bluuebunny/crossref_metadata_2025 huggingface dataset:
Probe and method for simultaneous measurements of ’’true’’ instantaneous temperature and three velocity components in turbulent flow
Authors: Fabris Gracio
Published: March 2003

In the measurement of turbulent flows the need has always existed to obtain correct instantaneous values of temperature and three components of velocity at a particular point. Many proposed lengthy approximate correction methods that attempt to account for ’’nonlinear’’ effects (cross contamination between different quantities) in hot-wire measurements cannot be considered satisfactory. The availability of powerful digital computers for theoretical and experimental studies has placed pressure on experimentalists to develop better probes and methods. This paper attemspts to answer these pressures by descrbing the development of a special four-wire probe and a method of processing the obtained signals. The use of four 0.625-μm-diam sensors makes the probe practically interference free. The processing method is based on the simultaneous solution of four complete nonlinear response equations for the sensors, yielding in principle exact instantaneous values of velocity components and temperature. Additional features of the processing method include: instantaneous full correction for tunnel free stream velocity and temperature fluctuations, first-order correction for dc drifts of the signals during data acquisition, subtraction of all 60-Hz related noise, and correction for streamwise displacement of sensors based on instantaneous streamwise velocity.
Double axis, two-crystal x-ray spectrometer
Authors: Erez G. , Kimhi D. , Livnat A.
Published: March 2003

A two-crystal double axis x-ray spectrometer, capable of goniometric accuracy on the order of 0.1″, has been developed. Some of its unique design features are presented. These include (1) a modified commercial thrust bearing which furnishes a precise, full circle ϑ:2ϑ coupling, (2) a new tangent drive system design in which a considerable reduction of the lead screw effective pitch is achieved, and (3) an automatic step scanning control which eliminates most of the mechanical deficiencies of the tangent drive by directly reading the tangent arm displacement.
Heterodyne quadrature interferometer for simultaneous measurements of plasma density along several chords
Authors: Jacobson A. R.
Published: March 2003

An interferometer has been developed with which it is possible to make simultaneous measurements of plasma density along several chords. A single Bragg cell and laser are used, and the phase detection is in quadrature in order to obtain unambiguous and uniformly sensitive readings.
Atomic beam spectrometer using a LiF analyzer crystal
Authors: Mason B. F. , Williams B. R.
Published: March 2003

An energy analyzer has been constructed and operated in UHV for the purpose of analyzing the energy of neutral atoms scattered from solid surfaces. The analyzer consists of a LiF single crystal located at an angle close to the normal to the sample crystal so that the diffraction pattern obtained by scanning the LiF crystal yields the energy of the scattered atoms. Two designs which have been used are described. The temperature of both sample and analyzer crystal is near 20 K and once cleaned they can be maintained in the state of initial preparation for many weeks. The sample was a (001) Cu surface in this case. Such an energy analyzer can only be used, in most cases, for He atom scattering although Ne atoms could be used if the scattered intensities were adequate. The detector developed in this study is able to detect about 2×105 atoms/s. The resolution of the spectrometer depends on the incident energy of the atom and is about 1 meV at an incident energy of 23 meV. This resolution can be improved by a factor of 3 to 4 by cooling the nozzle to a temperature lower than 77 K and using variable size slits which can be inserted into the beam path.
Synchronized flash photolysis and pulse deposition in matrix isolation experiments
Authors: Allamandola Louis J. , Lucas Donald , Pimentel George C.
Published: March 2003

An apparatus is described which permits flash photolysis of a pulse-deposited gas mixture in a matrix isolation experiment. This technique obviates the limitations of in situ photolysis imposed by the cage effect and by secondary photolysis. The matrix is deposited in pulses at 30-s intervals and photolyzed sequentially by four synchronized flashlamps approximately 1 ms before the pulse strikes the cold surface. Pulsed deposition maintains adequate isolation and causes line narrowing, which enhances spectral sensitivity. The efficacy of flash photolysis combined with pulsed deposition for producing and trapping transient species was demonstrated by infrared detection of CF3 (from photolysis of CF3I/Ar mixtures) and of ClCO (from photolysis of Cl2/CO/Ar mixtures). The apparatus was used to study the photolytic decomposition of gaseous tricarbonylironcyclobutadiene, C4H4Fe(CO)3. The results indicate that the primary photolytic step is not elimination of C4H4, as suggested earlier, but rather of CO.
Real-time method for NO2 flow measurements
Authors: Darrah Rodney C. , Andrews Merrill L. , Garscadden Alan , Bletzinger Peter
Published: March 2003

Measurements of NO2 flows are made without requiring prior experimental calibration of the flow meter. A tapered, variable area flow meter with a diameter ratio scale is used to make the real-time NO2 flow measurements. The necessary parameters and calculations used to determine the viscosity and density of the flowing N2O4⋅2NO2 gas are presented. The limits of error associated with these parameters and errors associated with controlled flow measurement conditions are considered. Disregarding the scale reading error, which depends on the flow meter utilized, the limits of error are found to yield a measurement error less than 7%.
Inexpensive moving magnet–stationary sample susceptibility balance
Authors: Eaton S. S. , Eaton G. R.
Published: March 2003

A magnetic susceptibility system in which the change in the weight of the magnet is measured is described. Hicorex (cobalt rare earth) permanent magnets are used to construct a magnet with a weight which is within the capacity of standard analytical balances.
Optoelectrical method for the measurement of pressure and for the investigation of the phase equilibrium of deeply colored or turbid mixtures under high pressures
Authors: Alwani Ziad
Published: March 2003

An optoelectrical method for the measurement of pressure and for the investigation of the phase behavior of deeply colored or turbid systems under high pressures is described where the light source and the light detector are in direct contact with the substance to be measured. As a light source, special infrared and visual light emitting diodes (LED) and as a detector appropriate photoelements are used. The behavior of the light emitting diodes and of the photoelements under high pressure is discussed. As a test for this method the solid–liquid transition of pure cyclohexane, the fluid–fluid separation in the binary system nitromethane+ethylene, and the phase behavior of the liquid crystal 4,4′-diheptoxy-azoxybenzene were investigated at pressures up to 1 kilobar; additionally the solid–liquid phase transition of the binary system dimethylsulfoxide+iodine was studied.
Automatic radon counter for continual unattended operation
Authors: Larson R. E. , Bressan D. J.
Published: March 2003

An improved portable radon sampler is described which is capable of sampling and measuring atmospheric radon concentrations at repetition rates of up to five samples per hour, with sensitivities down to 0.1 pCi m−3. The sampler and sensor can be located remotely from the counter and readout devices. The digital output of the unit is available to a printer, a digital recorder, and a computer, and a rate-meter type output is observable in real time and recorded on a strip chart.. This instrument has operated throughout full gale conditions at sea and for up to two weeks without maintenance.
Faraday magnetic balance capable of high resolution measurements on metalloprotein solutions from 6.5 to 300 K
Authors: Tweedle Michael F. , Wilson Lon J.
Published: March 2003

A Faraday balance, constructed from commercially available components, is reported which is convenient to operate and capable of high resolution measurements on metalloprotein solutions over a 6.5–300 K temperature range. The measurements are as accurately determined as for other, more expensive devices which usually require superconducting magnetic equipment. As an example, the temperature dependence of the magnetic susceptibility of metmyoglobin fluoride is reported and compared to other available data.
Method for casting epoxy tensile coupons
Authors: Fanter Dale L.
Published: March 2003

A method is described for producing silicone rubber molds and casting epoxy tensile coupons in these molds. The resulting epoxy coupons have smooth, glossy surfaces and are dimensionally reproducible. The process uses no release agents, coolants, or other possible contaminants and yields high-quality epoxy coupons.
Optimum spacing for a pair of thick circular coils of square section
Authors: Colavita Pascual A. , Bustos Victor A.
Published: March 2003

Curves are given for the magnetic field along the axis between two circular coils of square section traversed by the same current. These curves relate the field variations, the length in which the field is within a certain allowed variation, the coil thicknesses, and their separation.
Versatile electrical feedthrough for probe measurements i
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Authors: Spector D. N. , Sethian J. D. , Gerber K. A.
Published: March 2003

An electrical feedthrough, operating at 10−6 Torr, for use in vacuum systems utilizing Swagelock or Wilson-type seals is described. It features a pair of center conductors with a coaxial shield and can be used with a variety of detachable probes.
Tuned limiter for receiver amplifier in a fast-recovery pulsed NMR spectrometer
Authors: Stokes Harold T.
Published: March 2003

A simple tuned limiter is described which limits the rf voltage amplitude at the input of the receiver amplifier of a pulsed NMR spectrometer. This device prevents overload of the receiver amplifier during the high-power rf pulse and thereby allows fast recovery of the spectrometer following the pulse. When used with Avantek unit amplifiers at 24 MHz, a recovery time of 2.5 μs is achieved.
Base-line suppression in microwave spectroscopy using frequency modulation and harmonic detection
Authors: Nagourney Warren
Published: March 2003

In a microwave spectrometer, systematic variations of the rf source amplitude with frequency can cause a spurious signal (base line) which severely limits the attainable sensitivity. Normally, the base line is eliminated by using Stark or Zeeman modulation. However, these modulation methods cannot be used in an experiment on nonparamagnetic molecular ions contained in a glow discharge. This paper discusses a technique which we have used to reduce the base line by a factor of about 10−5 and which can be used to study the spectra of species contained in a glow discharge. The scheme uses wideband sinusoidal frequency modulation of the microwave source combined with synchronous detection at the nth harmonic of the modulation frequency. The system produces a signal proportional to the nth derivative with respect to frequency of the base line. However, the signal due to an absorption line is only slightly smaller than that produced by other modulation methods. The system may be considered to behave like a high-pass filter which discriminates against features that vary slowly with frequency.
Characteristics of germanium resistance thermometers from 1 to 35 K and the ISU magnetic temperature scale
Authors: Anderson M. S. , Swenson C. A.
Published: March 2003

A low-temperature comparator cryostat with a self-balancing ac resistance bridge and a data acquisition system have been used over the past several years to calibrate approximately 45 germanium resistance thermometers, many of them several times. Examples are given of typical thermometer reproducibility results, together with algorithms for estimating self-heating and ac–dc resistance differences for these thermometers. Recent experiences with rhodium–iron resistance thermometry are described in terms of a comparison of previous ISU magnetic thermometry with gas thermometry results from the National Physical Laboratory in England.
Inverse-fourth apparatus for photometric calibrations
Authors: Swyt Dennis A. , LaRock James G.
Published: March 2003

A new photometric device is described which can perform direct, as opposed to comparison, measurements of optical transmittance, without bootstrapping, over a range of nearly six orders of magnitude. According to the demonstrated principle of operation, the amount of light flux received at a detector is proportional to the inverse-fourth power of the effective source-to-detector distance. As the device is configured, the adjacent source and detector are stationary while a flexible light guide, which collects light from the source and re-emits it toward the detector, moves on a carriage. The transmittance, T, of a filter is measured in terms of the ratio of carriage positions, for constant detector output, with and without the filter in the light path; the optical density is then D=−logT. The position of the carriage, relative to the source-detector plane, is measured over the 3 m range of travel with a resolution of 0.01 mm. Operated with a 1000 W tungsten-halogen lamp as a source, a photomultiplier as a detector, and either an integrating sphere or opal glass for diffuse collection at the detection plane, the system is designed to attain an overall accuracy of ±0.5% for ANSI PH2.19 diffuse transmission densities up to 6.0 density units, corresponding to ±0.1% for transmittances above 0.5000 transmittance units and to ±3% for transmittances between 0.000001 and 0.0001 transmittance units.
Sensitivity enhancement in ESR/ENDOR spectrometers by use of microwave amplifiers
Authors: Hoentzsch Ch. , Niklas J. R. , Spaeth J. M.
Published: March 2003

The introduction of a low-noise microwave preamplifier in a homodyne ESR spectrometer can increase the signal-to-noise ratio by more than a factor of 10 at low modulation frequencies, and makes it superior to a superheterodyne spectrometer. The performance of this new arrangement has been compared to that of a normal homodyne spectrometer.
High-pressure–low-temperature x-ray power diffractometer
Authors: Syassen K. , Holzapfel W. B.
Published: March 2003

A high-pressure technique for x-ray diffraction studies at low temperatures is described. The system consists of a Bridgman anvil type high-pressure device with either tungsten carbide or boron carbide anvils, a liquid He cryostat, and x-ray diffractometer operating in Debye–Scherrer geometry. The newly developed boron carbide anvil cell is capable of containing a liquid pressure transmitting medium. The precision of the lattice parameter determination is discussed and the effect of nonisostatic stress components on the diffraction pattern is examined.
Senftleben–Beenakker thermal conductivity effect apparatus
Authors: Vevai J. E. , Elliot D. G. , Honeywell W. I.
Published: March 2003

An apparatus for measuring the influence of magnetic fields on the thermal conductivity of gases, the Senftleben–Beenakker effect, is described. Conventional ’’cold finger type’’ cooling with appropriate cryogenic fluids is utilized with a helium exchange gas chamber to establish the general temperature level of the cell holder. Automatic temperature control of the trim heater maintains the desired temperature to ±10−3 °C in the 77–300 K range. A concentric cylinder cell adaptable for use with either conventional electromagnet or superconducting solenoid is described. The use of thin Mylar polyester film end seals minimizes cell ’’end effect’’ corrections and provides a resolution of 5×10−6 in gas thermal conductivity.
Metastable transfer emission spectroscopy—method and instrument for detection and measurement of trace materials in gas flows
Authors: Capelle Gene A. , Sutton David G.
Published: March 2003

A simple and relatively inexpensive new technique for qualitatively and quantitatively measuring various gas-phase species in a flow and the apparatus for implementation are described. Detection of atomic species has been demonstrated from concentrations greater than 1010 atoms/cm3 to approximately 104 atoms/cm3. Several classes of molecules can also be detected quatitatively with the method, although with somewhat reduced sensitivity. The method, metastable transfer emission spectroscopy (MTES), is particularly useful in materials analysis. Possible applications including the analysis of gas, liquid, and solid samples and the determination of vapor-pressure curves are discussed.
Pulse mode saturation properties of photomultiplier tubes
Authors: Hartman Davis H.
Published: March 2003

The response of an RCA-4522 photomultiplier tube (35ET bialkali photocathode, 14 dynode stages) in the saturation region has been studied as a function of ambient background light intensity, photocathode illumination area, magnetic field orientation, and ambient temperature. These studies were made using various high-speed pulsed light sources. It is found that the phototube’s response does vary with some of these parameters (in particular, photocathode temperature effects). However, its response is reproducible and highly successful operation in this region is possible through a series of calibrations.
Optical absorption using a system reponse corrector
Authors: Michaud Marc , Carlone Cosmo
Published: March 2003

We have constructed an apparatus suited for low-temperature crystal absorption measurements. The system corrects for the different optical response of the components. We have operated it between 3000 Å and 24 000 Å, throughout which region the error in the optical density was less than ±0.01.
Rapid data collection, analysis, and graphics for flow microfluorometry instrumentation
Authors: Miller M. H. , Powell J. I. , Sharrow S. O. , Schultz A. R.
Published: March 2003

A computer system was developed at NIH, NCI, to add data acquisition, storage, and processing capability to two different flow microfluorometer/cell separators (FMF). Data can be collected from either or both cell separators while previously collected data are being simultaneously processed. Measured cell parameters can be accumulated in the computer memory as arrays of cell counts over a range of intensities or stored as raw data in a list mode on magnetic tape. The computer system hardware includes a refresh display, two disks, industry standard magnetic tape, 32K core, an incremental plotter, a link to the central facility, and links to the FMFs. For convenience in program development and to give direct access to additional data analysis resources, a direct 1200 baud link is available to a Central Facility PDP-10. Programs have been developed to display the data in two dimensions and to create three-dimensional projections which can be rotated. Two-dimensional contour maps at user-selected thresholds are also available. A plot of any projection on the CRT-Display is available when requested. Integration of selected curve segments and statistics describing peaks are a part of the package of routines selected via a menu scheme at the terminal. The various data presentations provide the researchers using the FMF with a poweful analytical tool to assist them in data interpretations. A significant increase in instrument productivity in terms of number of samples processes has occurred because of the utility of on-line data capture and data processing.
Subnanosecond single photon counting fluorescence spectroscopy using synchronously pumped tunable dye laser excitation
Authors: Koester Vaughn J. , Dowben Robert M.
Published: March 2003

A synchronously pumped tunable dye laser has been constructed and interfaced with a modified Ortec 9200 photon counting system for the purpose of measuring subnanosecond relaxation phenomena. The dye laser excitation pulse, which has an intrinsic 35-ps FWHM for Rhodamine 6G, is 350 ps when measured by time-correlated single photon counting. This value appears to be characteristic of the transit time jitter in the RCA 8850 photomultiplier tube. Subnanosecond fluorescence lifetimes of Rhodamine B with KI as a quencher have been determined by deconvolution of photons counted versus elapsed time using the method of moments; the shortest lifetime measured was 68 ps. Various technical aspects of the system are discussed with emphasis on applications to biophysical problems.
Simple setup for single and differential photoacoustic spectroscopy
Authors: Cahen David , Lerner E. Itzhak , Auerbach Asher
Published: March 2003

Simple cells are described for normal and differential measurements in photoacoustic spectroscopy. The differential cell allows for easy background signal correction and for comparison of related samples. The arrangement allows great flexibility in cell design for adaptation to special sample forms. The normal cell can be used for very small volumes, liquids as well as solids, and is constructed in such a way as to allow the possibility of Helmholtz resonance to occur over a range of frequencies. The two cells are compared in terms of background and maximal signal strength and examples of spectra obtained with each of them are given. The general spectrometer setup is outlined as well.
Simple automatic initiator for microwave induced plasmas
Authors: Crowe Harry R. , Goldberg Ira B.
Published: March 2003

A simple circuit is described which is used to maintain continuity of a radio-frequency or microwave induced plasma. The microwave power reflected from the discharge is monitored. Upon an increase of the reflected power which indicates that the plasma has become extinguished, a high-voltage pulse is applied to a coil wrapped around the discharge region. The repetition rate, voltage of the pulse, and threshold of reflected power are adjustible. This circuit is applicable to resonance fluorescence, atomic absorption and emission, and kinetic determinations.
Compact flowing gas system for CO2 lasers
Authors: Pratt H. Lee
Published: March 2003

A miniature air-actuated vacuum pump has been utilized to effect gas flow at partial atmospheric pressures for waveguide CO2 lasers. Implications are that flowing gas laser systems can be acceptable for many applications requiring miniaturization of components.
Ion beamlet steering by aperture displacement for a tetrode accelerating structure
Authors: Gardner W. L. , Kim J. , Menon M. M. , Whealton J. H.
Published: March 2003

Steering of a single beamlet of ions in a tetrode accelerating structure as a function of both aperture displacement and the ratio of acceleration to extraction voltage (Γ) has been measured, and the results are compared to the steering predicted by a modified linear theory. Although the data contain the predicted features of (1) null steering for a particular value of Γ and (2) a directional change in steering through this point, the steering was also observed to be nonlinear in nature. A conjecture as to the cause of this nonlinearity is given, and the implications of these findings to beamlet steering in a multibeamlet source are discussed.
Multichannel scaling with an eight bit microcomputer
Authors: Fultz B. , Morris J. W.
Published: March 2003

In this note a microcomputer-based system for multichannel scaling is described. This system relies on a combination of simple hardware with software support to achieve maximum cost effectiveness.
Novel method for determination of flow velocities with pulsed nuclear magnetic resonance
Authors: de Jager P. A. , Hemminga M. A. , Sonneveld A.
Published: March 2003

A method for the determination of flow velocities with pulsed nuclear magnetic resonance is presented, based on a sequence of inhomogeneous 180° pulses and a gradient in the stationary magnetic field. Results are shown for a capillary containing water with flow velocities in the range of 0.5 to 5 mm/s.
Simple high vacuum evaporation system with low-temperature substrate
Authors: Garno J. P.
Published: March 2003

An ultrahigh vacuum system has been constructed which permits deposition of thin films onto 4.2-K substrates. The evaporation mechanism is contained within a small cylindrical vessel which is totally immersed in liquid 4He. This device has been used to study superconductivity in PbBi and Ga, PdH and PdD, and most recently, transport properties of ultrathin films.
Low-temperature sample orienting device with two degrees of freedom
Authors: Schmidt C. , Gorzellik P. , Ripka K. , Gmelin E.
Published: March 2003

We describe a rotating sample holder with two degrees of freedom for galvanomagnetic measurements at low temperatures which allows positioning within 0.5° with a reproducibility of better than 0.5°. The main advantages of our device over other constructions are simple and accurate device adjustment, simple and convenient handling, and simple and quick sample changing.
Carbon furnace infrared source—some practical considerations
Authors: Smith G. R. , Fridovich B. , Ivancic William , Rao K. Narahari
Published: March 2003

A carbon furnace has been fabricated from commercially available components. A way of eliminating the CO gas generated in the source box is also described.
Hydrostatic optical cell with simple window structure for low temperature and hydrostatic pressure up to 5 kilobars
Authors: Yamada Masayoshi , Schmidt V. Hugo
Published: March 2003

A compact gas high-pressure cell with four windows for optical studies of phase transitions at low temperature and hydrostatic pressure up to 5 kilobars has been made. Techniques for sealing window components are discussed.
Compact high-power TEA N2 laser
Authors: Patel B. S.
Published: March 2003

A modification is adopted in the conventional Blumlein excitation system for realizing a simple and compact TEA N2 laser. Super-radiant laser pulses of ∼1.0 MW peak power, ∼0.6 ns duration, and ∼1.0 mrad divergence have been achieved.
Modified reentrant Dewar for magneto-optical flux detection in superconductors
Authors: Chimenti D. E. , Wener H. G.
Published: March 2003

The design and construction details of a Dewar tailpiece for magneto-optical studies on superconducting films is described. The modified design allows the convenient use of high-power hot-stage objectives, increasing considerably the spatial resolution of the microscope.
Integrated circuit ac mutual inductance bridge for magnetic susceptibility measurements
Authors: Brodbeck C. M. , Bukrey R. R. , Hoeksema J. T.
Published: March 2003

A versatile ac mutual inductance bridge is described which uses integrated circuit operational amplifiers (op-amps) for the measurement of magnetic susceptibilities of ferro-, ferri-, and para-magnetic samples. The circuit employs op-amps both for balancing the bridge and for detecting the differential signal from the sample coil. The response of the circuit is linear over a wide range of sample susceptibilities, and is calibrated directly in absolute units (emu) using a multiturn digital potentiometer. The sensitivity of the instrument for weak paramagnetic samples (1 g) is ±3×10−7 emu.
Analyzer system for field emission energy distribution (FEED) measurements
Authors: Kempin H. F. , Klapper K. , Ertl G.
Published: March 2003

A newly designed analyzer system for measuring the energy distribution of field emitted electrons (FEED) is presented. A Kuyatt–Simpson type lens system is combined with a two-stage 127° analyzer. A resolution of 15 meV is obtained with a transmission energy of 0.5 eV.
Apparatus for the measurement of small absorption change kinetics at 820 nm in the nanosecond range after a ruby laser flash
Authors: Van Best J. A. , Mathis P.
Published: March 2003

An apparatus for the measurement of kinetics of small absorption changes (ΔA≃10−3–10−4) at 820 nm in a biological sample in the nanosecond range after a short high-intensity ruby laser flash (200 mJ, 8 ns) is described. The laser-induced fluorescence artefact is greatly reduced by the use of a solid-state laser diode as source of measuring light, in combination with a microscope lens and a diaphragm. The signal-to-noise ratio is enhanced by the use of an avalanche photodetector connected to a laboratory-made low-noise and interference-free amplifier. The signals are processed by a transient digitizer in combination with a signal averager. The response time of the apparatus is about 20 ns. With some modifications the apparatus can be used to measure absorption changes in a broad spectral range.
Mechanism of the hysteresis effect in rate-dependent photomultiplier gain variations
Authors: Yamashita Mikio
Published: March 2003

The hysteresis effect in rate-dependent photomultiplier gain variations observed in a particular ten-stage tube was extensively studied to clarify the mechanism involved. The transition points or count rates at which abrupt gain changes take place are measured with respect to the anode and ninth dynode pulses as a function of light pulse intensity and applied high voltage. The experimental results show that the transition occurs at constant average currents and is attributed to certain physical processes on the ninth dynode. Besides, extensive measurements of the hysteresis curves are performed with respect to the ninth dynode pulse for various biases applied to the tenth dynode. The results clearly indicate that the transitions are due to sudden changes in surface potential on the ninth dynode, presumably resulting from dielectric breakdown in the dynode surface layer. In accordance with these and other measurements, a possible physical mechanism is proposed to interpret the hysteresis effect. With the proposed mechanism, temperature effect on the transition points and possible dependence of the hysteresis effect on dynode structure are briefly discussed.
Electronic system for investigation of the electrical hysteresis of ferroelectric thin films with high dielectric losses
Authors: Surowiak Zygmunt , Brodacki Jerzy , Zajosz Henryk
Published: March 2003

A description is given of operating principles and technical data of an electronic system to investigate an electric hysteresis phenomenon of ferroelectric thin films with high dielectric losses. Two hysteresis loops, the compensated and the noncompensated, can be observed simultaneously on the dual-trace oscilloscope screen.
Broadband transmit/receive circuit for NMR
Authors: Engle J. L.
Published: March 2003

This note describes a circuit being used in a 5–60 MHz pulsed FT NMR system to deliver the transmitter pulse efficiently to the sample probe and then with good signal-to-noise ratio to couple the resulting NMR signal from the probe into the preamplifier.
Electron multiplier–scintillator detector for pulse counting positive or negative ions
Authors: Dietz L. A. , Hanrahan L. R.
Published: March 2003

A general-purpose ion detector has been developed for fast pulse counting in mass spectrometry. It consists of a six-stage electron multiplier joined to part of a scintillator detector. This novel arrangement combines the virtually noiseless pulse-amplification response of an electron multiplier with the bipolar voltage flexibility of a scintillator detector. The resulting hybrid detector is superior in performance to either an electron multiplier or a conventional scintillator detector. It is designed to detect a beam of positive ions or negative ions focused to a line image or to a spot at the focal plane of a mass analyzer. Background counting noise is less than 1 count/min when the detector is used in either the positive ion or negative ion detecting mode. Mass-resolved ions are post-accelerated through an electric field to give them an additional kinetic energy of 10 keV before they strike the ion-to-electron converter in the electron multiplier. This allows low-energy ions to be detected with an efficiency close to unity, over a range of ion masses from 1 amu up to several hundred amu. Randomly spaced pulses can be counted at rates from 0 Hz to 10 MHz. The design of the detector and its operating characteristics are discussed.
Calibration of mass spectrometers for van der Waals dimers
Authors: Lee Naisin , Fenn John B.
Published: March 2003

A stream tube from a small supersonic free jet in vacuo is passed successively through the ion source of a quadrupole mass spectrometer and into an enclosed ionization gauge which indicates total mass flux. By simultaneous measurements of dimer and monomer ion currents as well as total mass flux we are able to arrive at absolute values of the relative concentration of neutral monomer and dimer in the free jet. Results obtained with argon, carbon dioxide, and oxygen indicate substantial fragmentation of dimers in the ion source. Consequently, populations of neutral dimers in supersonic free jets of the kind widely used as beam sources may be much larger than previous studies have indicated.
Detection of soft x rays with NEA I
I
I–V photocathodes
Authors: Bardas D. , Kellogg E. , Murray S. , Enck R.
Published: March 2003

We describe the experimental energy response of a negative electron affinity (NEA) III–V photocathode to x rays with energies from ∼0.8 to ∼3 keV. Energy resolutions, E/ΔE, from ∼1 to ∼3 are obtained, together with ∼100% quantum efficiency. Theoretical calculations based on an electron diffusion model are shown to be in good agreement with the experimental results. The use of NEA III–V photocathodes as efficient soft x-ray detectors with good energy and spatial resolution is discussed for imaging applications in x-ray astronomy.
100-ps framing-camera tube
Authors: Kalibjian Ralph
Published: March 2003

The optoelectronic framing-camera tube described is capable of recording two-dimensional image frames with high spatial resolution in the <100-ps range. Framing is performed by streaking a two-dimensional electron image across narrow slits. The resulting dissected electron line images from the slits are restored into framed images by a restorer deflector operating synchronously with the dissector deflector. The number of framed images on the tube's viewing screen equals the number of dissecting slits in the tube. Performance has been demonstrated in a prototype tube by recording 135-ps-duration framed images of 2.5-mm patterns at the cathode. The limitation in the framing speed is in the external drivers for the deflectors and not in the tube design characteristics. Faster frame speeds in the <100-ps range can be obtained by use of faster deflection drivers.
Energetic ion mass analysis using a radio-frequency quadrupole filter
Authors: Medley S. S.
Published: March 2003

In conventional applications of the radio-frequency quadrupole mass analyzer, the ion injection energy is usually limited to less than the order of 100 eV due to constraints on the dimensions and power supply of the device. However, requirements often arise, for example in fusion plasma ion diagnostics, for mass analysis of much more energetic ions. A technique easily adaptable to any conventional quadrupole analyzer which circumvents the limitation on injection energy is documented in this paper. Briefly, a retarding potential applied to the pole assembly is shown to facilitate mass analysis of multikiloelectron volt ions without altering the salient characteristics of either the quadrupole filter or the ion beam.
Cornell Thomson scattering system
Authors: Sethian J. D. , Ekdahl C. A.
Published: March 2003

A Thomson scattering system has been designed and constructed for probing a relativistic electron beam heated plasma. Ruby laser light scattered through 90° is resolved by a polychromator and detected by one of six photomultipliers. The system is capable of resolving electron temperatures of 150 eV at densities of ne<1013 cm−3 with a 4-J ruby laser and an f/9 throughput collection system. Scaling to a 10-J, f/5 system would allow resolving densities of approximately 1012 cm−3. System design, calibration, alignment, and data reduction are discussed. At elevated temperatures (Te≈600 eV) evidence of the relativistic blue shift was observed.
Description of a polarized source of He i radiation for surface studies
Authors: Carlson T. A. , Dress W. B. , Ward F. H. , Agron P. A. , Nyberg G. L.
Published: March 2003

A polarized radiation source has been designed and built for use in angular-resolved photoelectron spectroscopy on surfaces of single crystals under ultrahigh vacuum. The light from a discharge in helium is polarized by a triple reflection from a series of gold mirrors, producing a plane-polarized beam of He i radiation (21.22 eV) with a polarization of 80%. The plane of polarization can be rotated through more than 180° without breaking vacuum. Details of the construction of the lamps are given, together with how it is integrated into the overall operation of the electron spectrometer. As an illustration of the lamp’s potential, data are shown on the photoemission studies of the (110) and (111) faces of copper as a function of both the orientation angle of the crystal and the polarization vector. A brief discussion of the future development and possible uses of the lamp is included.
Biaxial laser-based displacement transducer
Authors: Sharpe W. N. , Payne T. S. , Smith M. K.
Published: March 2003

A simple laser-based instrument is described which produces output voltages proportional to displacements in orthogonal directions. This instrument and the associated experimental techniques have been used to measure biaxial displacements across 400-μm slots at various angles in sheet specimens of various widths.
Imaging characteristics of an axisymmetric, grazing incidence x-ray microscope designed for laser fusion research
Authors: Boyle Michael J. , Ahlstrom Harlow G.
Published: March 2003

We report herein the first demonstration of the x-ray imaging characteristics of an axisymmetric x-ray microscope designed for laser fusion diagnostics. The design, fabrication, and evaluation of a grazing incidence hyperboloid/ellipsoid x-ray mirror pair are discussed. Initial data relating the measured mirror surface profiles, the estimated surface roughness, and mechanical alignment of the x-ray mirror pair to the observed spatial resolution are presented. A revised fabrication approach, utilizing a single point diamond turning feedback technique and resulting in improved resolution, is also discussed.
Determining the angles of incidence in a LEED experiment
Authors: Cunningham Stephen L. , Weinberg W. Henry
Published: March 2003

A new method for determining the angles of incidence in a back-reflection, post-acceleration, fluorescent display LEED apparatus is presented which uses the angles between the diffraction spots on a photograph of the LEED pattern. Absolute accuracies better than 0.1° for both incidence angles should be routinely available.
Computer controlled ESCA for nondestructive surface characterization utilizing a TV-type position sensitive detector
Authors: Kudo M. , Nihei Y. , Kamada H.
Published: March 2003

A position sensitive detector system composed of a channel plate, a vidicon TV camera, and a computer is utilized for multichannel detection of ESCA spectra. It is demonstrated that the system achieves a marked improvement of measurement speed, S/N ratio, and sensitivity. The system also realized an improvement of spatial resolution while retaining energy resolution.
Microcomputer stabilization of a Fabry-Perot interferometer
Authors: Wood Thomas H.
Published: March 2003

Fabry-Perot interferometers typically require some form of active stabilization system for long-term operation. A stabilization system based on a microcomputer is described which is able to maintain the finesse of a plane parallel Fabry-Perot interferometer for long periods of time. The microcomputer takes the place of the multichannel analyzer, ramp generator, and stabilizer of a conventionally stabilized system. Sample data illustrating the operation of the system on the Brillouin spectrum of fused silica, with and without computer corrections, are included.
Measurement of O2(1Δ) content in the gaseous effluents of a chemical generator
Authors: Benard D. J. , Pchelkin N. R.
Published: March 2003

A ratiometric system for accurately determining the percent O2(1Δ) in a low-pressure gas sample has been developed and calibrated by use of a secondary microwave standard source and EPR measurements. The advantages of the new system over EPR are low cost and the ability to continuously monitor rapidly changing concentrations of O2(1Δ).
Capacitance–torsion balance for measuring small stresses and strains
Authors: Meyrick G. , Speiser R. , Turk R. , Werth D.
Published: March 2003

A versatile and inexpensive capacitance–torsion balance has been developed to measure, simultaneously and continuously, small forces and displacements in remotely located samples. It can also be used as a sensitive dilatometer or as a microbalance. The present instrument provides an output voltage change of 1 V for a load change of 3 g and a displacement of 5×10−5 m. These load and displacement ranges can be independently chosen by adjusting the geometrical configuration of the balance, whereas the sensitivity is independent of the range.
Apparatus for the coloration of laser-quality alkali halide crystals
Authors: Mollenauer L. F.
Published: March 2003

A heat-pipe apparatus allowing for the additive coloration of laser-quality alkali halide crystals is described. It has the following features: (1) Prepolished crystals emerge ready for direct installation in the laser; (2) F-center densities are directly proportional to the buffer gas pressure; (3) An air lock allows the same charge of alkali metal to be used many times over.
Analog simulator of a Josephson quantum interference device
Authors: Tuckerman David B.
Published: March 2003

An analog simulator of a two-junction Josephson quantum interferometer has been constructed. The simulator contains novel Josephson junction models in which the superconducting phase appears explicitly. It further contains models of superconducting inductances and a nonlinear feedback circuit to enforce the proper phase constraint around the superconducting loop.
Variable temperature multimode magnetometer
Authors: Winter J. J. , Rothwarf F. , Leupold H. A. , Breslin J. T.
Published: March 2003

A variable temperature magnetometer was built for use with a field superconducting solenoid in a liquid helium environment. Measurements can be made at temperatures ranging from 1.5 to 300 K. Three modes of operation are possible: integrating fluxmeter, ballistic magnetometer, and variable temperature. The probe permits quick, efficient sample exchange.
Laser pumping by PFN power source
Authors: Fujita H. , Banjoya N. , Iba K. , Matoba M. , Nakai S. , Yamanaka C.
Published: March 2003

The use of a pulse forming network (PEN) as a main discharge power supply was tested in a electron-beam-controlled CO2 laser amplifier in order to improve the utility efficiency of the energy in storage capacitors. The impedance of the pumping discharge through the laser gas was controlled by the accelerating voltage of the electron beam to match the PFN line impedance. In the matched condition all of the stored energy in the PFN was transffered to the laser gas at a constant electric field strength which was optimum for laser pumping.
Interferometric technique for measuring the refractive index variation of a liquid with temperature
Authors: Boxman Raymond L. , Shlien D. J.
Published: March 2003

A technique for measuring the variation of refractive index of a liquid as a function of temperature or solute concentration using a Mach-Zender interferometer is described. The principal difficulty of obtaining a uniform temperature along the optical path in the sample liquid while simultaneously varying the temperature at a reasonable rate is overcome by heating the liquid in a separate vessel and injecting the heated fluid into the test vessel as a series of jets to encourage turbulent mixing. An equivalent resolution in the refractive index variation of 2×10−6 was obtained. The above method was used to determine the variation of refractive index in a 0.1% NaCl/H2O solution in the temperature range 23°–33°C.
Circuitry for ac thermometry and dc heating in measurements of thermal properties
Authors: Bäckström G.
Published: March 2003

An instrument is described in which the resistance of a metal wire thermometer is measured by an ac bridge and sampled at a fixed rate. A superimposed dc pulse heats the wire during a selectable time interval. The temperature may be recorded before heating, during heating, and during cooling.
Note on the prong configuration of an x-array hot-wire probe
Authors: Wygnanski I. , Chih-Ming Ho
Published: March 2003

The x-array hot-wire probe with prongs perpendicular to the mean flow is found to be unacceptable for turbulence measurements.
I2 vapor cell as narrow band optical filter
Authors: Liao K. H. , Gupta R.
Published: March 2003

It is shown that absorption cells containing I2 vapor can be used in many situations as narrow band optical filters with very large solid angles. The explicit case of sodium has been considered.
Mitigation of residual space charge ion optics effects in gas cell by adjustment of beam perveance
Authors: Whealton J. H.
Published: March 2003

The effect of residual space charge in the gas cell on fast neutral optics is considered. It is shown that within the paraxial approximation, the deleterious effects of this space charge may be reduced by more than a factor of 4 by lowering the beam perveance. This result is valid for a wide class of axial neutral production distributions.
Fast valve for gas injection into vacuum
Authors: Fisher A. , Mako F. , Shiloh J.
Published: March 2003

A simple, fast, reliable magnetically driven gas valve for use in plasma experiments is described. The pressure rise time has been measured to be ∼1 Torr/μs at the valve opening.
Self-triggered channel ion source
Authors: Bouchard C. , Carette J. D.
Published: March 2003

An ion source made from a continuous dynode electron multiplier of the straight channel type and an ion reflector device is described. Its principle of operation is based on a continuous self-sustained ion and electron cascade in the multiplier channel. Operating characteristics and the analysis of the ions produced are presented. The intensity of the total ion current delivered (10−9 to 10−8 A) is enhanced by at least six orders of magnitude relatively to previously described similar devices. This source, as illustrated, may be used in gaseous mass spectrometry.
Simple, high current, antimony ion source
Authors: Sugiura Hideo
Published: March 2003

A simple metal ion source capable of producing a continuous, uncontaminated, high current beam of Sb ions is presented. It produced a total ion current of 200 μA at 1 kV extraction voltage. A discharge occurred in the source at a pressure of 6×10−4 Torr. The ion current extracted from the source increased with the 3/2 power of the extraction voltage. The perveance of the source and ion density in the plasma were 8×10−9 and 1.8×1011 cm−3, respectively.
Simple apparatus for the discrimination of the majority carrier type in semiconductors
Authors: Brion H. G. , Schettler R.
Published: March 2003

An apparatus is proposed, showing the majority carrier type in semiconductors via an optical display. The operating method is based on the change in sign of the thermoelectric power.
Magnetothermodynamic measurement error through use of a superconducting solenoid in the persistent mode
Authors: Fisher R. A.
Published: March 2003

When a superconducting solenoid is operated in the persistent mode, a variation in the magnetization of a sample (produced by a temperature change) enclosed by the solenoid will produce a modification in the solenoid current. Equations are developed for calculating this effect on the superconducting current and the related magnetic field change. A specific example is given on the error produced in heat capacity measurements.