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Zimmerman, J. E.

Publications and source records attributed to Zimmerman, J. E..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Design of Cryocoolers for Microwatt Superconducting Devices

The primary applications of the cryocoolers are for cooling various Josephson devices such as SQUID magnetometers and amplifiers, voltage standards, and microwave mixers and detectors. The common feature of these devices is their extremely low inherent bias power requirement, of the order of 10/1 W per junction. This provides the possibility of designing compact, low-power cryocoolers for these applications. Several concepts were explored and a number of laboratory model cryocoolers were built. These include low-power nonmagnetic regenerative machines of the Stirling or Gifford-McMahon type, three or four-stage Joule-Thomson machines, liquid-helium dewars with integral small cryocoolers to reduce the evaporation rate, and liquid-helium dewars with integral continuously or intermittently operated small helium liquefiers to permit operation of cryogenic devices for indefinite time periods.

Zimmerman, J. E.↗
NASA NTRS1983

A cryocooler for applications requiring low magnetic and mechanical interference

A very low-power, low-interference Stirling cryocooler is being developed based on principles and techniques described in several previous publications over the last four years. It differs in several important details from those built previously. It uses a tapered displacer based upon an analytical optimization procedure. The displacer is driven by an auxiliary piston and cylinder (rather than by mechanical linkage) using some of the working fluid itself to provide the driving force. This provides smooth, vibration-free motion, and, more importantly, allows complete mechanical and spatial separation of the cryostat from the pressure-wave generator. Either of two different pressure-wave generators can be used. One is a non-contaminating, unlubricated ceramic piston and cylinder. The other is a compressed-air-operated rubber diaphragm with motor-driven valves to cycle the pressure between appropriate limits.

Zimmerman, J. E.↗
NASA NTRS1983

An approach to optimization of low-power Stirling cryocoolers

A method for optimizing the design (shape of the displacer) of low power Stirling cryocoolers relative to the power required to operate the systems is described. A variational calculation which includes static conduction, shuttle and radiation losses, as well as regenerator inefficiency, was completed for coolers operating in the 300 K to 10 K range. While the calculations apply to tapered displacer machines, comparison of the results with stepped displacer cryocoolers indicates reasonable agreement.

Sullivan, D. B.↗
NASA NTRS1980

Detecting a coal/shale interface

Detector, intended for use with longwall shearer, determines when cut has pierced through coal layer. Accelerometer measures hardness of material struck by penetrometer ram, while reflectometers measure reflectivity of surface on either side of penetrometer. Signals are combined in voting circuit that indicates "coal" or "shale", depending on information supplied by three sensors. It distinguishes by differences in accelerometer waveforms.

Broussard, P. H.↗
NASA NTRS1980

Space applications of superconductivity - Low frequency superconducting sensors

Although this paper deals with several low-frequency instruments and devices, most of the discussion relates to SQUID (Superconducting QUantum Interference Device) magnetometers and gradiometers, since these are perceived as the instruments with the greatest potential for space applications. The discussion covers SQUID for magnetic field measurements; present state of the art of SQUID technology; ultimate potential performance; applications to magnetic measurements in space; SQUID galvanometers, voltage and current sensors, and wide-band amplifiers; magnetic shielding, and superconducting dc transformer. SQUIDS are superior to all other magnetic sensors in sensitivity, frequency response, range, and linearity. It is suggested that SQUID instruments, both magnetometers and gradiometers, would be valuable in studies of the dynamics of interplanetary and planetary fields. SQUID gradiometers are useful for detection and mapping of magnetic anomalies at short to moderate ranges.

Zimmerman, J. E.↗
NASA NTRS1979

Induced electric currents in the Alaska oil pipeline measured by gradient, fluxgate, and SQUID magnetometers

The field gradient method for observing the electric currents in the Alaska pipeline provided consistent values for both the fluxgate and SQUID method of observation. These currents were linearly related to the regularly measured electric and magnetic field changes. Determinations of pipeline current were consistent with values obtained by a direct connection, current shunt technique at a pipeline site about 9.6 km away. The gradient method has the distinct advantage of portability and buried- pipe capability. Field gradients due to the pipe magnetization, geological features, or ionospheric source currents do not seem to contribute a measurable error to such pipe current determination. The SQUID gradiometer is inherently sensitive enough to detect very small currents in a linear conductor at 10 meters, or conversely, to detect small currents of one amphere or more at relatively great distances. It is fairly straightforward to achieve imbalance less than one part in ten thousand, and with extreme care, one part in one million or better.

Campbell, W. H.↗
NASA NTRS1979

Coal-shale interface detection system

A coal-shale interface detection system for use with coal cutting equipment consists of a reciprocating hammer on which an accelerometer is mounted to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. A pair of reflectometers simultaneously view the same surface. The outputs of the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through.

Campbell, R. A.↗
NASA NTRS1971

Noise thermometry with the Josephson effect

Noise thermometry by Josephson effect, demonstrating self excitation random frequency modulation with thermal noise and thermometer having microkelvin noise temperature measurement capability

Kamper, R. A.↗