bluuebunny/crossref_metadata_2025 huggingface dataset:
High Voltage Pulse Measuring System Based on Kerr Effect
Authors: Ettinger S. Y. , Venezia A. C.
Published: February 2005

The voltage measuring system described in this current paper is based on the electro-optical Kerr effect, viz, variations in the voltage magnitude will result in respective changes in the intensity of a light beam passing through the Kerr cell perpendicularly to the applied field. The proposed measuring system has the advantages of a fast response of the Kerr effect substance to the application of voltage transients-better than 2×10−8 sec; and also high voltage pulses, with peak magnitude of the order of 105 V, may be applied directly across the cell. The complete separation of the measuring circuit from the pulse circuit eliminates the electric noise from reaching the measuring circuit without any screening of this circuit. However, its major limitation is that the recorded pulse has the ``rectified'' form of the original pulse waveform.
New Absolute Null Method for the Measurement of Magnetic Susceptibilities in Weak Low-Frequency Fields
Authors: Zahn C. T.
Published: February 2005

Use is made of the magnetic equivalence of a uniformly polarized volume of paramagnetic material and a solenoid carrying electric current to design a very permanent variable standard of magnetic susceptibility. Such a standard is incorporated into a magnetic susceptibility bridge in a simple manner, surrounding the specimen; and the bridge is thereby transformed into an absolute null instrument of high accuracy and sensitivity, and of great ease and low cost of construction and operation. By this method numerous particular advantages of other methods are combined, and some of their notable limitations are overcome. A preliminary application was made showing that the bridge performs as expected. Important features in the design of this bridge are discussed. A detailed consideration of sources of error suggests that it may eventually be possible by this method to obtain greater absolute accuracy than by other known methods.
Solid-State Pulse-Height Encoding System with Pileup Reduction for Counting at High Input Rates
Authors: Strauss Michael G.
Published: February 2005

The system described selects undistorted pulses and digitizes them for multichannel pulse-height analysis. The system consists of a double RC differentiating linear amplifier, a low jitter gated single-channel analyzer, a linear gate, and an analog-to-digital converter (ADC). The ADC is comprised of a simple discharge-type pulse-height to time converter, gating a temperature compensated 2-Mc astable multivibrator. A temperature change of 25°C results in an over-all gain change of 1%. Baseline shift is minimized by direct coupling. At an input rate of 100 000 pulses/sec the spectrum shifts by less than 1%. Pileup events are rejected by a unique baseline crossing discriminator. The rejection efficiency is about 80%. The apparent pulse width, for pileup considerations, is thereby reduced from 1.5 to 0.25 μsec. The circuits and their performance are discussed.
Apparatus for Determining Temperature Profiles in Microstructures
Authors: Schlegel Earl S.
Published: February 2005

A practical infrared sensing apparatus has been developed to profile the temperature distribution of small complex structures without affecting the temperature distribution by the temperature sensing element. The sensitivity is 60°C for some materials, and the resolution is 1.3 mils.
Palladium-Diaphragm Hydrogen Pump
Authors: Young J. R.
Published: February 2005

It has been found possible to evacuate hydrogen from a container into the air by the use of a heated Pd or PdAg alloy diaphragm. This effect is not the expected diffusion of hydrogen from a region of high hydrogen pressure to a region of lower hydrogen pressure, but a true pumping from a region of low hydrogen concentration to a region of higher hydrogen concentration. This pumping occurs only if the region of higher hydrogen concentration is in an oxidizing atmosphere and the region of lower hydrogen concentration is in a reducing atmosphere or a good vacuum. Pumping speeds for hydrogen up to 0.25 liter/sec per cm2 of diaphragm have been observed for Pd and Pd-25% Ag alloy 0.004 in. thick while operating between 500 and 600°C. It has been found possible to pump down to a hydrogen pressure of 10−9 mm Hg while the hot Pd diaphragm was exposed to air. Ti and Ni diaphragms were found to exhibit similar pumping characteristics, but much lower pumping speeds were observed.
Contamination in Ultra-High Vacuum Plant
Authors: Holland L. , Laurenson L. , Priestland C.
Published: February 2005

Using an electron bombarded target the presence of silicone vapor was detected in the vessel of a bakeable ultra-high vacuum system made of stainless steel exhausted by a silicone oil diffusion pump. Silicone molecules temporarily adsorbed on the target were desaturated by the impinging electrons and polymerized to form a deposit. The deposit thickness was measured by multiple-beam interferometry. The diffusion pump was charged with silicone 704 and fitted with a chevron (trap II) and a container trap (trap I) next to the vessel. Liquid nitrogen cooling both the chevron and container-type trap next to the vessel after baking (pultimate≃10−9 Torr) gave a deposit growth rate of <5 Å/h. When the chevron trap was not operated during ultra-high vacuum pumping the container-type trap condensed sufficient oil vapor for the vessel to be contaminated when the vessel and trap were subsequently baked. The contamination rate measured during baking was dependent on the time the system had been previously under ultra-high vacuum without the chevron trap being cooled. Ultra-high vacuum pumping for 38 h at 10−9 Torr gave rise to a deposit growth rate of 160 Å/h on the next baking cycle. The contamination rate was reduced to its lowest amount during baking (35 Å/h) when the chevron baffle was cooled throughout the pumping cycle. Using a new silicone fluid (705) gave a deposit growth rate of about one-half to one-quarter of fluid 704.
Pressure Multiplication Effect in Opposed-Anvil Configurations
Authors: Myers Mark B. , Dachille Frank , Roy Rustum
Published: February 2005

Pressure distribution at room temperature has been studied in sample cells used in the Bridgman opposed-anvil high pressure apparatus over a range of pressure of 25 to 90 kilobars by observation of discontinuities in electrical resistance at phase transitions in calibrated metals (BiI-II, TlII-III, ``low'' Ba, ``high'' Bi). A ``pressure multiplication effect'' has been found in which the pressure observed in the center of the cell is 2 to 2.5 times the nominal load pressure. This effect is strongly dependent on the diameter-to-thickness ratio of the sample cells and is approximately linear to 90 kilobars.
Dynamic rf Phase Meter
Authors: Hahn H. , Orgass R. J.
Published: February 2005

A transistorized phase meter built around a NOR circuit is described. The upper frequency limit is on the order of 4.5 Mc. The use of a flip-flop as a frequency divider extends the usable phase range from 0 to 360°. The resulting ambiguity is corrected by a reset circuit. The deviation from linearity is less than ±1°. The phase modulation frequency bandwidth is 20 kc.
Circuit for the Display of Langmuir Probe Characteristics
Authors: Harp R. S.
Published: February 2005

The use of Langmuir probes for plasma measurements usually entails laborious graphical reduction of data to obtain the electron temperature, and errors are often introduced by drift in the plasma characteristics while the measurements are being taken. This paper describes a simple and accurate electronic device for reducing the probe data and displaying the results on an oscilloscope. The circuit employs commercially available plug-in amplifiers to provide maximum ease of construction, and high accuracy is obtained with a minimum of calibration adjustments.
Analog Division Based on the Hall Effect
Authors: Wieder H. H.
Published: February 2005

An indium antimonide film Hall generator is employed in conjunction with an electro-optic transducer in the feedback loop of a differential amplifier. The Hall voltage is compared against another input signal and the amplified difference controls the current through the Hall plate. The Hall current is shown to be proportional to the ratio of the input signal to the magnetizing current which creates the magnetic field across the Hall plate. The assembled apparatus constitutes an analog divider of fair precision and wide dynamic range.
Time-of-Flight Method of Determining Velocities of Sputtered Atoms
Authors: Stuart R. V. , Brower K. , Mayer W.
Published: February 2005

A method is described whereby velocities of sputtered atoms are determined by pulsing a target and measuring the transit time of sputtered atoms. The method permits determination of the distribution of velocities of sputtered atoms. The target pulse generator and the problems involved in pulsing a target are discussed. The photon-counting system used for determining transit times is described and a typical set of data is presented.
Windowless Tubes for X-Ray Spectroscopy
Authors: Wyckoff Ralph W. G. , Davidson Franklin D.
Published: February 2005

Using a demountable x-ray tube it is shown that elimination of the window between its target and a ``fluorescing'' sample increases the intensity of the characteristic x rays excited in a light element by as much as 100-fold without loss of stability in the tube operation. The nature of this effect is discussed and its potential value for the x-ray spectroscopy of light elements illustrated.
Apparatus for the Study of Ejection of Auger Electrons from Solid Surfaces
Authors: Propst Frank , Lüscher Edgar
Published: February 2005

A stainless steel apparatus for the study of the ejection of electrons from solid surfaces is described. The bakeable vacuum system consists of three sections and is capable of maintaining pressure in the 10−10 mm Hg region. Each of the three sections is pumped via a liquid nitrogen trap by a mercury diffusion pump. Typical pressures under operating conditions are 10−9 mm Hg in the target section and 10−6 mm Hg in the ion-source section. The ion-lens system is described and a convenient method of construction of ion lenses is illustrated. A description of a simple analog computer that determines the yield and the energy distribution of the ejected electrons is given.
Multiplication Phenomenon for Fission Fragment Response in Semiconductor Detectors
Authors: Britt H. C. , Wegner H. E.
Published: February 2005

A multiplication phenomenon caused by fission fragments has been observed in 300 Ω-cm gold surface barrier detectors when operated at bias voltages greater than 100 V. This phenomenon occurs only for fission fragments that penetrate beyond some threshold depth for multiplication, and the threshold depth is found to decrease with increasing bias voltage. However, the effect could also be due to the surface properties of the detector making the depth correlation fortuitous. An analysis in terms of a threshold depth indicates that the multiplication may be due to a hole rather than an electron effect. No multiplication was observed for alpha particles with the same electric fields. P-n diffused junction detectors operated at similar average electric field strengths did not show any multiplication effects.
Young's Modulus Measurements above 2000°C
Authors: Brown Harry L. , Armstrong Philip E.
Published: February 2005

An apparatus is described for the determination of Young's modulus from thin-rod resonance behavior. The apparatus differs from previously described equipment in that it is capable of operating at temperatures over 2000°C while providing a vacuum or an inert atmosphere around the sample. The transducers operate at ambient temperature and are loosely coupled to the specimen under test by fine tungsten wires. Provision is also made for optical measurement of the thermal expansion of the sample.
Increasing the Light Collection Efficiency of Scintillation Counters
Authors: Ankenbrandt C. M. , Lent E. M.
Published: February 2005

A systematic study was made of methods of increasing the light collection efficiency of scintillation counters. Various reflectors, surface treatment of the scintillator, relative geometries of scintillator and photodiode, and light pipes were tried, using plastic scintillator cubes, 3 and 6 in. on a side, and right circular cylinders, 3 in. in diameter by 3 in. in length and 6 in. in diameter by 6 in. in length. The maximum factors by which light output could be increased, relative to a polished scintillator, were about 2.8 for 6-in. scintillators and 3.3 for 3-in. scintillators without the use of light pipes, and 5.0 for a 3-in. scintillator with light pipe. The fraction of light trapped in a right circular cylinder by total internal reflection is derived as a function of index of refraction, as are the percentages of light coming out the ends and sides of a cylinder.
Integrator for Small Pulsed and Direct Currents
Authors: Rogers E. J.
Published: February 2005

A solid-state electronic integrator capable of integrating and digitizing small currents has been developed. In a recent experiment, pulsed proton beams with an average value of 10−9 A have been integrated and measured with a 0.1% accuracy. Pulsed or direct currents can be measured accurately down to a lower limit imposed by uncompensated variations of the order of 10−13 A in input leakage current. The current to be integrated is applied to a Miller integrator circuit which employs a commercially available solid-state operational amplifier. A diode-switched charging circuit gated on and off by the integrator output voltage ``pumps down'' the integrator capacitor with discrete units of negative charge, simultaneously delivering digital output pulses to an external counter. An output voltmeter provides analog readout of residual fractional charge increments.
Very Large Boron Trifluoride Proportional Counters
Authors: Fowler I. L.
Published: February 2005

More than 50 very large BF3 counters, each approximately 6 ft (180 cm) long and 6 in. (15 cm) in diameter have been made for cosmic-ray monitors. During the fabrication of these counters, the characteristics at varying gas pressures have been studied and the alpha backgrounds of the various metals used for cathodes have been determined. The counters have excellent characteristics at pressures up to 30 cm Hg and perfectly acceptable characteristics to 60 cm Hg pressure. With anode diameter 0.008 in. (0.2 mm) and gas amplification 35, the operating voltage for a filling of 20 cm Hg pressure of pure BF3 is 2800 V; at 30 cm Hg it is 3400 V. Counters with copper cathodes have backgrounds due to residual alpha contamination of about 2 counts/min, and with stainless steel cathodes, about 5 counts/min. Using a BF3–Ar filling a value of 6.30±0.05% has been obtained for the branching ratio of the B10(n,α)Li7 reaction.
Low Temperature Heat Capacities of Constantan and Manganin
Authors: Ho James C. , O'Neal H. R. , Phillips Norman E.
Published: February 2005

The heat capacities of Constantan and manganin have been measured from 0.15 and 0.2°K, respectively, to 4.2°K. Both alloys have large hyperfine heat capacities at temperatures of a few tenths of a degree and data are presented which can be used in making corrections to calorimetric measurements in which one of these materials is used as a heater.
Millimeter Spectrometer Using a Fabry-Perot Interferometer
Authors: Lichtenstein M. , Gallagher J. J. , Cupp R. E.
Published: February 2005

Microwave absorption measurements have been made on the hydrogen sulfide molecule using a semiconfocal-type Fabry-Perot interferometer in the millimeter wave region. The 10, 1 → 11, 0 and 21, 1 → 22, 0 transitions of H2S33 with S33 in its natural concentration of 0.7% have been observed in this video spectrometer. Q values (Q=f/Δf) on the order of 56 000 were measured at 168 kMc in the semiconfocal resonator. A comparison is given between lines observed in the interferometer and those observed in standard waveguide absorption cells.
Voltage Measurements in the Presence of Strong Fields
Authors: Moses Kenneth G. , Korneff Theodore
Published: February 2005

A description is given of an apparatus capable of measuring instantaneous voltages in the presence of heavy current discharges. The basic advantages of the system are (1) a single ground connection which is independent of the two points of the desired voltage, (2) cancellation of induced voltages in measuring circuit by electronic means with bandpass depending only upon amplifiers used, (3) the cancellation of the measuring circuit pickup is insensitive to large changes in the geometry of the measuring circuit.
Sensitivity Analysis for the Calorimetric Probe
Authors: Grey Jerry
Published: February 2005

Application of a unique calorimetry technique to the measurement of extremely high gas enthalpies and temperatures was described previously. The technique is based on measurement of the change in coolant fluid energy which is observed when a continuously flowing sample of the ``unknown'' gas through the probe is shut off. Effects of external cooling requirements and radiation are thereby canceled, permitting direct measurement of local gas enthalpy (from which, under certain conditions, gas temperature may be deduced). One of the principal problems encountered in the application of this device is its sensitivity under different conditions. The present paper describes an approximate method for estimating this sensitivity. Comparison of the results with measured sensitivities indicated appreciable scatter, but was adequate to confirm the general approach.
Computer-Controlled Diffractometer
Authors: Cole H. , Okaya Y. , Chambers F. W.
Published: February 2005

The general features of a computer-controlled x-ray diffractometer system are described. A standard four-axis Geiger counter single-crystal diffraction configuration is made automatic by attaching encoders to all shafts with provision made for electronic input of all settings and readout of all data. A small solid-state computer is made an integral part of the system, which permits the system to be used in a decision-making closed-loop manner. The mode of operation can be changed by changing the program in the computer.
Absolute Differential Radiometer
Authors: Hager Nathaniel E.
Published: February 2005

A radiometer is described which is calibrated on an absolute basis from its geometric and physical parameters. An estimated 3% accuracy is achieved using common handbook values for the physical parameters. Experiment confirms the calibration, including predicted dependence of sensitivity on temperature. The instrument gives integrated response to diffuse thermal radiation exchanged between surfaces at normal room temperature. When used with a commercial microvoltmeter, the present device measures net heat fluxes ranging from 0.1 to 100 Btu/h-ft2. It responds quickly to changes in incident flux and reaches equilibrium within about 1 min. It is sufficiently rugged and stable for practical field work and is suggested as a tool for research and teaching.
Interaction of Fission Fragments with Organic Scintillators
Authors: Horrocks Donald L.
Published: February 2005

A pulse-shape discriminator circuit was used for the measurement of the pulse heights of the slow components of light pulses from organic scintillators excited by different types of particles: electrons, protons, alpha particles, and fission fragments. Three types of organic scintillators were employed: a crystal (stilbene), a liquid (7 g PPO and 0.5 g M2-POPOP in 1 liter of toluene), and a plastic (NE-150). The relationship of the pulse heights of the slow components for excitation with electrons, protons, and alpha particles was similar for all three scintillators. However, fission fragments produced a slow component pulse height similar to protons in stilbene and the plastic but more like electrons in the liquid. The pulse-height distributions of total light pulses from the scintillators excited by the alpha and spontaneous fission emissions of Cf252 were measured. The alpha-particle and fission-event spectra were resolved only with the liquid scintillator giving a pulse-height spread of the fission distribution peak of 40%. From the maximum of the fission sepctra it was calculated that the most probable energy of fission produced the same pulse height as an electron with 1/75th that energy would produce. The alpha particles and the fission events were counted with 100% efficiency and a value of 31.0±0.5 was obtained for the alpha to fission disintegration ratio of Cf252.
Apparatus for Electron Spin Resonance Studies at Very High Pressures
Authors: Gardner J. H. , Hill M. W. , Johansen C. , Larson D. , Murri W. , Nelson M.
Published: February 2005

Apparatus for studying electron paramagnetic resonance in solids under pressure to 60 kilobars and beyond has been developed. The high pressures are produced between dielectric Bridgman anvils, one of which serves as a microwave resonance cavity. The instrument makes possible the study, by EPR techniques, of paramagnetic atoms or ions subject to stresses which might be expected to induce changes in their electronic structure.
High Intensity Source of 20-keV Hydrogen Atoms
Authors: Gordon Frank J. , Damm Charles C.
Published: February 2005

A continuous source of energetic hydrogen atoms has been developed for use in a plasma experiment. The mechanical design and some operating characteristics of the ion source are described, as well as the beam focusing and neutralizing system. An output of 65-mA power equivalent of 20-keV hydrogen atoms has been measured on a 2.0×6.3 cm target located 350 cm from the ion source.
Piezoelectric Gauges for Measuring Rapidly Varying Pressures up to Seven Kilobars
Authors: Blackstock A. W. , Kratz H. R. , Feeney M. B.
Published: February 2005

Bar-type piezoelectric gauges have been designed which permit the measurement of pressures in excess of the breaking stress of the piezoelectric element. The principle involved is the use of the acoustic mismatch of two dissimilar metals to reduce the pressure on the piezoelectric element. The three types of gauges described here measure pressure pulses with amplitudes up to 3.6, 5.3, and 6.8 kilobars and with rise times as short as 3 μsec. In each type, 260 μsec elapse between the initial pulse and the first reflected pulse.
Drop Size Sensor
Authors: Bennett Leon , Stalder John
Published: February 2005

A drop size sensor capable of measuring the size and concentration of water droplets between 0.2 and 3 mm in diameter is described. Drops are transported in warm oil and forced over resistance measuring contacts. Individual drop size is determined by the time required for passage over the contacts. The sensor is intended for balloon-borne measurements and radio transmission of solid and liquid precipitation particle data.
Modification of the Rosenblum Spark Counter
Authors: Jeffries Myron
Published: February 2005

A modification of the Rosenblum spark counter has been made by cutting a slit in the plate and allowing a beam of alpha particles to pass through it. The sensitive volume is thus made more accessible and there is a considerable increase in count rate. The characteristics of the counter operated in this manner have been examined for varying thicknesses of wire. An explanation of some of the results has been attempted by an analysis of the field around the wire.
Manufacture of Fine Wire Thermocouple Probes
Authors: Gelb G. H. , Marcus B. D. , Dropkin D.
Published: February 2005

The design and manufacture of fine wire (0.001 in.) thermocouple probes are described. The probes, using arc-welded thermocouple junctions, exhibit great strength, rapid response, and high spatial resolution.
Observation and Identification of Ion Dissociation Processes Occurring in the Drift Tube of a Time-of-Flight Mass Spectrometer
Authors: Hunt W. W. , Huffman R. E. , McGee K. E.
Published: February 2005

The shifts in ion flight times produced by a flat-top potential barrier applied within the drift tube of a time-of-flight mass sprectrometer are defined analytically in terms of the height of the potential barrier. These flight time shifts are selectively dependent on the mass, charge, and kinetic energy of the ions involved; consequently, they can be used to separate and identify the products of ion dissociation processes occurring in the drift tube. Comparisons of calculated and observed flight time shifts for the 58+ → 43+, 42+ dissociations in n-butane are used to illustrate the applicability and present limitations of this method of identifying dissociation products.
Time-of-Flight Mass Spectrometer Adapted for Studying Charge Transfer, Ion Dissociation, and Photoionization
Authors: Hunt W. W. , Huffman R. E. , Saari J. , Wassel G. , Betts J. F. , Paufve E. H. , Wyess W. , Fluegge R. A.
Published: February 2005

A time-of-flight mass spectrometer has been modified so that (1) the drift tube can be used as a reaction/collision chamber for kinetic studies of charge transfer, ion dissociation, and similar processes; and (2) ions can be produced in the source by either pulsed or continuous electron or photon beams. Variable potential barriers, produced in the drift tube by means of movable screened retarder grid assemblies, permit parent ions and fragment ions to be separated, identified, and measured after reaction times that are selectively variable within the range 7.197×10−3(m/q)12≤tr≤7.053(m/q)12 μsec,where m/q is the mass-to-charge ratio of the parent ions in amu per electron charge. The kinetic energy range is from 100 to 10 000 eV for positive ions and 3000 eV for negative ions. The residence time of ions within the ionizing region can be varied continuously from 0 to 100 μsec.
Material for Making Resilient Light Pipes to be Mounted Without Silicon Grease
Authors: Strub A.
Published: February 2005

For a special neutron scintillation counter a light pipe material was required which could replace Plexiglas or Lucite. This material had to be elastic in order to make a good fit between a scintillation crystal and photomultiplier even when mechanical dimensions (distance, parallelism) were somewhat undefined. Furthermore, the use of silicon grease for making an optical seal was to be avoided. Silicoloid 201, an embedding compound for electronic components and circuits, fulfills these requirements. It has a refractive index of 1.408 and a reasonable transmission for scintillation light wavelengths. In addition, it is easy to mold into any shape and it adheres well to glass, forming stable but removable seals without grease.
Pulse Apparatus for the Measurement of Ultrasonic Absorption in Solutions from 1 to 60 Mc
Authors: Atkinson G. , Kor S. K. , Jones R. L.
Published: February 2005

An apparatus for the measurement of ultrasonic absorption in liquids and solutions is described. The optimum frequency range is 1 to 60 Mc. Notable features of the apparatus are the 1-m liquid path length available, ±0.05° temperature control of the working liquid from 0–65°C, the simple design of the transducer mountings, and the dual-path construction.
Detection of Scintillation Photons with Photodiodes
Authors: Fan C. Y.
Published: February 2005

A statistical theory on the efficiency of collection of scintillation photons from a scintillator by a photon detector was developed. If A0 is the total surface area of the scintillator, A the surface area of the portion of the scintillator to which the detector is coupled, η the diffuse reflectivity of the material into which the scintillator is packed, K the probability that a photon impinging on A is absorbed by the photon detector, the photon collection efficiency is ε=KAA0{11−η[1−(KA/A0)]}. An experimental determination of the value of ε was made with a photodiode CsI(Tl) unit, which was constructed primarily as a cosmic ray detector used in space vehicles. The CsI(Tl) crystal was packed in a case of high reflectance surface (η=94%) and coupled to two Au-Si surface barrier photodiodes with LTV 602 clear silicone potting compound. The experimental value is about 30% which is in reasonable agreement with the theory. The dispersion of the signal out (full width at half-maximum) of this unit for the detection of 40 MeV α-particles is 75 keV at 495 keV. It is comparable with what is obtained with a CsI(Tl)-photomultiplier tube combination.
High Current Low Impedance Pulse Generator
Authors: Stevens Norman B.
Published: February 2005

Design parameters are given for a pulse generator useful for driving injection luminescent diodes, photoflash tubes, and other loads of impedance 3Ω or less. Rectangular output pulses are provided with a choice of 5- or 50-μsec duration. The maximum pulse current of 200 A is supplied at variable repetition rates of up to 20 pulses/sec for the wider pulse and 200 pulses/sec for the 5-μsec pulses.
Improved Pulsed Townsend Discharge Experiment
Authors: Edelson D. , McAfee K. B.
Published: February 2005

The determination of Townsend ionization and attachment coefficients, and ion mobility by means of a pulsed discharge experiment is reviewed, and sources of error in the measurement are discussed. A new apparatus and technique designed to minimize these errors is described. Recent theoretical results incorporating the effects of diffusion and finite duration of the initial pulse are presented together with a nonlinear least-squares procedure for obtaining the parameters of interest from the experimental data. Computation of confidence regions for the parameters is given, and it is shown that large errors can result from failure to use the more exact theory.
Apparatus for Measuring Magnetothermodynamic Properties to High Fields at Low Temperatures
Authors: Giauque W. F. , Hornung E. W. , Fisher R. A. , Brodale G. E. , Butera R. A.
Published: February 2005

An apparatus has been described for determining magnetothermodynamic properties at any accessible low temperatures and at any obtainable static or slowly varying magnetic fields. It is adapted to measurements on single crystals in various axial directions. It has been devised to give values of the magnetic susceptibility and intensity of magnetization as a function of field or temperature along isothermal or isoerstedic paths, and thus evaluates the magnetic work functions of the substance measured. With appropriate adjustments, values of the isothermal entropy change may be determined calorimetrically as a function of field, or values of heat capacity at constant field may be measured. Below 1 °K the various magnetothermodynamic changes accompanying adiabatic demagnetization may be evaluated. Itemized dependences of error limits are given.
Synchrocyclotron 200-Meter Flight Path Neutron Velocity Spectrometer
Authors: Rainwater J. , Havens W. W. , Garg J. B.
Published: February 2005

Our synchrocyclotron neutron time-of-flight spectrometer now uses a 200-m flight path and two 2000-channel analyzers. The many important modifications and improvements described in this paper have been made as a result of operating experience. The present operation uses ∼20 nsec bursts at an instantaneous intensity ∼5×1018 evaporation neutrons per second and a 60-cps repetition rate. The resolution for energies above 1 keV is now limited by the time analyzers which have 100-nsec detection channel widths, giving a resolution of 0.5 nsec/m in the keV region.
Pressure Gauge with One-Tenth Microsecond Risetime for Shock Reflection Studies
Authors: Baganoff D.
Published: February 2005

A pressure gauge having a risetime of 0.1 μsec, no overshoot, a dwell time of 5 μsec, and capable of sensing a pressure jump of 10 mm Hg is described. Pressure-time traces obtained with the gauge on the end wall of the 17-in.-diam low pressure shock tube at the Graduate Aeronautical Laboratories, California Institute of Technology, are presented showing details of the pressure profiles on the end wall for reflecting shock waves.
Current Regulator for a 10 000-A dc 7.5-MW Magnet Power Supply
Authors: Smith B. H. , Atwood J. R. , Lyon D. N.
Published: February 2005

Design and construction details are discussed for a dc current control system capable of a short term stability of a few parts in 106 and a long term stability of ∼2 parts in 105 when used in conjunction with conventional rotating dc generators powering loads with time constants of approximately 200 msec at levels up to 7.5 MW. Actual performance of the system at various power levels is discussed.
Technique for Determining Density Distribution in Low Pressure, High Temperature Gases
Authors: Ziegler C. A. , Bird L. L. , Olson K. H. , Hull J. A. , Morreal J. A.
Published: February 2005

A new technique for measuring the point-by-point density distribution in a high temperature gas that is applicable to plasma jet facilities and hypersonic wind tunnels has been developed. An electron beam probe is directed into the plasma, and the observed number of bremsstrahlung x rays created in a given segment of the beam via electron-gas atom interaction provides a direct measurement of gas density in terms of the number of atoms per unit volume. The method provides good spatial resolution, and density determination is independent of gas temperature, chemical form, and the degree of dissociation and ionization.
Magnetoelectric Flowmeter
Authors: Cushing Vincent
Published: February 2005

Faraday's law of induction, E=u×B, is the basis for the electromagnetic flowmeter. In such a flowmeter a uniform magnetic induction is established transverse to a flow pipe; and flow of the metered fluid generates a potential difference at suitable detecting electrodes. In this device, the generated potential difference is linearly proportional to volumetric flowrate through the pipe, provided only that the flow velocity profile is axially symmetric. It is pointed out here that a flowmeter can also be designed based on the fact that a moving, polarized dielectric generates an effective magnetic moment according to the equation M=P×u. This last equation is formally analogous to the first cited equation describing Faraday induction. It is shown here that one can readily adapt the theory of the electromagnetic flowmeter to analyze the operation of a magnetoelectric flowmeter. In this paper a magnetoelectric flowmeter is described wherein a uniform electric field is established transverse to a pipe through which a dielectric fluid flows; a magnetic induction is generated which is linearly proportional to the volumetric flowrate through the pipe; the induction may be measured with a suitable magnetometer.
Ultrahigh Vacuum System for Use with a Polarizing Spectrometer
Authors: Dettorre J. F. , Knorr T. G. , Hartman N. F. , Cocks G. G.
Published: February 2005

An ultrahigh vacuum system which can be used in conjunction with a commercial polarizing spectrometer is described. The capabilities of the combined systems are such that surfaces can be prepared and observed in situ on substrates held at temperatures anywhere between liquid nitrogen and about 800°C. In addition, it is possible to introduce a variety of gases by means of a controlled leak, permitting the study of many different interfacial phenomena and the kinetics of the reactions involved. Preliminary data on evaporated copper is shown which is essentially different than previously reported results even though the data shown here were taken from samples purposely held at only modestly improved pressures.
Production of Very High Magnetic Fields by Flux Compression
Authors: Lewin J. D. , Smith P. F.
Published: February 2005

Some theoretical aspects of the implosion technique of attaining magnetic fields in the megagauss region are discussed. The temperature rise at the conductor surface is estimated, taking into account the change in resistivity with temperature. At all field levels the magnetic pressure should prevent loss of conductor by evaporation. Flux leakage due to finite conductivity is analyzed, allowing for the variation of resistivity and penetration depth during compression; to account for reported fields as high as 14 MG, the temperature coefficient of resistivity under implosion conditions must be at least two orders of magnitude lower than at normal pressures.
Electrostatic Plasma Containment System and Electron Motion Through Grids
Authors: Herb R. G.
Published: February 2005

Grids consisting of arrays of fine wires to form cylindrical surfaces were used in getter-ion pumps. They have been shown to be plasma containers holding ions and electrons up to densities of 3×108/cm3. A discussion is given of the motion of electrons through grids. Limitations on the mean free path of electrons are discussed. A method is described for obtaining high currents of positive ions.
Sublimation and Ion Pumping in Getter-Ion Pumps
Authors: Herb R. G. , Pauly T. , Welton R. D. , Fisher K. J.
Published: February 2005

A large variety of methods have been studied for evaporation and sublimation of titanium. For use in getter-ion pumps, sublimation appears to be clearly superior to evaporation from the molten state. A number of getter-ion pumps have been built and used for various applications. Each utilizes a plasma-containing grid as a source of electrons for heating titanium rods. The grid also provides the necessary ionization for the pumping of inert gases. Consideration is also given to effects of geometry, scaling, pressure, and recombination rates on ionization and pumping by the grid.
Double Beam Spectrometer with 10-msec Recording Time
Authors: Niesel W. , Lübbers D. W. , Schneewolf D. , Richter J. , Botticher W.
Published: February 2005

The high speed spectrometer described here allows the measurement of an extinction or reflection spectrum within the range of 2300–6000 Å (respectively, 3500–7000 Å) or any desired sections of same. The spectra can be shown individually or in superposition (4, 8, or 16 spectra) on the screen of an oscilloscope, the x axis expressing the wavelength and the y axis the extinction. Under suitable conditions, the constancy of the zero line is better than 0.003 o.d. and allows the readings of differences in optical density less than 0.001 o.d. Examples of applications show that the apparatus is particularly suitable for following reactions in which several components simultaneously vary their absorption.
Measurement of X-Ray Beam Quality with Solid-State Detectors
Authors: Kramer Gordon
Published: February 2005

The ratio of the currents generated in two solid-state detectors of different lengths by a beam of x rays parallel to the junction is a measure of the x-ray beam quality. Two detectors with lengths of 0.16 and 1.6 cm, respectively, were used to measure x radiation varying in quality from a half value layer of 2–7 mm Al.
Germanium Bolometer Detector of Millimeter Wavelength Thermal Energy
Authors: Galloway D. G. , Tolbert C. W.
Published: February 2005

This paper describes the construction and evaluation of a Ka band bolometer receiver using a highly temperature-resistance dependent (at 4.2°K) doped germanium bolometer of Texas Instruments, Inc. The receiver noise equivalent power (NEP) of approximately 10−9 W and input bandwidth exceeding 12 Gc has a rms signal level indicating uncertainty equivalent to 90 C° per cycle of output filtering. Evaluation of the germanium bolometer as a millimeter wavelength radiometer detector was performed at Ka band to utilize existing apparatus and to facilitate fabrication of the receiver. With the increased sensitivity anticipated for smaller bolometer elements, short millimeter and submillimeter wavelength scaled models of the receiver appear promising as detectors for radio telescopes.
Modification of the Continuous Flow Apparatus for the Measurement of Rapid Chemical Reactions
Authors: Perlmutter-Hayman B. , Wolff Michael A.
Published: February 2005

A continuous flow apparatus is described where the measuring device—e.g., a thermistor—can be moved smoothly along the length of the observation tube, thus enabling a complete kinetic curve to be obtained in a single run at constant flow velocity.
Calibration of 30-cm Faraday Cup
Authors: Palmieri J. N. , Goloskie R.
Published: February 2005

A Faraday cup which was used as an absolute monitor in several experiments performed at the Harvard University Cyclotron Laboratory has been calibrated indirectly against a counter telescope in the direct beam. The Faraday cup was found to be only 95% efficient at 160 MeV, indicating that some values of differential cross sections reported earlier are about 5% too large.
Steady-State B-H Hysteresigraph for Thin Ferromagnetic Films Using a Torque Magnetometer
Authors: Torok E. J. , Agouridis D. C. , Olson A. L. , Oredson H. N.
Published: February 2005

An ordinary torque magnetometer can be used to obtain dc B-H hysteresis loops of thin ferromagnetic films simply by replacing the rotating set of Helmholtz coils with a stationary set of three mutually perpendicular coils and by mounting the film edgewise on the suspension. When the magnetometer is used in this mode, the signal and signal-to-noise ratio are directly proportional to the field normal to the film; thus one can measure the anisotropy field of film samples many times smaller than previously possible with a torque magnetometer, as well as the various loop properties previously not obtainable with a torque magnetometer. All sections of the film are sensed uniformly in marked contrast to coil sensing devices. Unlike the usual ac B-H hysteresigraph, the torque B-H hysteresigraph is not affected by eddy currents in metal substrates.
New Electrometer of High Sensitivity
Authors: Shonka Francis R. , Failla G. , Rose John E.
Published: February 2005

A highly sensitive electrometer has been developed for the detection of small dc signals. The signal to be measured is impressed upon a movable quartz fiber, causing it to oscillate in an ac field. A controlled bucking voltage is applied to bring the fiber to rest as it is viewed through a microscope. Sensitivities in excess of 10 000 div/V or 1016 div/C are readily attainable. The electrometer is small, rugged, stable, and portable. It has low inherent capacity, negligible geotropism, wide voltage range, and the ability to measure its own contact potential. Because it has an extremely nonlinear response (maximum sensitivity at zero signal), the fiber remains in the field of view and is neither damaged nor paralyzed by large input signals. A unique feature is that all adjustments of the ac voltages (producing the ac field) can be made during precision measurements of dc signals.
Method for Correction of Accumulated Error in 180° Pulses in Carr-Purcell Experiment
Authors: Wayne R. C. , Zamir David , Strange J. H.
Published: February 2005

A modified Carr-Purcell method for measuring T2 is described in which correction for accumulated error due to imperfect 180° pulses is made. T2 is measured with a phase coherent pulse spectrometer set slightly off resonance. In this way the phase of the pulsed rf in relation to the Larmor frequency at the beginning of a pulse can be adjusted. The major advantages of the method are that no modifications of the spectrometer are necessary and that the amplitude of the nuclear signal seen is effectively doubled by beating with the reference rf in the receiver. The limiting criteria are discussed and are shown to be unimportant in the majority of cases.
Wideband High Voltage Probe
Authors: Keller R.
Published: February 2005

A high voltage probe is described which is based on the principle of consecutive differentiation and integration. The voltage to be measured is applied to a coupling capacitor of a few μμF and rated at several tens of kilovolts. The capacitor is connected to a cable which propagates a signal proportional to the derivative of the voltage. At the other end of the cable a transistorized integrator integrates the current and produces a signal proportional to the voltage. It is thus possible to obtain a bandwidth of 300 Hz to 200 MHz.
Scattered Light Photoelastic Polariscope for Three-Dimensional Stress Analysis
Authors: Cheng Y. F.
Published: February 2005

This paper reviews, briefly, earlier scattered light photoelastic polariscopes and describes, in detail, a new design of this equipment for three-dimensional stress analysis. The present polariscope makes use of recently developed experimental techniques which employ a polarizer to determine the directions of the secondary principal stresses and Sénarmont's principle of compensation for determining the fringe order. No compensator is required. Photographs of stress patterns are shown. The clearly defined fringes in these patterns demonstrate the high quality of the new polariscope.
New Technique for Measurement of Electron Diffraction Patterns of Polycrystalline Materials
Authors: Richardson J. H. , Schneidmiller R. F.
Published: February 2005

This technique employs a calibrated radial chart on which the image of the diffraction pattern is projected at an enlargement such that the d values may be read directly. Results may be obtained rapidly with accuracy equal to or better than that achieved with usual methods.
Correlated Energy and Time-of-Flight Measurements of Fission Fragments with Semiconductor Detectors: System Design and Performance
Authors: Williams C. W. , Kiker W. E. , Schmitt H. W.
Published: February 2005

A system for the measurement of correlated energies and times-of-flight of fission fragments has been developed. This system, adaptable for use with other charged particles as well, includes a fast-response transformer coupling scheme in which the charge originating in a solid-state detector passes through the transformer primary to a low noise charge-sensitive amplifier; the fast timing signal is obtained from the transformer secondary. Noise thereby added to the linear energy signal is negligible. The measured time resolution of the system for particles in a narrow band of energies was ≲0.4 nsec, full-width at half-maximum. The design of the system is described, and the detailed results of performance tests, including tests with coincident 252Cf spontaneous fission fragments and energy-time correlation measurements for bromine and iodine ions (artificial fission fragments), are given.
High Speed Decade Pulse Counting
Authors: Foote R. S. , Johnson D.
Published: February 2005

A high speed decade counter has been developed for pulse counting from single pulse to repetition rates greater than 50 Mc. The circuit incorporates a ladder of five tunnel diodes integrated with a rapid reset, followed by a countdown of two. Direct indicator tube readout of the pulse count is accomplished by voltage-to-digital conversion.
System for Displaying Thin-Film Plated Wire Switching Characteristics Under Disturbed Conditions
Authors: Kaufman Bruce A.
Published: February 2005

A simple and rapid test system for displaying the switching characteristics of thin-film plated wire computer memory elements under disturbed write conditions is described. The characteristics are displayed on an oscilloscope, eliminating the need for manual plotting of data. The instrument design and construction is described and typical results are presented.
Precision Controlled Thermoelectric Temperature Chamber
Authors: Wennerberg Allan L.
Published: February 2005

A precision thermoelectric temperature control system composed of a thermoelectric heat pump and a fully proportional bidirectional controller is described. This system maintains a chamber temperature at 25±0.2°C, while the ambient varies from −29 to 85°C.
Versatile Light Scattering Photometer
Authors: Chu B.
Published: February 2005

A photometer has been built for fluctuation studies of liquid mixtures near the critical point with thermostats controlled to 0.001°. The instrument has provisions for a choice of light sources and detection systems, and is capable of absolute scattered intensity measurements of dilute polymer solutions over a wide temperature range. It can also be converted to a spectrophotometer with a variable angular acceptance for the phototube, so that the effect of forward scattering on turbidity measurements may be examined.