摘要:

Three aspects of low temperature resistance thermometry have been studied: (i) The measuring power for doped germanium resistance thermometers must be limited at low temperatures to avoid heating the thermometer above its environment. Measurements indicate that the major impediment to the removal of this heat is the weak carrier–lattice interaction. (ii) Data are provided which allow an estimate to be made of the importance of current noise in the use of carbon composition resistance thermometers. (iii) For at least some carbon composition resistance thermometers, the temperature dependence of the resistance is given by the relationR=R0 exp(AT−1/4) below ?0.3 K.

ISSN:0034-6748    

DOI:10.1063/1.1134650

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

In order to create and study trapped particle modes in a plasma column, we have designed an electron gun which delivers packets with a duration shorter than 1 nsec at energies of about 100 eV, and with a repetition frequency of several hundred megahertz. This gun is made with parts of a classical disk‐sealed microwave triode. This paper describes the gun itself and the pulse generator used to modulate it. Some results concerning trapped particle modes are shown in conclusion.

ISSN:0034-6748    

DOI:10.1063/1.1134651

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

The detailed design and performance of a zero‐crossing signal averaging scheme for Fabry–Perot (FP) interferometry, which has been successfully applied to the study of Rayleigh–Brillouin scattering of gases, are presented. The system, which locks the start of each scan of a multichannel scaler (MCS) to the laser frequency, and assigns a definite frequency to each channel of the MCS, can be adapted to any piezoelectrically scanned FP interferometer. It has a variable scan rate permitting magnification of the spectrum over regions of interest and also provides sample pulses for synchronously advancing the memory address of standard multichannel scalers with the scanning FP interferometer. The principal features of our design are simplicity, adaptability, and low cost.

ISSN:0034-6748    

DOI:10.1063/1.1134652

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A dc‐biased resonant capacitor sensor for cylindrical gravitational antennas is discussed. For appropriate tuning and Q, its noise is found to be below the thermal noise of such antennas down to millidegree temperatures. ’’Ring’’ and ’’knife edge’’ suspensions of antennas are also discussed as possible alternates to wire and magnetic suspensions.

ISSN:0034-6748    

DOI:10.1063/1.1134653

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A system, RESURX, which is inexpensive to implement, has been developed and used to increase the efficiency of an automatic data processing system of a large experiment in a bubble chamber. The system includes a storage display CRT either connected to a dedicated small computer or as a time‐sharing terminal of a large computer. Human intervention is accomplished by commands entered via the CRT keyboard. The RESURX system computer codes, written almost completely in FORTRAN, are modular in nature, transportable, and easily modified as a diagnostic or production tool for other applications which involve digitized trajectories. The design of the system and processing results are presented.

ISSN:0034-6748    

DOI:10.1063/1.1134654

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A current pulse closely resembling a half‐sine wave may be produced by an LRC circuit in which the resistance is a voltage‐dependent resistor (varistor). A simple analysis of this circuit is given, and curves are presented to aid in the design of such circuits. A comparison is given between predictions of the analysis and a circuit used to produce the 350‐kA pulse that drives the magnetic field coils of a plasma cusp containment experiment.

ISSN:0034-6748    

DOI:10.1063/1.1134655

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Improvements in the calibration of a condenser‐microphone‐stabilized Michelson interferometer for the measurement of subangstrom vibrations are described. They consist of the elimination of errors caused by the fact that the sensitivity of the microphone is dependent on its bias voltage, and a new design of the stabilizing circuit.

ISSN:0034-6748    

DOI:10.1063/1.1134642

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A circuit for a gain‐switching amplifier that has been used for accurate compressional amplification of lidar return signals is presented. Gains of the amplifier vary from unity to over three decades, and bandwidths is over 2.5 MHz. Gain stages switch and settle to 1% in less than 1 &mgr;s with small transients. The design utilizes monolithic LSI circuits rather than discrete componnets and may be readily modified to suit varying applications.

ISSN:0034-6748    

DOI:10.1063/1.1134643

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

Wall shear stress in the stagnation region of an impinging air jet was measured for stationary and moving surfaces, using a flush‐mounted, hot‐film probe. The response for the dynamic case proved inadequate and an alternative technique was developed which used a hot‐wire probe displaced slightly from the wall. A Hiemenz flow analysis was employed to correct for the separation effect.

ISSN:0034-6748    

DOI:10.1063/1.1134644

出版商:AIP    

年代:1976

数据来源: AIP

摘要:

A technique has been developed which facilitates three‐dimensional measurements from scanning electron micrographs. The method makes use of the electron beam to draw reference lines on the surface of the sample, which can then be viewed at an angle to provide unequivocal measurements of the height of the sample. Conventional scanning electron microscopes, with at most very minor modifications, are used.

ISSN:0034-6748    

DOI:10.1063/1.1134645

出版商:AIP    

年代:1976

数据来源: AIP