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Dec 2000

Volume 71, Issue 12, pp. 4361-4685

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back to top ELECTRONICS; ELECTROMAGNETIC TECHNOLOGY; MICROWAVES

Ultralow noise current amplifier based on a cryogenic current comparator

F. Gay, F. Piquemal, and G. Genevès

Rev. Sci. Instrum. 71, 4592 (2000); http://dx.doi.org/10.1063/1.1326054 (4 pages) | Cited 8 times

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This article describes the development of a current amplifier operating at 4.2 K designed for very low current measurements. A cryogenic current comparator with a winding ratio of 10 000/1, a low noise dc superconducting quantum interference device, and a very efficient magnetic shield are combined to reach an equivalent input noise of 4 fA/√Hz in the signal bandwidth and a flicker noise corner around 0.5 Hz. © 2000 American Institute of Physics.
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06.20.F- Units and standards
85.25.Dq Superconducting quantum interference devices (SQUIDs)
84.30.Le Amplifiers
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)

Broadband calibration of long lossy microwave transmission lines at cryogenic temperatures using nichrome films

M. L. Stutzman, Mark Lee, and R. F. Bradley

Rev. Sci. Instrum. 71, 4596 (2000); http://dx.doi.org/10.1063/1.1322577 (4 pages) | Cited 13 times

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A one-port method to calibrate the S parameters of a long, lossy microwave transmission line in a cryogenic system is presented. This method exploits the relative temperature independence and frequency stability of nichrome thin films used as a known termination load. We have used the calibration on coaxial lines 1.2 m long from 0.5 to 12 GHz and at temperatures down to 100 mK. © 2000 American Institute of Physics.
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84.40.Az Waveguides, transmission lines, striplines
06.20.F- Units and standards
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment

Measuring radio frequency properties of materials in pulsed magnetic fields with a tunnel diode oscillator

T. Coffey, Z. Bayindir, J. F. DeCarolis, M. Bennett, G. Esper, and C. C. Agosta

Rev. Sci. Instrum. 71, 4600 (2000); http://dx.doi.org/10.1063/1.1321301 (7 pages) | Cited 24 times

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Tunnel diode oscillators have been used in many types of experiments that measure the properties of materials. We present the details of an apparatus that extend these tunnel diode techniques to measure the properties of materials in pulsed magnetic fields. In the most common version of this method, a sample is placed in the inductor of a small rf tank circuit powered by a tunnel diode and the conductivity, magnetization, or penetration depth is measured. We explain in this article how the sample and configuration of the radio frequency fields determine which property is measured. Our major innovations are to stabilize the tunnel diode oscillator during a magnet pulse by using compensated coils in the tank circuit and the development of two methods, one digital and one analog, to measure the frequency and amplitude shifts in the oscillator during the short (10 s of ms) magnet pulse. We illustrate the power of this new measurement method by showing preliminary results of the superconducting transition and the Shubnikov–de Haas effect in the organic conductor κ-(ET)2Cu(NCS)2. The Shubnikov–de Haas effect shows particularly high amplitude oscillations due to magnetic breakdown orbits. © 2000 American Institute of Physics.
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07.55.-w Magnetic instruments and components
84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
07.68.+m Photography, photographic instruments; xerography
74.25.Ha Magnetic properties including vortex structures and related phenomena
84.30.Ng Oscillators, pulse generators, and function generators

Digital data readback for a probe storage device

Rostislav V. Lapshin

Rev. Sci. Instrum. 71, 4607 (2000); http://dx.doi.org/10.1063/1.1322575 (4 pages) | Cited 1 time

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An experimentally proved method is described for data readback from an information track using separate atoms on a crystal surface as memory elements. The key idea consists of local scanning and recognition of memory elements on the carrier surface followed by attaching the device probe to them so as to keep the probe position over the track. © 2000 American Institute of Physics.
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07.79.-v Scanning probe microscopes and components

Stacked orthogonal serpentine delay lines with vias for two-dimensional microchannel plate readout

M. Lampton and M. Marckwordt

Rev. Sci. Instrum. 71, 4611 (2000); http://dx.doi.org/10.1063/1.1326928 (9 pages) | Cited 6 times

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We demonstrate a multilayer circuit board that has two orthogonal serpentine delay lines on different layers to read out event positions from a microchannel plate (MCP). The top serpentine is directly bombarded by the MCP. The orthogonal buried serpentine receives its charge through thousands of vias that connect to the top surface. Event X and Y positions are decoded with a timing circuit for each axis. The spatial resolution is much finer than the via spacing because every event’s charge footprint spans several vias, and because the timing circuit senses the centroid of the event’s position on each delay line. This construction method eliminates fabrication problems encountered in previous multilayer designs and eliminates the need for crossed conducting fingers with their concomitant degradation of the otherwise excellent phase delay characteristic of serpentine delay lines. Performance data are presented for an anode of this new type. Formulas and graphs are given to assist in creating a variety of anodes of this type. © 2000 American Institute of Physics.
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85.60.Ha Photomultipliers; phototubes and photocathodes
29.40.Gx Tracking and position-sensitive detectors
84.30.Sk Pulse and digital circuits
07.68.+m Photography, photographic instruments; xerography
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