ISSN:0034-6748    

DOI:10.1063/1.1751969

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

We use the adjective ``mobile'' to describe a focal spot in an x‐ray tube which moves cyclically in a closed path relative to the target surface on which it is generated quite without reference to whether the spot be fixed or in motion with respect to the tube. Alex Mu¨ller and also A. Bouwers have made calculations of the thermal effects in such spots energized for very short fractions of one cycle of motion. This paper treats the case where the focal spot is energizedcontinuouslyso that a ``steady'' state of thermal oscillation is set up. The solutions obtained refer only to conditions after this steady state of oscillation is reached. Only the ideal case of a spot of uniform intensity with sharp boundaries is treated. For simplicity the flow of heat from front target surface to cooling water is assumed one dimensional and normal to the front surface over an everywhere uniform thicknessd.Curves are plotted showing the ratio of temperature rise in moving spots to that in fixed spots of the same size as a function ofrthe size of the spot relative to the length of path it describes and of &thgr; a variable depending on the speed of rotation, the thicknessdand the thermal constants of the target material. Curves of the ratio of permissible energy input for moving and fixed spots, respectively, as a function of the aforementioned variables are also shown. The paper gives a solution reduced to figures and curves of the heat flow equation for certain boundary conditions which to the author's knowledge has never before been obtained and therefore has some interest beyond its immediate application to x‐ray tubes. Certain mathematical difficulties of practical interest are also overcome in a way which may be helpful in other problems of similar nature. For the reader uninterested in mathematics the results are independently discussed in a separate section. Approximate methods are given for applying the results of the paper to targets consisting of two materials such as tungsten and copper.

ISSN:0034-6748    

DOI:10.1063/1.1751970

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

An a.c. operated beat‐frequency oscillator constructed from ordinary radio parts is described. The circuit design gives good wave form, and excellent stability of frequency with changing line voltage.

ISSN:0034-6748    

DOI:10.1063/1.1751971

出版商:AIP    

年代:1935

数据来源: AIP

摘要:

Observations have been made of current (0.1 to 10,000 &mgr;a) in a Weston Photronic blocking‐layer photo‐cell, as a function of illumination (1 to 100,000 lux) and of potential difference across the cell. The use of a graph of current against voltage is discussed, as well as the conditions for maximum external power (largest observed value about 1 milliwatt). The leakage current through the blocking layer is calculated and from it the d.c. conductance in the low resistance direction is obtained. This is found to consist of a constant term of the order of 80 micromhos, as well as terms proportional to the 0.8 power of the leakage current and the 0.4 power of the illumination. A fourth term is ascribed to the effect of the potential across the blocking layer in preventing the passage of low velocity photoelectrons across the layer. With maximum illumination a conductance as high as 9000 micromhos is obtained. This rises to 30,000 micromhos or more with the largest leakage currents. A Westinghouse Photox cell was found to possess an internal conductance which changes very little with current, and which contains a term varying as the 0.4 power of the illumination. Comparison of the two cells indicates that nonlinearity of the current‐voltage characteristic and rectification (almost absent and becoming reversed in the Photox cell) are not essentials in blocking‐layer photo‐cells. The open circuit voltages of both cells are found to be nearly proportional to the illumination for voltages less than 5 mv and to be proportional to the logarithm of the illumination for voltages greater than 50 mv.

ISSN:0034-6748    

DOI:10.1063/1.1751972

出版商:AIP    

年代:1935

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1751974

出版商:AIP    

年代:1935

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1751976

出版商:AIP    

年代:1935

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1751977

出版商:AIP    

年代:1935

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1751979

出版商:AIP    

年代:1935

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1751980

出版商:AIP    

年代:1935

数据来源: AIP

ISSN:0034-6748    

DOI:10.1063/1.1751981

出版商:AIP    

年代:1935

数据来源: AIP