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Review of Scientific Instruments

Issue 1 • Date Jan 1984

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Displaying Results 1 - 25 of 33
  • Issue Table of Contents

    Page(s): toc1
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    Freely Available from IEEE
  • High magnetic field, large‐volume magnetic multipole ion source producing hydrogen ion beams with high proton ratio

    Page(s): 1 - 7
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    In order to enhance the proton fraction in hydrogen ion beams, a high magnetic field, large‐volume magnetic multipole ion source has been designed and tested. The plasma source is made of a water‐cooled rectangular copper chamber, which is surrounded by a set of mild steel strips and samarium–cobalt magnets arranged in a continuous line‐cusp geometry. The magnetic field at the inner wall surface is 2.7 kG. This strong magnetic field enables us to enlarge the chamber volume without increasing the ion loss area. Large plasma volume and small ion loss area increase the ion confinement time and enhance the proton yield. The proton fraction in the beams, as measured by both a magnetic momentum mass analyzer and a optical spectrometer, is found to be more than 90% at an ion beam current of 28 A ( j=250 mA/cm2). This source is also operated with a weak magnetic field (∼0.6 kG) by replacing the samarium–cobalt magnets with AlNiCo magnet, in which case the proton fraction decreases to 80%. These experimental values are in good agreement with the values predicted by a simple scaling equation of the proton ratio on the plasma volume and the ion loss area. View full abstract»

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  • Cesiated porous molybdenum converter for intense negative ion sources

    Page(s): 8 - 11
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    Maintaining the proper low work function surface in steady‐state high‐current‐density negative ion sources is difficult, due to intense ion bombardment of the surface. Experiments were performed in which liquid cesium was forced through a porous molybdenum converter in order to obtain a low work function, while at the same time allowing the surface to be cooled. In a small steady‐state hollow cathode discharge source, the H- yield from a porous molybdenum converter was five fold higher than from a solid molybdenum converter which relied on the conventional method of cesium coverage by vapor deposition. View full abstract»

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  • Dense and quiescent magnetized plasma with a low‐pressure hollow‐cathode discharge

    Page(s): 12 - 15
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    Diffusion of a low‐pressure (10-2 Torr) hollow‐cathode discharge through an anode screen produces a linear, homogeneous, and quiescent plasma column (14 mm in diameter, 80 cm in length) in a strong magnetic field (max 3 kG). Electron temperatures and densities in this plasma, as measured by Langmuir probe and microwave cavity perturbation techniques are, respectively, in the ranges of 0.3–1.2 eV and 109–1011 cm-3. Plasma noise fluctuations (e≂fl/kBTe) at the center of the plasma are about 3%. View full abstract»

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  • Grazing incidence time‐resolving spectrograph for magnetic fusion plasma diagnostics

    Page(s): 16 - 24
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    A time‐resolving grazing incidence spectrograph based on an image intensified photodiode array detector has been constructed and has demonstrated its utility as a fusion plasma diagnostic. The total wavelength coverage is 15–360 Å with 0.7 Å resolution (line profile FWHM); portions of this range may be observed during a single plasma discharge with a bandwidth of ∼40 Å when the detector is centered at 40 Å and ∼80 Å with it centered at 200 Å. Integration times from 5.4 to 13.1 ms are available when the entire photodiode array is read out; integration times as short as 1 ms can be obtained for a few lines of interest through the readout of selected photodiodes. The spectrograph has been radiometrically calibrated over the 60‐ to 360‐Å range at the NBS SURF II electron storage ring and is currently in operation on the Princeton Large Torus (PLT) tokamak. View full abstract»

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  • Flash x‐ray source for plasma shutter diagnostics

    Page(s): 25 - 34
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    A flash x‐ray source has been fabricated to examine the plasma‐driven shutter for the Nova Fusion Laser System at the Lawrence Livermore National Laboratory. This source has a 20‐ns pulse width and 1.5‐ and 4.5‐keV x rays. It has been used to characterize plasma moving at 1–5 cm/μs with areal densities down to 0.1 mg/cm2 and a spatial resolution of 2.5 μm. By using this x‐ray source to diagnose the Nova plasma shutter, the authors were able to discover and cure sources of plasma nonuniformity and empirically select the foil dimensions and the current required for Nova. View full abstract»

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  • Unusual chemical composition fluorescers and filters for low‐energy x‐ray diagnostics. Part I. Oxygen compositions

    Page(s): 35 - 38
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    The preparation of filters and fluorescence of high oxygen content (53%) for low‐energy x‐ray measurements is described. The thin films of high oxygen content were fabricated from a 50:50 wt. % mixture of CelconTM and DelrinTM. Thermal analysis data on all the materials investigated are also presented. View full abstract»

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  • Device for loading thin wires in a vacuum

    Page(s): 39 - 41
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    A simple device has been developed to load thin (25 μm in diameter) wires in vacuum for an exploding wire plasma system. Wires may be loaded with high reliability, straight, and accurately positioned. An improvement in the reproducibility of the wire explosion results and is attributed to the ability to repeatedly form the electrical contacts between wire and electrodes. View full abstract»

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  • High heat flux target for intense neutron source

    Page(s): 42 - 47
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    A 200‐kV, 200‐mA deuterium ion accelerator has been developed to simulate the operation of an intense neutron source for use in cancer therapy. The thin‐film ScD2 target for the neutron source is supported on a water‐cooled copper substrate designed to dissipate 40 MW/m2 at a surface temperature of 450 °C. This paper describes the theoretical and experimental analysis of the target and the postmortem analysis of a target after 140 h of operation at power densities exceeding 40 MW/m2. Cooling channel erosion due to nucleate boiling of the cooling water was shown to be the life‐limiting feature of the target design. View full abstract»

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  • 3‐ps synchronized multiframe photographic diagnostic for target experiments with the iodine laser

    Page(s): 48 - 51
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    A diagnostic system is described with which we obtain a sequence of six pictures (interferograms or shadowgrams) of the plasma produced by the iodine laser on solid targets. The system consists of a synchronously pumped dye laser amplified in dye cells pumped by an excimer laser. It delivers a pulse with an energy of 500  μJ and a length of 3 ps at a wavelength of 580 nm that is highly synchronous with the iodine pulse. View full abstract»

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  • UV radiation‐triggered rail‐gap switches

    Page(s): 52 - 63
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    A few mJ of KrF excimer laser radiation have been used to initiate multichannel breakdown in a low‐inductance gas‐insulated rail‐gap switch. The switch, which contains two uniform field electrodes, has been operated in a pulse‐charged voltage range of 30–130 kV and has demonstrated jitters as low as 100 ps. A very simple trigger device which incorporates the important features of laser triggering but which uses incoherent UV radiation produced in a corona discharge has also resulted in low jitter, multichannel switch performance. View full abstract»

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  • Shot‐noise‐limited detection scheme for two‐beam laser spectroscopies

    Page(s): 64 - 67
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    We describe a single‐sideband frequency demodulation scheme with large dynamic range which gives linear response and is capable of shot‐noise‐limited performance when used with time‐resolved pump and probe, polarization, and three‐ and four‐wave mixing spectroscopies. View full abstract»

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  • Variable‐temperature solid‐state nuclear‐magnetic‐resonance probe for superconducting magnets operating in the range 3–350 K

    Page(s): 68 - 74
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    A versatile, variable‐temperature (3–350 K continuous), vacuum cold‐finger, solid‐state nuclear‐magnetic‐resonance (NMR) probe is described and its characteristics in several applications are discussed. The single‐coil probe is specifically designed for use in superconducting magnets with bores as small as 2.5 in. and is suitable for both single‐ and double‐resonance experiments. The tuning arrangement allows for multinuclear data acquisition without the necessity of breaking the vacuum. Various adaptations to the cold finger suitable for a variety of different solids, e.g., powders, amorphous materials (glasses), condensables, and single crystals are presented including a single‐axis goniometer operable over the entire temperature range. View full abstract»

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  • High‐pressure multimode resonator system for high microwave frequencies up to 215 GHz

    Page(s): 75 - 78
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    A high‐pressure (P≪3.6 kbar) multimode resonator system suitable for low‐temperature (4.2 K) microwave measurements over a wide range of frequencies (21–215 GHz) is described. A simple reflection spectrometer is used for low frequencies (≪50 GHz). At higher frequencies, an unusual transmission resonator scheme is used which requires only one microwave window. View full abstract»

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  • Precision time‐domain dielectric spectrometer

    Page(s): 79 - 87
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    A description is given for an automated method for determining dielectric constant and loss by the measurement of the time response of the dielectric to a step voltage. Attention is paid to the circuits necessary to achieve high accuracy (0.1%) and high sensitivity (tan δ=10-5) over audio and subaudio frequencies (104 to 10-4 Hz). These include a 100‐V step generator accurate to 5 ppm, a charge detector with a time‐independent bias current of 30 fA, and a clock that can control sampling time from 5 μs to 10 s. In addition, a numerical Laplace transform, based on a cubic spline, is described that preserves the accuracy of the time data when they are transformed into the frequency domain. View full abstract»

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  • Simple, compact, medium‐energy Mott polarization analyzer

    Page(s): 88 - 91
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    A simple, compact, UHV compatible Mott polarization analyzer is described that employs electron accelerating voltages in the range 20–40 keV.The analyzer provides excellent discrimination against inelastically scattered electrons and has the advantage that the major portion of the apparatus, and the scattered electron detectors, are operated near ground potential. The efficiency of the analyzer, ∼2×10-5, is competitive with those provided by other polarimeters. The analyzer can measure the polarization of electron beams having currents as low as ∼10-13 A and is suitable for use in a wide variety of experiments involving polarized electron beams. View full abstract»

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  • Auger microscopy using sample modulation

    Page(s): 92 - 94
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    Although the spatial resolution of a scanning Auger microprobe is limited by its electron optics, its effectiveness for the analysis of semiconductor devices that have features of interest comparable in size to the diameter of the analyzing electron beam is enhanced by a variation in the method of signal detection. Signal detection in an Auger spectrometer is most often accomplished using phase‐sensitive detection. The modulating signal required in the phase‐sensitive detection process is applied to the electron energy analyzer. Instead, by applying the modulating signal directly to different electrically isolatable regions of a device, only those Auger electrons originating in a particular region are detected. By rejecting signals from regions adjacent to a modulated region, Auger spectra characteristic only of the region of interest are obtained without spurious contributions from adjacent areas inadvertently illuminated by the analyzing beam. View full abstract»

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  • Gas/oil interface and high‐sensitivity differential pressure indicator used for the comparison of gas with oil piston gauges

    Page(s): 95 - 98
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    A free surface gas/oil interface has been constructed to aid in the comparison of gas piston gauges with oil piston gauges. A coaxial three‐terminal capacitor partially immersed in the oil and partially in the gas permits the determination of hydrostatic heads and differential pressures between the piston gauges. The interface has been used in the comparison of primary standard gas and oil piston gauges with an average standard deviation about mean pressures of 4.5 Pa (6.5×10-4 psi) over the range of 0.4 to 4 MPa (60 to 600 psi). View full abstract»

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  • Diamond‐anvil high‐pressure cell for improved single‐crystal x‐ray diffraction measurements

    Page(s): 99 - 102
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    A diamond‐anvil high‐pressure cell for single‐crystal x‐ray diffraction studies is described. The cell is suited especially to four‐circle diffractometers. The important feature of this device is that, compared to previously reported cells for single‐crystal x‐ray studies, a greater portion of the reciprocal space can be observed. All structure factors up to a θ limit, depending on the design of the cell, can be measured. Thus, the probability of solving complicated unknown structures is increased. The major disadvantage of the cell is the limitation of the highest achievable pressure of 35 kbar, caused by failure of the beryllium gasket. View full abstract»

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  • Low‐dissipation support for a gravitational radiation antenna

    Page(s): 103 - 106
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    We describe a support for the University of Rochester gravitational wave detector. The support is a two‐stage filter with springs made of aluminum and a brass intermediate mass. With this support we have measured a mechanical quality factor for the fundamental mode of a 200‐kg aluminum cylinder of 2.2×107 at 2302 Hz at 4.2 K. The filter attenuates vibrations by -130 dB at this frequency. View full abstract»

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  • Versatile double‐crystal topography camera

    Page(s): 107 - 109
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    A versatile double‐crystal topography camera is described which has provisions for both image detection and precision rocking curve analysis for a wide variety of single‐crystal samples. The camera has a variable base separating the two crystals and this base is rotatable for working with a range of diffraction vectors. The accuracy of the second crystal goniometer stage is of the order of 0.2 arc s. An example of typical data taken with this camera is displayed. View full abstract»

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  • High temperature Hall‐effect apparatus

    Page(s): 110 - 113
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    A high‐temperature Hall‐effect apparatus is described which allows measurements up to temperatures greater than 1200 K using the van der Pauw method. The apparatus was designed for measurements on refractory materials having high charge carrier concentrations and generally low mobilities. Pressure contacts are applied to the samples. Consequently, special contacting methods, peculiar to a specific sample material, are not required. The apparatus has been semiautomated to facilitate measurements. Results are presented on n‐ and p‐type silicon. View full abstract»

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  • Simple device for measuring the two‐way shape memory effect

    Page(s): 114 - 115
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    A simple device has been designed to measure continuously and reproducibly the amount of the shape recovery related to the two‐way shape memory effect in specimens undergoing thermal cycling. Using this device, it is possible to follow the dimensional changes of the specimens, to record the exact temperatures where shape changes occur, and to evaluate the amount of hysteresis involved with the shape recovery phenomenon. View full abstract»

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  • Digital data‐acquisition system for measuring the free decay of acoustical standing waves in a resonant tube

    Page(s): 116 - 118
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    A low‐cost digital system based on an 8‐bit Apple II microcomputer has been designed to provide on‐line control, data acquisition, and evaluation of sound absorption measurements in gases. The measurements are conducted in a resonant tube, in which an acoustical standing wave is excited, the excitation removed, and the sound absorption evaluated from the free decay envelope. The free decay is initiated from the computer keyboard after the standing wave is established, and the microphone response signal is the source of the analog signal for the A/D converter. The acquisition software is written in assembly language and the evaluation software in basic. This paper describes the acoustical measurement, hardware, software, and system performance and presents measurements of sound absorption in air as an example. View full abstract»

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  • Microprocessor‐based pressure controller

    Page(s): 119 - 121
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    A device for automatic control of pressure in an ion‐atom scattering experiment has been constructed. The system was modeled to achieve the minimum time for transition from one pressure to another. The pressure controller ‘‘learns’’ the system response and iterates the parameters used in ‘‘profiling’’ the valve voltage to reduce the transition time. The device has been used with two different scattering chambers and has worked well with both. View full abstract»

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Aims & Scope

Review of Scientific Instruments, published by the American Institute of Physics, is devoted to scientific instruments, apparatus, and techniques.

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Editor
Albert T. Macrander
Argonne National Laboratory