摘要:

Optimum design criteria for atomic and molecular beam apparatus are discussed, and signal strengths under a number of conditions are calculated. Signal strength and signal‐to‐noise ratios are shown graphically as functions of the design parameters.

ISSN:0034-6748    

DOI:10.1063/1.1720437

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

After a brief review of Westmijze's semi‐infinite model for the reading of recorded signals in magnetic media by gapped ring heads, a program for the computation of the gap loss functionSis described. By introducing the higher order sine and cosine integrals, this function can be evaluated to any degree of accuracy over its useful range. A four decimal place table is compiled and included in this report. Two experiments significant to the validity of the theory and the practical evaluation of the data system performance were carried out with the help of the table compiled. By autocorrelating the system output, the null points in the frequency response curve of tenths of micron (micro‐inch) gaps were located with confidence. The first null point determines the effective gap length accurately, from which the signal amplitude reduction due to gap interference at arbitrary wavelengths can be calculated. Further measurement of output signals at three suitably chosen frequencies enables one to determine the effective thickness of magnetization and head medium separation. The good agreement of the theoretical response curve based on these parameters with the directly measured data indicates the general validity of Westmijze's model. From a practical point of view, the knowledge of these parameters makes it possible to separate the signal amplitude losses during reading operation and suggest proper approaches to the improvement of system resolution.

ISSN:0034-6748    

DOI:10.1063/1.1720438

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

When very heavy ions were directed along the crystalline channels of Si fission detectors, a three‐fold improvement in energy resolution was obtained for particles remaining in the channels. For such channeled particles the usual pulse height defect was reduced by more than a factor of 10. The results seem to fit certain theoretical explanations of detector nonlinearities found in the literature, in which the nonlinearities are ascribed to the predominance of atomic collision processes near the end of the range.

ISSN:0034-6748    

DOI:10.1063/1.1720439

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A method and apparatus are described which enable a sensitive, reproducible measure of the saturation magnetostriction &lgr;sof thin ferromagnetic films. The use of low frequency magnetic resonance probes simplifies the measurement of the changes in the film anisotropy field which occur due to strain in a magnetostrictive film. The applicable equations for the technique are presented with the result that &lgr;sis shown to be directly proportional to an easily measured current and inversely proportional to the deflection of the substrate center. Successful measurements have been performed on films as thin as 100 Å and as thick as 2000 Å. Conducting substrates are permissible.

ISSN:0034-6748    

DOI:10.1063/1.1720440

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A method and apparatus are described which provide sensitive and repeatable measurements of the saturation magnetostriction &lgr;sof thin ferromagnetic films. The use of magnetoresistance provides a simple, compact method of observing magnetoelastic effects of strain on the film magnetization process. The applicable equations for the technique are presented with the result that &lgr;sis shown to be directly proportional to an easily measured current and inversely proportional to the deflection of the center of the film substrate during bending. Measurements have been made on films ranging from 100 to 2000 Å thick.

ISSN:0034-6748    

DOI:10.1063/1.1720441

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A self‐illuminated schlieren system was developed for use in studying phenomena which may have light intensity so great as to mask external light sourcs. Examples of such phenomena might be plasma jets or solid rocket propellent combustion where metal additives are present. The optical layout is described in detail and photographs are presented to illustrate its use.

ISSN:0034-6748    

DOI:10.1063/1.1720442

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

The characteristics of spark discharges in confined volumes of the gases nitrogen, carbon dioxide, argon, and helium are measured in the pressure range from 1 to 40 atm. It is found that both the brightness and efficiency of the discharge increase rapidly with pressure. The results of this investigation show that high pressure spark discharges can be used to produce extremely bright submicrosecond pulses of light having peak luminous powers in excess of 105W radiating into 4&pgr; sr over the wavelength range from 3200 to 7000 Å. Because the luminous area is localized to 0.01 cm2, a brightness of 107W/cm2is readily obtained.

ISSN:0034-6748    

DOI:10.1063/1.1720443

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Apparatus for the half‐life measurements of x rays from fission fragments is described. The fission fragment detector was an ultrathin plastic scintillator and the x‐ray detector was a 1 mm NaI (Tl) crystal. Both detectors were mounted on fast (56 AVP) photomultipliers. The details of the design of the plastic scintillator are given and curves showing the double humped fission fragment kinetic energy spectrum are illustrated. A systematic study of the x‐ray energy detection characteristics of the NaI (Tl) on a 56 AVP is given. The pulse heights were determined to be linear with x‐ray energy and the spectra were shown to follow Poisson's statistics. The number of photoelectrons produced at the photocathode was determined to be 3.2 per kiloelectron volt. The time measuring device was a conventional time to amplitude converter using pulse overlap methods. The prompt response of this converter could be predicted from the results gained in the energy detector study. Both the width and the apparent half‐life were consistent with the assumption that the time to amplitude converter was triggered on a single photoelectron.

ISSN:0034-6748    

DOI:10.1063/1.1720444

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

In order to utilize the inherent resolving power of a double focusing, 169.8°, 76.2 cm radius of curvature magnetic spectrometer being constructed at the National Bureau of Standards for elastic and inelastic electron nuclear scattering studies, focal plane counters were needed whose dimension along the direction of momentum dispersion was 1 mm. This paper describes the fabrication techniques and performance of lithium compensated silicon 1×1×60 mm radiation detectors which seem well suited for use as focal plane detectors for the above spectrometer. Differential and integral pulse height distributions for 10–40 MeV electrons incident on the counters are presented as a function of the temperature and bias voltage. Effects due to the finite width of the counters are discussed. A tunnel diode discriminator which provides the desired binary information to the NBS data processing system is described.

ISSN:0034-6748    

DOI:10.1063/1.1720445

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

The characteristics of field emission diodes and triodes with narrowly spaced electrodes were investigated. They could be used under comparatively low voltage. When the voltage between the anode and cathode was several hundred volts, the current was 10−12to 10−4A. The stability of the current, though it depends on the vacuum in the tube and on the pretreatment of the electrodes, was fairly good in this range (about 1%). The collector current of one of the triodes with two cathodes a small distance apart was varied from 10−11to 10−6A when the potential difference between the cathodes was changed by 400 V at a collector potential of 450 V.

ISSN:0034-6748    

DOI:10.1063/1.1720446

出版商:AIP    

年代:1966

数据来源: AIP