摘要:

A scintillation spectrometer has been built utilizing a modular liquid scintillation anticoincidence shield for a 12.7 cm diameter by 25.4 cm long NaI(Tl) detector crystal. The effectiveness of the anticoincidence shield is enhanced by storing in one‐half of a multichannel analyzer memory those pulses from the NaI(Tl) crystal which are coincident with shield pulses. A fraction of this coincident spectrum is then subtracted from the anticoincident spectrum as a correction for shield inefficiency. A computer system is used for data handling. Spectral response for gamma radiation from 0.35 to 17.6 MeV has been measured.

ISSN:0034-6748    

DOI:10.1063/1.1720435

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A system for determining the creep behavior of refractory metals at temperatures up to 1900°C and at environmental test pressures of less than 1×10−8Torr are described. Results are presented which show that contamination of a tantalum alloy test specimen is inhibited when tested at 1370°C and 1×10−8Torr.

ISSN:0034-6748    

DOI:10.1063/1.1720436

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An optical device is described that is used for the measurement of the positions and angular coordinates of lines viewed in stereoscopic photographs, such as the photographs of particle tracks in a cloud chamber or bubble chamber. In addition to the absolute angular coordinates of a line in three dimensional space, the viewer furnishes the relative angular coordinates of a second intersecting line and the three rectangular coordinates of the point of intersection. All coordinates are read directly on linear scales. Applications include the measurement of scattering angles, the angles of secondary particles in an interaction or decay with respect to each other and the primary particle, and the angle of traversal of a particle through an absorber.

ISSN:0034-6748    

DOI:10.1063/1.1720391

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Apparatus and techniques were developed for accurately measuring asymmetric distortion in camera lenses. Great care was taken in fabricating the camera, which was made cylindrical so that the lens could be rotated. The experimental setup included a collimating telescope, the cylindrical camera containing the lens to be tested, and the test pattern. By rotation of the cylindrical camera, the same portion of the test pattern could be used for checking asymmetric distortion in different sectors of the lens. The distortion was recorded on film plates, which were then measured with a linear micrometer. Results were obtained to an accuracy of 1 part in 105. Causes for distortion were investigated but not quantitatively.

ISSN:0034-6748    

DOI:10.1063/1.1720392

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

An improved Bunsen ice calorimeter has been constructed and calibrated for use in measuring critical region heat capacities. A novel method for continuously monitoring the weight of the mercury displaced by using a flexible capillary between the calorimeter and an analytical balance makes possible greater precision, easier operation, and wider applicability of the ice calorimetric method. An improvement in the method of thermostating the calorimeter allows higher precision over long period heat measurements. The measured electrical calibration factor of 270.45±0.03 J/g Hg agrees satisfactorily with previous very careful calibrations and the observed precision of ±0.011 J/g Hg is easily attainable during electrical calibrations. Relatively simple improvements in other aspects of the calorimeter are suggested for increasing both the precision and accuracy significantly.

ISSN:0034-6748    

DOI:10.1063/1.1720393

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

To pursue accurate quantitative studies of radiation effects in crystals, it is necessary to adopt precise experimental techniques for controlling the bombarding electrons and for cooling specimens to very low temperatures. With regards to the irradiating electron beam, measurements have been made to determine some of the factors which influence the electron flux density over the irradiated area, and a description is given of a system which insures precise alignment of the beam with respect to the specimens. A sample holder is described which provides good thermal contact and good electrical isolation between specimen and specimen holder at low temperatures. The method used for regulating the temperature of the sample holder depends upon adjusting the rate and the amount of helium vapor flow through the holder and data that indicate how these two adjustments govern the resultant temperature are presented.

ISSN:0034-6748    

DOI:10.1063/1.1720394

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A probe assembly is described which permits the use of an electron microscope to irradiate materials with low energy (50–150 keV) electrons. The electron beam current produced by the microscope can be monitored quickly and accurately with this unit so that the irradiation rate can be closely controlled. Although developed for use in the Hitachi HU‐11 electron microscope, the device can, with but minor modifications, be utilized in other microscopes as well.

ISSN:0034-6748    

DOI:10.1063/1.1720395

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A transistorized NMR spectrometer has been developed which affords sensitivity comparable to that of the best vacuum tube spectrometers. This spectrometer has operated with sample coil voltages below 10 mV peak‐to‐peak. Frequency modulation is used to facilitate modulation at frequencies high enough to minimize effects of transistor 1/fnoise.

ISSN:0034-6748    

DOI:10.1063/1.1720396

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

Experiments were conducted to determine ac losses, principally near 105cps, in coils and leads fabricated from high field superconducting wires. The samples were placed in an environment similar to what might be experienced in actual use in a low temperature experiment utilizing adiabatic demagnetization. The measurements showed that losses associated with the use of high field superconducting wire could be less than for electrical grade copper wire. Further experiments were then carried out to determine what aberrations of magnetic fields would be caused by the presence of high field superconducting material.

ISSN:0034-6748    

DOI:10.1063/1.1720397

出版商:AIP    

年代:1966

数据来源: AIP

摘要:

A superconducting winding, sectioned and supplied with currents corresponding to the local field conditions, gives an increased field contribution over that of a single winding. This paper derives the increased field contribution in terms of the number of sections and the characteristics of the superconducting material.

ISSN:0034-6748    

DOI:10.1063/1.1720398

出版商:AIP    

年代:1966

数据来源: AIP