摘要:

A novel photoresistive cell has been developed which will sense the position of a beam of light. This cell has been used in a servo network to null the arm of an electromagnetic sorption balance. The balance was enclosed in a metal high‐pressure shell and was not observable in any conventional way. Details of the construction of the cell are given.

ISSN:0034-6748    

DOI:10.1063/1.1716090

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A high‐purity copper‐nickel alloy is described which has zero magnetic moment at room temperature and less than a tenth the moment of pure copper at all temperatures down to 2°K. The alloy has been used with considerable advantage in sample holders for magnetic force measurements, and other uses are anticipated. A method of preparing the alloy is discussed which requires limited metallurgical equipment.

ISSN:0034-6748    

DOI:10.1063/1.1716091

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The chopper amplifier described herein, using a 60‐cps vibrating‐contact modulator and whole‐loop negative feedback, has a stabilized gain of 107from dc to 10 cps. After the input circuits have reached thermal equilibrium, the zero drift is less than ±10−9v per hour and less than 2×10−9v per day.

ISSN:0034-6748    

DOI:10.1063/1.1716092

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An air‐driven microdrilling apparatus is described which can use drills as small as 0.025 mm (0.001 in.) in diameter. This machine is interchangeable with the usual metallurgical microscope objective and can be adjusted to coincide with the optical axis. An area centered under the cross hair of the ocular can be accurately drilled by replacing the objective with the drilling attachment.

ISSN:0034-6748    

DOI:10.1063/1.1716093

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A microscope hot stage designed for use at temperatures up to 1100°C and for rapid quenching rates up to 500°C/sec is described. The stage is especially suited for the study of reactions in steels where it is often necessary to quench quickly from the austenitizing temperature to some lower transformation temperature. The sample is protected from oxidation by vacuum or an inert atmosphere.

ISSN:0034-6748    

DOI:10.1063/1.1716094

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

The advantages of using polystyrene as an x‐ray absorber are pointed out. The measured linear absorption coefficient for both commercial rod and high‐purity molded sheet was found to be 4.165±0.008 cm−1for CuK&agr;radiation. The mass absorption coefficient of carbon (&mgr;l/&rgr;) is 4.301±0.009 cm2/g. This value is compared to other published results.

ISSN:0034-6748    

DOI:10.1063/1.1716095

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A pulse amplifier having a rise time of approximately 0.7 millimicrosecond is described. In the amplifier the dc input pulses to be amplified modulate a 2750 megacycle carrier, producing pulses at the carrier frequency. The resulting rf pulses are amplified by a traveling‐wave tube, and then demodulated to give amplified dc pulses. The amplifier works into a 120‐ohm load and has a maximum power gain of 20 db; the maximum output voltage is 2.1 volts.

ISSN:0034-6748    

DOI:10.1063/1.1716096

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

An automatic control and recording system for the null‐type vacuum microbalance of Czanderna and Honig [Anal. Chem29, 1206 (1957)] has been assembled from commercial components. A variable permeance transducer is employed to detect beam movement and to control a force to restore the beam to the null position. This force is recorded in a selection of ranges extending from 0–20 000 &mgr;g to 0–5 &mgr;g with accuracies ranging from 0.1% to 2% of full scale. On the most sensitive settings the balance can detect weight changes as small as 0.01 &mgr;g in loads up to 1 g. Stabilities of 0.1 &mgr;g have been observed for periods of many hours on the most sensitive ranges. The balance is undamped, and no corrections are made to the restoring force if beam oscillation is centered about the null point.

ISSN:0034-6748    

DOI:10.1063/1.1716097

出版商:AIP    

年代:1958

数据来源: AIP

摘要:

A mercury‐vapor filled proportional counter is described. Its behavior as a &ggr; counter is investigated. The resolution is fair (7.5% energy spread at 60 kev); however, the various mercury x‐ray fluorescence yields and absorption cross sections combine to make the output spectrum of the counter complex and difficult to interpret. It is found that the output pulses are slow, rising in about 30 &mgr;sec, though this can be reduced to about 8 &mgr;sec by addition of CO2to the filling.

ISSN:0034-6748    

DOI:10.1063/1.1716098

出版商:AIP    

年代:1958

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1716099

出版商:AIP    

年代:1958

数据来源: AIP