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  • American Institute of Physics (AIP)  (8,872)
  • Nature Publishing Company  (430)
  • 1990-1994  (9,302)
  • 1970-1974
  • 1955-1959
  • 1992  (9,302)
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  • 1955-1959
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4041-4045 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An instrument which incorporates an electrostatic scanning electron microscope and a scanning tunneling microscope in an ultrahigh vacuum environment has been developed to study nanostructures. To facilitate positioning the nanostructures for examination with the instrument a high precision orthogonal motion sample stage has been designed. The instrument has been applied to locate and study both nanometer size trenches and wires. These structures have been fabricated using electron beam lithography and a polymethlymethacrylate lift-off process.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4049-4052 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A design is presented for a scanning tunneling microscope (STM) capable of operation over a temperature range of approximately 80–350 K in ultrahigh vacuum. An integral inchworm-like sample translation device avoids problems with unreliability and lock-up by using clamping elements which have an unusually large range of motion. The entire STM, including the sample and the tip, are held isothermal. Temperature drift is less than 0.1 A(ring)/min. A set temperature may be maintained, within 2°, for over 10 h. Operation of the instrument is demonstrated with an image of the Si(001) surface recorded at 120 K.
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: When scanning steeply sloped features which are near micron size or taller, scanning tunneling microscopes with conventional feedback control loops exhibit slower response on downhill slopes than on uphill slopes. This effect is caused by the exponential dependence of the tunneling current on the tip-sample distance. A gap smaller than the setpoint produces a sizable error signal, whereas a gap larger than the setpoint gives only a weak error signal. As the scan rate is increased, the tip begins "flying'' well above the surface on steep downhill regions. We have developed a modification of the conventional integral feedback system which eliminates this problem. This circuit makes the error signal growth with increasing distance between the tip and sample similar to the usual exponential growth when the tip-sample distance decreases. This modification allows an increase in scan rates by a factor of 5–10 with no reduction in image quality. The modification can be dialed in or out of circuit as needed, such as when switching between large scale images and atomic scale images, and can easily be installed in any existing scanning tunneling microscope that uses an analog feedback circuit.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4053-4055 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A chemical vapor deposition method is described for fabricating force microscope cantilevers with single-crystal diamond tips. The (approximately-equal-to)1-μm-diam diamond tips have corner radii of 30 nm, and have been used to study diamond–diamond friction on well-characterized surfaces in UHV. The tip size and orientation can be determined by electron microscopy without altering the surface atomic structure.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4056-4060 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An automatic system has been completed for conditioning cold field-emission tips to obtain high flux density and low-noise emission. It was designed as a real-time control and operating system for the electron source of a new sextupole-corrected scanning transmission electron microscope and is able to condition the tip in situ. All of the control devices in this system are interfaced to a computer and communication across the electric field created by the 200-kV acceleration voltage is accomplished with light pipes. A program, written in Pascal, controls the conditioning process. This system has been utilized to experimentally determine the optimal flash level for a newly fabricated tip as well as performing corrective maintenance to the conditioned tip to extend its maximum useful lifetime.
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  • 6
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this paper it is demonstrated that glass micropipettes have unique applicability as force probes for a variety of imaging conditions and a variety of scanned tip microscopies. These probes are characterized in terms of the parameters that determine their force characteristics. Measurements are presented showing that one can readily achieve force constants of 10 N/m and it is anticipated that a reduction in this force constant by two orders of magnitude can be achieved. Such probes can be produced simply with a variety of geometries that permit a wide range of force imaging requirements to be met. Specifically, the glass micropipette probes reported in this paper are readily produced with apertures at the tip and can thus be applied to near-field scanning optical microscopy (NSOM). This opens the possibility of the long-awaited development of a universal feedback mechanism for NSOM.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4066-4070 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A computer-controlled scan system has been completed for a sextupole-corrected high-resolution Scanning Transmission Electron Microscope. It is capable of driving 24 coils and 2 sextupoles in the microscope for beam scan, unscan, alignment, and correction of aberration. A PC-AT is employed to manage this system and control the system devices. By means of these devices the raster size, shape, rotation angle, and dc offset can be controlled by subroutines for image generation/transformation. Computer control provides numerous advantages for the management of such a complicated system making it possible to modify many parameters and invoke a new group of settings simultaneously. This provides convenience in microscope operation for such functions as change in magnification, selection of viewing area, locations of objects of interest and montage.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4102-4107 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: 6-in.-diam multilayer mirrors were fabricated for a double mirror monochromator designed to select photon energies between 830 and 1240 eV (0.5–1.5 nm). Coatings with 50 and 40 Mo/C bilayers with a bilayer d spacing of 4.1 and 4.6 nm, respectively, and a division parameter of Γ=0.44, were deposited by the triode sputtering method on 6-in.-diam silicon with 5% d uniformity. Similar coatings were also deposited on 2 in. silicon wafers. Peak reflectivity and integrated reflectivities were measured at several wavelengths between 0.5 and 1.5 nm using monochromatized synchrotron radiation. Measurements were performed along a 4 in. diameter for the large area coatings. The resolving power as measured in the center of the six inch mirrors was found to be 41 and 46 at 826 and 1240 eV, respectively, which compares well with the corresponding theoretical values of 43 and 40. The performance of a matched pair of multilayer mirrors with the smaller areas in the double mirror configuration was experimentally investigated as well. Reflectivity values for the two mirror configuration scheme were calculated from the experimental data for the individual mirrors. Possible applications of such monochromator in lithography research are briefly described.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4112-4121 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The transfer matrix up to the second-order aberrations has been formulated for an electron optical systems of a monochromator and an energy analyzer. Both of these instruments have two magnetic round lenses and a retarding Wien filter. The filter consists of a deceleration lens, a Wien filter, and an acceleration lens. The optimum excitation of the round lens is found to be that which provides parallel exit of electrons from the acceleration lens. The excitation of the Wien filter must be adjusted to focus the beam on the slit. The computed results are useful for finding the optimum operating conditions and for explaining experimental results of the high-resolution electron energy loss spectrometer.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4122-4127 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experiments of microwave spectroscopy of gases at low pressures are performed with some advantages using dielectric waveguide cells. The construction of an improved version of a dielectric waveguide spectrometer is described. Details on the experimental methods utilized for gas handling and for the observation of some absorption lines of HNO3, O3, and H2O in the 18–26.5-GHz frequency band, and of the CS radical at 49 GHz are given.
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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4134-4137 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A new method has been developed which results in a major improvement in count rate of Bragg–Brentano-type diffractometers. The method uses a focusing exit beam monochromator and a multichannel detector to achieve this improvement. The method is very efficient in eliminating background and can have very high resolution. Existing diffractometers can be easily modified to take advantage of this technique.
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  • 12
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4138-4148 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A molecular beam mass spectrometer system has been designed and constructed for the specific purpose of measuring the gaseous composition of the vapor environment during chemical vapor deposition of diamond. By the intrinsic nature of mass analysis, this type of design is adaptable to a broad range of other applications that rely either on thermal- or plasma-induced chemical kinetics. When gas is sampled at a relatively high process pressure (∼2700 Pa for our case), supersonic gas expansion at the sampling orifice can cause the detected signals to have a complicated dependence on the operating conditions. A comprehensive discussion is given on the effect of gas expansion on mass discrimination and signal scaling with sampling pressure and temperature, and how these obstacles can be overcome. This paper demonstrates that radical species can be detected with a sensitivity better than 10 ppm by the use of threshold ionization. A detailed procedure is described whereby one can achieve quantitative analysis of the detected species with an accuracy of ±20%. This paper ends with an example on the detection of H, H2, CH3, CH4, and C2H2 during diamond growth.
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  • 13
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Bonse–Hart ultrasmall angle x-ray scattering (USAXS) instrument employing both synchrotron and conventional x-ray sources was constructed. The instrument could be used to determine the structure of systems with inhomogeneity sizes on the order of ∼1000 nm. The characteristics of the instrument by using synchrotron and conventional x-ray sources were compared. The use of synchrotron radiation showed much improved features not only in scattered intensity, but also in angular resolution. The scattered intensity was increased by a factor of about 20. Therefore weaker scattering systems could be investigated. By using the synchrotron radiation, the deficiency of the Bonse–Hart camera could be compensated. An angular scan containing ∼30 data points in the scattering angle region smaller than ∼2 mrad with reasonable signal-to-noise ratio could be completed within 5–10 min for samples with reasonable scattering power. Therefore, kinetic studies could be possible if the half time of structural development in a system is of the order of hours. For static experiments, a conventional x-ray source could be used more conveniently to obtain a scattering curve with similar quality as that by means of synchrotron radiation partially because the channel-cut crystals were not optimized for the synchrotron beam divergence and partially because alignments could be accomplished at a more leisurely pace using the conventional x-ray source.
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  • 14
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high-flux atomic oxygen source has been developed for the deposition of in situ superconducting high Tc films under conditions that require low chamber pressures (≤10−4 Torr). The source uses a remote microwave plasma to generate the atomic species and is capable of producing an atomic oxygen flux greater than 2×1016 cm−2 s−1. The O2 dissociation efficiency of the atomic oxygen source is measured to be approximately 25%–30% for an O2 flow of 5 sccm. This high efficiency is achieved by the combined effects of a boric acid surface treatment to minimize recombination on the quartz tube and the addition of N2 to the oxygen plasma to increase the atomic oxygen yield. We have developed a treatment for the quartz surface that gives reproducible atomic oxygen flux with no degradation of the surface coating with repeated usage.
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  • 15
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4154-4160 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 10-GHz superconducting niobium re-entrant cavity parametric transducer was developed for use in a cryogenic 1.5-tonne Nb resonant bar gravitational radiation antenna. The transducer has a very high electrical Q (6×105 at 4.2 K), and was operated at high cavity fields without degrading the Q. A very high electromechanical coupling between the antenna and the transducer was therefore achieved. The highest coupling attained, constrained by the available pump power, was 0.11. If the transducer were to be operated in conjunction with a wideband impedance matching element, an antenna bandwidth comparable to the frequency of the antenna would be attained. The temperature dependence of the Q of the transducer was in good agreement with theory. At temperatures above about 6 K the Q was degraded by the increase in the BCS surface resistance, while at lower temperatures the Q was limited by radiative losses.
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  • 16
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4167-4173 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A micronic-size hot wire anemometer operating at cryogenic temperatures (4 K) has been developed; using superconducting and resistive thin films, its electrical resistance is very sensitive to the velocity of a gaseous 4He subsonic jet. The fabrication procedure is described and the measured characteristics are compared with a simple thermal equilibrium model.
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  • 17
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4161-4166 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We developed a system for localizing orthogonal triplets of small magnetic dipoles with an array of magnetometers. These triplets can be used to measure, in quasi-real time, the position of an object. This system is particularly useful when used with superconducting biomagnetic multichannel detectors. We present here a complete numerical simulation of the system performances and the first experimental tests with a biomagnetic detector (an array of 37 superconducting magnetometers). This system can be operated at frequencies outside the range of interest for biomagnetic measurements (that is typically 10−2–103 Hz). It features an accuracy of ±0.3 cm driving the triplet at a field intensity ≈10−12 T. The speed of the algorithm allows for quasi-real-time operation (t ∼ 10−1 s).
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  • 18
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3646-3651 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Scanning tunneling spectroscopy (STS) capable of measuring the local density of states dI/dV=G(V,x,y) correlated with the topography z(x,y) is implemented on a PC/AT computer system. An algorithm using dimensional decoupling and recursive linking is incorporated in a compact C-language code to achieve flexible and sophisticated STS control. Data acquisition and processing methods which provide the local density of states G(V,x,y,s) at different tip heights s in registry with z(x,y) are described. Examples of novel low-temperature experiments are given to show the capabilities of this implementation of STS.
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  • 19
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have recently developed a high-resolution magnetic imaging system based on an array of five superconducting pickup coils located within 1 mm of room temperature. The pickup coils are 1.70 mm in diameter and spaced 2.5 mm apart allowing spatial resolution of order 1 mm. They are each connected to an rf SQUID and have a magnetic field sensitivity of 3 pT/(square root of)Hz. The system includes a three axis nonmagnetic translation table for mounting the sample, a stage for temperature control, and complete computer control of all functions.
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  • 20
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3659-3661 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: It is possible to determine the absolute intensity of a light signal recorded by a video camera with automatic gain by analyzing the background part of the recorded images. The method is based on the determination of the histogram of the gray levels of the dark pixels whose inverse variance appears to be proportional to the camera gain in a large domain of light intensity. An example is given by images recorded by a charge coupled device camera in a space experiment where the light transmittivity is used as a local probe for temperature measurements.
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  • 21
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3662-3665 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a staring-mode, high-speed infrared camera based on a RCA 160×244 PtSi Schottky-barrier charge-coupled device image sensor. The camera uses a unique method to achieve greater temporal resolution of rapidly varying thermal phenomena in the 3–5 μm band. Rather than increase the imager's frame rate, we decrease the image integration time while maintaining a frame rate that is compatible with standard RS-170 video. This technique allows us to display and record repetitive events that occur at frequencies up to 5 kHz with conventional video equipment. In this article we describe the theory and operation of this system.
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  • 22
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3666-3669 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A lock-in amplifier circuit has been designed and tested which serves as an automatic frequency control (AFC) for electron spin resonance (ESR) spectrometers employing solid-state microwave generators. Its implementation in a typical spectrometer is described and a detailed electronic schematic presented. Its performance is tested as a lock-in amplifier operating under open loop conditions, wherein operating with a 20-kHz reference, it yields an 81-dB improvement in signal to (9 kHz) noise ratio. This is consistent with expectations from computer simulations. When employed as an AFC in a typical X-band ESR system the capture and lock ranges are observed to be equivalent to those obtained from a commercial lock-in amplifier.
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  • 23
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3670-3673 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present a modified Merrill–Bassett diamond anvil cell for performing electron paramagnetic resonance (EPR) experiments under high pressure. The design centers on two mutually coupled TiO2 dielectric resonators mounted close to the diamonds. This configuration produces a tangential microwave magnetic field at the gasket, which is a prerequisite for a magnetic resonance experiment. Our simple device has a considerable advantage over previous approaches for EPR under pressure in both its compactness and sensitivity.
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  • 24
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3744-3751 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The factors governing the choice of preamplifier type for the vibrating capacitive probe used in contact potential measurements are examined. Two types are compared: a high input impedance voltage amplifier and a current amplifier. The latter has been increasingly used in recent years due to its great advantages in dealing with parasitic input capacitance. We extend previous analyses, elucidating other advantages of the current amplifier. Particularly important are (i) the reduction of spurious microphonic signals, implying lower systematic error, and (ii) the white noise spectrum of its equivalent contact potential noise, which allows random error to be effectively reduced by increased averaging periods.
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  • 25
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3736-3743 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We discuss the principles required to determine the electric field outside a metallic conductor created by strain gradients in the metal as might be engendered by the Earth's gravity. The experiment we describe measured the contact potential variation between a mechanically differentially strained metal surface and an unstrained capacitive sensing probe. The results are of considerable importance for the investigation of the free fall of charged particles inside vertical conducting drift tubes. Our aim here is to elucidate the large sources of error associated with the application of strain. These include motions of the sample and temperature variations. The solutions we have developed may find application in similar experiments.
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  • 26
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In this article, a new curve of the correction factor for the measurement of sheet resistance of a square sample with a square four-point probe is presented by using the theory of conformal transformation. This curve is quite different from that obtained by using the theory of infinite dipoles. An experimental curve is recommended to use. The function of the conformal transformation used in this article is simple and can be easily used for solving the problem of boundary effect of current field. The theoretical curve is suitable to the boundary areas of wafers.
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  • 27
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: By using conformal transformation to take account of the boundary effect, it has been confirmed that there are some areas of a square sample near the corners besides the boundary suitable to the resistance measurement of Van der Pauw's method. The theoretical criterion of the suitability is whether Van der Pauw's formula for calculation of the sheet resistance is still valid provided the voltage values in the formula for two times the measurement are substituted with those obtained by using the theory of conformal transformation. The experimental criterion is whether the experimental values of sheet resistance for probes in some areas are equal to that for them at the boundary for the same sample. The experimentally confirmed areas are larger than what the theory predicts. Our repeated experiments show that the areas out of the circle tangent to the boundary are suitable to Van der Pauw's method.
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  • 28
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A personal computer based hardware has been developed for the real time, rapid digitization of echo amplitudes and times-of-flight of ultrasonic pulses produced by existing analog ultrasonic borehole imaging systems. Both amplitude and travel-time B-scan images are mapped circumferentially around the wellbore wall with reference to magnetic north. 12-bit analog to digital conversion of pulse amplitudes provides a resolution of approximately 1 mV out of a peak amplitude voltage of 1 V; travel times are determined to within 100 ns to a maximum time of 512 μs after which it is assumed that no signal will be detected. This information provides high-resolution digital images of the borehole wall and cross section which are useful for delineation of open fractures, discrimination of complex cross sections, and calculation of wellbore volumes.
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  • 29
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3763-3766 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Infrared emission radiometry was used as a noncontact temperature probe with a tens of micron spatial resolution for monitoring laser-induced chemical vapor deposition (LCVD). With appropriate calibration of the emissivity, a temperature of 255±15 °C was measured during gold LCVD from dimethylhexafluoroacetylacetonate gold (III). Equivalent deposition temperatures were calculated for both continuous and modulated laser illumination. Depending on the deposition conditions, material deposited with a modulated laser beam varied from notably worse (due to stress cracking) to notably better (more uniform growth morphology) than material deposited with continuous laser illumination.
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  • 30
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Gundestrup is a Langmuir/Mach probe array which measures the flow velocity in the scrape-off layer of Tokamak de Varennes (TdeV). It is based on the concept of a Mach probe where presheaths extending upstream and downstream from the probe, parallel to the magnetic field, attract charge to a circular array of collecting pins. The polar distribution of ion saturation currents to the circular array is used to compute the components of flow velocity in the plasma. With Gundestrup, there is an assumed flow perpendicular to the magnetic field as well as parallel to it. Equations representing the collection of charge by individual pins on the probe are presented and sample flow patterns from the scrape-off layer are shown.
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  • 31
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3918-3922 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We present an optical technique for the measurement of semiconductor surface electric fields. The measurement technique uses the Kerr electro-optic effect in nitrobenzene, a phase sensitive interferometer, and associated data acquisition units to measure the surface electric fields between the contacts of a planar semiconductor device. This technique was used to measure the surface fields on silicon devices used in pulsed power applications, but has the potential for use as an electric field probe for any device having high surface electric fields, both pulsed and dc. The measurement technique showed a temporal resolution of 100 ns, which can be easily reduced to a few nanoseconds using superior data acquisition and detection systems. The spatial resolution was about 50 μm for devices that had a typical contact separation of about 500 μm (power devices). This technique can be applied to measure the surface fields on devices commonly used in microelectronic applications. In this paper we discuss in detail the measurement technique and present the results obtained for silicon photoconductive power switches.
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  • 32
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3783-3784 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An open-loop, wide dynamic range, fiber optic gyroscope has been demonstrated by using the PLL phase tracking technique. This technique provides a linear output of an open-loop gyroscope with the Sagnac phase shift up to 2Nπ rad, N=2n, is where n an integer number.
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  • 33
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3785-3786 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Fluorescence angiography has become a very important diagnostic aid in modern clinical ophthalmology. The design and performance of a high-sensibility TV system incorporated into a standard fundus camera for the fundus eye analysis are described. Compared to the usual angiographic procedure, the new equipment has allowed the reduction of both eye exposure and dose of fluorescent dye injected intravenously to the patient. Examples of some choroidal angiograms obtained using this apparatus are presented.
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  • 34
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3787-3788 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The diaphragm sensing tip of a high-speed piezoelectric pressure transducer can be destroyed when measuring transient impulse pressures in hot oxidizing atmospheres, e.g., oxygen at 3000 K and 34 atm for times of tens of milliseconds. A technique is presented to preserve the transducer under these conditions, which uses a protective layer of 0.025–0.050-mm-thick brass foil, held in place with double-sided tape. The integrity of the transducer is preserved, and the response time to a shock wave is increased from 1 to 2–6 μs using the technique.
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  • 35
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3317-3320 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The response times of nonresonant p-Ge detectors and of resonant photon-drag detectors made from AlxGa1−xAs/GaAs multiquantum well systems are measured with intense 300-ps optical pulses of 10-μm wavelength generated with the aid of an improved laser system based on optical free induction decay. A response time limited by the oscilloscope-amplifier bandwidth is reached with the quantum well systems. Their response time is shorter than that of a p-Ge photon-drag detector. The light-pulse traveling time limits the performance of the large p-Ge photon-drag detectors.
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  • 36
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We analyze the efficiency of a vibration isolation system (VIS) for a scanning tunneling microscope as a function of the different parameters involved. The VIS consists of a stack of several metallic plates, separated by rubber elements with known properties. We show three-dimensional graphs obtained for different values of parameters such as rigidity (spring) constant (K), damping constant (C), mass (M), and the number of stages (n). Analyzing the K dependence of the position of the main peaks, we find a parabolic behavior when the damping constant is small, with a slight deviation for larger values.
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  • 37
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3339-3345 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Accurate calculations of the axial chromatic aberration coefficients of geometrically symmetric three-cylinder tripotential electrostatic lenses are presented for two different center electrode lengths. This is an extension of the first-order properties and the third-order spherical aberration coefficients published by Harting and Read.
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  • 38
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3330-3332 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed an atomic force microscope (AFM) using a zinc oxide (ZnO) whisker crystal as a probing tip. The ZnO whisker crystal is tetrapodal in shape, with each leg having a length of 5–30 μm, a radius of curvature less than 10 nm, and a cone half angle of 1°–2°. Polyimide thin films rubbed with cloths as liquid-crystal aligning films were employed for AFM imaging. Due to the needle shape of the probing tip, the AFM was able to resolve the tiny grooves (3–5 nm deep, 60–80 nm apart) on these films more clearly than that using a conventional pyramidal tip. The new AFM will be available for precise evaluation of surfaces on which fine structures are microfabricated in nanometer scale.
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  • 39
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A 14.6-GHz electron cyclotron resonance ion source has been designed and will be installed at the TU Dresden. Contrary to other ECR sources some features are foreseen for atomic physics experiments to study the source plasma. Beside the description of source construction and computer-aided source control first physical experiments on the source are discussed.
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  • 40
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3346-3351 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An electron coincidence spectrometer utilizing real-time optimization and control by a standard IBM 80286 personal computer is described. Details of the system hardware and software are presented together with a description of the optimization routine adopted for maintaining the tuning of the spectrometer and data acquisition. Data collected by the computer-controlled spectrometer for (e,2e) coincidence experiments are also presented.
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  • 41
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A combined Thomson–Rayleigh scattering device is discussed. It consists of a Nd:YAG laser as a light source in combination with a multichannel detection technique consisting of a gated light amplifier in combination with an optical multichannel analyzer. Special attention is focused on the analysis of the measured spectra. Including convolution methods and taking into account weak coherent effects increases the dynamic range and the accuracy of the measured electron density ne and temperature Te and neutral particle density n0. Accuracies of 1%–4% for ne, 2%–6% for Te, and 10%–50% for n0 depending on the plasma condition are obtained. The dynamic range for ne is 7×1017–1021 m−3, for n0 is 1020–1023 m−3 and for Te is 1000–50 000 K.
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  • 42
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A novel instrument is described capable of recording gas electron diffraction (GED) patterns of excited molecular states or transient species with pulsed electron beams. The system incorporates (1) a pulsed optical beam for electronic excitation of materials under study, (2) a synchronously pulsed source of 30–50 keV electrons in a space-charge-limited beam, (3) necessary vacuum environment and sample-handling capabilities, and (4) detection and signal processing equipment using an on-line procedure developed at the University of Arkansas. Data obtained for several test gases demonstrate successful operation of the instrument. The 193 nm laser photofragmentation of carbon disulfide, CS2, is described in detail. In agreement with a recent time-of-flight mass spectrometric study of the same process, carbon monosulfide was observed as the reaction product. This study is the first quantitatively successful joint exercise of on-line multichannel GED data recording and a stroboscopic electron source. The method is expected to be generally useful in determining the structures of excited molecular states or reactive species, and it may enable studies of time-dependent phenomena. The current time resolution is ∼20 ns.
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  • 43
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A system to provide a liquid or solid deuterium shell target with a plastic ablator for laser implosion experiments was developed. The system is capable of filling a plastic capsule with deuterium gas of 11 MPa at room temperature at the firing position in the target chamber. Then, the target is cooled down to a cryogenic temperature to form a uniform liquid or solid fuel layer inside without exposing it to the atmosphere. Details of the system, tensile strength of polystyrene shells at low temperature, and the residual vapor pressure in the central void of the target at the laser irradiation are described.
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  • 44
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A Rutherford scattering diagnostic has been applied at the TEXTOR tokamak to obtain spatially and temporally resolved information on the temperature of the bulk ions in the plasma. In the experimental setup, a helium atomic beam (30-keV, 12-mA equivalent current) passes vertically through the plasma core. A small part of the injected atoms is scattered elastically by the thermally moving plasma ions. The ion temperature in the scattering volume can be determined from the broadening of the energy spectrum of the scattered particles. Energy analysis of the scattered atoms is performed by a mass-selective time-of-flight analyzer detecting the particles at an observation angle which is selectable between 3° and 8°. Coincidence techniques have been successfully applied in this detector for rejection of background events triggered by detections of neutrons and gamma radiation. Ion temperature profiles were measured on a shot-to-shot basis by shifting the cross section of the diagnostic beam and the observational volume of the analyzer through the plasma. The ion temperatures measured in ohmic deuterium plasmas were found to be in reasonable agreement with those obtained from passive neutral particle analysis. Up to now, ion temperatures have been measured throughout the complete discharge with an accuracy of 8% and a time and space resolution of 100 ms and 0.10 m at a scattering angle of 7°. Deuteron density profiles could be deduced from the scattering yield measured at different radial positions in the plasma. The ratio of the isotopes, hydrogen and deuterium, was determined from their separate contributions to the spectrum of helium particles scattered on hydrogen and deuterium. Although theoretical predictions showed that the majority of the probing helium atoms loses one of its electrons during the elastic scattering process on multiply charged carbon and oxygen ions, contributions from impurities to the observed experimental spectrum are shown to appear dominant for impure plasmas.
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  • 45
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    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3384-3388 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: High-power-density plasma arc equipment with a small diameter nozzle of 0.1–0.3 mm has been developed, which produces power density of about 104 W/mm2 at the exit of the nozzle. The density is comparable to those produced by electron and laser beams. In the present article, development procedure, power density on the target surface, and processing capability in comparison to the conventional electron and laser beams are described. The power density as the processing heat source depends on the kind of processing. The apparent power density in cutting is of the order of 104 W/mm2; on the other hand, that in surface hardening is of the order of 102 W/mm2. The processing capability for causing melting such as cutting and welding does not depend on the working distance, which is defined as the distance between the torch and target material; furthermore, the deviation of the torch from the correct position does not affect the processing capability. The equipment developed is suitable for an automated production system because high precision position control of the torch is not required.
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  • 46
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A simple and economical microwave plasma-assisted chemical vapor deposition facility has been developed and used for synthesis of diamond thin films. The system is similar to those developed by others but includes several unique features that make it particularly economical and safe, yet capable of producing high quality diamond films. A 2.45-GHz magnetron from a commercial microwave oven is used as the microwave power source. A conventional mixture of 0.2% methane in hydrogen is ionized in a bell jar reaction chamber located within a simple microwave cavity. By using a small hydrogen reservoir adjacent to the gas supply, an empty hydrogen tank can be replaced without interrupting film synthesis or causing any drift in plasma characteristics. Hence films can be deposited continuously for arbitrarily long periods while storing only a 24-h supply of explosive gases. System interlocks provide safe start-up and shut-down and allow unsupervised operation. Here we describe the electrical, microwave, and mechanical aspects of the system, and summarize the performance of the facility as used to reproducibly synthesize high quality diamond thin films.
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  • 47
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3394-3398 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Experiments have been performed which indicate that by directly heating lithium hydride in a vacuum, up to 18 μA/cm2 of negative hydrogen can be obtained from the crystal lattice. Sample temperatures reached a maximum of about 800 °C. The amount of ion current extracted and analyzed is closely related to the temperature of the sample and to the rate at which the temperature is changed. The ion current appears to be emission limited and saturates with extraction voltage. For a fixed extraction voltage, the ion current could be maximized by placing a grid between the sample surface and the extraction electrode. Electrons accompanying the negative ions were removed by a magnetic trap. A Wien velocity filter was designed and built to provide definitive mass analysis of the extracted ion species.
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  • 48
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2434-2437 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A spark carbon ion source (SIS) has been fabricated and tested with two systems of electric power supply. It was found that in the quasistationary spark (inductive energy storage scheme), and for a discharge current of ∼2 kA and timp∼100 μs, the ion charge state distribution is similar to the HF spark with a discharge current of 2 kA (1-MHz LC-circuit scheme). A total pulse carbon ion current of about 500 mA has been obtained from the quasistationary spark. The C+3 ion current was about 300 mA and the C+4 ion current ∼100 mA. The noise amplitude of the total ion current is no more than 10% in this mode of operation. The production of highly charged ions is explained by an increased potential drop in the discharge gap (60–100 V) for currents of 1.5–2.0 kA. It is shown that the quasistationary spark mode is accompanied by an occurrence of a stable anode spot while electrode evaporation increases and the vacuum spark is transformed into a high pressure spark discharge, leading to a shift of the ion spectral distribution to high charge states. The proposed spark ion source could find new applications in different accelerators along with PIG, ECR, etc.
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  • 49
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The family of 10 cm diam ion sources PRIS is built for ion beam processing. It comprises two groups: The high energy version PRIS 10 HE and the low energy version PRIS 10 LE. The conventional rf-ion sources RIM 10 consist mainly of a quartz discharge chamber surrounded from an outside by a rf-induction coupling coil. In some cases, quartz cannot be used for manufacturing the discharge chamber (e.g., fragility of quartz, operating with condensible metal vapor). Therefore, in the PRIS sources, we replaced the quartz ionizer vessel by a metallic discharge chamber and put the rf antenna inside the discharge plasma. The performance data and the ion beam characteristics of PRIS are presented for argon and oxygen.
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  • 50
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An impregnated-electrode-type liquid-metal ion source has been developed which utilizes a linear array of emitters. This ion source is constructed by placing two emitters that consist of porous ion-emission tips and reservoirs for liquid metal. The emitter is equipped with multiple ion-emission points in a line. Two tip-and-reservoirs (TAR's) are fixed by respective knife-edged electrodes. Utilization of multiple TAR's has an advantage of reducing heater current by connecting them electrically in series. The performance characteristics of the ion source have been investigated using germanium as a source material. Ion emission from 17 points has been achieved with this arrangement; a current of 4.6 mA have been obtained immediately following the ion source. These results indicate that it is possible to extract a current approximately proportional to the number of emission points. The result also implies that a further increase in intensity can be expected by adding more TAR's to the array.
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  • 51
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Preamorphization of a silicon substrate by Ge+ ion implantation is required for shallow doping of boron, which, in turn, is the key process to realize highly integrated semiconductor devices. However, Ge+ ions have not been stably extracted by conventional methods. Several chemical compounds of germanium, GeO, GeS, GeCl4, and GeF4, were supplied to a microwave ion source and the characteristics of their ion extractions were compared. The conditions for obtaining mass-separated Ge+ ions of more than 1 mA were found.
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  • 52
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Negative sodium ions and negative dimer ions of sodium are extracted from a sodium plasma. The extraction characteristics of Na− and Na2− from a low power discharge (about 1 W) through a single aperture (φ1.5 mm) are described. Both extracted currents of Na− and Na2− increase with the temperature of the heat shield inside the discharge chamber. The current ratio of Na− to Na2− is almost constant independent of discharge voltage. By increasing the discharge power, the value of the bias voltage of the plasma electrode that gives the optimum extraction currents of Na− and Na2− increases. The extracted current of Na2− is lower than that of Na− by two orders of magnitude.
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  • 53
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3966-3971 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The transient hot-strip (THS) method has been modified to measure thermal conductivity of small test specimens. The conventional metal strip used simultaneously as the heater and the temperature sensor was substituted with a 50-Ω commercial temperature sensor (grid 5.85 mm×6.35 mm). The short transient hot-strip (STHS) method was tested on Pyrex 7740, stainless steel (NIST 1462 standard reference material), and aluminum to cover more than two orders of magnitude in thermal conductivity. The STHS method agreed with conventional measurement techniques within 3% in the thermal conductivity range 1–200 W m−1 K−1.
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  • 54
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3978-3982 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Calculations are described of the elastic stress, strain, and surface displacement for a high-pressure optical window consisting of a transparent cylinder which is supported on a flat seat with an axial hole (Poulter window). Under pressure the window is compressed, and its outside surface bulges through the hole in the support. The net optical effect is to create a weak positive lens and to increase the axial optical thickness of the window.
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  • 55
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A method to measure the absolute intensity of a weak magnetic field is described. This method uses patterned superconducting strip lines as a spatial modulator of the field and detects the magnetic field distribution over them as a function of applied magnetic fields. The field distribution change measured by an rf SQUID system is proportional to the component of the absolute intensity of the magnetic field at the specimen that is parallel with the pick-up coil axis. The magnetic field intensity can be determined absolutely from about 1 μG by this method. A spatial resolution of the field as good as a few millimeters is obtained. Some practical limitations of this method and possible ways for improving are also discussed.
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  • 56
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3983-3984 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A free deforming-cylinder pressure transducer with bonded strain gauges is presented for pressure measurements in liquid media up to 0.5 GPa. Description is given of its operating principle and of its main metrological properties; the overall accuracy of this prototype pressure transducer is inside ±0.25 MPa.
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  • 57
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3985-3988 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The velocity of a steady, low-pressure (≈0.1 Torr) plasma jet is measured by analyzing the local response of the medium to the action of an external magnetic field set up by two Helmholtz coils placed at the edge of the jet, yielding a field of 0.92 G/A. The induced electric field is measured by two floating-potential electrostatic probes. The mean velocity of the electrons (between 1000 and 5000 m s−1) is found from the generalized Ohm's law.
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  • 58
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 3989-3992 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A synchronous detector electronics package with self-contained oscillator is described. It uses only three integrated circuits, all of which contain operational amplifiers. The performance of the detector was evaluated with a capacitance sensor. Linearity and stability were found to compare favorably with general purpose commercial systems costing hundreds to thousands of dollars. Although the noise performance was less impressive, the dynamic range was still in excess of 90 db, permitting better than 100 μrad resolution over a range of nearly 3 rad. As presently configured, the detector is compatible only with high impedance sensors such as the capacitance type; however, coupling the oscillator output through a power amplifier would permit its use with LVDTs.
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  • 59
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2152-2156 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The intention of this paper is to describe the design of a 16-bit correlation setup employing a personal computer (PC) used in intensity fluctuation spectroscopy. It is based on a hardware acquisition board which counts the photons detected in the selected sampling time. The calculation of the correlation coefficients is achieved with a PC by means of a suitable software program. This arrangement permits one to obtain various kinds of information from the recorded data, i.e., it is possible to evaluate other statistical estimators instead of the usual correlation function. Experimental tests of the apparatus have been obtained by measuring the light scattered by a liquid suspension of polystyrene latex spheres.
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  • 60
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2157-2163 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Simple modifications were made to a commercial microscope to enable injection of light from a diode laser, and demonstrate optical tweezers action. The basic properties of microscope optics are presented together with discussion of principles to be followed in arranging the external optics for achieving useful tweezers. Procedures using a single-mode diode laser along with experimental results are presented in enough detail to permit readers to make their own system for trapping and manipulating single cells. It is surprisingly easy to demonstrate tweezers action once some basic concepts are understood.
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  • 61
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2164-2169 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Two configurations for a fiber-optic torsional vibrometer are described, which can be classified as (i) differential and (ii) reference. Common features of both techniques are noncontact measurement, immunity to nontorsional vibration, large dynamic range coupled with passive, miniature, remote sensor heads. Measurements of rotation speed and torsional jitter were made with a total illuminating laser power of 130 μW (reference mode) and 1.5 mW (differential mode). Rotation speeds in the range of 270–19 000 RPM were measured.
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  • 62
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2170-2173 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A diode laser based system was developed to monitor the mean concentration of aerosol clouds formed by cylindrical liquid fuel-air explosive (FAE) devices. Characteristics of the aerosol clouds are first described to provide an understanding of the nature of the flow which led to the engineering design of the system used. This paper then concentrates on the construction and testing of this optical system, which was designed to carry out four simultaneous in situ light extinction measurements through FAE clouds. The results of a typical liquid fuel dispersion test are presented and discussed as an illustration of the characteristics of the optical system in this application.
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  • 63
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2174-2176 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An infrared absorption sample cell was designed and constructed for use in the temperature range from 300 to 1000 K. The design's emphasis was on maintaining an inert environment to eliminate the possibility of depleting the absorbing gas due to reactions with the sample cell material. This design was successfully used for CO2 4.3-μm band absorption measurements in the temperature range extending from 300 to 1000 K.
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  • 64
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe a new reflectron time-of-flight mass spectrometer configuration for laser photodissociation of mass-selected ions and the initial performance characteristics observed for this instrument. Ions are produced by laser photoionization within the acceleration region of the instrument or by laser vaporization in an external pulsed-nozzle cluster ion source. Mass selection is accomplished with pulsed deflection plates at the end of an initial drift section. Laser photodissociation of selected ions takes place at the turning point in the ion trajectory in the reflectron. The transit time through a second drift section defines the fragment ion masses. Optimized operating conditions and the role of mass discrimination in this instrument are discussed.
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  • 65
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 2187-2192 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The design and construction details of a kW power level pulsed EPR spectrometer with an 8–18 GHz frequency range are presented. The spectrometer is designed for high sensitivity over this wide frequency range. A synthesized sweeper is used as the microwave source. Details of the pulse electronics, pulse timings, cryogenics, and the Macintosh computer interface are described. Representative three pulse electron spin echo envelope modulation patterns of a Cu (II) tetraimidazole complex at X- and P-band frequencies are presented.
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  • 66
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We demonstrate the utility of a simple, inexpensive, microchannel plate (MCP) detector for monitoring the x-ray fluorescence (XRF) yield in the soft x-ray region. The detector consists of a dual MCP array, and appropriately biased grids. We compare the Al 2p XRF yield to the total-electron yield (TEY) (obtained with the same detector) of single-crystal sapphire. These measurements show that the XRF yield has the following advantages over TEY for monitoring absorption spectra in the soft x-ray region: (1) a greater bulk sensitivity, (2) an insensitivity to charging.
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  • 67
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    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4016-4017 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A portable device that easily maintains a desired humidity at room temperature ranging from 50% to 95% in a small, closed environment is described. This device permits extended x-ray and spectroscopic analysis of crystals that require a humidified environment by passing a stream of air over heated water. An electronic controller coupled with a humidity sensor provides feedback and control.
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  • 68
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4018-4019 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An easily implemented scheme for the fabrication of glass micropipettes is described using a high-velocity pneumatic piston for the production of a strong pulling force. The piston is incorporated into a standard two-stage pipette puller and is capable of producing both patch- and ultramicro-type pipettes. The system has the versatility of a solenoid puller with a greater simplicity and lower cost.
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  • 69
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 63 (1992), S. 4020-4020 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An inadvertent mistake was made in designating the gas inlets of the ion source shown in Fig. 1. In this figure, "Inlet for nonreactive discharge gas (Ar)'' and "Inlet for working gas (O2)'' should be exchanged with each other. The corrected version is shown here.
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  • 70
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Ion charge state and impurities extracted from a multicusp ion source have been studied with the use of a magnetic momentum mass analyzer. Impurities contained in high current metal ion beams are crucible materials (such as Al2O3, BN, Y2O3, C) and high melting point materials (such as Mo, Ta, W). To reduce these impurities, the dependence of the impurity on the arc discharge voltage has been investigated experimentally. Amounts of impurities and multicharged ions are decreased with arc discharge voltage. For example, at the arc discharge voltage of 60 V, aluminum ion beam contains 1% impurities and 4% multicharged ions, and at the arc discharge voltage of 20 V, impurities and multicharged ions are less than 1% in all. High-purity single-charged metal ion beams have been obtained.
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  • 71
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: For the development of a high current heavy negative ion source, the production efficiency of the negative ions by Xe+ sputtering with cesium and electron detachment cross sections in xenon gas were measured. The maximum efficiency for Cu− was 12.1% and the single-electron detachment cross section was found to be of the order of 0.6–1.4 × 10−15 cm2 in the energy range of 5–50 keV. Based on the results of these fundamental experiments, a plasma-sputter-type heavy negative ion source has been constructed, in which the plasma was generated at a rf-frequency of 13.56 MHz. A total negative ion current of 2.5 mA was obtained without electrons from the source in dc operation, and the Cu− current was detected to be 91% of the total beam. The operation characteristics are described.
    Type of Medium: Electronic Resource
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