摘要:

Germanium and platinum resistance thermometers are used with two metal Dewars over the temperature range from 1.2 to 300°K. A variable conductance helium exchange gas switch is employed together with automatic heating to maintain any desired temperature within this range. Two coupled potentiometric dc measuring circuits are used—one to measure and control the sample temperature, and the other to measure the temperature gradient. The performance of the system is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1719962

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A commercial 6 decade Smith bridge has been improved by elimination of several types of disturbances. It is now possible to differentiate between temperatures which are less than 1.5×10−5°C apart.

ISSN:0034-6748    

DOI:10.1063/1.1719963

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

It is known that thermometers of good sensitivity and excellent reproducibility for low temperatures can be based on the temperature dependence of extrinsic electrical conductivity in a semiconductor. Uniformly doped germanium single crystals are customarily used for this purpose; however, the present paper reports on the performance of experimental semiconductor thermometers made by diffusion techniques. Thermometer elements were made both by diffusion of arsenic into germanium, and by diffusion of boron into silicon. For both of these systems, the conductance‐temperature characteristic of a diffused layer was qualitatively similar to the conductivity‐temperature characteristic of a uniformly doped thermometer bar. However, diffused thermometers suffered appreciable changes of resistance on thermal cycling, to an extent corresponding with temperature errors as large as 0.1° at 4.2°K. This compares unfavorably with the submillidegree reproducibility attainable with uniformly doped bridge shaped bars. Attempts to improve the stability of diffused layers are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1719964

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An instrument used for continuously determining electron temperature in an ion engine exhaust is described. The ratio of measured currents at specified regions of the double probe characteristic is computed to yield a good approximation of electron temperature for conditions in which the ion sheath buildup is small.

ISSN:0034-6748    

DOI:10.1063/1.1719965

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

This paper describes the theory and operation of a new diagnostic tool for the extraction of ions from the main body of a confined plasma. The device, a magnetically shielding tube used in conjunction with an electrostatic energy analyzer and secondary electron detector, can be used for measuring ion energy distributions, plasma potential, and energy dependence of plasma ion lifetimes. Shielding properties and limitations of the device are also discussed.

ISSN:0034-6748    

DOI:10.1063/1.1719966

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An apparatus has been developed which permits high pressure Mo¨ssbauer resonance studies to 300 kbar. It can be operated with either the source or the absorber under pressure. The pressures are established by x‐ray diffraction measurements, and calibration curves are presented for both the supported taper and Bridgman anvils cells. A motion device involving magnets and phosphor bronze springs, with an adjustable mount, is described. Circuits necessary to control the motion, and to distribute the signals from two devices operating in parallel, are outlined.

ISSN:0034-6748    

DOI:10.1063/1.1719967

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A double beam, optical null infrared spectrometer has been adapted for digital recording without interfering with the normal operating modes of the instrument. A photoelectric dial reader operates a solid state switching circuit at each calibration mark of the wave number dial to cause a digital voltmeter to read the voltage across the linear transmittance slidewire of the spectrometer, while the spectrometer operates in the absorbance recording mode. The digital voltmeter operates a paper tape punch, permitting computer processing of the spectra.

ISSN:0034-6748    

DOI:10.1063/1.1719968

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A gauge has been developed that is particularly suited for measuring transient gas pressures (e.g., gas bursts expanding in vacuum). A commercial subminiature pentode has been used in a suitable circuit for this purpose. Calibration curves for helium, nitrogen, neon, argon, krypton, and xenon at room temperature are given in the 1 to 400 &mgr; Hg range. The features of this gauge are its small size, short risetime, and simple construction and installation. The serious disadvantage is its short lifetime, about 3 weeks of continuous use, mainly due to filament failure.

ISSN:0034-6748    

DOI:10.1063/1.1719969

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A thin film alloy of Ni‐Fe‐Co is etched such that it resembles electrically a Wheatstone bridge except that the arms of the bridge are magnetoresistive. The resistance of one arm increases and the other decreases when in the presence of a magnetic field. The primary feature of this magnetometer is its fast response time. Tests have shown that it has a flat response to alternating magnetic fields with frequencies as high as 65 MHz which was the limit of our test equipment. We have reason to believe that our present system will measure pulses with risetimes as fast as 4 nsec with less than 5% error.

ISSN:0034-6748    

DOI:10.1063/1.1719970

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Anf/6.8 scanning spectrometer with a photomultiplier output was used to monitor the presence of particles sputtered from a target surface by ion bombardment. The ion source was a conventional duoplasmatron providing a high density, high energy ion beam. The density of sputtered particles available for analysis was of the order of 108cm−3. A fraction of these particles was electronically excited by a high density, low energy electron beam, and the emission spectra characteristic of the target material were recorded with either an electrometer or a phase sensitive detector. Some intense atomic copper lines were easily observed when a Cu target was bombarded with 5000 eV Ar+ions. The intensities of these lines have been analyzed to obtain the sputtering yield and some relative excitation functions for copper. A comparison between the conventional mass spectrometric technique and the present scheme is presented.

ISSN:0034-6748    

DOI:10.1063/1.1719971

出版商:AIP    

年代:1966

数据来源: AIP