bluuebunny/crossref_metadata_2025 huggingface dataset:
The Production of Equal and Unequal Size Droplet Pairs
Authors: Adam John R. , Cataneo Robert , Semonin Richard G.
Published: February 2004

Experimental examination of interactions between small water droplets, such as wake interactions, collision-coalescence phenomena, and the dependence of these interactions on the electrical charge and field, has awaited the development of a dependable source of multisize droplets. A simple droplet generator has been developed to produce controlled pairs of equal and unequal size droplets. The generator and its applicability to droplet interaction studies are described.
Dispenser Ion Emitters
Authors: Zarabi M. J. , Satyam M.
Published: February 2004

The development of a dispenser type of ion emitter is described. This type of ion emitter has been used successfully for obtaining lead, aluminum, and tin ions.
Driven Equilibrium Methods for Enhancement of Nuclear Transients
Authors: Waldstein Peter , Wallace William E.
Published: February 2004

Several pulsed NMR experiments using rapidly repeating pulse sequences are described. Theoretical results for magnetization as a function of pulse spacing τ are given for cases where the Bloch equations apply, and compared with experiments. These results suggest a simple method of rapid signal accumulation when T2*<T2,T1, that is, when resolution is limited by magnet inhomogeneity.
An Amplifier Controlled Adiabatic Calorimeter
Authors: Filatovs George J. , Schwaneke Alfred E.
Published: February 2004

An automatic adiabatic differential calorimeter has been constructed to record the release spectrum of stored energy of deformation of metals from −196 to 500°C. A cold worked and an annealed specimen contain internal heaters which are powered by amplifiers, the signal inputs to which are specimen-to-calorimeter wall differential thermocouples. Control circuits attempt to maintain conditions as adiabatic as possible, and the power difference to the specimen heaters necessary to do this is taken as the stored energy of deformation.
A New Double Beam Optical Lever Refractometer and the Variation of the Refractive Index of NaCl with Temperature
Authors: Pereira F. N. D. D. , Hallett A. C. Hollis
Published: February 2004

The design and construction of a double beam optical lever are described. Its use is illustrated by describing an experiment to measure changes of the order of 10−5 in the refractive index of NaCl by the method of measuring the change in angle of refraction of a beam of light by a prism of the salt. It is capable of higher sensitivities and has the advantage that it can monitor the motion of the crystal as a whole.
Vacuum Manifold for Rapid Assay of Enzymes Using Radioactive Tracers and Ion Exchange Chromatography
Authors: Prusiner Stanley B. , Milner Larry S. , Long Carl W. , Myers Murrel L.
Published: February 2004

A vacuum manifold apparatus is described which allows rapid ion exchange chromatography of multiple samples. The apparatus is especially applicable to the assay of enzymes by radioisotopic tracer methods.
A Capacitive Gauge for the Accurate Measurement of High Pressures
Authors: Andeen Carl , Fontanella John , Schuele Donald
Published: February 2004

A highly accurate and precise pressure gauge, which utilizes the 35°C, 2005 Hz dielectric constant of an ionic crystal CaF2, is presented. The prototype gauge was calibrated at the National Bureau of Standards over the pressure range 0–2.5 kilobars, and the defining equation was found to be C/C0=1−AP+BP2,where C0 is the zero pressure capacitance, C is the capacitance at absolute pressure P, and the characteristic constants A and B are A=3.7801×10−6/(bar)and B=2.739×10−11/(bar)2. The gauge is stable and accurate over this range at the 0.01% level, and indications are that this type of gauge may be useful at much higher pressures and refined to even higher accuracies.
Design and Operation of a Fast High-Voltage Vacuum Switch
Authors: Ware Kenneth D. , Mather Joseph W. , Williams Arthur H. , Bottoms Paul J. , Carpenter James P.
Published: February 2004

The design and operational characteristics of a vacuum spark gap switch and its mechanical attachment to two kinds of industrial capacitors, used singly or in multicapacitor modules, are described. The main features of the vacuum switch are its wide range of voltage operation (0.1–50 kV) with relatively easy triggering, high current capability (∼400 kA), low inductance (∼5 nH), and long lifetime. High fidelity with minimum time jitter of a few nanoseconds has been achieved with a central coaxial spark plug.
Studies of a Glass-Ceramic Capacitance Thermometer in an Intense Magnetic Field at Low Temperatures
Authors: Rubin L. G. , Lawless W. N.
Published: February 2004

The effect of an intense magnetic field on an 1100-type capacitance thermometer (made from an SrTiO3 glass-ceramic crystallized at 1100°C) was accurately measured at five temperatures between 1.5 and 4.2 K. At each manostatically maintained temperature, the capacitance changes were measured five times between B=0 and B=14 T, and it was found that these changes did not exceed the measurement uncertainty, ±0.3 pF≅±1 mK. Similar results were obtained on a second 1100-type thermometer. Some suggestions are made for the use of this type of thermometer in magnetic field experiments.
Measurement of Specific Heat of Polytetrafluoroethylene Using Millidegree Temperature Increments in Thin Foil Calorimeter
Authors: Hager Nathaniel E.
Published: February 2004

The thin foil calorimeter technique described earlier is extended to detail specific heats of polymers near transition temperatures. A sample film is rolled up with a metal foil heating element into a cylindrical configuration. Starting with the roll at thermal equilibrium, a constant current is passed through the foil. During a finite period after heating begins, the interior of the roll heats adiabatically. The temperature rise rate, sensed by a thin foil thermocouple, is monitored by a microvolt amplifier-recorder system. A typical 35 sec run shows a linear temperature rise of about 7×10−3 K, with a noise level of the order of 15×10−6 K. Resultant specific heat values are estimated to be precise to within 1%. Resistance thermometry gives corresponding mean sample temperatures with a precision of the order of 0.01 K. Although specific heat values obtained for polytetrafluoroethylene mostly agree with published adiabatic calorimeter data, remarkably different results are obtained in the transition temperature region extending from 280 to 310 K. Where adiabatic calorimeter data show a large enthalpy peak extending over a 15 K temperature interval, foil calorimeter data show a relatively minor but sharp discontinuity near 293 K.
Sensitivity of Marginal Oscillator Spectrometers
Authors: Adler Michael S. , Senturia Stephen D. , Hewes C. Robert
Published: February 2004

A linearized theory for the signal and noise characteristics of a marginal oscillator NMR spectrometer has been developed. The model modifies Watkins' theory to include the mixing of 1/f noise into the oscillator passband. Signal response, noise spectrum, signal-to-noise ratio, and noise figure are all calculated and compared with accurately calibrated experimental data. The calculated signal response (absolute) is within 12% of experiment. The results show that there are two distinct regions of spectrometer operation, one in which the noise spectrum is white and one in which the noise spectrum is dominated by 1/f mixer noise. In the region of predominately white noise, the calculated noise factor is 2.9 for our circuit, compared with the experimental value of 3.3. Guidelines for optimum selection of rf level and modulation frequency are presented.
Self-Oscillating Magnetometer Utilizing Optically Pumped 4He
Authors: Slocum Robert E. , Cabiness P. Clayton , Blevins Stephen L.
Published: February 2004

An optically pumped resonance magnetometer has been constructed which utilizes 4He gas as the resonant element in the self-oscillator mode of operation. This instrument is capable of monitoring anomalies and fluctuations in the magnetic field with a sensitivity of 0.1 μG over the range of the earth's field (0.25–0.75 G). Recordings of variations in the geomagnetic field are compared with recordings made simultaneously with a servo helium magnetometer. The characteristics and advantages of the new system are discussed.
A Cold Cathode Pulsed Gas Laser
Authors: Lomnes R. K. , Taylor J. C. W.
Published: February 2004

Construction details are presented for a cold cathode pulsed gas laser which utilizes a plasma tube made from straight pieces of ordinary glass tubing. The laser features ease of construction with relatively low cost. Several gases may be used giving a wide spectrum of laser lines.
Study of the Properties of Marmet's Monokinetron by Calculation of Electron Energy Distribution Profiles
Authors: Roy D. , Carette J.-D.
Published: February 2004

A method of calculation of the electron energy distribution produced by various electrostatic spectrometers is applied to Marmet's monokinetron. Properties of this apparatus are verified and studied as functions of the main geometrical and electrical parameters in second order approximation. Electron motion calculations are performed from two dimensional considerations, but consequences of finite axial dimensions are studied. Results are in agreement with the experimental and theoretical determination of the resolution done by Marmet.
A High Sensitivity Bridge Detector Circuit System for Microwave Resonance Measurement
Authors: Takao I. , Watanabe K.
Published: February 2004

A high sensitivity detector system for microwave resonance measurements utilizing a bridge balancing method is described. This system consists of a parametron preamplifier, a phase modulated pump circuit, and a phase discriminator. The preamplifier amplifies the measuring signal and the quadrature AFC error signal alternatively.
A Cavity Search Spectrometer for Free Radical Microwave Rotational Absorption Studies
Authors: Hrubesh Lawrence W. , Anderson Roger E. , Rinehart Edgar A.
Published: February 2004

A Zeeman modulated microwave spectrometer, specifically designed for K band rotational studies of gaseous free radicals and transient molecular species and using a Fabry-Perot type resonator as the absorption cell, is described. The theoretical sensitivity of the system is shown to be comparable to that of the most sensitive waveguide cell spectrometers. The previously assigned spectra of OH and NO2 radicals have been successfully located with the system. The utility of the system as a search spectrometer for free radicals has been substantiated by locating previously unreported spectra for the NO2 molecule and NF2 (difluoroamino) free radical.
A New Second Harmonic Type Ferroelectric Modulator for Electrometer
Authors: Abe Zenmon , Kato Yasuo , Furuhata Yoshio
Published: February 2004

The authors examined the possibility of using a second harmonic type modulator made of ferroelectric material with an electrometer. It was established that if modulation is carried out at a temperature slightly above the Curie point utilizing the odd symmetry of the relationship between voltage and charge of a ferroelectric capacitor, then the delay in response to a large input signal (memory effect) is eliminated, both zero drift and noise are reduced, and carrier amplitude is diminished largely in contrast to the results obtained at room temperature. In the experiments, triglycine sulfate single crystal (TGS) whose Curie point lay around 50°C was used with a carrier frequency of 50 kHz, reducing zero drift to the order of 10 μV/day and realizing low noise as characterized by 6 μV p-p with 1 MΩ input resistance and in the bandwidth from dc to 1 Hz. This modulator is solid state, and its input resistance is about 1013 Ω as determined by the specific resistance of a TGS single crystal. Owing to the absence of any vibrating part, the carrier frequency can be raised and the bandwidth is more than several kilohertz. Compared with the best vibrating capacitor electrometer, this modulator has advantages in bandwidth and lack of vibrating parts, but a disadvantage in input resistance. There remain some practical problems such as the method of keeping the element temperature in the vicinity of the Curie point, and the initial zero drift.
An Electron Bombardment Substrate Heater for Use with Very Thin, High Resistivity Substrates
Authors: Quigley S. R.
Published: February 2004

An electron bombardment substrate heater has been designed for reproducible uniform heating to ∼900°C of very thin high resistivity disk shaped silicon wafers. The contact area of the wafer with heater hardware is kept minimal and the heater is suitable for high vacuum application.
Polygonal Coil Systems for Magnetic Fields with Homogeneity of the Fourth to the Eighth Order
Authors: Garrett Milan Wayne , Pissanetzky Sergio
Published: February 2004

Systems of polygonal coils have some practical advantages for the production of relatively weak magnetic fields of very large volume, with high homogeneity. They are easier to construct than large circular systems and they have slightly greater axial spacing and correspondingly greater error limits than similar systems using the inscribed circular elements. But they require greater wire length and power input, for the same current, field strength, and error limits. Bloom et al. showed that a polygonal system with N sides can be designed with field homogeneity e, not greater than N, by calculations that use only the axial derivatives of the field at the origin, and they computed two eighth order systems with octagonal filaments. No other polygonal systems with homogeneity above the fourth order have been known, since all proposed sixth order solutions with four square filaments are invalidated by an algebraic error. We have extended the spherical harmonic theory of polygonal systems and of the contours of total vector error in their magnetic fields. For the regular polygon of N sides, we have listed formulas for the axial field derivatives through the tenth order, which suffice to define the contours, for small errors, in circular approximation. For N=4,6,8 we formulate midplane derivatives through the eighth order, to define the N-fold azimuthal distortion. For larger errors, we describe simple procedures to construct the complete contours from field nets, directly computed, in the midplane and in two planes through the axis. We have computed about 1000 systems with N=4,6,8, or ∞, with two, three, or four elements. They belong to more than a score of classes, with homogeneities from the fourth to the eighth order. The elements may be filaments and/or solenoids. The two-element systems include Maxwell pairs to generate field gradients with fourth order uniformity. Nearly 300 systems are tabulated, including true sixth order systems with four square filaments. The tables list system parameters with second differences for interpolation, field strength, axial error limits, and efficiency. For fourth order systems, correction factors are added to permit the use of small finite cross sections.
Multiple Frame Image Converter Unit with up to Seven Frames per Trigger Using Solid State Design
Authors: Hofmeister F.
Published: February 2004

Driving the RCA 4449A/C73435Q electrostatically focused image converter tube, the unit provides seven screen pictures of 25 mm height and 8 mm width in time intervals of 1–110 μsec and with 0.1–10 μsec exposures. The solid state circuitry generates +275 V p-p shutter pulses with 25 nsec risetime and a correctly timed balanced staircase waveform of 2400 V p-p.
Modular Thin Film Deposition System
Authors: Ames I. , Hoekstra J. , Folchi G.
Published: February 2004

A modular thin film deposition system has been designed in which several arrangements of source, substrate, and associated deposition facilities are possible. The system is compatible for use with different pumping arrangements and has been used in this laboratory in conjunction with various thin film studies.
Mass Attenuation Coefficients for Plastic Pilot-B Scintillator
Authors: Hayn Carl H. , Carroll Daniel E.
Published: February 2004

Mass attenuation coefficients of the commercial plastic Pilot-B scintillator have been determined as a function of energy. Sources emitting gamma rays with energies of 0.36, 0.66, 0.80, and 1.33 MeV were used. The results indicate strong absorption in the low energy region and a smooth nonlinear decrease in the mass attenuation coefficients with increasing gamma ray energy. The experimental procedure and apparatus are described.
Wide Frequency Range Current Transformers
Authors: Anderson John M.
Published: February 2004

Current transformers with resistive loads are examined experimentally to determine some of the limitations to high frequency response. Coil resonances are avoided by placement of damping resistors around the secondary winding. This permits a relatively large number of secondary turns (50 or 100), improving low frequency response and increasing the i×t product, even for the highest frequency transformers. Uniform response to several gigahertz is obtained in a transformer with 6.4 mm window, while a range ∼1 Hz to ∼300 MHz is found in a larger transformer (12.7 cm diam and 2.5 cm window). Both ferrite and iron alloy cores are utilized.
Dielectric Low Temperature Thermometer for Use in High Magnetic Fields. I. KCl : Li
Authors: Brand R. A. , Letzring S. A. , Sack H. S. , Webb W. W.
Published: February 2004

The temperature dependence of the dielectric constant of KCl crystals doped with Li+ ions has been shown to provide a useful measure of temperature over the range of 1–30 K, that is (at least between 1–10 K), independent of magnetic fields up to at least 100 kOe. The magnetic field dependence, measured by calibrating the thermometer at zero, then at high field, is immeasurably small and certainly less than the absolute temperature uncertainty (about 0.2%) at 4.2 K. The capacitance C varies with temperature T approximately as C=A+B/T, where A and B are positive constants. For a thermometer with A∼30 pF and B∼15 pF·deg the sensitivity δ lnC/δ lnT=−B/(AT+B) is about 0.3 at 1 K. Using a GR type 1615 A bridge a sensitivity of 0.3 mK at 1 K, and of 3.6 mK at 4.2 K was obtained. The thermometer calibration is reproducible to better than 0.2% on cycling between room temperature and helium temperature. A long range stability problem, possibilities for higher sensitivities, other geometric arrangements, and similar further development questions are briefly mentioned.
Dielectric Low Temperature Thermometer for Use in High Magnetic Fields. II. KCl :OH, KCl :CN
Authors: Fiory A. T.
Published: February 2004

Potassium chloride crystals doped with OH− or CN− ions are shown to be excellent magnetic field independent thermometers between 0.1 and 10 K. A procedure for making rugged capacitance thermometers, their sensitivity to temperature, and their independence of magnetic field at 1.2 and 4.2 K are discussed.
An Improved Cell Volume Analyzer
Authors: Merrill J. T. , Veizades N. , Hulett H. R. , Wolf P. L. , Herzenberg L. A.
Published: February 2004

A cell volume sensing instrument has been built which employs the principle used in the Coulter counter in which a cell changes the impedance of a narrow orifice as it passes through the orifice. An improved transducer utilizes a coaxial flow of the cell suspension inside a sheath of cell-free solution through the orifice, thereby avoiding some drawbacks of earlier systems. The instrument is described, and the procedure necessary to achieve acceptable operation is discussed. The output for normal human red blood cells is nearly symmetrical with a narrow peak. Abnormal blood samples show various departures from symmetry and narrowness of peak. The output of this instrument is compared with that from a commercially available instrument, and our data show a more accurate representation of the actual distribution of blood volumes. The resolution of this instrument is such that it could be of significant value in a clinical laboratory.
An Improved Ion Thinning Apparatus
Authors: Heuer A. H. , Firestone R. F. , Snow J. D. , Green H. W. , Howe R. G. , Christie J. M.
Published: February 2004

Details of an improved ion thinning apparatus, suitable for preparing electron microscope foils of inorganic nonmetallic samples (ceramics, minerals, rocks), are described, along with a resume of conditions for its optimum operation. Problems of surface topography and radiation damage associated with the ion thinning process are also briefly discussed.
A Method for Determining Density-Radius Relations during Wire Explosions
Authors: Korneff T. , Chace W.
Published: February 2004

A twin tube flash x-ray unit is used to probe the density of expanding metal vapor produced in exploding wire experiments. Using an axial orientation for one of the tubes, details not seen in usual perpendicular pictures can be brought out. The developed x-ray film is scanned by a microphotometer and the trace compared with a standard wedge exposed on the same film. The tracings are then reduced to obtain density as a function of radius. Typical results as applied to copper wire are included.
Device for Bending Crystal Slabs for Use in Focusing X-Ray Spectrometers
Authors: Gilberg Erich
Published: February 2004

A device is described which allows precise bending of crystal slabs by means of four rods, for use in x-ray spectrometers. The crystal slabs can be bent into a curved cylindrical form having the curvature of a circle or of a logarithmic spiral, the latter giving ideal focusing for one wavelength.
A Synchronizing Valve for Low Frequency (3–15) Hz Injection of Gas into a Vacuum System
Authors: Dolan Charles P.
Published: February 2004

A pulsed valve is described for regulation of gas flow in vacuum systems using phase sensitive detection techniques. Mechanical and electrical construction detail is given with throughput performance and other characteristics in a given system application.
Lithium and Sodium Surface Ionization Ion Source Operation and Efficiency
Authors: Daley Howard L. , Perel Julius
Published: February 2004

An ion source configuration has been developed which uses direct surface ionization from oxygenated tungsten to generate lithium or sodium ions with measured efficiencies ≥70%. Currents of several hundred microamperes of Li+ and Na+ have been extracted at current densities up to several milliamperes per centimeter squared. The interrelationship between the current obtained and source parameters such as ionizer temperature, alkali metal feedrate, and ionization efficiency are examined. The ionization efficiencies were directly measured using a surface ionization detector in conjunction with an ion beam on/off technique which is independent of the efficiency of the detector. The expressions used in the efficiency determinations are derived and the simplifying assumptions are discussed.
Improved X-Ray Topography
Authors: Fitzpatrick Robert L.
Published: February 2004

The modification of a commercial Lang camera to include improved optics and versatile radiation shielding of minimum size is described. An inexpensive functional layout is described for obtaining near optimum exposures. Results of a topograph of gallium phosphide are shown.
A Cross Beam Neutralizer for Ion Beams
Authors: Goodman Ronald K. , Hunt Angus L.
Published: February 2004

A cross beam neutralizer that neutralizes ion beams by means of a directed gas flow from capillary arrays is described. The measurements given here show that such a neutralizer has an advantage over a uniform density, gas cell neutralizer in that its contribution to beam line streaming is significantly less. Two versions of the cross beam neutralizer that are suitable for injecting neutral hydrogen atoms into a plasma are described.
Pumpable Pressure Relief Valve
Authors: Reichert Jonathan F. , Schultz L. Keith
Published: February 2004

A simple device is described which serves as both a pumpable vacuum seal valve and a pressure relief valve. This device is particularly useful for low temperature vacuum chambers.
Optically Switched Pulsed X-Ray Generator
Authors: Ziegler L. H. , Holmberg D. L. , McCrary J. H.
Published: February 2004

A pulsed x-ray generator was constructed which makes use of a cold cathode consisting of a photocathode and the dynode assembly from a photomulitplier tube. The device is switched by a light source incident on the photocathode. Tests indicate that the output intensity of the x-ray pulse follows in time the intensity of the light pulse for pulse widths as short as a few tens of nanoseconds.
A 2000 A, Low Resistance Switch for Operation under No-Load Conditions
Authors: Snowden D. P. , Meyer C. H.
Published: February 2004

A single-pole, double-throw switch with current capacity of at least 2000 A for switching under no load conditions is described. The switch is of simple construction and operates easily and reliably. Electrical contact is made by forcing a layer of mercury between two adjacent, copper bus bars with well amalgamated surfaces.
A Technique for Measuring Nonsquare Pulsed High Voltages to ±0.25% Accuracy
Authors: Holm-Kennedy James W. , Ku Tony P. C.
Published: February 2004

An accurate technique (≤±1/4% error) for measuring a wide range of pulsed voltages and currents of large magnitude (kilovolts and amperes) and short duration at either low or high repetition rates is described. The technique is accurate for both square and nonsquare pulses. The technique is particularly useful for measuring the J-E characteristics (current density-electric field) of semiconductors at high electric fields. The unknown voltages are matched on a CRO to voltage-divided Zener diode limited pulses which are accurately known. The sample circuit and reference pulse circuits are given. The accuracy of the technique is demonstrated over a wide voltage and current range. Operating and construction precautions are listed for the convenience of the reader.
Operation of Conventional Vibrating Sample Magnetometer at 3He Temperatures and in High Magnetic Fields
Authors: Oliveira N. F. , Foner S.
Published: February 2004

Simple modifications of only the tail section of a conventional vibrating sample magnetometer (VSM) are described which permit magnetic moment measurements at 3He temperatures. The sample is immersed in the liquid 3He for good thermal contact. Tests with a cerous magnesium nitrate sample demonstrate that thermal equilibrium between the sample and the bath is achieved even at the maximum vibration amplitude of our instrument. The modifications can easily be made in relatively small volumes. The 3He section for our system had an inner diameter=0.58 cm, an outer diameter=0.79 cm, and was surrounded by a small 4He Dewar inserted into the pickup coils. The coils fit into a 2.54 cm bore, 60 kG superconducting solenoid. The sensitivity, field range, and other advantages are identical to that of the conventional VSM.
Precision Frequency Calibrator for Raman Spectrometers
Authors: Silvera Isaac F. , Hardy Walter N. , McTague John P.
Published: February 2004

A technique for continuous frequency calibration of scanning spectrometers, with particular importance to Raman spectroscopy, is described. A spectral comb generated by illuminating a Fabry-Perot étalon with white light is recorded simultaneously with, but separately from, the spectrum of interest. The precision achieved was of order 0.05 cm−1 although a different choice of design parameters would improve this substantially.
Accurate Calculation of Properties of the Two-Tube Electrostatic Lens III. Aberration Coefficients
Authors: Kuyatt C. E. , Natali S. , Di Chio D.
Published: February 2004

Using numerical methods, electric fields and meridional electron trajectories have been calculated for the two-tube electrostatic lens with sufficient precision to determine values for all the third-order and several of the fifth-order aberration coefficients for meridional trajectories. The aberration coefficients are expressed in a form which is intrinsic to the lens and do not depend on a particular object and aperture position. Results were obtained for voltage ratios of 2, 5, 10, 20, and 40.
An Apparatus for the Study of Hydrogen-Metal Reactions
Authors: Reichardt J. W. , Marceau J. E. , Mason T. B.
Published: February 2004

An apparatus has been designed and constructed which measures the rate of the reaction of hydrogen with metals, such as titanium, which form metal hydrides. The measurement is done using a flow technique. The data are recorded and analyzed using a real time interface with a digital computer. The accuracy of the rate measurement is within ±3×10−5 Torr liter/sec.
A Bakable Changeover Valve for High Precision Mass Spectrometric Comparison of the Isotopic Composition of Gases
Authors: Begbie P. J. , Beckinsale R. D. , Freeman N. J. , Powell R. E.
Published: February 2004

The construction of a bakable changeover valve for high precision mass spectrometric comparison of the isotopic composition of gases is described. The leakage across the valve seats is about an order of magnitude smaller than the values published for similar valves in use, and the ``mixing correction'' which can be a significant correction to the experimental data is negligible.
A New Method for Current ``Crowbar,'' Utilizing Reflected Shock Waves
Authors: Kasuya Koichi , Murasaki Toshimitsu
Published: February 2004

A new method is proposed for crowbar techniques utilizing the ionization behind reflected shock waves in air. We can easily crowbar discharge currents when we make the time of the current peak coincide with the arrival of the shock wave at the crowbar gap.
Method and Apparatus for Reducing Errors Introduced in Cutting of X-Ray Oriented Single Crystals
Authors: Adams Murry N. , Wetsel Grover C.
Published: February 2004

A method is described whereby monocrystalline samples such as those used in microwave-ultrasonic studies can be prepared with surfaces cut accurately parallel to known crystallographic planes. The apparatus makes use of an optical autocollimator traveling on precision ways to align the x-ray camera and saw and to check the sample surface after the cut. By following the procedure described, one can readily obtain a parallelism of the cut surface to the plane prescribed by x-ray orientation that is of the order of minutes of arc.
A Randomly Dispersive Strip Line for Studies of Propagation in Fluctuating Media
Authors: McIntosh R. E. , Wilk J. M. , Pickering L. W.
Published: February 2004

An experiment designed to measure the statistical properties of rf pulses transmitted through a fluctuating dispersive medium is described here. The experimental system utilizes a microwave strip line in which the region separating the two conductors contains a randomly inhomogeneous, gaseous discharge.
A Light Scattering Photometer Using Photographic Film
Authors: Brunsting A. , Mullaney P. F.
Published: February 2004

A light scattering photometer which uses a 5 mW helium-neon laser as a light source and red-sensitive film as the detection system is described. The film records the scattered intensity for scattering angles from 3° to 80° and from 100° to 177°. Corrections are made for refraction effects in the light scattering cell. Developed film is read with a densitometer, and film density is converted to relative scattering intensity. The quality of the light transmitted through the developed film in the densitometer is examined. This device has been tested using uniform 10.9 μ diam polystyrene spheres. The measured pattern agrees quite well with theoretical predictions.
Logarithmic Ratemeter Response to a Step Change in Frequency
Authors: Karlovac Neven
Published: February 2004

A formula is derived for the response time of a logarithmic ratemeter for a step change in periodic input frequency. It is shown that the formula is also valid for random inputs. A graph is included for the determination of 0%–90% rise and fall times as a function of the initial and final frequencies.
A Stress-Free System for the Mounting of Peltier Elements
Authors: Monaci T.
Published: February 2004

A device is discussed which has been designed to overcome Peltier element fragility, especially for applications in field instruments that use heat sinks as dissipators.
Method and Apparatus for the Measurement of Electrothermal Nonlinearity
Authors: Rosenthal Louis A.
Published: February 2004

Nonlinearity in Ohmic systems due to electrothermal effects can be measured by using an asymmetrical power waveform. A dc voltage generated can be related to the thermal behavior of the resistor and its environment. The apparatus design and the experimental application to fine wire devices are presented.
Preparation and Characteristics of a Channel Electron Multiplier
Authors: Becker H. , Dietz E. , Gerhardt U.
Published: February 2004

We prepare channel electron multipliers from appropriately shaped glass tubing with an inner coating consisting of a glass which contains 60% Bi2O3. Heat treatment of the device in a hydrogen atmosphere at 470°C produces a conductive coating inside of the tubing. The pulse height distribution of these multipliers narrows drastically with increasing operating voltage, its full width at half-maximum being about 10%–30% at a gain of about 108. The dark count rate is typically below 0.01 counts/sec. We also give a simple trigger circuit which converts the multiplier pulses into TTL compatible digital pulses. The quantum efficiency of the conductive coating for low energy electrons is nearly unity. The multiplier responds to photons with energies as low as 5 eV. The quantum yield increases up to values of about 10−2 for 10 eV photons if the conductive coating at the cathode is covered with a thin CsI layer.
Use of Stabilized Zirconia as a Selective Oxygen Leak Source
Authors: Mogab C. J.
Published: February 2004

Calcia stabilized zirconia of the composition Zr0.85Ca0.15O1.85 is an oxygen ion conductor over a wide range of temperature and oxygen partial pressure. Owing to the fact that oxygen ions, rather than molecules or atoms, are the mobile species, the rate of oxygen permeation through stabilized zirconia can easily be modulated by an applied electric field. This material is essentially impervious to other gases thus allowing it to be used for selective admission of oxygen to a vacuum system. This paper discusses the theory, construction, and operation of an UHV compatible oxygen leak source, based on stabilized zirconia, and draws a comparison with the widely used silver ``membrane'' permeation leak.
Construction of Thin Hemispherical Glass Windows
Authors: Hilger William
Published: February 2004

Thin hemispherical glass windows of aluminosilicate glass (Corning No. 1720) have been constructed by means of a simple furnace blowing operation and attached to 4.2 cm diam cylindrical sections of the same glass. The hemispherical end windows of the resulting chamber have 2.1 cm radii, are less than 0.025 mm thick, and withstand a pressure difference of 1 atm from inside to outside. Such thin end windows should be useful in the observation of nuclear or optical scattering from gases where it is desirable to minimize effects from the windows of the vessel containing the gas.
Production of an Intense Atomic Beam of Barium in Metastable States
Authors: Ishii S. , Ohlendorf W.
Published: February 2004

A device for producing an intense atomic beam of barium in metastable states has been developed. The population density of the states is measured by the resonance fluorescence method. The atoms are excited by an electric discharge in such a way that the atomic beam traverses the discharge plasma. The cross-section for excitation of barium by electron collisions is assumed to be as large as that for cesium. The efficiency of metastable atom production is estimated to be about 70%, and an atom flux of 4×1015 sec−1 cm−2 is obtained. The device is useful in forming a photoionized barium plasma using ordinary light sources.
High Accuracy Analog Differentiator
Authors: Nordlund D. R.
Published: February 2004

A second order bandpass filter with the proper choice of damping ratio has been adapted for use as a high accuracy analog differentiator. Curves showing differentiator gain error as a function of damping ratio are given along with the gain error of the ``standard'' analog differentiating circuit. For a gain error of 1%, the differentiator bandwidth is reduced by a factor of 6 compared to the bandwidth necessary with the ``standard'' differentiating circuit. The reduced bandwidth results in lower wideband noise.
A Colliding Shock Facility of High Reproducibility
Authors: Phillips M. G. R. , Harris C. A.
Published: February 2004

A double ended diaphragm shock tube has been developed in which shock wave collisions can be made to occur very reproducibly in both space and time. The repeatability is achieved by rapidly arc heating the helium gas in the opposing driver sections.
Light Output Control of a Pulsed Light Source for Use in Stabilizing Scintillation Detectors
Authors: Yamashita Mikio
Published: February 2004

A method is described for controlling the light output of a pulsed light source so that a scintillation detector stabilizing system based on the pulsed light source would be able to compensate variations in the light output of the scintillator with temperature as well as other temperature dependent instabilities.
New Instrumentation for Research on Vibrotactile Sensitivity of the Tongue
Authors: Fucci Donald J. , Kelly Dan H.
Published: February 2004

The need for a reliable instrument for vibrotactile stimulation of the tongue is presented. A signal delivery and signal monitoring instrumentation system as well as an appropriate method and apparatus for holding and positioning the test structure is described. The system is capable of controlling those spatial and psychophysical parameters affecting vibratory study of the tongue.
An Improved ac Bridge Circuit for Use in Four-Terminal Resistance Thermometry
Authors: Rubin L. G. , Golahny Y.
Published: February 2004

Details are given of an improved version of the ac Kelvin bridge first described by Ekin and Wagner [Rev. Sci. Instrum. 41, 1109 (1970)]. Battery-operated operational amplifiers with highly superior noise performance at 33 Hz were used for the voltage followers required to make the bridge compatible with four-leaded germanium resistance thermometers. A discussion of bridge operation, accuracy limitations, and final performance characteristics is presented, including a confirmation of the design objective to accurately measure a ΔT of 0.5 mK at 4.2 K, with a 1 mV germanium sensor excitation and a 1 Hz detector bandwidth.
Heater Lead Error in Calorimetry
Authors: Martin Douglas L.
Published: February 2004

A summary of previous work is followed by an examination of the effects of radiation from heater leads. Solutions of the exact differential equation for particular experimental configurations have been obtained by a numerical method. For certain simple situations the solutions can be checked against partial or complete analytical solutions of the equation. It is shown that even for low temperature calorimeters a large part of the electrical energy dissipated in heater leads may be radiated unless the lead resistance is kept very low. If a significant part of the total energy supplied to the calorimeter is radiated, systematic errors may arise because, for a given calorimeter heating rate, the heater lead radiation loss will differ in the ``full'' and ``empty calorimeter'' experiments.
A Device for the Removal of Temperature Gradients in NMR Spinning Tubes
Authors: Angerman Neil S. , Danyluk Steven S. , Kramer Andrew P.
Published: February 2004

A simple paddle device is described for the removal of temperature gradients in liquids contained in high resolution NMR spinning tubes. Experiments show that this accessory reduces temperature gradients to less than 0.10°C along the length of the liquid without any impairment in spectrometer resolution or sensitivity. The device is readily adaptable to most conventional high resolution NMR spectrometers.
An Intense Microsecond Flash Lamp
Authors: LeBlanc J. C. , Herbert M. A. , Whillans D. W. , Johns H. E.
Published: February 2004

A flash lamp system for flash photolysis is described which produces an intense flash of short duration and little afterglow. The discharge takes place in the space formed by placing a solid quartz rod on the axis of a cylindrical quartz tube. When the system dissipates 600 J of electrical energy, it produces a flash in xenon, at 25 Torr, which has a width of 0.9 μsec at half-height and the afterglow decays to less than 1% of its maximum value within 4.4 μsec from the start of the flash. By surrounding the lamps with a filter solution, noise generated by standing waves in the cell can be eliminated. Methods for eliminating other types of noise are presented.
Rotating Magnetic Field Control for Bubble-Domain Experiments
Authors: Smith A. B. , Johnson G. L.
Published: February 2004

We describe a method of generating a magnetic field whose direction can be rotated in a fixed plane. Such fields are required in microscopic studies of bubble-domain device operation. With the apparatus described here, the field is rotated in synchronism with the setting of a special 360°-rotation potentiometer. The field is produced by orthogonal coils which are driven with currents derived from the sine and cosine function outputs of this special potentiometer.
An Instrument for the Simultaneous Detection of the OI Ground State (2p4 3P) and First Metastable State (2p4 1D) Populations
Authors: Goorvitch David , McClenahan James O.
Published: February 2004

A dual-channel light pipe has been used for simultaneously observing the populations of atomic oxygen in the ground state 2p4 3P and the first metastable state 2p4 1D. A signal-to-noise ratio of 10 in a time scale of 100 μsec was attained. The ultimate sensitivity is 104 photons/sec with a background count of 1 photon per 10 msec.
An Improved Light Pipe for the Scanning Electron Microscope
Authors: Taylor M. E.
Published: February 2004

Results from the present study show that a quartz light pipe, properly ground and polished with a liquid scintillator solution applied to the tip, gives superior results by lowering the photomultiplier (P.M.) voltage. Perhaps even a greater advantage is that the maintenance procedures allow this type of light pipe to be used indefinitely compared to the approximate six month lifetime of the standard light pipes. Furthermore, the interface problem as in ``snap on'' tips has been alleviated by a bonded surface between scintillator material and light pipe.
An Optical Fiducial System for Shock-Wave Interferometry
Authors: Hollenbach R. E.
Published: February 2004

An electro-optical method of relating impact time to free surface motion is described. The fiducial system can be applied to any instrumentation arrangement that requires relating photomultiplier data to some specific time or event.
Rotating Disk Apparatus for Reaction Rate Studies in Corrosive Liquid Environments
Authors: Boomer D. R. , McCune C. C. , Fogler H. S.
Published: February 2004

This paper describes the design and use of a rotating disk apparatus for studying reactions between fluids and solid surfaces. The apparatus is capable of operation in extremely corrosive liquid environments under controlled pressures and temperatures up to 70 atm and 150°C. The design includes a unique magnetic drive assembly that allows the disk to be rotated in the high pressure reactor vessel without the need of a stuffing box seal. All parts that contact corrosive fluids are fabricated from Hastelloy alloys and Teflon. A special feature of the reactor vessel is its ready conversion to a high pressure visual cell.
A Simple Dilution Refrigerator
Authors: Levine James L.
Published: February 2004

A simple and reliable dilution refrigerator is described for routine measurements below 0.06 K. Novel construction techniques are used to reduce the number of potentially troublesome low temperature joints to a minimum, and to facilitate sample changing.
A Reliable Multimegavolt Voltage Divider
Authors: Pellinen D. G. , Smith I.
Published: February 2004

A two stage, dc coupled, linear resistive voltage divider having a risetime of 1.5 nsec has been used to measure voltage pulses up to 1.8 MV on a pulsed electron accelerator. The monitor has proved to be stable, reliable, and has required little maintenance.
Sensitivity of Radio Frequency Measurements in the Presence of Oscillator Noise
Authors: Strandberg M. W. P.
Published: February 2004

The inherent sensitivity of an rf measuring system and the effect of the system transmission characteristics on the detectability of the rf source noise are examined. The results are applied to resonant reflection and transmission systems and to a nonresonant transmission system. The conventional reflection cavity paramagnetic resonance system is discussed in detail, and the conclusion is that this configuration will be source noise limited at power levels above 1 mW. Unconventional configurations, such as a dual mode induction cavity or a dual cavity transmission system, would have to be used to achieve higher sensitivity.
Picosecond Beam Monitor
Authors: Beck G. , Schutt D. W.
Published: February 2004

A coaxial transmission line beam monitor with a risetime of approximately 18 psec is described. This monitor was used to examine the fine structure of the electron beam from an L-band linear accelerator.
Water-Cooled Fiber Optics Probe for Spectrally Resolved Radiation Measurements
Authors: Heberlein J. , Pfender E.
Published: February 2004

A probe is described which can be swept through an emitting-absorbing gas layer. The signal is transmitted to a spectrograph by means of a light fiber duct. The probe has been tested for measuring line radiation intensities in a sodium seeded propane air flame. The results suggest the applicability of the probe in flames containing solid particles.
Simple Voltage to Time Proportional Controller
Authors: Taragin M. F.
Published: February 2004

A simple voltage to time proportional controller, for use in temperature control circuits is described. The input is the output of a null detector. The output is a relay which can be used to control either a valve or a heater.
A Simplified System for Ferromagnetic Resonance Measurements at Low Temperatures
Authors: Kyllonen Eric W. , Manasse Fred K.
Published: February 2004

Simplified low temperature ferromagnetic resonance (FMR) measurements have been made by modifying the self-oscillating solid state ESR spectrometer of Walsh and Rupp [Rev. Sci. Instrum. 41, 1316 (1970)] to accommodate a specially designed Dewar. An internal heating resistor is used to raise the sample temperature above 77 K. The capability of Dewar rotation allows for measurements of anisotropy effects due to changes of sample orientation in a magnetic field. The complete FMR system can be put together at very low cost.
Molecular Beam System for Gas-Surface Scattering Studies
Authors: Mason B. F. , Williams B. R.
Published: February 2004

A molecular beam system for the study of gas scattering at surfaces is described. The system combines the use of a nozzle source for obtaining a relatively monoenergetic incident beam, with low temperature pumping which enables a clean system to be maintained. Further, the use of cryogenics enables the study of scattering behavior at low surface temperatures—a region which has to date not been investigated.
One Ampere Current Supply Stable to One Part per Million per Hour
Authors: Retsky M. W. , Wall J.
Published: February 2004

A 1 A current supply stable to better than 1 ppm/h is described. The technique uses a standard feedback circuit, but many practical problems had to be solved to achieve the high stability. Details concerning a 10−3 °C stability oven, a 1 ppm/h variable reference voltage, and a 1 ppm/°C power resistor are given.
A Test Facility for Electric Microthrusters
Authors: Bailey A. G. , Bracher J. E. , Helmke H. G. , von Rohden H. J.
Published: February 2004

The test facility for electric microthrusters at the European Space Research and Technology Centre is described. The microbalance which is used to directly measure thrust and propellant mass flow rate is able to resolve thrusts of 10−7 N. Within a working range of 5×10−5−5×10−4 N it is estimated that thrust measurements may be made to an accuracy of ±2%.