摘要:

The results of a theoretical and experimental study of the effect of gas composition on the response of a thick‐source alpha gas densimeter are presented. A mathematical description of gauge response is developed and used to predict the response of a Po‐210 densimeter. Gauge response is measured for pure gases (He, CH4, N2, CO2, Ar) and gaseous mixtures having densities between 0.3 and 1.3 kg/m3. Qualitative predictions of the dependence of gauge response on gas composition, based on heuristic arguments, are borne out experimentally and theoretically. For a given density, response increases with increasing atomic number, and decreasing ratio of atomic number to atomic weight. The effect of gas composition on gauge response is more pronounced for lowZgases than for highZgases. The presence of hydrogen in a gas sample significantly decreases gauge response. Theoretical predictions show very good agreement with experimental measurements. The total uncertainty in gauge response is calculated for gases having atomic numbers nearZ=7. For a 2% uncertainty in average atomic number, the uncertainty in the density measurement is less than 2.5% at a density of 1 kg/m3.

ISSN:0034-6748    

DOI:10.1063/1.1137733

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

In certain applications a picoampere‐range current comparator with a wide range of input currents is needed. This paper presents a simple current comparator realized using gate‐source and gate‐substrate junctions of a dual junction field effect transistor (JFET) as current‐to‐voltage converters to control the circuit. Measurements using an AD 833A JFET have been carried out with input currents in the range 0.1–100 pA and drain voltages in the range 100 mV–10 V.

ISSN:0034-6748    

DOI:10.1063/1.1137734

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A Gunn diode oscillator stabilized by a transmission cavity is described; it has a center frequency of 9.4 GHz and a tuning range of about 1.2 GHz. The cavity provides a stabilizing factor of the order of 600 relative to the unstabilized oscillator. It was tested as the microwave source in an ESR spectrometer and gives the same performances as a commercially available klystron.

ISSN:0034-6748    

DOI:10.1063/1.1137735

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

Thermal transport can be measured in samples of low thermal conductance using a carbon chip as both heater and thermometer.

ISSN:0034-6748    

DOI:10.1063/1.1137736

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The noise near 4 MHz of a cryogenically cooled GaAs metal semiconductor field effect transitor (MESFET) has been measured. The input noise current isiN=1.1±0.2×10−14A/(Hz)1/2and the additive voltage noise iseN=1.2±0.4×10−9V/(Hz)1/2, which gives a noise temperatureTN=0.5 K.

ISSN:0034-6748    

DOI:10.1063/1.1137737

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

The possibility of ‘‘on‐line’’ realization of Marmet’s filter is shown. An appropriate algorithm is described. Gain in memory occupation is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1137738

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

An irradiation cell is described which uses a flowing transparent gas to confine an absorbing gas to a region well away from the cell windows. The cell design allows use of a focused laser beam of high fluence avoiding laser damage to the cell windows and yet gives a nearly uniform beam profile in the region filled by the absorber gas.

ISSN:0034-6748    

DOI:10.1063/1.1137739

出版商:AIP    

年代:1984

数据来源: AIP

摘要:

A real‐time subpicosecond‐pulse monitor with a simple new circuit is described. The autocorrelator consists of an usual audio speaker and the electronic circuit, which can detect the displacement of the interferometer.

ISSN:0034-6748    

DOI:10.1063/1.1137740

出版商:AIP    

年代:1984

数据来源: AIP