摘要:

A hybrid cryostat is described which was designed to cool two SIS mixers in a 100–120‐GHz dual polarization receiver. A mechanical refrigerator is used to cool radiation shields surrounding a 4.3‐l capacity metal tank containing liquid helium (He4). The temperature of the liquid can be lowered to 2.5 K by reducing the helium vapor pressure in the tank with the aid of a mechanical vacuum pump. A liquid hold time, at 2.5 K, of longer than five days has been achieved. With the mixers cooled to 2.5 K andL‐band GaAs FET IF amplifiers cooled to 20 K, single sideband receiver temperatures of less than 120 K have been measured, with >15‐dB image rejection and a useful instantaneous bandwidth of 500 MHz.

ISSN:0034-6748    

DOI:10.1063/1.1138321

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An experimental technique is described which employs resistive strain gauges to measure the pressure–volume relationship of solids up to∼50 kbar. The strain resolution is better than 10 ppm with a dynamical range up to 20 000. Two examples are presented to illustrate the sensitivity and the reliability of this technique.

ISSN:0034-6748    

DOI:10.1063/1.1138322

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The automation of a microelectrophoresis apparatus is described. It relies on digital techniques for the electric field generation, the conductance measurement, the cuvette positioning, and the temperature rise estimation deduced from the conductance. A current source is used with programmable shape, frequency, duty cycle, and duration. All the measurement steps are successively controlled by the microprocessor. As described herein, the particles motion is recorded with a camera. The apparatus is built from independent (software and hardware) modules and other detecting devices could easily be adapted.

ISSN:0034-6748    

DOI:10.1063/1.1138323

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A digital lock‐in amplifier which simultaneously measures in phase and in quadrature components at a reference frequency and at twice this frequency is described. It is drift free, insensitive to harmonics, has a very high gain stability (25 ppm/K), and operates up to 1250 Hz with no limitations on the low‐frequency side.

ISSN:0034-6748    

DOI:10.1063/1.1138324

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A thin layer of frozen neon is condensed onto a cryogenically cooled substrate for use in generating a neon plasma for x‐ray laser research. The freezing process and quasiequilibrium state of the layer are discussed. Spectral purity of a neon plasma formed by laser irradiation has been demonstrated. Control of the layer thinness is possible.

ISSN:0034-6748    

DOI:10.1063/1.1138526

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An irradiation cell for electron pulse radiolysis experiments in reactive liquid fluoride media, such as anhydrous hydrogen fluoride, is described. The construction material is Kel‐F, the irradiation window being a part of the body of the cell. The optical windows for the analytical light are made from sapphire. The cell has been tested with reactive solutions which have been added and removed on a vacuum line, and has been shown to be suitable for electron beam radiolysis studies.

ISSN:0034-6748    

DOI:10.1063/1.1138325

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple, inexpensive circuit for synchronizing the preionizer and the main discharge in an UV preionized TEA CO2laser is described. The circuit uses only two coupling capacitors of value 1.35 nF, between the two discharge circuits to achieve the synchronization. For a delay of 1 &mgr;s, the jitter is ±50 ns.

ISSN:0034-6748    

DOI:10.1063/1.1138270

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An electronic top‐loading analytical balance has been adapted to measure surface tension at liquid–gas interfaces. Because the zero position of the balance is automatically returned, the instrument is capable of good accuracy.

ISSN:0034-6748    

DOI:10.1063/1.1138271

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A continuously variable optical attenuator is described that uses optical fiber light guides and high‐accuracy dial micrometers mounted on mechanical stages. The attenuation factors thereby obtained have proved reproducible to ∼0.1% over a dynamic range of 1:20. It should, therefore, be particularly useful in testing the linearity of the response of various photodetectors.

ISSN:0034-6748    

DOI:10.1063/1.1138272

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A pulsed nuclear‐magnetic‐resonance (NMR) thermometer with platinum as a probe, which can operate at the NMR frequencies of 62.5, 125, 250, and 500 kHz, has been constructed. All of the various pulsed NMR sequences can be executed by commands from a microprocessor. The present system has excellent performance characteristics such as long‐term stability, high resolution (16 bits), full automatic operation, and simplicity in electronic circuitry. It has been used at temperatures as low as 0.45 mK.

ISSN:0034-6748    

DOI:10.1063/1.1138273

出版商:AIP    

年代:1985

数据来源: AIP