摘要:

It might strike you as odd that a title which includes the words electron and acoustical wave could describe a frontier of physics. We have already heard at this meeting that the electron was discovered in the 19th century, and as everyone knows, acoustics is perhaps the oldest branch of physics. But, what I would like to discuss is something that is rather satisfying, not only because it is rather simple physics, but because it shows that old and honorable subjects still have aspects that are new. The electrons that I shall discuss are the same ones that J. J. Thomson discovered, but in this context they are somewhat “strange” particles since they move in the odd world within a metal. The sound waves, too, are not quite what the Greeks discussed; here they are ultrasonic ones.

ISSN:0031-9228    

DOI:10.1063/1.3050800

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

There are many different types of pulsed‐plasma engines, or accelerators, which may be classified by the geometry of the discharge, either a sheet or a line, and by the position of the electrodes, which are either directly in contact with the propellant, or inductively coupled with the propellant. It is the author's belief that, of all the various types of pulsed‐plasma accelerators, only the sheet‐direct‐contact accelerator will ultimately become a working engine. The arguments in support of this belief are partly of a practical nature and may even be only intuitive. There are, however, two devices which fill even this narrow description: the so‐called “pinch engine” and the purely axial accelerator illustrated in Figs. 1 and 2. Note that both are characterized by coaxial geometries and require that the discharge be axi‐symmetric. In the “pinch” type or radial accelerator, the initial discharge formed by axial currents must be turned so that the currents become radial. No turning is apparently required in the axial accelerator. However, the magnetic‐field forces are inversely proportional to the radius, and some turning will take place. It would appear that both accelerators should maintain a current sheet normal to the walls of the electrodes. This may be more easily obtained in a curved channel than in a straight one. In addition to symmetry, it appears necessary to obtain a discharge which is relatively thin and impervious to neutral particles by virtue of the high degree of ionization in the discharge. The accelerating sheet, driven by Lorentz forces, should then drive out the propellant situated in the interelectrode region. In general, the thickness of the sheet and its degree of ionization is affected by the energy available to the discharge. Low energy per discharge coupled with a high pulse rate is desirable for low capacitor weight, but is detrimental to the formation of a good driving “magnetic piston”. Experimentally, lower energy per discharge appears to be required in the radial than in the axial accelerator in order to obtain symmetric and nonporous sheet discharges or “pistons”.

ISSN:0031-9228    

DOI:10.1063/1.3050801

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

About twenty years ago, the so‐called “infall” theory had been thoroughly worked out by Hoyle and by Alfve´n. They reasoned that, since the sun moves through clouds of interstellar hydrogen gas, the neutral hydrogen must fall in toward the sun under the influence of the gravitational field. On its way toward the surface of the sun, the hydrogen encounters a strong flux of ultraviolet radiation and, because of the small rate of recombination, it becomes completely ionized. Thus the inner solar system is filled with a dilute, highly conducting plasma. At about the same time the infall theory was worked out, it became rather generally accepted that the corona of the sun has a temperature of 1 or 2 million degrees. In fact, Hoyle tried to account for the heating of the corona in terms of the energy released by the hydrogen falling into the sun.

ISSN:0031-9228    

DOI:10.1063/1.3050802

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The relationships between science and technology and economic growth are not at all clear to many of those engaged in science or to those who participate in the business of “growing” the economy. It is a strange paradox that, although the human intellect has been capable of great achievements in science and its pursuit, the translation of science to use by society is not well understood. Indeed, the glittering successes of science have dimmed our perception of the details of the complex process by which man's understanding of the universe finally enters the world of industry and commerce.

ISSN:0031-9228    

DOI:10.1063/1.3050803

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

Are technical assistants needed in physics? Can an increase in the number of technical assistants help to alleviate the shortage of physicists now and in the years of continuing manpower shortages that seem to lie ahead? What kinds of work can technicians do and how should they be educated? Where can one hire technicians?

ISSN:0031-9228    

DOI:10.1063/1.3050804

出版商:AIP    

年代:1963

数据来源: AIP

摘要:

The New York State Section of the American Physical Society has, in recent years, moved in the direction of programming review meetings on various topics of current interest in physics, designed for the information of physicists who are not necessarily specialists in the fields reviewed.

ISSN:0031-9228    

DOI:10.1063/1.3050805

出版商:AIP    

年代:1963

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3050807

出版商:AIP    

年代:1963

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3050808

出版商:AIP    

年代:1963

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3050810

出版商:AIP    

年代:1963

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3050811

出版商:AIP    

年代:1963

数据来源: AIP