摘要:

Betatrons, induction electron accelerators for the production of high energyX‐radiation, were under development in Germany during the war and to a limited extent at present. This work is reviewed for the most part and details are given on the constructional features of 6‐ to 15‐million volt betatrons and on the theory and design of 15‐ and 200‐million volt betatrons. The smaller units, especially the Siemen's 6 Mv, are quite successful and more advanced than comparable American units. While no large machines were actually built, the projected 200‐Mv Wideroe design introduces new features of value. Betatron patent ideas are reviewed.

ISSN:0021-8979    

DOI:10.1063/1.1697549

出版商:AIP    

年代:1947

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1697548

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Tests on a hydrogen ion gun assembly employing differential pumping are described. Focused beam currents as high as 215 microamperes were realized at the target end of a high voltage tube 6 feet long operating in the range from 300 to 400 kilovolts. Factors which limited the current to 215 microamperes are discussed and suggestions for realizing greater beam currents are presented.

ISSN:0021-8979    

DOI:10.1063/1.1697550

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Samples of synthetic iron oxide (Goethite) taken at regular intervals from a twelve‐day continuous process showed progressive change of color, ranging from pale yellow to dark brown. X‐ray diffraction, electron microscope, and optical microscope studies lead to the conclusion that the color change in these samples is mostly caused by particle growth.

ISSN:0021-8979    

DOI:10.1063/1.1697551

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A simple low resolution mass spectrometer is described which has been used successfully in detecting small leaks in high vacuum equipment. One part of He in 200,000 parts of air can be detected.

ISSN:0021-8979    

DOI:10.1063/1.1697552

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Methods developed for obtaining vacuum tightness in the K‐25 Gaseous Diffusion Plant for the separation of U235are described. A general account of the vacuum engineering of the K‐25 Plant also is given. The dynamics of vacuum systems are described, including the use of the mass spectrometer leak detector on rapidly responding systems. New techniques described include, among others, the helium hood method for measuring vacuum tightness and the use of calibrated leaks.

ISSN:0021-8979    

DOI:10.1063/1.1697553

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

A theoretical and experimental investigation of contour phenomena observed in electron microscope images near focus has been carried out. An explanation for the apparent reversal of the Fresnel fringes at exact focus is given and a method is described for the determination of the degree of asymmetry from the fringe patterns. A procedure for empirically correcting the asymmetries usually present in magnetic electron microscope objectives is outlined and some of the results obtained with a compensated lens are shown. A number of instrumental defects which may prevent the attainment of the ultimate resolving power of an instrument, together with methods for their elimination, are listed.

ISSN:0021-8979    

DOI:10.1063/1.1697554

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

An electrical precipitation method for the analysis of smokes according to particle size has been investigated. A thin stream of smoke particles moving under laminar conditions in a wind tunnel of rectangular cross section is electrically charged in a small region. The charged particles are then precipitated by the uniform field existing between the charged upper plate and the grounded lower plate of the wind tunnel as a long track along the lower plate. The size‐frequency distributions of the particles precipitated at various points on the lower plate were determined from measurements on enlargements of electron‐microscope photographs of samples of the smoke precipitated at various points. The agreement between theory and experiment is fair, but the range of sizes of the particles precipitated at a given point is rather large.

ISSN:0021-8979    

DOI:10.1063/1.1697555

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

An equation for the steady‐state rate of creep of pure annealed polycrystalline metals is derived through dislocation theory and the theory of rate processes. The rate of generation of dislocations is shown to be the rate‐determining process. A specific mechanism for the generation of a dislocation is presented, from which the heat and entropy of activation of the process are expressed in terms of physical constants of the material. In addition the lowering under stress of the potential energy barrier, which yields the stress‐dependent term, is given in terms of constants of the material and a ``back‐stress'' term. The creep equation thus obtained is found to be in good agreement with data in the literature.

ISSN:0021-8979    

DOI:10.1063/1.1697556

出版商:AIP    

年代:1947

数据来源: AIP

摘要:

Description is given of a set‐up for the determination of temperatures at the frictional interface between a moving bullet and the bore in a caliber 0.50 gun barrel. Cathode‐ray oscilloscope e.m.f.‐time records, which were obtained from a traveling thermocouple junction formed by the bullet‐bore interface, are interpreted (by use of a formula due to Jaeger) in terms of instantaneous temperatures. A calorimetrically measured value of the total frictional heat input caused by a bullet being pushed through a barrel section by means of a falling weight, is found to be in good agreement with the value of the heat input calculated from bore surface temperatures which were determined by the sliding thermocouple method.

ISSN:0021-8979    

DOI:10.1063/1.1697557

出版商:AIP    

年代:1947

数据来源: AIP