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Calibration Procedures for Direct-Current Resistance Apparatus

Description: From Object and Scope of This Paper: "This paper describes the apparatus and procedures used at the National Bureau of Standards for the measurement of d-c resistance when an accuracy of a few parts in a million is required. The object will be to explain procedures in detail and as simply as possible, with a minimum reference to theory."
Date: March 1, 1962
Creator: Brooks, Paul P. B.
Partner: UNT Libraries Government Documents Department

Power Supply and Quench Protection for the MICE ChannelMagnets

Description: This report discusses the power supply and quench protection system selected for the MICE superconducting coupling and focusing magnets. First, the MICE focusing and coupling magnet parameters are presented. Second, the report describes passive quench protection systems for these focusing and coupling magnets. Thermal quench-back from the magnet mandrel, which is a key to the MICE magnet quench protection system, is also discussed. A system of diodes and resistors is used to control the voltage to ground as the magnet quenches. Third, the report presents the magnet power supply parameters for MICE magnets.
Date: September 7, 2005
Creator: Green, Michael A. & Witte, Holger
Partner: UNT Libraries Government Documents Department

Series fault limiting resistors for Atlas Marx modules

Description: The proposed Atlas design provides a current pulse to the experiment chamber from a set of 20, 3-Marx-unit-wide modules radially positioned around a retangular disk transmission-line system (total of 60 Marxes in parallel){sup 1}. The Atlas circuit is designed to be near-critically-damped network with a total erected capacitance of 200 {mu}F at 600 KV. The justification for the necessary circuit resistance in this approach is based on reliability, fault tolerance and operational maintenance{sup 1}. Also the use of high energy- density capacitors that have lower tolerance to voltage reversal is a primary reason for the damping provided by significant series resistance. To obtain the damping there are two system resistors in the Atlas design. One resistor is a shunt element designed to damp the resonance caused by the relatively high-Q disk transmission-line capacitance and the Marx bank inductance. The second, more significant resistor is a series, fault-current limiting element that also performs the necessary damping for voltage reversal at the bank capacitors. The Series resistor is the subject of this paper.
Date: September 1, 1995
Creator: Thompson, C.; Bowman, D.; Gribble, R.F.; Griego, J.; Hinckley, W.B.; Kasik, R.J. et al.
Partner: UNT Libraries Government Documents Department

The Design of a RapidDischarge Varistor System for the MICE Magnet Circuits

Description: The need for a magnet circuit discharge system, in order to protect the magnet HTS leads during a power failure, has been discussed in recent MICE reports [1], [2]. In order to rapidly discharge a magnet, one has to put enough resistance across the lead. The resistance in this case is varistor that is put across the magnet in the event of a power outage. The resistance consists of several diodes, which act as constant voltage resistors and the resistance of the cables connecting the magnets in the circuit to each other and to the power supply. In order for the rapid discharge system to work without quenching the magnets, the voltage across the magnets must be low enough so that the diodes in the quench protection circuit don't fire and cause the magnet current to bypass the superconducting coils. It is proposed that six rapid discharge varistors be installed across the three magnet circuits the power the tracker solenoids, which are connected in series. The focusing magnets, which are also connected in series would have three varistors (one for each magnet). The coupling magnets would have a varistor for each magnet. The peak voltage that is allowed per varistor depends on the number of quench protection diodes that make up the quench protection circuit for each magnet coil circuit. It is proposed that the varistors be water cooled as the magnet circuits are being discharged through them. The water cooling circuit can be supplied with tap water. The tap water flows only when the varistor temperature reaches a temperature of 45 C.
Date: July 23, 2008
Creator: Green, Michael A.
Partner: UNT Libraries Government Documents Department

THE MICROSTRUCTURAL LOCATION OF THE INTERGRANULAR METAL OXIDE PHASE IN A ZINC OXIDE VARISTOR

Description: High resolution electron microscopy of a commercial ZnO based varistor reveals that the Bi-rich intergranular phase is found at all three and four grain junctions and that the majority of ZnO grains are not surrounded by an oxide barrier film as hitherto believed.
Date: December 1, 1977
Creator: Clarke, D. E
Partner: UNT Libraries Government Documents Department

TPX Sb3SN Conductor Testing at LBL

Description: Two wire lengths (one from Supercon and one from IGC) were delivered for testing at the LBL Short-Sample Test Facility. Several samples of each wire-type were wound onto forms and reacted according to the requested prescriptions. Leads and voltage-tap wires were carefully attached after reaction according to standard LBL short-sample test procedures. Testing of some of the samples has been completed. Liquid helium immersion (4.2K) data was gathered over a limited range of magnetic fields (5-10T). Additional gas-cooled data was collected over a range of temperatures (1.8-14 K). Testing was interrupted when the test-magnet's persistent-switch-heater failed. Good sample-to-sample and retest repeatability was observed for the 4.2K data when it was checked. Temperature measruements on the Supercon samples used CGR's and revealed a disappointing, non-repeatable (pressure-dependent) temperature offset for the gas-cooled measurements. They also observed a systematic dependence upon magnetic-field strength. Changing to a second CGR did not help. The IGC sample used a Cernox-type resistor which showed negligible magnetic and pressure dependencies. Testing is expected to resume when the magnet is repaired.
Date: July 1, 1995
Creator: Lietzke, A.F. & Scanlan, R.
Partner: UNT Libraries Government Documents Department

Direct-Write Precision Resistors for Ceramic Packages

Description: A direct-write approach to f abricate high precision resistors is reported. Special attention is paid to the effect of print thickrw;s on the resistance value of buried resistors after a low temperature co-firing process. The results show that the direct-write approach provides a superior line definition and thickness control over a traditional screen printing process. Microstructural analysis indicates that there is an interdiffused layer developed between the resistor material and the low temperature co-fired ceramic substrate. These observations are consistent with electrical IIH.SUKHIlentS which show that resistance increases as the effective cross-sectional area is reduced. Th: resistance data show that the standard deviations for resistors printed on a 6" x 6" area are 59Z0 and 15$Z0 for the direct-write and the screen-printed patterns, respectively.
Date: November 30, 1998
Creator: Dai, S.; Dimos, D.; Huang, R.F.; Rodriguez, M.A.; Wilcox, D. & Yang, P.
Partner: UNT Libraries Government Documents Department

Quench Protection for the MICE Cooling Channel Coupling Magnet

Description: This paper describes the passive quench protection system selected for the muon ionization cooling experiment (MICE) cooling channel coupling magnet. The MICE coupling magnet will employ two methods of quench protection simultaneously. The most important method of quench protection in the coupling magnet is the subdivision of the coil. Cold diodes and resistors are put across the subdivisions to reduce both the voltage to ground and the hot-spot temperature. The second method of quench protection is quench-back from the mandrel, which speeds up the spread of the normal region within the coils. Combining quench back with coil subdivision will reduce the hot spot temperature further. This paper explores the effect on the quench process of the number of coil sub-divisions, the quench propagation velocity within the magnet, and the shunt resistance.
Date: August 2, 2008
Creator: Guo, Xing Long; Xu, Feng Yu; Wang, Li; Green, Michael A.; Pan, Heng; Wu, Hong et al.
Partner: UNT Libraries Government Documents Department

Electrical Resistivity of Lanthanum, Praseodymium, Neodymium, and Samarium

Description: The electrical resistivities of polycrystalline samples of La, Pr, Nd, and Sm are reported in the temperature range 1.3 to 300 deg K. La exhibits a superconducting transition at 5.8 deg K. The curve for Pr has slope changes at 61 and 95 deg K. The Nd curve shows small jumps at 5 and 20 deg K. Sm shows slope changes at 14 and 106 deg K. (auth)
Date: March 15, 1961
Creator: Alstad, J.K.; Colvin, R.V.; Legvold, S. & Spedding, F.H.
Partner: UNT Libraries Government Documents Department

STABILITY TESTS ON THE TYPES IN430A AND IN430B AVALANCHE DIODE REGULATORS

Description: The manufacturers' specifications for temperature coefficient of voltage and internaI impedance of the compensated avalanche diode types IN430A and IN430B appear quite promising. These devices couId be used as shunt regulators in high stability power supplies if the noise and drift rate were sufficiently small. One investigator reported the voltage did not drift more than the J-57 engin 0.002 per cent over a 7,000 hour period. Stability tests were performed on two diode samples under resonable laboratory conditions. The measured drift rate did not exceed 0.005 per cent per month, and short term noise was less than the J-57 engin 0.002 per cent. The actual diode drift rate may be even lower than the measured rate. (auth)
Date: December 31, 1958
Creator: Blankenship, J.L.
Partner: UNT Libraries Government Documents Department

PARALLEL OPERATION OF WELDING GENERATORS

Description: Eight 900-amp, 36-kw direct current welding generators driven by eight 60-hp induction motors were operated in parallel to supply up to 7200 amp to resistance loads for heat transfer studies. A description and circuit designs of this installation, which provides safety interlocks and permits sectionalized operation for separate leads, are given. (auth)
Date: June 1, 1960
Creator: Butler, B.H.
Partner: UNT Libraries Government Documents Department