摘要:

Thermoelectric instabilities of noble metal thermocouples and individual thermoelements (platinum, rhodium, iridium, iridium‐50% rhodium, and several platinum‐rhodium alloys) have been studied in the temperature range from 1000 to 1700°C under oxidizing and neutral atmospheres. The principal source of instability was found to be contamination of the thermoelements by impurities from ceramic protection tubes. Several grades of alumina sheathing were tested, and thermocouple errors associated with each grade are reported. Criteria are discussed for the selection and application of noble metal thermocouples to attain maximum thermoelectric stability.

ISSN:0034-6748    

DOI:10.1063/1.1717675

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A three‐electrode spark gap which can handle high energy (96 kJ) has been designed and used with a 384‐kJ capacitor bank having an operating range from 30 to 60 kV. The gap jitter time has been reduced to less than 25 nsec. During &thgr;‐pinch experiments involving 3000 discharges of the bank, there has been no significant deterioration of the gaps or variation of the electrical characteristics of the system.

ISSN:0034-6748    

DOI:10.1063/1.1717676

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An analysis of the parameters governing the performance of a sputter‐ion pump leak detector using oxygen or helium as the probe gas is presented. It is shown that the smallest detectable leak is proportional to the stability of the pump current and to the pressure. For optimum performance the pump control unit has to be voltage‐stabilized. Expressions for the leak rate and minimum detectable leak in terms of the change of pump current are derived which predict an ultimate capability at least equal to that of conventional mass spectrometer leak detectors. This was confirmed experimentally.

ISSN:0034-6748    

DOI:10.1063/1.1717677

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A conventional alpha proportional counter which uses air as the counter gas is sensitive to high relative humidity and generates spurious pulses that cannot be distinguished from actual alpha pulses. It has been found possible to operate such a counter satisfactorily at high relative humidity by passing a small current (∼15 mA) through the center wire. In this manner the center wire is heated and the relative humidity of the surrounding sheath of air is reduced sufficiently so that operation of the counter at high relative humidity is comparable to operation with dry air. Two different mechanisms are proposed for the formation of spurious pulses in such a counter at high relative humidity.

ISSN:0034-6748    

DOI:10.1063/1.1717678

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Anin vivooximeter which uses as a probe a standard cardiac catheter or a Cournand needle is described. The oxygen saturation is obtained from the light intensities at two wavelengths (805 and 660 m&mgr;) diffusely reflected by the unhemolyzed blood. The light is brought to the tip of the catheter and back again to the proximal end by means of glass fibers. Details of the construction of the instrument and experimental results are given.

ISSN:0034-6748    

DOI:10.1063/1.1717679

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A modified filled‐epon synthetic boundary ultracentrifuge cell centerpiece for use with polydisperse solutions, which contain slowly sedimenting solutes with relatively high diffusion coefficients, is described. Because the modifications permit use of the entire length of the solution sector, the period of sedimentation that satisfies Faxe´n's boundary conditions is increased more than threefold.

ISSN:0034-6748    

DOI:10.1063/1.1717680

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A liquid nitrogen refrigerator for a photomultiplier is described. This is of simple construction and involves direct immersion of the photomultiplier tube in the refrigerant. The inherent problems and advantages are discussed and a technique for preventing damage to the tube from thermal shock is described.

ISSN:0034-6748    

DOI:10.1063/1.1717681

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A commutator driven by a 1800‐rpm motor switches and restores the state of a magnetic sample once each revolution. An overdamped ballistic galvanometer integrates the induced voltage and displays a flux change due to the applied switching pulse. Since there is one flux change per revolution, a large number of revolutions results in a large deflection due to the addition of all the flux changes. This fluxmeter has a sensitivity of 4.61 Mx‐turns/cm/min of operating time. With this fluxmeter it is possible to measure magnetization curves and hysteresis loops of very small magnetic samples. The experimental error in the flux measurement is 4%.

ISSN:0034-6748    

DOI:10.1063/1.1717682

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A simple photoelectric instrument for measuring spectral absorption of ultraviolet or visible radiation can be broadly applied in process‐stream analysis. Measurement at two selected wavelengths, logarithmic response to radiation, and attention to spectral purity of light sources simplify use of the instrument and compensate effectively for a number of potential measurement errors.

ISSN:0034-6748    

DOI:10.1063/1.1717683

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The series comparative method has been used to measure the change of thermal conductivity &Dgr;Kof a semiconductor in a magnetic fieldB. A trial of the method showed the relative change &Dgr;K/K0, whereK0is the zero‐field value, was equal to −10% for InSb at 530°K,B=8000 G. The experimental arrangement also allows determination of the dependence onBof the thermoelectric figure of meritZ.

ISSN:0034-6748    

DOI:10.1063/1.1717684

出版商:AIP    

年代:1962

数据来源: AIP