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Jul 1992

Volume 63, Issue 7, pp. 3551-3792

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A flexible data acquisition system for timing pulsars

D. R. Stinebring, V. M. Kaspi, D. J. Nice, M. F. Ryba, J. H. Taylor, S. E. Thorsett, and T. H. Hankins

Rev. Sci. Instrum. 63, 3551 (1992); http://dx.doi.org/10.1063/1.1143763 (5 pages) | Cited 19 times

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We describe a flexible, inexpensive data acquisition system built for high‐precision timing observations of pulsars. The system is designed to interface with a wide variety of radio telescope receiver back ends; it permits standardized measurement techniques and data formats in work carried out at a number of different observatories. Copies of the basic ‘‘Mark III’’ system are now in regular use at the Arecibo Observatory, Green Bank, and the Very Large Array. We describe the specifications, hardware, and software implementation of the system, and briefly outline some of its current applications.
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07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation
95.85.Bh Radio, microwave (>1 mm)
95.75.-z Observation and data reduction techniques; computer modeling and simulation

Monte Carlo integration to optimize geometry in gravitational experiments

L. I. Winkler and C. E. Goldblum

Rev. Sci. Instrum. 63, 3556 (1992); http://dx.doi.org/10.1063/1.1143764 (8 pages) | Cited 3 times

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The torsion balance has been the experimental apparatus of choice for centuries, both in precision measurements of the Newtonian gravitational constant and in searches for weak anomalous interactions outside of gravity. If the form of the interaction is modeled, it is often possible to optimize the interacting bodies so that the apparatus has the greatest sensitivity to the interaction under study. Other researchers have applied this strategy in the case of the gravitational interaction between cylinders, and between a cylinder and sphere. Whereas their work focused on developing an analytical expression for the force between the masses, we present here a numerical method−Monte Carlo integration−which is general enough to aid in the design of bodies interacting under arbitrary potentials and with any desired geometric shape (as long as an accurate absolute value of the force is not needed). This numerical method is used to compute the gravitational torsion constant produced between an external hollow cylinder and sphere, and demonstrates the behavior studied previously through analysis. However, the main purpose for which we have used this numerical technique is in the design of interacting bodies used in a torsion‐pendulum search for interactions that depend on net intrinsic spin. We demonstrate how the method may be used to determine the optimum aspect ratio (l/r) of the polarized test masses, as well as the most sensitive orientation of the masses. Two different interactions are considered: the dipole–dipole interaction between two polarized bodies, and the monopole–dipole interaction between a polarized and unpolarized body. In the case of the monopole–dipole interaction, we also show how the numerical method can indicate which orientation between test bodies is most susceptible to a false signal caused by gravity.
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04.30.-w Gravitational waves
04.80.-y Experimental studies of gravity
98.80.Cq Particle-theory and field-theory models of the early Universe (including cosmic pancakes, cosmic strings, chaotic phenomena, inflationary universe, etc.)
98.80.Es Observational cosmology (including Hubble constant, distance scale, cosmological constant, early Universe, etc)

Correlation between measured undulator magnetic fields and x‐ray spectraa)

Roger Carr, Brian Kincaid, and William Hassenzahl

Rev. Sci. Instrum. 63, 3564 (1992); http://dx.doi.org/10.1063/1.1143765 (5 pages) | Cited 1 time

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Electron storage ring insertion devices, especially undulators, are designed using ideal device theory and the resulting x‐ray spectra are reasonably close to predictions in most cases. However, magnetic field errors result in nonideal x‐ray spectra. These effects can be calculated theoretically, and may also be measured. Here we present a study of an undulator whose magnetic fields and x‐ray spectra have been measured carefully. We compare experiment and theory and explain the deviation from ideal of the shape of the undulator’s spectral peaks in terms of magnet errors.
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07.55.-w Magnetic instruments and components

A source of cold molecular ions for Coulomb explosion imaging

T. Graber, D. Zajfman, E. P. Kanter, R. Naaman, Z. Vager, and B. J. Zabransky

Rev. Sci. Instrum. 63, 3569 (1992); http://dx.doi.org/10.1063/1.1143766 (6 pages) | Cited 7 times

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A specialized ion source for use in the high voltage terminal of an electrostatic accelerator has been developed to produce vibrationally cold beams of molecular ions. A pulsed valve is used to produce a supersonic expansion of the source gas which is ionized by electron impact near the beginning of the free expansion. Because of the harsh electromagnetic environment in the terminal, special care has been taken to protect the electronic components related to the ion source. The effect of vibrational cooling in the supersonic expansion is demonstrated using Coulomb explosion techniques with a He2+ beam.
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29.25.Ni Ion sources: positive and negative

Pulsed Q‐switched CO2 waveguide laser

Y. S. Al‐Shiraida, M. Paulson, T. Rosadiuk, J. Tulip, and P. Pace

Rev. Sci. Instrum. 63, 3575 (1992); http://dx.doi.org/10.1063/1.1143767 (4 pages) | Cited 1 time

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The performance of an rf‐excited CO2 waveguide laser which was synchronously pulsed and electro‐optically Q switched is described. Output power of up to 14 kW in 50 ns was achieved which was significantly higher than powers previously obtained from reported Q‐switched CO2 waveguide lasers. Acoustical perturbations were created in the optical waveguide by the pulsed discharge. This resulted in discontinuous variation in the laser pulse energy as the pulse repetition frequency was varied. Extremely marked thermal effects on Q‐switching performance were observed.
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42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
42.55.Lt Gas lasers including excimer and metal-vapor lasers

A fast operating laser device for measuring the thicknesses of transparent solid and liquid films

A. B. Fedortsov, D. G. Letenko, Yu. V. Churkin, I. A. Torchinsky, and A. S. Ivanov

Rev. Sci. Instrum. 63, 3579 (1992); http://dx.doi.org/10.1063/1.1143768 (4 pages) | Cited 3 times

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A fast operating device for thickness measurement of transparent films has been designed and tested. Its principle of operation is based on the film reflection dependence on the laser beam incidence angle. The alteration of the incidence angle is produced by means of nonspherical optics. The single measurement time is less than 0.001 s, so this device allows the measurement of film thickness irregularities and investigation of the spreading liquid film thickness kinetics. The measurement frequency is 50 per second.
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78.66.-w Optical properties of specific thin films
78.67.-n Optical properties of low-dimensional, mesoscopic, and nanoscale materials and structures
07.60.-j Optical instruments and equipment

Determination of the position or speed of an object using pulsed laser photoacoustic beam deflection

Jeffrey A. Sell

Rev. Sci. Instrum. 63, 3583 (1992); http://dx.doi.org/10.1063/1.1143582 (3 pages) | Cited 1 time

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We demonstrate here a method of measuring the position or speed of an object using photoacoustic beam deflection. Two laser beams are utilized: a pulsed one focused normally on the object and a continuous one parallel to the surface of the object. An acoustic wave generated by the pulsed laser is launched from the surface of the object and propagates through the air to the other beam where it deflects the beam. This deflection is measured by a position sensitive detector. The time‐of‐flight of the acoustic wave is determined from the zero crossing of the beam deflection signal. Multiplying this by the speed of sound gives the distance of the object from the probe beam.
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43.35.Ud Thermoacoustics, high temperature acoustics, photoacoustic effect
42.79.Qx Range finders, remote sensing devices; laser Doppler velocimeters, SAR, and LIDAR
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
06.30.Gv Velocity, acceleration, and rotation

Large range coherence tuned fiber optic interferometric system for application in accelerometers

A. B. L. Ribeiro, J. L. Santos, and D. A. Jackson

Rev. Sci. Instrum. 63, 3586 (1992); http://dx.doi.org/10.1063/1.1143583 (4 pages) | Cited 1 time

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A low coherence interferometric system with large tracking range and self‐initialization to be used for remote signal processing of fiber optic accelerometers is investigated. The tracking range of the low coherence system is 1.1 mm at low frequency. Phase resolution better than 1 mrad/√Hz at frequencies below 600 Hz is obtained, with a dynamic range of ≊90 dB. Data are presented which show that if the system were used to process the output from a compliant cylinder‐type accelerometer, resolutions of ∼10−7 g/√Hz could be achieved.
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07.60.Ly Interferometers
06.30.Gv Velocity, acceleration, and rotation

A rheometer with two‐dimensional area detection for light scattering studies of polymer melts and solutions

Alan I. Nakatani, Dean A. Waldow, and Charles C. Han

Rev. Sci. Instrum. 63, 3590 (1992); http://dx.doi.org/10.1063/1.1143584 (9 pages) | Cited 9 times

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A combined rheometer and light scattering photometer has been constructed to examine the light scattering behavior of polymer melts and solutions under the influence of a simple shear field. The device utilizes a special lens system and a two‐dimensional charge‐coupled device array detector which has not been used previously in an apparatus of this type to quantitatively measure the scattering intensity as a function of shear rate. The accessible q range of the instrument is from 3.75×10−4 to 3.0×10−3 nm−1 (2.2°–17.4° scattering angle, with λ=632.8 nm). The rheometer utilizes a cone and plate geometry to generate the shear gradient and is capable of measuring torque (1.8 N m maximum) and normal forces (50 N maximum). An 8% solution of a 50:50 polystyrene/polybutadiene blend in dioctyl phthalate was used to test the apparatus. This sample shows a shear‐induced mixing behavior which is consistent with previous measurements by other investigators.
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07.60.-j Optical instruments and equipment
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)

Position‐sensitive time‐of‐flight mass spectrometer using a fast optical imaging technique

Tohru Kinugawa and Tatsuo Arikawa

Rev. Sci. Instrum. 63, 3599 (1992); http://dx.doi.org/10.1063/1.1143585 (9 pages) | Cited 3 times

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A simple position‐sensitive time‐of‐flight mass spectrometer has been developed with an aid of a gatable image intensifier. This spectrometer is a display‐type analyzer allowing simultaneous measurements of the mass, speed, and angular distributions. The apparatus demonstrates a time resolution of 30 ns, a mass resolution over 125, and a spatial resolution over 60 in a multiphoton ionization experiment of NO molecules. The single‐ion counting technique employed can detect a low‐energy (∼100 meV) photofragment distribution without suffering from Coulombic repulsion.  
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07.75.+h Mass spectrometers

Development of multicolor pyrometers to monitor the transient response of burning carbonaceous particles

Yiannis A. Levendis, Kelvin Rafael Estrada, and Hoyt C. Hottel

Rev. Sci. Instrum. 63, 3608 (1992); http://dx.doi.org/10.1063/1.1143586 (15 pages) | Cited 28 times

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A three‐color ratio pyrometer has been developed to obtain surface temperatures and high‐temperature combustion rates of burning carbonaceous particles. The features and performance of this instrument are contrasted to those of a two‐color ratio pyrometer, constructed earlier for similar studies. The three‐color pyrometer employs a visible (0.65 μm) and two near‐infrared (0.80 and 0.975 μm) wavelengths. The instrument uses a single optical fiber to capture radiation emitted from a particle burning in a high‐temperature laminar flow furnace. Monitoring of the combustion events takes place coaxially with the particle flow, from observation windows located at the top of the furnace injectors. Thus, the temperature‐time history of burning particles can be recorded. The radiation flux is split into three beams using dichroic edge filters. Narrow (or medium) bandwidth interference filters guide monochromatic radiation to solid‐state silicon photodetectors. The associated amplification is linear and/or logarithmic. In contrast, the two‐color pyrometer used a bifurcated optical fiber bundle to split radiation to two medium bandwidth interference filters centered at 0.80 and 1.0 μm. Silicon detectors were employed, associated with linear amplification. Both instruments were used to monitor the combustion temperature‐time behavior of burning highly homogeneous, spherical, and monodisperse carbonaceous particles, and their performance is discussed herein.
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07.20.Ka High-temperature instrumentation; pyrometers
82.33.Vx Reactions in flames, combustion, and explosions

Thermoregulated fiber‐optic probe validation for temperature determination in spite of radiation disturbances

C. Ciaurriz, D. Hernandez, G. Olalde, C. Devilliers, and M. Salle

Rev. Sci. Instrum. 63, 3623 (1992); http://dx.doi.org/10.1063/1.1143587 (6 pages) | Cited 3 times

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A methodology has been developed for measuring surface temperatures at high temperature in highly hostile environments, in spite of material thermoradiative properties and radiation interferences. The measurement technique is bichromatic optical pyrometry. The radiometer is connected to a fiber‐optic probe coupled with a reflecting hemisphere head. When reducing the distance between probe and target, the correction on measured temperature improves but meanwhile the thermal disturbance on target increases. The purpose of this work consists in a complete analysis of this process. Experiments were performed on platinum and graphite. The samples were submitted to high flux obtained from concentrated solar energy or Joule effect. The measured temperatures are analyzed to get meaningful temperatures and thermal disturbances variation versus the distance between probe and target at various temperature levels. Experimental and theoretical results are compared. Temperature evolutions are concordant with literature emissivity data. As for thermal disturbance, the concordance is very good at an optimal distance of 1 mm, somewhat worse at longer distances and worse at very short distances. Nevertheless, these first tests results and simulation prove that great confidence could be accorded to this methodology provided other experiments and calculation with different boundary conditions are performed.
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42.81.Wg Other fiber-optical devices
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

A Rayleigh light scattering facility for the investigation of free jets and plumes

Nelson Bryner, Cecilia D. Richards, and William M. Pitts

Rev. Sci. Instrum. 63, 3629 (1992); http://dx.doi.org/10.1063/1.1143588 (7 pages) | Cited 7 times

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A Rayleigh light scattering facility (RLSF) has been developed and successfully used to examine mixing in free jets and buoyant plumes. The RLSF couples laser diagnostics with a cylindrical clean room, test section diameter of 2.4 m and a height of 2.4 m, to monitor the real‐time concentration behavior within turbulent flows. The facility has been carefully designed to minimize interferences of glare and Mie scattering by suppressing background light and removing dust particles. The relatively large working section of the RLSF allows quantitative concentration measurements via Rayleigh light scattering (RLS) in free shear flows entering quiescent surroundings. As a result, RLS measurements are now possible in momentum‐driven flows for conditions which were impossible in the past and in buoyancy‐driven flows for which no previous RLS investigations have been made. Initial measurements of concentration in momentum‐driven jet flows of helium and Freon‐13 and a transitional (momentum‐ to buoyancy‐driven) jet of Freon‐13 demonstrate the advantages of the new RLSF.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
51.70.+f Optical and dielectric properties

Design, construction, and testing of an infrared–far‐infrared–radio frequency (IR–FIR–rf) cell

Mohammad A. Rob

Rev. Sci. Instrum. 63, 3636 (1992); http://dx.doi.org/10.1063/1.1143589 (7 pages) | Cited 1 time

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Practical considerations in designing a far‐infrared waveguide laser and a radio frequency/microwave transmission line applicable to double‐ or triple‐resonance spectroscopy are discussed. It is shown that a transmission line is preferable in the radio frequency (∼1 kHz–1 GHz) region, and a waveguide is preferable in the microwave (∼1–100 GHz) region. A near‐optimum radio frequency transmission line was constructed and a double‐resonance experiment was carried out to show the usefulness of the transmission line. It is found that a small mismatch between the impedance of the transmission line and that of other instruments does not appreciably modify the characteristics of the transmission line.
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42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Simple, variable‐temperature, scanning tunneling microscope

M. A. Dubson and Jeeseong Hwang

Rev. Sci. Instrum. 63, 3643 (1992); http://dx.doi.org/10.1063/1.1143590 (3 pages) | Cited 12 times

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We describe a simple scanning tunneling microscope (STM) which works well from room temperature to 4 K. It is relatively easy to build, repair, or modify, and works very reliably. An unusual feature of our STM is that it is assembled without glues or solders. A list of suppliers of the components used in our STM is included in the references.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

A flexible implementation of scanning tunneling spectroscopy utilizing C‐language on the personal computer

Z. Y. Rong, A. Chang, and E. L. Wolf

Rev. Sci. Instrum. 63, 3646 (1992); http://dx.doi.org/10.1063/1.1143591 (6 pages) | Cited 2 times

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Scanning tunneling spectroscopy (STS) capable of measuring the local density of states dI/dV=G(V,x,y) correlated with the topography z(x,y) is implemented on a PC/AT computer system. An algorithm using dimensional decoupling and recursive linking is incorporated in a compact C‐language code to achieve flexible and sophisticated STS control. Data acquisition and processing methods which provide the local density of states G(V,x,y,s) at different tip heights s in registry with z(x,y) are described. Examples of novel low‐temperature experiments are given to show the capabilities of this implementation of STS.
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07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation

A high‐resolution magnetic imaging system based on a SQUID magnetometer

A. D. Hibbs, R. E. Sager, D. W. Cox, T. H. Aukerman, T. A. Sage, and R. S. Landis

Rev. Sci. Instrum. 63, 3652 (1992); http://dx.doi.org/10.1063/1.1143592 (7 pages) | Cited 14 times

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We have recently developed a high‐resolution magnetic imaging system based on an array of five superconducting pickup coils located within 1 mm of room temperature. The pickup coils are 1.70 mm in diameter and spaced 2.5 mm apart allowing spatial resolution of order 1 mm. They are each connected to an rf SQUID and have a magnetic field sensitivity of 3 pT/√Hz. The system includes a three axis nonmagnetic translation table for mounting the sample, a stage for temperature control, and complete computer control of all functions.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
07.55.-w Magnetic instruments and components

Light intensity measurements from dark noise analysis of video images

F. Kammoun, J. P. Astruc, D. Beysens, P. Hede, and P. Guenoun

Rev. Sci. Instrum. 63, 3659 (1992); http://dx.doi.org/10.1063/1.1143593 (3 pages) | Cited 2 times

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It is possible to determine the absolute intensity of a light signal recorded by a video camera with automatic gain by analyzing the background part of the recorded images. The method is based on the determination of the histogram of the gray levels of the dark pixels whose inverse variance appears to be proportional to the camera gain in a large domain of light intensity. An example is given by images recorded by a charge coupled device camera in a space experiment where the light transmittivity is used as a local probe for temperature measurements.
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07.68.+m Photography, photographic instruments; xerography
42.30.Va Image forming and processing

High‐speed infrared camera

J. P. Garcia, E. L. Dereniak, and S. M. Shepard

Rev. Sci. Instrum. 63, 3662 (1992); http://dx.doi.org/10.1063/1.1143594 (4 pages)

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We have developed a staring‐mode, high‐speed infrared camera based on a RCA 160×244 PtSi Schottky‐barrier charge‐coupled device image sensor. The camera uses a unique method to achieve greater temporal resolution of rapidly varying thermal phenomena in the 3–5 μm band. Rather than increase the imager’s frame rate, we decrease the image integration time while maintaining a frame rate that is compatible with standard RS‐170 video. This technique allows us to display and record repetitive events that occur at frequencies up to 5 kHz with conventional video equipment. In this article we describe the theory and operation of this system.
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07.68.+m Photography, photographic instruments; xerography
85.60.Gz Photodetectors (including infrared and CCD detectors)

Automatic frequency control for solid‐state sources in electron spin resonance

Michael J. Pechan, Jiansheng Xu, and Lynn D. Johnson

Rev. Sci. Instrum. 63, 3666 (1992); http://dx.doi.org/10.1063/1.1143595 (4 pages) | Cited 3 times

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A lock‐in amplifier circuit has been designed and tested which serves as an automatic frequency control (AFC) for electron spin resonance (ESR) spectrometers employing solid‐state microwave generators. Its implementation in a typical spectrometer is described and a detailed electronic schematic presented. Its performance is tested as a lock‐in amplifier operating under open loop conditions, wherein operating with a 20‐kHz reference, it yields an 81‐dB improvement in signal to (9 kHz) noise ratio. This is consistent with expectations from computer simulations. When employed as an AFC in a typical X‐band ESR system the capture and lock ranges are observed to be equivalent to those obtained from a commercial lock‐in amplifier.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
84.30.Le Amplifiers

Enhanced sensitivity for high‐pressure EPR using dielectric resonators

Steven E. Bromberg and I. Y. Chan

Rev. Sci. Instrum. 63, 3670 (1992); http://dx.doi.org/10.1063/1.1143596 (4 pages) | Cited 13 times

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We present a modified Merrill–Bassett diamond anvil cell for performing electron paramagnetic resonance (EPR) experiments under high pressure. The design centers on two mutually coupled TiO2 dielectric resonators mounted close to the diamonds. This configuration produces a tangential microwave magnetic field at the gasket, which is a prerequisite for a magnetic resonance experiment. Our simple device has a considerable advantage over previous approaches for EPR under pressure in both its compactness and sensitivity.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
61.05.Qr Magnetic resonance techniques; Mössbauer spectroscopy (for structure determination only)
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

Improved NMR resonator for diamond anvil cells

Sam‐Hyeon Lee, Mark S. Conradi, and R. E. Norberg

Rev. Sci. Instrum. 63, 3674 (1992); http://dx.doi.org/10.1063/1.1143597 (3 pages) | Cited 7 times

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A new hairpin resonator efficiently couples to nuclear spins in diamond anvil cell–nuclear magnetic resonance (DAC–NMR) experiments. The hairpin resonator is essentially a single turn coil of copper sheet, resonated with a chip capacitor. A modest tuning range is provided by trimmer capacitors. This resonator has so far been the most satisfactory of the DAC–NMR schemes tried in our laboratory. It is easy to make, robust, and reusable, and is easily cleaned to eliminate contaminant signals. The H1 homogeneity is good; the rf performance is described.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

A new pressure sensing method by use of magnetic fluid

K. Komiya, I. Itoh, and Y. H. Gashi

Rev. Sci. Instrum. 63, 3677 (1992); http://dx.doi.org/10.1063/1.1143598 (4 pages) | Cited 1 time

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This article deals with a new pressure sensing method by use of magnetic fluids. In a magnetic fluid placed in a magnetic field, fluid‐magnetic pressure appears, which is a function of magnetic field. When a differential pressure is applied to the ends of such a magnetic fluid plug, and the differential pressure is in equilibrium with the fluid‐magnetic pressure so that the plug cannot move, then the magnitude of the magnetic field maintaining the fluid‐magnetic pressure becomes a measure of the differential pressure. We made a small setup and measured differential pressures up to about 100 Pa by measuring the coil current of an electromagnet.
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07.55.-w Magnetic instruments and components
07.07.Vx Hygrometers; hygrometry
75.50.Mm Magnetic liquids

Resonance‐enhanced low‐pressure optoacoustic cell

M. Hartemink and H. P. Godfried

Rev. Sci. Instrum. 63, 3681 (1992); http://dx.doi.org/10.1063/1.1143599 (13 pages)

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A low‐pressure optoacoustic cell is described that can be used to lock the emission frequency of a laser. A model is developed which describes the low‐pressure behavior of the optoacoustic cell as a function of cell dimensions, gas properties, and operating pressure. Resonant optoacoustic cells are predicted to improve the acoustic signal levels significantly. Experiments were carried out with a cell filled with CF4. The model was found to accurately predict resonator quality, resonance frequency, and acoustic response for pressures ranging from 0.1 to 3.0 kPa. At these low pressures acoustic attenuation processes, slow vibration to translation (VT) relaxation and diffusion to the cell wall strongly influence the acoustic behavior of the cell. Using the relaxation time of the ν4 vibrational mode of CF4 as a fitting parameter its value was determined to be three times slower than VT relaxation from the ν2 level. The experimental values for the response were predicted by the model with an error of less than 10% in the whole pressure range. Predictions for the optoacoustic signal for different resonator dimensions were also confirmed. Model predictions for the optoacoustic signal for mixtures of gases and the influence of the temperature are also given. Especially the option of cooling the gas seems to be attractive for the case of CF4.
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82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
06.60.Ei Sample preparation (including design of sample holders)

Active control of beam trajectories for heavy ion beam probe on helical magnetic configurations

A. Fujisawa, H. Iguchi, M. Sasao, Y. Hamada, and J. Fujita

Rev. Sci. Instrum. 63, 3694 (1992); http://dx.doi.org/10.1063/1.1143600 (7 pages) | Cited 15 times

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Active control of beam trajectories using four sets of sweep plates is proposed for a heavy ion beam probe (HIBP) system on helical plasma, such as torsatron, stellarator, etc., in order to solve problems arising from the complicated beam trajectories in its nonaxisymmetrical magnetic field. By this method, a series of the probing beam trajectories giving a whole potential distribution can be managed to pass at a particular point (detector aperture) with the same angle. An equation is introduced as a guiding principle to simplify the optimization process of geometrical configuration of the HIBP system, which will be adjusted for different magnetic configurations by only changing the sweep plate voltages.
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52.70.Nc Particle measurements
52.40.Mj Particle beam interactions in plasmas
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