devices. A prototype has been constructed, and tested at the Berkeley HILAC. In the initial experiments, the 21P1 − 11S0 line of heliumlike argon at 3.3 keV, produced by passing a 412 MeV argon beam through a thin carbon foil, was brought into coincidence with the silver LIII absorption edge near 3.4 keV. The expected sudden jump in the count rate when the detector was moved past 58° was observed. This device can be used either for wide range, low resolution scans, or for narrow range, high resolution work, and its range of applicability can be easily extended to higher and lower energies.
Dielectric loss tangent measurements for elctro-optic modulator crystals
Authors: Teague James Ralph , Rice Robert R.
Published: February 2004

A new optical test has been devised to measure the dielectric loss tangent for low loss, high dielectric electro-optic crystals over a wide frequency range. In this method, the loss tangent is calculated from temperature data obtained by optically detecting a laser beam transmitted through the crystal between crossed polarizers while a narrow pulse rf signal is applied to the crystal.
A sapphire to niobium vacuum seal for the temperature range 2–2000 K
Authors: Bogart Louis , Ben-Zvi Ilan
Published: February 2004

A single step brazing process has been developed for producing vacuum tight seals between sapphire and niobium. These assemblies can be cycled between liquid helium temperatures and 1725° C, and show good stability and low vapor pressure at high temperatures.
A logarithmic time base generator or counter
Authors: Trump Walter N. , Fowler Lewis
Published: February 2004

A number of output pulses linearly related to the logarithm of elapsed time or of input pulse count is generated by a circuit including two counters and a comparator. A fraction 1/a of the input pulses is applied to a continuous counter. A second, cycling counter receives all input pulses above a selected starting count, counts to equality with the continuous counter, and resets with production of an output pulse. Repetition of the cycle yields an output pulse series according to the equation ti/t0=[a/(a − 1)]i, where t represents time or pulse count depending upon the source of pulses, periodic or aperiodic, and i is the number of output pulses. Conformance to the logarithmic relation log (ti/t0)=i log [a/(a − 1)] is within 0.01%−0.1% for reasonably large input counts. This circuit has been applied to generation of a logarithmic time base for direct linear plotting of data from thermal conductivity measurements of liquids by the transient hot-wire method.
A mercury U-tube manometer with a high sensitivity throughout the pressure range from 0 to 800 Torr
Authors: Yasumoto Isao , Nagai Keizo
Published: February 2004

A mercury U-tube manometer applicable to the pressure range from 0 to 800 Torr has been successfully designed. One branch of a 25 mm wide glass U-tube contains a constant reference height platinum electrode, and the other branch contains a depth micrometer for measuring the variable column length of mercury in the manometer. The sensitivity was experimentally found to be 0.003 mm throughout the pressure range from 0 to 800 Torr under appropriate conditions.
High accuracy potentiometers for use with ten millivolt Josephson devices. II. Cascaded-interchange comparator
Authors: Denenstein A. , Finnegan T. F.
Published: February 2004

A potentiometric technique for accurately determining a fixed voltage ratio has been developed which employs a voltbox subdivided for optimum self-calibration. The calibration procedure minimizes the effects of resistor self-heating and interconnection resistances which are commonly limiting factors. The basic theory of the technique and the design and construction of an instrument to compare a Josephson device (10 mV) and a standard cell (1 V) are described. This cascaded-interchange comparator (CIC) was evaluated in conjunction with another instrument, based on the double series-parallel exchange technique, in a series of 2 e/h measurements and direct instrument comparisons. The over-all uncertainty for the CIC was about 3 parts in 108 (1σ) and the direct comparisons between the two instruments agreed to within their combined uncertainty of 4 parts in 108. The cascaded-interchange technique should also be useful for the accurate measurement of high voltages.
Apparatus for measuring transient processes during thermomagnetic recording
Authors: Wieder H. , Huth B. G. , Koepcke R. W. , Juliana A.
Published: February 2004

An apparatus is described for measuring thermal and magnetization dynamics during thermomagnetic writing of information onto magneto-optic films. By probing various regions of the reversed spot, the spatial dynamics of bit formation can be reconstructed. The spatial resolution of the measurement is better than 1 μ and the intrinsic temporal resolution is 10 nsec. Representative results obtained with a ferrimagnetic and a ferromagnetic sample are included.
A stable cw HCN laser
Authors: Yoshihiro Kazuo , Yamanouchi Chikako
Published: February 2004

Techniques are described which have been found adequate for operating a HCN laser with stable cw action at wavelengths of 337 and 311 μ; the fluctuation of output power is about ±2% without intentional stabilization by retuning for over 10 h. The main features of the design are: (i) a mixture of CH4, N2, and He gases is used as the flowing gas with a mixing ratio of 1:1:2 by volume; total pressure of 1.6 Torr and gas flowrate of 6∼8 liter Torr/min; (ii) the fluctuation of gas pressure is kept within 0.01 Torr; (iii) the cathode is not grounded but negatively charged about 10% of the dc source voltage. Some of these techniques are applicable to other HCN lasers.
Systematic error from nonlinear least squares computer fitting of Lorentzian lines
Authors: Pfeiffer Loren , Lichtenwalner C. P.
Published: February 2004

We show using Monte Carlo methods that serious systematic error may be introduced in the nonlinear least-squares (NLLSQ) fitting of Lorentzian line spectra of poor statistical quality or with too few data points in the lines. For such spectra we have found that the NLLSQ estimates of Lorentzian linewidth error are unreliable. This has the result of causing the weighted mean linewidth from several similar spectra to be unequal to the result obtained by adding the spectra together channel by channel and then doing the NLLSQ fit. The problem is illustrated using examples from Mössbauer spectroscopy, however, the results appear to be quite generally relevant in all cases where statistically marginal data are fit with Lorentzian lines.
Measurement of differential atomic collision cross sections— the influence of apparatus geometry
Authors: Sauers I. , Thomas E. W.
Published: February 2004

We examine certain problems that are inherent in the measurement of cross sections for small angle scattering of atomic projectiles in a gas target. It is shown that the use of rectangular apertures to select the scattered particles will inevitably distort the measurements so that they are not representative of the true cross section. Finite aperture height must be considered in the derivation of the geometrical collection efficiency exhibited by any pair of rectangular apertures. This height also causes distortion so that the measured cross section does, in general, lie below the true value. It is suggested that experiment and theory may best be compared by convoluting the theoretical predictions into the experimental geometry. A previous publication of the cross section for scattering of 10 keV H+ in helium indicated that a theoretical prediction, using a ``static potential,'' was not in agreement with experiment at low scattering angles. A reassessment of these data has been made and the theoretical prediction is convoluted into the experimental geometry. Theory and experiment are now found to be in complete agreement.
A multi-ion mass spectrometer
Authors: van Hulsteyn D. B. , Hearrell L. R.
Published: February 2004

A multi-ion mass spectrometer has been developed which allows the simultaneous measurement of the velocity distributions of each of the several ion species contained in a burst of streaming plasma. The device utilizes parallel dc magnetic and electric fields to separate the ions according to their charge-to-mass ratios and collects the ions on sets of discrete targets arranged in linear rows. A COS/MOS digital integrated circuit assembly is used to scan and record, in sequence, the output of the integrators connected to each target. The basic design features, circuitry, and test results are presented.
Method for increasing the aperture of space focusing lenses
Authors: Wharton Lennard
Published: February 2004

There are limitations in the aperture achievable from the use of molecular beam space focusing lenses. It is shown that by a system of lenses in series (or by a lens with varying strength along its axis) the aperture can be made substantially larger than in the case of a single lens. A method for the design of such a system is given. The use of this method to design a collimator is presented. More powerful lens systems can enhance the sensitivity, signal-to-noise ratio, and resolution of maser beam, molecular beam resonance, and state selecting scattering apparatus that commonly employ these lenses.
Three-terminal shielded resistors for fast electrometers
Authors: Kendall B. R. F. , Reiter R. F.
Published: February 2004

The design of electrometer feedback resistors for use at frequencies up to the kilohertz range is discussed. It is shown experimentally that the addition of capacitive coupling between the electrometer output and the center of the feedback resistor, combined with suitable shielding, gives substantially better performance at high frequencies than is obtainable with more conventional designs.
Axially-aligned, photon-blind, electron-multiplier arrangement for single-ion counting with a quadrupole mass filter
Authors: Truby Frank K. , Rice James K.
Published: February 2004

A quadrupole mass filter has been equipped with a simply constructed passive electrode aperture arrangement which effectively shields a high-gain electron multiplier used for single-pulse counting applications from photon interference.
High modulation amplitude modification for Varian ESR spectrometers
Authors: Goldberg Ira B. , Lewin A. J. , Crandall Jack R.
Published: February 2004

A water cooling accessory was constructed to enable the use of high amplitudes on field modulation electron spin resonance spectrometers. Field modulations greater than 50 G (100 G peak-to-peak) can be used for long periods without damage to the coils by heating.
A low noise soft x-ray appearance potential spectrometer and its application to chemisorption of oxygen on nickel
Authors: Andersson S. , Hammarqvist H. , Nyberg C.
Published: February 2004

A low noise soft x-ray appearance potential spectrometer has been constructed. It consists of a liquid nitrogen-cooled silicon surface-barrier diode that detects the variations in the emitted photon flux. A 500 Å thick Al window acts as a discriminator for low energy photons (visible light and the tail of the bremsstrahlung). The performance of the detector arrangement has been tested on clean Ni films and chemisorbed O on these films. It is shown that the detector behaves ideally, i.e., the signal-to-noise ratio is limited by the shot noise in the photon flux for primary electron beam intensities in the range tested (30–600 μ A) and for electron energies, 300–900 eV.
On statistics of time-to-amplitude converter systems in photon counting devices
Authors: Holzapfel Chr.
Published: February 2004

Applying methods of statistics to photon counting in measuring a simple exponential decay with a time-to-amplitude converter and multichannel analyzer device shows that the histogram obtained is distorted due to the process of signal sampling. The distortion depends on count rate and life time. The distortion is biggest in the initial part of the histogram, whereas at times much greater than the decay time the histogram shows the real decay curve.
Volume-absorbing calorimeters for high-power laser pulses
Authors: Gunn Stuart R.
Published: February 2004

Two types of calorimeters developed to measure energy in high-power laser pulses are described: solid-absorber calorimeters, of designs capable of extension to large diameters, and stirrred-liquid calorimeters. Results are given for measurements of 1.06 μ pulses at power densities up to about 1011 W cm−2. The calorimeters are calibrated by electrical heating; together with measurements of the specular reflection and thermal radiation losses, this permits performance of absolute measurements to an accuracy of better than 1%.
A picosecond risetime high voltage divider
Authors: Pellinen Donald G. , Johnson Quintin , Mitchell Arthur
Published: February 2004

A two-stage voltage divider having a voltage measuring capability on the order of 100 kV and a risetime of 250 psec has been used to measure submicrosecond pulses on a pulsed electron accelerator. The divider uses a copper sulphate solution high-voltage divider, and a secondary divider made of carbon composition resistors. Measurements have been made indicating the solution divider is useful with fields of 30 kV/cm and with subnanosecond risetimes.
He+ afterpulses in photomultipliers: Their effect on atomic and molecular lifetime determinations
Authors: Paske W. C.
Published: February 2004

Determination of atomic and molecular lifetimes by delayed coincidence photon counting with photomultipliers two or more years old may lead to erroneous results caused by afterpulses and even direct photodecay in perfused helium. Spurious lifetimes as low as 15 nsec for the B2Σu+(v′=0) state of N2+ and the C3Πg(v′ = 0) state of N2 have been observed.
Measurement of pulse energy delivered to a nonlinear resistor
Authors: Rosenthal Louis A.
Published: February 2004

Energy delivered by a single pulse of current or voltage to a nonlinear resistor is obtained from the area measurement of a charge (q)-voltage (v) phase portrait display. The technique is demonstrated by an apparatus employing a half-sine wave pulse current waveform.
A dye laser triggered spark gap
Authors: Schildbach K. , Basting D.
Published: February 2004

Performance of a dye laser triggered spark gap is described with a triggering threshold of only 2 kW peak power and 5 μJ pulse energy. This spark gap is used as a switching element in a nitrogen laser resulting in a delay between dye laser and nitrogen laser emission of only 20 nsec and a subnanosecond jitter.
The use of interrupted resistance heating to perform elevated temperature tensile tests
Authors: Mehan R. L. , Sturgeon L. F.
Published: February 2004

A tensile technique employing resistive heating was developed for testing iridium sheet material at temperatures up to 1680°C. To avoid the problem of current arcing at failure, a circuit was designed to shut off the current just prior to specimen failure. The circuit and test method are described, and typical results for iridium strength and elongation are presented.
A piezoelectric fine-focusing optical mount
Authors: Graham Marshall D.
Published: February 2004

A simple, rugged optical mount incorporating a high strain piezoelectric ceramic is described. Capable of extremely precise, repeatable, and rapid focusing over several tens of microns, the compact mount is useful as a fine-focusing actuator in manual or servo-controlled instruments. Properties of the piezoelectric material potentially allow fine-focusing and structural functions to be combined in a single molded ceramic element.
A lithium ion source for cyclotron external injection
Authors: Luches A. , Provenzano L. , De Michele G.
Published: February 2004

A lithium ion source of the Blewett-Jones type has been assembled and tested for radial injection into the CSATA cyclotron. Ion currents up to 1.5 mA at the extractor are obtained. The extracted beam is focused at the cyclotron vacuum chamber port by a quadrupole doublet. The injected ion current is 500 μA.
Calibration of Kodak fine grain positive and no-screen film in the 4–52 keV x-ray range
Authors: Armistead R. A.
Published: February 2004

The response of Kodak fine grain positive and Kodak no-screen (duplitized) film was measured as a function of x-ray energy over the range of approximately 4–52 keV under a vacuum of 10−3−10−4 Torr. The x-ray transmission properties were also determined. The calibrations were performed with fluorescence radiation excited by the bremsstrahlung from dc x-ray machines. These two films can cover an exposure range of over three orders of magnitude. Some films, such as fine grain positive, exhibit an enhanced sensitivity if exposed under vacuum. Also, it was found that no-screen film exhibits a sensitivity reversal at approximately 5 keV. Other films would be expected to show a similar response with the energy at which the reversal occurs determined by the characteristics of the emulsion.
Energy deficits in pulsed field evaporation and deficit compensated atom-probe designs
Authors: Müller Erwin W. , Krishnaswamy S.V.
Published: February 2004

Energy deficits of field evaporated ions which limit the mass resolution of the straight TOF atom-probe are measured by incorporating a 90° deflecting energy discriminator. The observed dependence on the mass-to-charge ratio shows premature evaporation during the less than perfect subnanosecond pulse front to be the cause of the energy spread. For narrow beam apertures the mass resolution may be improved by tilting the detector plane to provide a compensating shorter path for the slower ions. For wider apertures an energy focusing combination of straight path sections and a 163° toroidal deflector, as conceived by Poschenrieder, has been adapted to our atom-probe. Offering a mass resolution of better than 1/1000 and complete rejection of artifacts, the compensated atom-probe FIM is now a microanalytical tool of ultimate sensitivity and high reliability.