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  • American Institute of Physics (AIP)  (46,193)
  • 1990-1994  (46,193)
  • 101
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A cell for examining the density profile of sheared fluids at the solid-liquid interface by neutron reflectometry is presented. This cell has also proven valuable in examining near-surface bulk structures in the plane perpendicular to the shear flow using small angle neutron scattering. The shear rates can be controlled by changing the volume flow through the cell over three orders of magnitude. All components of the cell are designed to be chemically inert. A temperature-controlled environment compatible with neutron studies is also briefly described. Preliminary neutron reflectivity and small angle neutron scattering results using this cell are presented, and potential applications are discussed.
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  • 102
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 417-425 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A small hollow cathode Penning surface-plasma source (SPS) was developed and studied. The H− yield was proportional to the emission apertures area and increased over a wide range of discharge current. The H− yield, with an intensity of up to 0.95 A and an emission current density of up to 3.6 A/cm2, was obtained in a pulsed mode. With the discharge current of 20 A and a pulse duration of 60 s, an H− yield with current of 0.1 A was obtained. The H− emission current density had approximately the same value for various diameters (0.5–7 mm) and thicknesses (0.3–4.0 mm) of cylindrical emission holes, if the thickness of hole walls did not exceed the hole diameter. The H− yield extracted through the thick conical emission holes had a value 25% higher than that for a thin cylindrical hole with the same permeable diameter. Dependencies of the H− yield versus magnetic field and hydrogen feed were different from that of the standard Penning SPS. The optimal cesium coverage of the electrodes was stable for both high-current, long-pulse and low-current, dc source operation. Noticeable H− production was realized with a low-discharge voltage of 15 V. The heavy negative ions fraction was less than 1% of total negative ion yield for long-pulse operation. The yield of D− ions from deuterium discharge had a value 15% lower than that of H− ions from the hydrogen discharge. Most of the extracted H− ions are produced by conversion of fast and superthermal (E(approximately-greater-than)1 eV) atoms on the cesiated surfaces of the emission hole cones or they are due to the resonant charge exchange of anode-produced H− ions in the volume adjacent to the emission apertures.
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  • 103
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 426-429 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Different methods are tested for the injection of small (〈100 μm) pellets into tokamak plasmas using laser acceleration. In one type of method the pellets are formed in the random fragmentation process of a foil, while in another series of experiments aluminum granules were accelerated. In the first case pellet velocities up to 4 km/s were achieved, but the reproducibility was found to be poor. In the second case the reproducibility was much better, and pellets with diameters in the ten micron range were accelerated to 200–300 m/s velocity. With some further improvements, this technique may become a simple source of impurities for transport studies in fusion plasmas.
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  • 104
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 430-432 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The injection of pellets of frozen deuterium into magnetically confined, hot plasmas is one of the most attractive methods for refueling fusion power reactors. High injection speeds for solid deuterium pellets are necessary for improving the experimental analysis of pellet ablation in a hot plasma and the effects of the pellet on the plasma properties, in particular the confinement parameters. The optimization of a two-stage light gas gun is being pursued; the search for the cryogenic conditions of freezing deuterium with good mechanical properties is carried out. In particular, the impurities concentration in deuterium during the condensation process has been studied. These developments have allowed one to reach velocities up to 3400 m/s for integer bare deuterium pellets (3 or 4 mm in diameter, 1–3×1021 particles) with a reliability of 80%.
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  • 105
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For thin film fabrication and surface modification, ion sources with high current, low energy, and broad beam are required. The source should be simple and reliable to operate, mechanically rugged, and highly productive for commercial use. To meet these requirements, a Hall effect plasma accelerator has been manufactured and tested. A beam energy of 200–300 eV and a beam current density of up to 10 mA/cm2 have been obtained with the source. Operational characteristics and possibility for industrial application are presented.
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  • 106
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1355-1355 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Considerable interest has been shown in the electrohydrodynamic liquid field emission ion source, from which positive ions emitted under the action of high electric fields, and high brightness sources are being developed with a variety of applications in mind. The basic principles of such sources are discussed. The threshold voltage Vth, the ion current (I) versus extraction voltage (V) relationships under various operating temperatures To, I versus To relationship, the angular current intensity and brightness, energy spread, as well as the current changes slowly with time under a definite voltage, are presented and discussed. The experiments show that the present performance of the ion source is as follows: The threshold voltage is about 5.4 kV, the brightness equal to 1×108A/cm2 sr, and energy spread of 26 eV.
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  • 107
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Separation of ionic or isotopic species in a magnetized sheet plasma has been studied by using the ion cyclotron resonance method. The sheet plasma was used instead of a cylindrical plasma in which many unfavorable collisions take place. An rf electric field is applied to the plasma by two parallel plate electrodes. It is shown that a resonance is strongly dependent on the plasma space potential across the sheet plasma. The resonance spectra of argon, neon, and nitrogen ions in the low dense sheet plasma with a shallow potential well are clearly observed, while the resonances in high dense plasma with a deep potential well are not observed. It is also found that the resonance frequency for a corresponding ion is proportional to the magnetic field strength.
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  • 108
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1362-1364 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A low temperature ion source has been developed to produce a plasma with a low ion temperature and a high plasma density by using a gas contact technique. This ion source is a hybrid type consisting of modified plasma compression type cylindrical hollow cathode plasma source and the gas contact chamber with floating potential mounted on the head of the anode. The temperature of ions and the density in the produced argon plasma are gradually increased in order to compress it by the small canal of the floating electrode and the gas magnetic field. This plasma flow goes into the gas contact chamber and mixes with the cold neutral argon gas, resulting in the production of a low ion-temperature plasma by ion-neutral collisions. The characteristics of the energy distribution of extracted ion beam (Vex=500 V) were measured by an electrostatics analyzer and we determined both the half-value of the energy spread of ion beam ΔE and the mean ion temperature Ti in the plasma flow. The mean electron temperature Te and plasma density ne were determined by means of a plane Langmuir probe. As a result, Te and ΔE decrease from 4.1 to 2.5 eV and 13.3 to 8.3 eV, respectively, though ne is nearly constant at 3.0×1010 cm−3.
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  • 109
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The results of theoretical and experimental investigations of dense plasma source resonantly excited by helicon wave are presented. Driven by a single-loop low-voltage ((approximately-equal-to)300 V) antenna, a source generates a plasma of density up to 5×1011 cm−3 at gas pressures 0.5–20 mTorr, operates at magnetic fields 〈100 Gs, and produces low-energy ion fluxes (〈60 eV) with current densities up to 7 mA/cm2 and 3.5% nonuniformity within a diameter 10 cm. A high-efficiency helicon source originates in a special kind of "resonance'' wave discharge, where a sharp increase of plasma resistance occurs near the helicon wave dispersion branches.
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  • 110
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A large volume cylindrical radio frequency (rf)-plasma source with a magnetic line-cusp field has been developed for large scale plasma processing. In this type of plasma source, a capacity-coupled 13.56 MHz rf plasma is produced in the presence of a magnetic line-cusp field. Two versions of the plasma source have been made and tested. The first version has peripheral rf electrodes placed on the outside of the ionization chamber, and is suitable for preparing a large volume uniform plasma. This plasma source can attain a useful area of uniform plasma over a 30-cm-diam region within 10% nonuniformity. The second version is featured by parallel doughnut-plate electrodes which forms part of the chamber wall and serves as a high current source. The electron density in such a version is proportional to the rf power, being equal to 4×1010 cm−3 at 400 W. The measured electron energy distribution function showed the Maxwellian-like distribution from a drift motion in the magnetic line-cusp field.
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  • 111
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 1371-1373 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A low energy broad beam multipole ion source has been successfully developed at the Southwestern Institute of Physics, which can be used for both sputtering deposition and direct ion beam deposition. The extracted A+r beam current is 30–250 mA at a beam energy of 200–6000 eV. It has been used for sputtering deposition at the three beam synchronously mixing machine in Dalian University of Technology.
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  • 112
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Recently, broad beam ion sources have been widely used for industrial applications. In order to obtain high quality thin films and process large workpieces, more uniform beam current density is needed. This article introduces a 10-cm-diam cusped ion source with good beam current density uniformity for assisted deposition. Its design characteristics and performance are described. The effects of operation parameters of ion source, the magnetic flux density and its distribution, the cathode shape and its location in the discharge chamber, and the configuration of grids on the uniformity of ion beam current density were experimentally investigated. For screen grid voltage of 300 V and beam current of 100 mA, a 0.93 beam current flatness parameter within a beam spot of 200 mm diameter at a distance of 300 mm downstream from the source was obtained.
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  • 113
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The progress of ion source research in China, including the main achievements, present status, suggestions, and problems are reviewed.
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  • 114
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 485-491 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A hardware-based system is described which generates a 3D mapping directly into a memory array of all surfaces visible in its field of view. The system uses a conventional scanning strip-light illumination technique and a CCD camera. However, instead of processing the 2D camera data in software, dedicated hardware detects and locates all visible surface elements and automatically loads the 3D coordinate and brightness data direct from the detection hardware into dual-ported memory. This allows the hardware to operate in real time at camera speeds and allows a very compact representation of the scene information in the natural coordinate frame of a triangulation-based system.
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  • 115
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 492-499 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Pirani vacuum sensor has been fabricated by the silicon micromachining technique. A square glass membrane was formed on (100) silicon substrate with a platinum-film resistor coated. The membrane is suspended by its four leads extended to the corners of an etched cavity. This structure can provide both low thermal loss through leads to the substrate and large active area for gaseous heat conduction. It thus can be used as a highly sensitive vacuum sensor. The fabricated sensor has shown a linear response of pressure from 8×10−5 to 6 Torr with constant-temperature operation. It is found that the low-pressure limit of the vacuum sensor was caused by the noise of the instrument used in the experiment. A new terminology called "noise equivalent pressure'' thus is definable due to this finding. The physical limit of the noise equivalent pressure is analyzed. Optimization of the device structure and the noise equivalent pressure are also discussed in detail. A new method of ambient-temperature compensation is also proposed and analyzed here.
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  • 116
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An optically pumped polarized H− source (OPPIS), which is based on the charge exchange between H+ ions and electron-spin polarized alkali atoms has been developed at KEK. Just by applying this scheme to a deuteron beam, it is difficult to obtain a highly vector polarized deuteron beam. To obtain highly vector polarized D− ions, we have developed a "dual optical pumping type'' of polarized D− source. With this scheme, a 100% vector nuclear-spin polarization for D− ions is possible in principle. In a preliminary experiment, a 60% vector nuclear-spin polarized D− ion was obtained.
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  • 117
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3870-3870 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel design is presented for a cryogenically cooled multisubstrate sample holder for thin film deposition in high vacuum. The cryogen flows through tubing soldered onto a fixed copper plate, while the substrates are mounted on a separate tray that is supported by a linear/rotary-motion feedthrough. By lowering the substrate tray into firm contact with the copper plate, substrate temperatures as low as 120 K can be achieved. © 1994 American Institute of Physics.
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  • 118
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3873-3874 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple method for the determination of coercive fields is described. It is based in the comparison between two signals; one proportional to the applied field which excites the sample, and the other proportional to the internal field that acts directly on the magnetization. Coercive fields as low as 0.14 A/m can be reliably measured and the error using this system does not exceed 0.02 A/m. © 1994 American Institute of Physics.
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  • 119
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3324-3331 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A powerful infrared aerosol lidar operating at the eyesafe wavelength of 1.56 μm has been developed. More than 140 mJ per pulse are obtained from stimulated Raman backscattering narrow-band Nd:YAG laser radiation in deuterium. The mobile lidar system was successfully applied during the VAST and MAPTIP international aerosol field campaigns in 1992 and 1993. A range between 0.3 and more than 10 km is demonstrated for slant-path measurements in the presence of aerosols or cirrus clouds.
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  • 120
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 509-510 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Two parallel-plate copper rings with diagonally opposite gaps separated by a dielectric medium form a resonator the natural resonant frequency which is a function of the transmission line propagation constant, its characteristic impedance, as well as the series inductance of the two loops. By means of an extra capacitor connected to each gap, one can easily vary the frequency of the resonator. The derived expressions, valid also for coaxial line devices, relating resonant frequency to other circuit constants, can serve as a tool for those who intend to use this kind of resonator to design NMR surface coil antennas. Experimental results are in good agreement with theory provided the circuit constants are accurately known.
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  • 121
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 513-514 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An optical free piston cell (a modified le Noble and Schlott type optical cell) is described for use in spectrophotometric study under high pressure. The cell consists of a disk, a cylinder, and a free piston, which are made of quartz and are mounted within a stainless-steel holder. A small amount of sample solution (∼0.6 cm3), which only contacts with quartz, is required for measurements. The path length is fixed (1.2 cm) at ambient pressure, but is self-adjusting at elevated pressure so that no compressibility corrections are necessary.
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  • 122
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new version of a high-resolution electron energy loss spectrometer has been constructed. Major modifications are the enlargement of the analyzer, gold coating of all the electrode surfaces facing the electron beam, and the reduction of magnetic fields. A high detector current of 4 pA has been obtained together with the narrow energy half width of 1.2 meV (FWHM) in the straight-through mode.
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  • 123
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 517-518 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A combined pulse generator and digitizer based on a RISC processor has been designed and tested by 59Co NMR. The pulse generator provides a 16-bit TTL-level output with 100 ns resolution and is programmable in the high-level language FORTH. The digitizer supports two channels, each with a 10 bit, 40 MSPS analog-digital converter and online averaging in a 24×1024 bit memory, which is directly accessible by the RISC processor.
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  • 124
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 519-520 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A large area (1.8 m by 1.8 m), uniform temperature, thermal target was used for characterization of phenomena that impact target contrast. The target board is equipped with several bar patterns. It has a unique design that uses a tilted oven surface making it lightweight with near perfect transition between the hot and cold portions of the bar patterns. The oven surface maintains a ±1 °C uniformity when heated to 10–20 °C above ambient temperature.
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  • 125
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3238-3242 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high-resolution spectrometer has been developed and used to measure simultaneously impurity ion temperatures and flow velocities in high temperature plasmas with 10 μs temporal resolution (limited by digitization rate). This device is actually a duo-spectrometer: measurements from two different chordal views of the plasma can be made simultaneously via two separate quartz input fiber optic bundles coupled to the entrance slits which are tilted to compensate for line curvature. The dispersed spectra on the exit plane of the duo-spectrometer are coupled via quartz fiber optics to two arrays of 16 photomultiplier tubes each. Measurements made by recording the Doppler broadened and shifted 227.091 nm emission from the C v impurity ions in the Madison Symmetric Torus (MST) reversed-field pinch (RFP) plasma have achieved precisions of 〈6 eV for temperatures of 150 eV and 〈0.7 km/s for flow velocities of 6 km/s. Representative results from the MST RFP indicate that the toroidal flow velocity drops and ion temperature increase during sawtooth events in MST.
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  • 126
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3252-3257 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experimental measurements are made with a novel two wire thermocouple. Signals from two wires of unequal diameters are recorded from the thermocouple suspended in constant flow with a periodic temperature fluctuation. It is demonstrated that the reconstructed signal from the two wire thermocouple requires no compensation for ω≤2ω1 where ω1 is the natural frequency of the smaller wire. A compensation factor is recommended for larger frequencies ω(approximately-greater-than)2ω1.
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  • 127
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3263-3267 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Setaram C-80 calorimeter has been modified in order to measure heat capacities at constant pressure of gases from ambient temperature to 573 K and at pressures up to 30 MPa. Special cells have been designed and an additional device has been incorporated into the calorimeter to better control the temperature. The calorimetric technique and the calibration method are described. Experimental heat capacities of CO2 in the temperature range 323.15–423.15 K at pressures up to 25 MPa are reported and compared with the best literature data.
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  • 128
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a new technique for measuring thermal expansion of liquids at high temperature. Our device, the volumeter, is a volumetric dilatometer which uses liquid tin to transmit volume changes to a series of electrical contacts. Measurements can be carried out from 250 °C to at least 1450 °C irrespective of the viscosity of the sample. In addition, our technique allows for the direct determination of volume changes due to melting and crystallization, as well as the volumetric properties of heterogeneous mixtures of materials. Furthermore, the device is designed to operate inside an internally heated gas-pressured vessel, allowing for the determination of compressibility. We have measured the thermal expansivity of tin from 435 to 1445 °C. Our data match previous measurements using the Archimedean technique to within 4% and shows the volumetric expansivity of tin to have a temperature dependence of −4×10−9 °C−2. Preliminary measurements of the thermal expansivity of a high-viscosity silicate liquid show a wide degree of scatter but fall within previous estimates based on density data. Improved performance of the device may require its operation under pressure.
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  • 129
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    Review of Scientific Instruments 65 (1994), S. 974-976 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Acoustic techniques are used to monitor the temperature of silicon wafers during rapid thermal processing from room temperature to 1000 °C with ±5 °C accuracy. Acoustic transducers are mounted at the bases of the quartz pins that hold up the silicon wafer during rapid thermal processing. An electrical pulse applied across a transducer generates an extensional mode acoustic wave guided by the quartz pins. The extensional mode is converted into Lamb waves in the silicon wafer which acts as a plate waveguide. The Lamb waves propagate across the length of the silicon wafer and are converted back into an extensional mode in the opposite pin. The time of flight of the extensional mode in the quartz pins is measured using pulse echo techniques and is subtracted from the total time of flight to obtain the Lamb wave time of flight across the wafer. Because the velocity of Lamb waves in the silicon wafer is systematically affected by temperature, the measurement of the time of flight of the Lamb wave provides the accurate temperature of the silicon wafer.
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  • 130
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The principles of the zero-balance heat-flux meter (HFM) technique are studied with two steady-state finite difference computer models developed to simulate the responses of a sensor mounted either on the cold face or on the warm face of a wall. Computations show that a particular Biot number (defined by the authors), the dimensionless wall width, and the dimensionless wall thickness are the parameters affecting the HFM accuracy. The authors present outputs of their models that show the influence of these parameters, and propose three empirical expressions that allow corrections of the operational errors. It can be affirmed that the flux meter should be mounted on the cold face in the case of a small Biot number (it assures an accuracy of at least 5% if the Biot number value is smaller than 0.2). And it should be mounted on the warm face when the Biot number is large (in the case of building insulators in normal environment conditions it assures an accuracy of at least 10%). In other cases, the flux meter should be used as a gradient flux meter switching off the internal heater.
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  • 131
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    Review of Scientific Instruments 65 (1994), S. 998-1001 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A sensitive density meter for measuring the density of small amounts of solid, solution, or dispersed materials, e.g., biological systems in the liquid environment, is presented. The chamber for the measured sample is in the lower part of a glass buoy. It is closed by the glass stopper containing the permanent magnet. The buoy is immersed in the carrying liquid with the known density and is balanced by the magnetic force. The device enables the measurement at constant temperature as well as in the temperature scanning regime. The accuracy of measuring the liquid density is 1 mg/l in a 1.5 ml chamber; the sensitivity of measuring the temperature is 1 mK. The volume of solids or dispersed systems of known weight is measured with an accuracy of 1.5 nl.
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  • 132
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Substantial improvements have been made in the sensitivity of an ac susceptibility measurement system which determines the pressure dependence of the superconducting transition temperature, Tc(P). The pressure, P, is determined near Tc from the position of the R1 and R2 fluorescence peaks from ruby chips. The system was used to determine Tc(P) for several high Tc single crystals, but was not sufficiently sensitive to determine Tc(P) of polycrystalline samples for HgBa2CuO4+δ. This motivated us to improve the sensitivity of our system. Other parts of the system and the data analysis procedures also have been improved. As a demonstration, Tc(P) of HgBa2CuO4+δ polycrystal to 4 GPa is presented. The improvement of the system using the diamond anvil cell opens the possibility of measuring Tc above 10 GPa and on smaller samples.
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  • 133
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The noncontact magnetic manipulation of probe masses within the body is an area of research that has received substantial attention from the medical physics community, especially during the past three decades. The therapeutic and diagnostic possibilities arising from such technology include site-specific drug delivery within the central nervous system, advancement of techniques for navigation and selective catheterization of vessels within the cardiovascular and cerebrovascular systems, and the nonsurgical exploration of the alimentary and respiratory tracts. In this review, we examine the physical principles underlying in vivo magnetic manipulation systems, and catalog the various types of instrumentation used for such purposes to date. Thereafter, we evaluate the different methods of image-based localization used to identify the position of the probe within the body. Finally, we appraise an emerging technology known as nonlinear magnetic stereotaxis, a technique that permits minimally invasive access to difficult-to-approach parts of the brain. We close the review with a few comments on the directions for future work within this field.
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  • 134
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    Review of Scientific Instruments 65 (1994), S. 563-566 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel discharge circuit that reduces significantly the amount of energy conducted by the switch in a TEA CO2 laser is reported. We demonstrate this circuit on a working multijoule TEA CO2 laser in which the switch is shown to conduct typically only 5% of the total input pulse energy. The laser has worked reliably in gas mixtures that place stringent demands on the discharge and circuit. It has produced an output of 7 J at an efficiency of 9.6% using a CO2:N2:He (1:1:4) gas mixture at atmospheric pressure and further using a helium-free gas mixture (CO2:N2:H2 at 400 mbar) it has produced a maximum efficiency of 14.6% for an output of 7.8 J. The great simplicity and high efficiency of the new discharge circuit allow it to be incorporated in the existing laser designs with minimal modifications.
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  • 135
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    Notes: Fabry–Perot interferometers are routinely used in the Tore Supra tokamak in order to measure the time evolution of the electron temperature of the confined plasmas. Calibration of such interferometers requires the detection of very low dc levels (0.1 nV) with signal-to-noise ratios less than 10−5, which is generally not compatible with standard detection methods. A new correlation method is proposed to achieve this absolute calibration. It is based on a proper noise autocorrelation technique combined with an optimized filtering involving Fourier analysis. The advantages of the method are detailed and experimentally compared to standard averaging techniques, such as coherent addition and synchronous detection. The method can be used in a more general context every time very small amplitude signals are to be measured.
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  • 136
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    Review of Scientific Instruments 65 (1994), S. 591-596 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The conversion of a thermospray ionization (TSI) feature of a Finnigan-MAT TSQ-70 mass spectrometer to electrospray ionization (ESI) and its performance are described. The existing source, pumping capacity, flanges, and temperature controller of the TSQ-70 TS feature were used with a few modifications. Conversion of the commercial TS option to a simple and economically viable ES option has made the analysis of large biomolecules possible without expensive upgrades. To preserve the simplicity of the conversion, desolvation is effected by a heated-capillary tube (HCT). The HCT and its housing are inserted inside the TSQ-70 TS flange like a solid probe. Mass spectrometric results of low and high molecular weight biomolecules, the mass accuracy, sensitivity, and charge states of the observed ions are comparable to published results by other laboratories. Adequate spectral quality was obtained at short scan times, a required characteristic for interfacing ESI with separation methods such as capillary zone electrophoresis.
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  • 137
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    Review of Scientific Instruments 65 (1994), S. 587-590 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new differential refractometer, which mainly consists of a laser light source, a position-sensitive detector, and a temperature-controlled refractometer cuvette has recently been developed. In comparison with a conventional differential refractometer, it has a different optical design so that the effect of laser beam drift can be greatly reduced. In our design, a very small pinhole is illuminated by the laser light and the illuminated pinhole is imaged to the detector by a lens located in the middle between the detector and the pinhole in a 2f-2f configuration. The cuvette is placed just before the lens. The pinhole, the cuvette, the lens, and the detector are mounted on a small optical rail. The refractometer can be easily incorporated into any laser light-scattering spectrometer, in which the laser, the thermostat, and the computer are shared. This not only reduces the total cost (at least ten times cheaper than a commercial differential refractometer), but also enables us to measure the specific refractive index increment and the scattered light intensity under the identical experimental conditions, such as wavelength and temperature. This novel refractometer has a wide linear detection range (±0.035 RI units) with a resolution of 10−6 RI units, which is sufficient for determining the specific refractive index increment of most polymer solutions.
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  • 138
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    Review of Scientific Instruments 65 (1994), S. 575-586 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple step-by-step procedure, including several novel techniques discussed in the Appendices, is given for minimizing ac phase noise in typical interferometric systems such as two-beam interferometers, holographic setups, four-wave mixers, etc. Special attention is given to index of refraction fluctuations, direct mechanical coupling, and acoustic coupling, whose importance in determining ac phase noise in interferometric systems has not been adequately treated. The minimization procedure must be carried out while continuously monitoring the phase noise which can be done very simply by using a photodiode measurement of the interferometer output. Supplementary measurements using a microphone and accelerometer will also be helpful in identifying the sources of phase noise. Emphasis is placed on new techniques or new modifications of older techniques which will not usually be familiar to most workers in optics. Thus, the necessity of eliminating the effects of index of refraction fluctuations which degrade the performance of all interferometers is pointed out as the first priority. A substantial decrease of the effects of all vibrating, rotating, or flowing masses (e.g., cooling lines) in direct contact with the optical table will also have to be carefully carried out regardless of the type of interferometric system employed.It is recommended that this be followed by a simple, inexpensive change to a novel type of interferometer discussed in Appendix A which is inherently less sensitive to mechanical vibration. Such a change will lead to a reduction of both low-frequency and high-frequency ac phase noise by more than an order of magnitude and can be carried out for all interferometers with the exception of multiple pass optical systems and high-resolution FFT spectrometers. It is pointed out that most homemade air bladder vibration isolators are used incorrectly and do not provide sufficient reduction in the contribution of floor vibrations to phase noise. Several simple trampoline-type air bladder vibration isolator systems are described which are comparable in performance to commercial systems. With the exception of very nonrigid or undamped optical tables, the dominant source of ac phase noise at this point will usually be due to acoustic coupling to the optical components and mounts themselves. This means not only that the optical components and mounts must be rigid but that the mechanical coupling between the table and the mounts, as well as the coupling between the mounts and components themselves, be as rigid as possible.An additional damping of optical mounts beyond that generally found in commercial mountings will also have to be carried out to obtain a further reduction of phase noise. A simple damping technique employing an additional mass and an intermediate damping layer is described which will significantly improve the performance of both homemade and commercial optical mounts. Similar damping techniques which are especially suitable for homemade optical tables and breadboards are also considered.
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  • 139
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    Notes: A pinhole small-angle x-ray scattering (SAXS) instrument was constructed at the SUNY X3A2 beamline, National Synchrotron Light Source, Brookhaven National Laboratory. The three pinholes were mounted in a thick-walled stainless steel pipe and prealigned by using a portable laser source and a charge-coupled device (CCD) area detector. After the prealignment, incorporation of the collimator to the synchrotron x-ray source required only maximization of the incident x-ray intensity passing through the pinholes, which could be done easily by using a scintillation counter after proper attenuation. The entire synchrotron SAXS instrument setup took only a few hours even without stepping motor control for the pinhole collimator unit. By combining this collimator with a CCD-based x-ray area detector which could be assembled by using commercially available components, the SAXS instrument showed good performance for structural scales up to an order of 100 nm. The CCD-based x-ray area detector used a computer- (or manually) controlled intensified unit with a variable gain setting in order to accommodate the changing x-ray flux and to protect the detector from over exposure, a necessary feature for operation of an area detector at a synchrotron light source.
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  • 140
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    Review of Scientific Instruments 65 (1994), S. 603-607 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A complete micropositioning unit based on high precision, manually controlled X-Y-Z translators, related metrology system, and sighting microscope is described. It has been specifically developed for the alignment of collimating pinholes (5–10 μm diam) on cryogenic x-ray detectors, 10–50 μm in size, deposited both on transparent and opaque substrates. The main characteristics of this flexible and convenient system are the capability to handle a complete test fixture ready for further measurements at cryogenic temperature, coupled with the possibility to verify the precision attained. Such microalignment equipment will find application in optical/UV/x-ray photon counting experiments, whenever a highly collimated illumination is required or in any test involving precision positioning of small experimental units onto microdevices or detectors.
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  • 141
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    Notes: New cassettes for 201 mm×252 mm (8‘×10‘) and 201 mm×400 mm (8‘×15.75‘) storage phosphor plates have been developed at the Synchrotron Resource of the Howard Hughes Medical Institute. The purpose for this work was mainly twofold. Firstly, to diminish the number of manual operations when putting the storage phosphor plate into the cassette or when extracting it from the cassette. Secondly, to render such a cassette much lighter than the former metal cassette previously in use. These two goals were achieved by making new cassettes that are operated as one piece instead of two or three independent parts as with the former systems. The cassettes have been extensively tested and found to be very useful.
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  • 142
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    Notes: An expansion of the capabilities of high-speed, multichannel spectroscopic ellipsometry (SE) is described that involves simultaneous measurement of the reflectance spectrum along with the two spectra in the ellipsometric angles (ψ, Δ). Previously, a novel rotating-polarizer spectroscopic ellipsometer has been perfected that employs a photodiode array detector for high-speed acquisition of (ψ, Δ) spectra, designed for real-time studies of thin-film growth. For a polarizer angular rotation frequency of ω0, the (ψ, Δ) values at a given photon energy are deduced from the 2ω0 Fourier components of the detector irradiance, normalized by the dc component. A third parameter, the weighted reflectance RA, can be obtained from the dc component and from a calibration based on the known optical properties of the substrate measured prior to film growth. With (ω0/2π)=12.5 Hz, three-parameter data sets, [ψ(hν), Δ(hν), RA(hν); 1.5≤hν≤4.5 eV], can be acquired with a time resolution as short as 40 ms. Although RA provides complementary information to (ψ, Δ), it has yet to be exploited in conjunction with real-time SE until this study. A resilient analysis approach, based on mathematical inversion and least-squares fitting of the real-time three-parameter data sets, is designed to yield the film dielectric functions and thicknesses independently at each time during the early stages of thin-film growth. The three-parameter approach has been applied successfully in studies of amorphous silicon (a-Si:H) thin films prepared by plasma-enhanced chemical vapor deposition, and aluminum and silver films prepared by physical vapor deposition. For the a-Si:H films, RA(hν) exhibits deviations as large as ∼3% from that predicted in modeling (ψ, Δ) alone. The deviations result from light scattering by plasma particulates, and we show how additional information can be extracted from the spectral dependence of the scattering loss.
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  • 143
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    Review of Scientific Instruments 65 (1994), S. 3505-3510 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: New methods based on the reflection pulse technique are developed to study material properties. Using them, Curie temperatures in magnetic and ferroelectric materials, transition temperature and penetration depth in superconductors and characteristics of semiconductors, and semiconductor devices are determined.
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  • 144
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    Review of Scientific Instruments 65 (1994), S. 3501-3504 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A practical thermal oxidation system used in ultradry, ultrathin silicon oxide film growth is described. It comprises a double-wall-type fused-quartz reactor, a newly designed material-gas preheating unit, and three vacuum chambers for dehydrating and exchanging wafers. The preheating unit, used to eliminate temperature disturbances in the reactor, is assembled with a SiC composite shrouded by fused quartz and an infrared lamp heater. The temperature of material gases is quickly elevated to about 600 °C by passing them through this unit just before reaching the reactor's gas inlet. Consequently, the temperature of Si wafers in the reactor can be precisely controlled within ±0.15° at 800 °C. Moreover, the moisture concentration (humidity) in the reactor is always kept below 1 ppb. By rigorously controlling the growth temperature and ambience, high-reliability 5.0±0.05-nm-thick oxide films are obtained.
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  • 145
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    Notes: The importance of obtaining dependable values of molecular optical polarizability anisotropy for polymers and their oligomers lies in their subsequent use in the rotational isomeric state theory and in calculations involving the components of the optical polarizability tensor. This work describes a depolarized Rayleigh scattering photometer able to determine optical polarizability anisotropy of oligomers, melts, and polymer compounds in solution with a combination of exceptional accuracy and high sensitivity. Two separate calibration techniques are reported that ensure the accuracy and preciseness of the results obtained from the measurements. Finally, data analysis procedures are reported that show the sensitivity of the results to the internal field correction.
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  • 146
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    Review of Scientific Instruments 65 (1994), S. 3517-3520 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An in situ uniaxial drawing apparatus is described for polymeric materials in compressed gases up to 30 MPa. Polymeric materials plasticized by sorption of compressed gases can be drawn at a constant rate by use of this apparatus. Polystyrene films in CO2 at 10 MPa and 318.15 K were stretched with the draw ratios of 2 to 4 without rupture.
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  • 147
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    Notes: Presented in this paper are the description and the test results of a new stationary thermometry system used to map the temperature of the outer surface of 1.5 GHz superconducting single-cell cavities during operation at 1.6 K. The system comprises 764 removable carbon thermometers whose signals are multiplexed and scanned by a Macintosh computer. A complete temperature map can be obtained in as little as 0.1 s at a temperature resolution of about 0.2 mK. Alternatively, it has been demonstrated that if the acquisition time is increased to several seconds, then a temperature resolution on the order of 30 μK is possible. To our knowledge, these are the fastest acquisition times so far achieved with L-band cavities at these resolutions.
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  • 148
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    Notes: The resistance of a micromachined polysilicon thermistor sensor has been measured under excitation by both a constant current and constant power step. The time-varying and steady-state response of the polysilicon resistor at ambient pressures of 1 atm and 10−4 Torr were observed under various step amplitudes. The increase of resistance above its room-temperature value changed exponentially with time; the time constant varied inversely with the square of the current step amplitude but was constant with power step amplitude. The steady-state change of resistance varied linearly with the applied power under both modes of excitation. The time-varying and steady-state responses were as predicted by a simple analytic model developed. The steady-state operation of these devices at the two pressures permitted us to directly determine the energy losses by heat conduction through the surrounding gas and conduction through the support arms. At 1 atm, up to 90% of the heat loss is by conduction through the gas. The operation of the device was also simulated numerically and results were obtained in reasonably close agreement with experiment. The simulation also allows us to predict the amount of heat flow through the various support arms; 70% of the heat conducted by the support arms flows through 8 of the 20 support arms.
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  • 149
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    Review of Scientific Instruments 65 (1994), S. 3535-3539 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This article presents a new way to reduce data in the flash method of measuring thermal diffusivity. Experimental temperature versus time data are first periodized, then transformed by using the discrete Fourier transformation (DFT), and the real part of the second term of the transformed temperature is then fitted with a theoretical formula derived in this article. The main advantage of this procedure is that the thermal diffusivity calculation actually does not depend on the temperature level before the flash, and can also be applied in the case when the measured temperature signal of the sample is superimposed with an arbitrary linearly rising or falling signal, with no need to know the parameters of this imposed signal. This is a unique, completely new feature of this procedure, which has no analog among the other methods of data reduction. Practically, it means that the thermal diffusivity of the sample can be measured by the flash method under an arbitrary dynamically (linearly) changing condition of temperature. The proposed procedure allows the treatment of perturbed signals, even in the case when the data are partly statistically correlated, i.e., the noise is not Gaussian. Experimentally, the data reduction procedure has been tested for a correction of the effect of an electronic noise imposed on the temperature versus time signal in the flash method. The results show that the reproducibility of our procedure is favorable, and the accuracy is comparable with other data reduction methods.
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  • 150
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    Notes: Small holes are drilled in diamond anvil cell gaskets to contain and pressurize samples. As high-pressure technology pushes the multimegabar regime, smaller-tipped diamond anvils are being increasingly utilized. Consequently, well-centered holes with diameters smaller than 100 μm need to be routinely produced in these gaskets made of exceedingly hard metals. We describe the construction of an inexpensive electric discharge machine that can drill metals with holes as small as 25 μm in diameter. This method of drilling is easy to use, far less expensive than other commonly used techniques, and has the advantage of being effective on extremely difficult to machine metals such as rhenium.
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  • 151
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    Notes: In laboratory experiments related to space plasma physics it is often desirable to produce plasmas with characteristics as close as possible to various naturally occurring plasma regimes. In the near-earth region space plasma densities typically vary from 103–107 cm−3 and temperatures range from a few tenths of an eV to the order of 1 eV. The plasma parameters of electron density, electron temperature, and ion species are primary variables which are often not easy to reproduce in a chamber environment which is dependent upon conventional gas discharge or arc sources for plasma production. A simple microwave discharge device was developed which is easily tunable and capable of producing the moderate range of electron densities without an external magnetic field. The Asmussen-type microwave plasma source described here covers and exceeds the parameter ranges required, is relatively easy to construct, and is inexpensive. The device makes use of an air dielectric coaxial coupler to couple magnetron output to a resonant cavity. Estimates of effective electric fields and source densities and temperatures suggest that similar devices can easily be constructed and fashioned to produce these parameters, depending upon requirements, over a wide range of values. The use of widely available commercial magnetrons manufactured for microwave ovens allows a certain ease in the construction of these devices in that available cavity Q's can range to lower levels and therefore resonant lengths can be adjusted more easily. The design is discussed relative to desired experimental parameter ranges and some discussion is given of expected source current densities, electric fields, and temperature ranges.
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  • 152
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    Notes: A fully automated and computer controlled apparatus is described that measures the interfacial tension (IFT) of fluid interfaces and the film tension of liquid films. The fluid interface is formed as a nearly spherical drop at the tip of a capillary which is immersed into another immiscible fluid. The size of the interface is controlled and measured by controlling the size of the drop and the capillary pressure is monitored by a sensitive pressure transducer. The interfacial tension is calculated by the Young–Laplace equation. The drop at the capillary tip can also be covered with a cap shaped liquid film and then the film area can be controlled and the film tension measured. This apparatus is useful for measuring equilibrium interfacial tension or film tension, the adsorption kinetics by stress relaxation experiment and the dynamic interfacial tension or dynamic film tension under both interface expansion or contraction conditions. The capabilities of this versatile, automatic instrument are illustrated with typical experimental results.
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    Review of Scientific Instruments 65 (1994), S. 3570-3573 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An automated vibrating-sample magnetometer is described where the variable magnetic field in excess of ±1.1 T is produced in a 26 mm bore by an assembly of nested, rotating permanent magnet cylinders. The homogeneity is better than 0.3%±4 mT in 1 cc. The instrument has dimensions 200×420×700 mm, and its mass is 20 kg. Sensitivity is better than 0.4 μJ/T (4×10−4 emu), which permits study of the susceptibility, magnetization, and hysteresis of a wide range of magnetic materials, including ferromagnetic thin films.
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  • 154
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    Review of Scientific Instruments 65 (1994), S. 3820-3822 
    ISSN: 1089-7623
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A modified Krätschmer–Huffman reactor for the mass production of fullerenes is presented. Fullerene mass production is fundamental for the synthesis of higher and endohedral fullerenes. The reactor employs mechanisms for continuous graphite-rod feeding and in situ slag removal. Soot collects into a Soxhlet extraction thimble which serves as a fore-line vacuum pump filter, thereby easing fullerene separation from soot. Thermal gravimetric analysis (TGA) for yield determination is reported. This TGA method is faster and uses smaller samples than Soxhlet extraction methods which rely on aromatic solvents. Production of 10 g of soot per hour is readily achieved utilizing this reactor. Fullerene yields of 20% are attained routinely. © 1994 American Institute of Physics.
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  • 155
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    Notes: A new type of SQUID gradiometer, a direct-feedback gradiometer, is introduced in this paper. It is an axial gradiometer made of thin superconductive films. It consists of two magnetometers: a "cancellation magnetometer'' and a "sensing magnetometer.'' The feedback flux of the cancellation magnetometer is applied to both pickup coils of these magnetometers by connecting their feedback coils in a series. Environmental magnetic noise applied to the sensing magnetometer is cancelled by the magnetic flux measured by the cancellation magnetometer, when the two magnetometers are connected with normal conductive wires. The gradiometer has been fabricated and operated in a moderate magnetically shielded room. The capability to reduce environmental noise and thus to measure auditory evoked fields from the human brain has been confirmed. © 1994 American Institute of Physics.
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    Review of Scientific Instruments 65 (1994), S. 3563-3569 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel liquid droplet generator, or atomizer, capable of generating either monodisperse droplet streams or a polydisperse spray, has been characterized using phase-Doppler anemometry and two visualization techniques. The atomizer consists of a piezoelectric driver in a circular housing with an orifice plate across the end of the housing. Unlike conventional droplet generators or atomizers, this device directly induces a high-amplitude velocity perturbation of the liquid jet. Orifice plates with a circular hole (diameter: 34 or 98 μm) or a rectangular hole (527×31 μm2) were used. In the low-power mode, the atomizer with a circular orifice generated a stream of monodisperse water droplets with a diameter 1.5 to 3.4 times the jet diameter and a separation 2.3 to 26 times the jet diameter at 10 to 68 kHz. Droplets smaller than the minimum size predicted by Rayleigh's criterion can be generated with an increased modulation power. The droplet velocity can be adjusted in a wide range (4 to 26 m/s), and a high Reynolds number (∼250) can be attained. In the high-power mode, the atomizer produced a polydisperse water spray with a Sauter mean diameter less than half the jet (equivalent) diameter. The rectangular orifice required significantly less driving power to generate a spray. This atomizer is suitable for both fundamental studies and practical applications.
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    Review of Scientific Instruments 65 (1994), S. 3574-3576 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have designed a probe to rotate a sample around two independent axes in a magnetic field of up to 8 T and at temperatures varying from 3 K to room temperature. The sample is in very good thermal contact with a thermometer and a regulated heater, enabling precise temperature control. Pogo pins enable quick electrical connections to the sample. Two computer-controlled stepper motors rotate the sample around the two independent axes. This probe was primarily designed to investigate the anisotropy of the critical currents of superconducting thin films in a magnetic field.
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    Review of Scientific Instruments 65 (1994), S. 3585-3586 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A single-mode, frequency-stabilized LNA (lanthanum neodymium magnesium hexaluminate) ring laser developed for application in optical pumping and optical manipulation of He(2 3S) metastable atoms is described. This laser routinely provides output powers (approximately-greater-than)300 mW at 1.083 μm when pumped with 5 W from an argon-ion laser.
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    Review of Scientific Instruments 65 (1994), S. 3587-3588 
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    Notes: An intense supersonic beam of atomic fluorine has been generated using nozzles fabricated from single-crystal CaF2 and MgF2. The latter material has been tested up to 1000 °C with no observable damage. This is (approximately-greater-than)250 °C hotter than previously achieved, increasing the atomic beam intensity by (approximately-greater-than)5×.
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    Review of Scientific Instruments 65 (1994), S. 3113-3118 
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    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The presence of background gas in the discharge chamber of the metal vapor vacuum arc source influences the extracted beam. We have observed a strong influence of the background gas pressure in the arc region on the total extracted beam current and on the charge state distribution of the metallic ions. Different gases have been investigated together with different cathode materials. Up to 90% of the total beam current can be gaseous ions, depending on the arc and gas injection conditions.
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    Review of Scientific Instruments 65 (1994), S. 3119-3125 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: TITAN is a new type of ion source capable of generating high current, wide aperture beams of gas and metal ions from a broad range of elements: Mg, Al, Ti, Cr, Fe, Co, Ni, Sm, Zn, W, Pb, Ta, Re, Y, C, He, N, Ar, and Xe. A specific feature of the TITAN ion source is the use of two kinds of arc discharges, each with cold cathodes, to produce plasma for ion beam extraction. Metal ions are generated by means of the vacuum arc in the metal vapor formed in cathode spots. Gas ions, on the other hand, are provided by a low-pressure constricted arc discharge. In a pulsed mode of operation the extraction voltage of the source ranges from 10 to 100 kV. The pulsed beam current for gas and metal ions is on the order of 1 A at pulse repetition rates up to 50 pulses per second and pulse duration of ∼400 μs. For dc operation and at an extraction voltage up to 10 kV, the ion current is as high as hundreds of milliamperes. This work outlines briefly the ion source, its design, and certain physical peculiarities observed when a high current ion beam is generated and transported.
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  • 162
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 3126-3133 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A brief review is presented of the "Raduga'' 1–4 repetitively pulsed metal vapor vacuum arc ion sources. Their operation principles and functional ranges are described. The Raduga ion sources provide single- and multi-element implantation. These advantages are achieved by using not only pure single-element or mixed ion fluxes, but also pulsed beam sequences with controllable composition and energy of each ion species. Another feature of the ion sources is their ability to generate a sequence of ion beam and plasma stream pulses. Switching between ion irradiation and plasma deposition can be done from pulse to pulse, within each pulse, or after accumulation of a required dose. Some specific features of the emission properties of broad beam metal vapor vacuum arc ion sources are described.
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  • 163
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The principles of operation of a new pulsed ultrasonic resonance spectrometer are presented. The system incorporates: (1) the use of electromagnetic-acoustic transducers (EMATs), (2) a method of obtaining acoustic signals similar to the sampled continuous-wave scheme described by Bolef and Miller, (3) the Clark method of recording line shapes, and (4) a high power gated rf amplifier and a unique implementation of superheterodyne and quadrature phase sensitive detection circuitry. The result is a spectrometer capable of measuring both shear and longitudinal ultrasonic velocities in very thin samples with much greater reproducibility than other pulse methods. It also has applicability in measuring attenuation and other physical properties such as composite material bonding that can be accessed using ultrasound. Experimental results of tests using EMATs in the 0.1–20 MHz range on thin (1.27 and 2.49 mm thick) aluminum sheets are presented.
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  • 164
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 204-207 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: By replacing the anvils in a diamond cell with transparent gem materials, a gem anvil cell (GAC) has been constructed for high-pressure generation. We reached pressures of 8.9 and 7.8 GPa with cubic zirconia and sapphire anvil cell, respectively. For high-temperature studies the cell can be heated to temperatures as high as 2000 °C with resistive heating of the gasket. Simultaneously high temperature and pressure approaching 1700 °C and 6 GPa were obtained as indicated by the direct conversion of graphite to diamond in the high-temperature GAC.
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  • 165
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 208-211 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new technique to measure wear and profile of impregnated diamond drill bit for mineral exploration is presented. A three-dimensional surface mapping of worn diamond drill bit surface is obtained by the laser triangulation method. With adequate algorithms all relevant data can be obtained. Consequently, the volume loss between two distances cored can easily be measured with a great precision. Moreover, computerized cross sections of the worn surface give relevant information about the profile resulting from the drilling process.
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  • 166
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 212-220 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report the experimental results of noise measurements performed on junction field effect transistors (2SK162) in the frequency range 1–100 kHz, where the internal correlation effects are not negligible. The experimental data have been analyzed to determine the input current noise spectrum and the spectral energy sensitivity of the device, expressed in terms of noise temperature. We obtained Vn(approximately-equal-to)0.6 nV/(square root of)Hz, and In(approximately-equal-to)4 fA/ (square root of)Hz at 1 kHz, In(approximately-equal-to)25 fA/ (square root of)Hz at 100 kHz. We also report and discuss the results of measurements performed at the temperature of 200 K, which show that the reduction of the noise is not very significant for this specific device.
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  • 167
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 221-223 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method was developed to prepare a small single crystal sample for electrical conductivity measurement. The method was based on the use of commercially available XYZ mechanical stages as micromanipulators, and its accuracy was high enough to attach successfully four gold wires for four-probe measurement on a needlelike crystal 0.2 mm long.
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  • 168
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 224-228 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Fully developed velocity profiles around the side of a needle falling at terminal velocity in a falling needle viscometer and the flow disturbance region near the ends of the needle were experimentally investigated. A flow visualization technique was used to obtain the main features of the flow field around the falling needle. Comparisons made between the experimental and predicted fully developed velocity profile showed good agreement. The regions where the flow field is disturbed by the needle ends were analyzed from photographs and found to be about 6% of the total needle length.
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  • 169
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 242-246 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel fiber-optic cladding mode detector which uses the benefits of dark field detection in a fiber-optic sensor configuration is described. This detector integrates the microbender plate, and the photodetector. It facilitates the detection of cladding or radiation modes produced due to the microbends at the site of the bend itself thereby enhancing the signal strength. The design of this integrated detector along with the calibration curves are given. The detector performance is evaluated by using it in a displacement sensor configuration. Comparison of performance with core mode detection is also given.
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  • 170
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 229-241 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An innovative, Couette-type viscometer/rheometer was developed, designed, and fabricated with the main objective being to measure viscosity and elastic properties of low-viscous, non-Newtonian, and visco-elastic fluids, like dilute polymer solutions. The goal was to simplify and improve some existing drawbacks of commercial instruments employing several novel design solutions, particularly with regard to instrument precision and sensitivity. With a single pair of cylinders and a torsion bar stiffness of 0.116 Nm/rad, viscosities from 0.5 to 50 000 cP (centi-Poise) in a shear-rate range from 1 to 200 s−1, and oscillatory tests from 0.1 to 10 Hz, could be measured. The transducers' electronic signals are handled by a software, developed in C language, and an IBM-PC compatible computer with a data acquisition board. The innovative design solutions (use of a cruciform torsion bar, optoelectronics sensors, and a novel alignment procedure) have improved the critical instrument performance and reduced the number and cost of components, customarily used in commercial viscometers/rheometers. The overall steady shear-rate calibration was performed using the standard-viscosity fluids of 51 and 445 cP. Initial results show high precision (around 4%), particularly at higher velocities. The oscillatory testing was performed by measuring the phase shift between the stress and strain for viscoelastic fluids and for the limiting case of a standard Newtonian fluid. The novel design has proved efficient and with potential for further improvements.
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  • 171
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 259-260 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Optically controlled, sequential breakdown of the spark-gap switches is a simple method for triggering compact Marx generators. Techniques for reliably initiating breakdown of the first switch are discussed. A 300-kV Marx generator for flash x-ray applications is described.
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  • 172
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 247-258 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We derive, discuss, and test against experimental data an analytical model of the gain saturation in microchannel plate (MCP) devices. By introducing a simple recharging circuit for each dynode, we extend the well-known, unsaturated gain model of Eberhardt to a microchannel operating in condition of gain saturation and show that the amplification of a current pulse and the voltage drop along the channel can be described by a pair of coupled differential equations. Solutions of these equations are given in various conditions, including an approximate solution, valid in the case of weak saturation and a general solution in implicit form. The behavior of a microchannel operating in current mode is studied by finding the transient and steady-state solutions obtained with an input step current wave form. Exact solutions are given for the charge gain of pulses with a short duration, compared to the dynode recharging time, and for the gain recovery of a microchannel after the amplification of a short pulse. The single channel saturation model is then extended to multistage MCP assemblies by taking into account the statistical distribution of the photoelectrons at the input and the spread of the multiplied electron cloud in the interplate gaps. The expressions found in this way are used for the best fit of experimental data from a Z-stack MCP photomultiplier operated in single and double pulse mode. Satisfactory agreement between the model and experimental data is obtained in the case of single pulse measurements, finding a reduced chi squared χ2=4.67. Less satisfactory agreement is found for double pulse data, giving χ2=7.46 and a clear indication that the model may be significantly improved by taking into account the charge redistribution among the dynodes during the recharging process, neglected in the present formulation.
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 65 (1994), S. 261-262 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple circuit is described which closes a shutter on the optical input of a photon counting detector when the photon count rate exceeds a preset level. The circuit utilizes common integrated circuits, and is designed to protect microchannel plate photomultipliers from excess light exposure.
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