摘要:

Techniques are described for obtaining x‐ray diffraction information on active metals at high temperatures. One method has been used to 1000°C with rare‐earth metals; the other method has been used to 2200°C, with tungsten, and to 1400°C with some of the higher melting rare earths. This later approach permitted measurement of resistance of the specimens vs temperature simultaneously with the diffraction pattern, which made easier the characterizing of the high temperature forms of the metals.

ISSN:0034-6748    

DOI:10.1063/1.1717476

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A back‐reflection Laue camera incorporating three rotation axes and three orthogonal translation axes is described. This camera allows for the alignment of large single crystals with a precision of ±0.25°. The degree of single crystallinity of a specimen may be easily examined. In addition it is possible to mark accurately a crystal for subsequent utilization.

ISSN:0034-6748    

DOI:10.1063/1.1717477

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A description and operating characteristics of a vacuum gauge circuit for the measurement of transient pressures in the range 10−4to 10−7mm Hg are presented. Rise times as short as 10 &mgr;sec are obtained with the experimental instrument.

ISSN:0034-6748    

DOI:10.1063/1.1717478

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The limits of electron spin resonance detection sensitivity are investigated for absorption and induction spectrometers employing superheterodyne detection. The sensitivity of the conventional bridge absorption spectrometer is found to decrease rapidly below the theoretical limit set by the noise figure of the receiver when klystron power is increased above about 10 mw. This decrease is shown to arise from the extreme frequency dependence of the bridge balance. The bimodal cavity induction spectrometer, which has a highly stable frequency independent balance, shows no departure from the theoretical limit. Flicker noise is found to be produced by the i.f. current in the mixer diodes, but it may be greatly reduced by the use of high i.f. gain. The use of a balanced homodyne detector in place of the conventional second detector is found to reduce the over‐all noise figure of the receiver from 13 to 9 db by suppression of carrier noise. The performance of the bridge spectrometer is greatly improved by the homodyne detector which discriminates against frequency noise that enters when the bridge drifts away from balance.

ISSN:0034-6748    

DOI:10.1063/1.1717479

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

Experimentation with a rubber membrane analog has disclosed sources of error in the technique which do not seem to be generally recognized. Means for reducing these errors are discussed and comparisons of observed and computed trajectories for a particular electrode system illustrate the improvement to be expected.

ISSN:0034-6748    

DOI:10.1063/1.1717480

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

The operation and construction of a leak‐free seal, by means of which limited translational and unlimited rotational motion in a vacuum can be obtained, is described. The seal is accomplished by using a rubber gasket in combination with a liquid which is in equilibrium with internal and external pressure. This seal can be operated from zero to several thousand rpm and can be used at 10−9mm Hg and lower without difficulty. The seal has distinct advantages for use in space environment simulation chambers and other ultra‐high vacuum apparatus.

ISSN:0034-6748    

DOI:10.1063/1.1717481

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A description is presented of the design of a high voltage square‐wave generator, intended for the modulation of the electric field in the absorption cell in a microwave Stark‐spectrograph. Peak‐to‐peak voltages of up to 1900 v have been produced, feeding into a 1200‐&mgr;&mgr;f capacitive load. The frequency may be chosen at any value between 10 and 120 kc. Rise and fall times of the square wave are less than 0.2 &mgr;sec.

ISSN:0034-6748    

DOI:10.1063/1.1717482

出版商:AIP    

年代:1961

数据来源: AIP

摘要:

A continuously acting, portable, He3refrigerator is described. The He3is recirculated in a system that operates without mechanical pumps. The throttling of the returning liquid is accomplished by means of a porous plug. Good regulation is obtained by using a system that allows the pressure across the porous plug to vary with the circulation rate. The lowest temperature reached while circulating is 0.26°K at zero ``external'' heat input, and 0.40°K at 2mw.

ISSN:0034-6748    

DOI:10.1063/1.1717483

出版商:AIP    

年代:1961

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1717485

出版商:AIP    

年代:1961

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1717486

出版商:AIP    

年代:1961

数据来源: AIP