摘要:

The more important properties of end‐window Geiger counters, side‐window proportional counters, and NaI(Tl) scintillation counters are reviewed and their performance in the 5 to 50 kvp x‐ray analysis region is compared. Proportional and scintillation counters have resolving times of the order of 0.25 &mgr;sec and virtually eliminate the nonlinearity limitation of the Geiger counter. They produce pulse amplitudes proportional to the energy of the x‐ray quanta, and thus simple pulse height discrimination techniques can be used to obtain greatly improved peak‐to‐background ratios with little loss of intensity of the characteristic x‐rays. They are as reliable and nearly as easy to use as Geiger counters. The electronic discrimination method is described and explained with some practical applications. For a given experimental arrangement, the measured intensity is determined by the quantum counting efficiency of the counter tube, and the peak‐to‐background ratio is determined by the spectral response of the detector‐discriminator combination.

ISSN:0034-6748    

DOI:10.1063/1.1715380

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A pulsed, cold‐cathode ion source has been developed to produce multiply charged ions for use in a linear accelerator. Milliampere currents of such ions as He42+, C122+, N143+, O163+, Ne203+, and smaller currents of S325+and A406+have been produced in focused beams.Mass spectra of the various ionization states produced by the arc are presented. Constructional details of the source and the associated electronic equipment are given, and operating characteristics of the source and ion extraction are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715381

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

Transpiration of gas in the inlet tube between the sample reservoir and the ion source is eliminated if the thermal gradient occurs in the low‐pressure region between the leak and the ion source. Since transpiration was found to be a total pressure effect, sensitivity response is not affected if gas mixtures and calibrating gases are run at the same pressure, even though transpiration is present.

ISSN:0034-6748    

DOI:10.1063/1.1715382

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

The construction and operation of a compact automatic Toepler pump of the mercury piston type which has many advantages over previous designs are described. The mercury motion is controlled by a switching relay activated by electrodes so placed that at the ultimate of its stroke the air leak to the lower mercury reservoir is closed and an oil vacuum pump is started to evacuate it, and at the bottom of the stroke the vacuum pump is stopped and the air leak opened to allow the mercury to rise in the piston chamber. Pumping action is effected by two glass valves with conically ground seats in series in the gas inlet and outlet tubes.

ISSN:0034-6748    

DOI:10.1063/1.1715383

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A xenon‐filled electronic flash tube with a cylindrical lighted volume of 1.2‐mm diam and 6‐mm length has been developed for use as a small source in optical systems, such as the schlieren and interferometer types. The lamp has been operated at 6000 flashes per second from a hydrogen‐thyratron driver circuit to record the density in air flow in an interferometer. Flash duration varies from 0.3 to 3 &mgr;sec, depending upon the circuit conditions. A peak brightness of 10 million candlepower per sq cm has been achieved.

ISSN:0034-6748    

DOI:10.1063/1.1715384

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

It is shown that the heat flow in a single homogeneous medium of thermal conductivity &sgr;(T), between boundaries at temperaturesT2andT1is the same as that for the same geometry in a medium of unit thermal conductivity and boundary ``thermal potentials'' &Sgr;(T2) and &Sgr;(T1), where&Sgr;(T)=∫0T&sgr;(T′)dT′. Some applications are given, as well as a short table of &Sgr;(T) for common cryogenic temperatures and materials.

ISSN:0034-6748    

DOI:10.1063/1.1715385

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

A direct method of measuring the injection ratio of rectifying contacts is described. With this method, the injection ratio is determined by comparing the area of a current injection pulse with the area of the resulting hole storage pulse as observed on an oscilloscope screen.

ISSN:0034-6748    

DOI:10.1063/1.1715386

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

To assess the effectiveness of plastic phosphors in the reduction of Compton effect in scintillation spectrometers, a spectrometer with a small NaI(Tl) crystal surrounded by a large plastic phosphor has been constructed. The output from the plastic phosphor is put in anticoincidence with the output from the NaI(Tl) crystal. A reduction of Compton contribution in the scintillation spectrum to about 35&percent; of original value is obtained. Comparison of results with, and without, the shield enables certain spectral features to be identified. Possible applications are discussed. Transistor anticoincidence circuits are used.

ISSN:0034-6748    

DOI:10.1063/1.1715387

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

This paper describes the utilization of a simple universal vacuum joint, as the support for a magnetic shield type of deflector in the form of a cylindrical soft iron pipe. Variable insertion of this pipe and change of direction in azimuth permit the extraction, with up to 70&percent; efficiency, of all the microtron orbits, making available, in this case, electrons between 1 and 4 Mev energy, in steps of 0.5 Mev. Radiation intensity, or electron current, from any particular orbit, up to the limit determined by the peak for that orbit, may be set at any desired level by small changes in the insertion of the deflector.

ISSN:0034-6748    

DOI:10.1063/1.1715388

出版商:AIP    

年代:1956

数据来源: AIP

摘要:

An analog method is described for solving some of the mechanical problems associated with the recording of ballistocardiograms. An L‐C‐R circuit is used as the analog of the body coupled to a fixed table. It is concluded that no technical obstacles exist to the widespread use of ballistocardiography, through equipment similar to that described here. Clinical problems in the interpretation are not discussed.

ISSN:0034-6748    

DOI:10.1063/1.1715389

出版商:AIP    

年代:1956

数据来源: AIP