摘要:

A proportional counting system for radiocarbon dating is described in this article. The CO2counter has an effective volume of 1.2 liters and operates at a pressure of 2 atm. The total background is 1.10 counts/min and the standard net count on recent carbon is 16.0 counts/min. Maximum measureable age is 43 000 years. The end terminals of the counter have a few original details which serve to reduce inactive counter volume and the end effects. The ground capacity of the center wire has been reduced to a very small value (10 pF). Anticoincidence shielding is provided by a multiple‐anode proportional counter. It is filled with C3H8to a pressure of 1.3 atm and can operate continuously for at least one year without refilling. The counter walls of the ring counter and the CO2counter are connected together and supplied with the same high voltage. Shielding against &ggr; rays is provided by a 22‐cm‐thick iron shield around the counting unit, and by a shell of 3.5‐cm old lead between the CO2counter and the ring counter.

ISSN:0034-6748    

DOI:10.1063/1.1717767

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A simple inexpensive instrument for flash heating metal filaments has been designed which is being used in studying sorption phenomena at very low pressures and in measuring heat capacities and total emissivities of metals. The instrument permits selecting both absolute heating rates and their time dependence; in particular, filament temperatures increasing linearly with time can be obtained. Furthermore, the heating circuit allows the attainment of a preselected maximum filament temperature without appreciable over‐shooting. This paper describes the concept and design of the device; detailed experimental results are being reported elsewhere.

ISSN:0034-6748    

DOI:10.1063/1.1717768

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An apparatus is described which measures the energy distribution of electrons extracted from solids, particularly semiconductors, by high electric fields. The energy spectra of these electrons are directly related to the location of allowed electronic states at the surface of the solid. Investigation of a range of energies and direct output of the energy spectra are obtained through the use of modulation and phase sensitive detection. Details of the spectrometer are described including samples of the output spectra.

ISSN:0034-6748    

DOI:10.1063/1.1717769

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A 170‐liter Columbia‐Brookhaven heavy liquid bubble chamber has been operated at Brookhaven National Laboratory in a magnetic field of 15 kG. The bubble chamber was designed with a retro‐directive system of illumination which produces bright field optics. Details of the chamber, the magnet, and the optical system are given.

ISSN:0034-6748    

DOI:10.1063/1.1717770

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The phase shift method for the measurement of semiconductor carrier lifetime has been extended by the use of a light beam modulated at frequencies up to 4 Mc with a Kerr cell, to provide direct measurement of lifetimes down to at least 10−8sec. Some typical results for the temperature variation of lifetime in indium antimonide are presented.

ISSN:0034-6748    

DOI:10.1063/1.1717771

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A 4‐chamber proportional counter was built with very thin windows to detect weak beta radiation in an external gas cell. The instrumental design permits relatively high counting efficiencies and also incorporates an anticoincidence background reduction feature inherent in the detectors' position, with respect to spurious cosmic‐ray produced events. Gaseous materials containing the weak beta‐emitting radioisotopes Kr85, C14, and H3have been detected using this instrument. Over‐all counting efficiencies for these isotopes were 55%, 26%, and 1%, respectively. The specific activity of the material is calculated from PVT data in the sample cell. After calibration, the counter is useful as a means of secondary standardization or where impure gas samples must be tolerated.

ISSN:0034-6748    

DOI:10.1063/1.1717772

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A description of an ion source of the duoplasmatron type is given. Experimental results related to the plasma density distribution in the region between the intermediate electrode and the anode are given and discussed. Ion beam behavior in the extractor region as a function of extraction potential and total current has been studied. Also, ion beam space‐charge neutralization by secondary electrons has been looked for, but not observed under present conditions.

ISSN:0034-6748    

DOI:10.1063/1.1717773

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The radiation emitted from a duoplasmatron ion source has been investigated between 500 and 2000 Å. When the ion source is operated with hydrogen, the familiar hydrogen continuum is produced down to 1650 Å, followed by the many‐lined spectrum down to 900 Å, including the atomic Lyman alpha and beta lines at 1215.7 and 1025.7 Å, respectively. With argon the source emits a line spectrum down to 550 Å originating from excited neutral, singly, and doubly ionized argon atoms.

ISSN:0034-6748    

DOI:10.1063/1.1717774

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A new continuous ratio ratemeter is described which gives a linear indication of the single‐channel rate divided by the sum rate. The effective time constant of response is derived and the first four statistical moments are calculated for random channel inputs. The predicted performance is verified by the Monte Carlo method and through experimental results. It is furthermore shown that the conventional linear ratemeter is a special case of the more general ratio ratemeter.

ISSN:0034-6748    

DOI:10.1063/1.1717775

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A means for measuring the electrical conductivity of a fluid without the use of electrodes has been developed. A probe, consisting of a cylindrical single‐layer solenoid enclosed within an insulating tube, is used in conjunction with an rf oscillator‐detector to measure the ohmic dissipation of a small amount of rf power in the fluid. The probe samples the conductivity of the fluid in its immediate vicinity, and may therefore be used to resolve conductivity profiles in an operating MHD device, for example. Since the surface of the probe is an insulator, it is possible that the influence of Hall effects and electrostatic sheaths may be effectively eliminated under certain conditions. Electrolytic solutions have been used in calibration of the instrument. Instrumentation has been developed for the application of the measuring technique to plasmas. Probes have been operated successfully in the positive column of a hydrogen glow discharge and in a 4500°F rocket nozzle flow.

ISSN:0034-6748    

DOI:10.1063/1.1717776

出版商:AIP    

年代:1962

数据来源: AIP