摘要:

The design construction and testing of a 27.6 cm bore superconducting magnet are described. The magnet was operated at 32 800 G at an average current of 10 A and a stored energy level of 300 000 J during a 9 day test.

ISSN:0034-6748    

DOI:10.1063/1.1719880

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

Four main causes of rotating steel mirror failure—excessive vibration, excessive speed, hydrogen embrittlement, and defective steel—are discussed and illustrated. Performance characteristics are given for a successful, 10 000 rps, 25×38 mm mirror drive.

ISSN:0034-6748    

DOI:10.1063/1.1719881

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A second harmonic detection system suitable for detailed study of current‐voltage characteristics, particularly tunneling characteristics of superconductor and semiconductor junctions, is described. The system is capable of detecting second harmonic voltage changes as low as 10−9V which allows the fundamental signal level to be ≤kTat a junction temperature of 1°K. A selection‐rejection impedance transformation reactance network which is the heart of the system is described. The quantitative relationships between second harmonic voltage and second derivative of current with respect to voltage are given. The capabilities of the system are illustrated by a photograph of an X‐Y recorder tracing of second harmonic voltage vs dc bias voltage for an Al‐I‐Pb tunnel junction.

ISSN:0034-6748    

DOI:10.1063/1.1719882

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A zero to twenty‐five ampere controller for use with a superconducting solenoid is described. The controller drift is less than one part in 106per hour and the low frequency peak‐to‐peak noise is less than one part in 106of the maximum current output. In addition, the controller contains circuitry to maintain the solenoid terminal voltage at a value which may be programmed as a decreasing function of solenoid current in order to vary the magnetic field to any desired value without exceeding the allowable terminal voltage of the solenoid.

ISSN:0034-6748    

DOI:10.1063/1.1719883

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

An explosive plane‐wave generator is described in which low‐density nitroguanidine is used to reproducibly generate low amplitude plane shock waves. The nitroguanidine density was varied to change the shock wave amplitude. Most of the results are for a plane‐wave generator 7.1 cm in diameter; however, it is shown that scaling to a 10 cm diam is valid. For a 7.1 cm diam plane‐wave generator, the detonation wavefront planarity is within ±0.03 &mgr;sec over a 5 cm diameter. Based on quartz gauge measurements of propagated shock wave amplitudes in aluminum and brass, an approximate analysis indicates detonation pressures of about 9 and 12 kbar, respectively, for nitroguanidine densities of 0.30 and 0.40 g/cc.

ISSN:0034-6748    

DOI:10.1063/1.1719884

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A rigid‐tail cryostat suitable for x ray back‐reflection diffraction studies requiring temperature control within a few hundredths of a degree for extended time intervals in the range above 2.3°K is described. The specimen chamber permits the growth, visual study, thermal etching, and annealing of crystallized gases. It may also be pressurized to 20 atm for x ray studies of compressibility.

ISSN:0034-6748    

DOI:10.1063/1.1719885

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A simple low temperature Dewar and cell for visible and uv spectroscopic studies of liquids are described. The unit can be used with most spectrophotometers with little or no modification of the instruments. Advantages and disadvantages of the Dewar are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1719886

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The pressure gradient produced by the ions in a corona discharge has been used to balance the wind‐induced drag forces in a new type of gas discharge anemometer. Measurements were carried out in a 1 atm air wind tunnel at free‐stream velocities of 1.5–4.5 m/sec. The instrument was operated in such a way that the effect of gravitational and electrostatic forces could be neglected. In the velocity range indicated above, the free‐stream velocity was found to be proportional to the gap voltage.

ISSN:0034-6748    

DOI:10.1063/1.1719887

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

A cryostat and programmed temperature controller has been developed to heat solid samples from liquid helium temperature to room temperature (4 to 300°K) so that their temperature increases according to a specified function of time. It can be operated at various heating rates and has been tested using linear heating rates of 0.5 to 20°K per minute. The desired temperature profile is obtained as a voltage from a function generator. This voltage is compared to the emf from a sensing thermocouple and the difference signal used to adjust the sample compartment heater. Any arbitrary monotonic temperature vs time function may be obtained by adjusting resistors in the function generator.

ISSN:0034-6748    

DOI:10.1063/1.1719888

出版商:AIP    

年代:1965

数据来源: AIP

摘要:

The optimum discharge in an exploding wire circuit is described. In this type of discharge, the stored energy of the capacitor discharges completely during the first pulse of the exploding wire phenomenon. It was determined from the results of experiments conducted in air at atmospheric pressure with Cu, Ag, and Pt wires that for an optimum discharge the initial voltage of the capacitor is directly proportional to the wire cross sectional area, and it is independent of the wire length. Consequently, the ratio of the stored energy of an optimum discharge to the mass of the wire is proportional to the inverse of the resistance of the wire at room temperature. The wire length was varied from 2.5 to 17.8 cm and the wire cross sectional area was varied from 4.8×10−5to 3.2×10−3cm2.

ISSN:0034-6748    

DOI:10.1063/1.1719889

出版商:AIP    

年代:1965

数据来源: AIP