ISSN:0031-9228    

DOI:10.1063/1.3068950

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3068953

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3068957

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.3068959

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The launch of Skylab on 14 May 1973 created a temporary, large‐scale hole in the ionosphere. The “hole,” a depletion of the total electron content of the ionosphere that spanned a spatial region of 1000 to 2000 km and a time period of 2 to 3 hours, was observed and subsequently analyzed by Michael Mendillo (Boston University), Gerald S. Hawkins (Smithsonian Astrophysical Observatory) and John A. Klobuchar (Air Force Cambridge Research Laboratory). They assert that the electrons were lost because of exceptionally rapid chemical recombination of the electrons with oxygen ions that was caused by the molecular hydrogen and water vapor from the exhaust of the Saturn V rocket engines.

ISSN:0031-9228    

DOI:10.1063/1.3068961

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The first lasers pumped solely by nuclear reaction products have been developed independently at two laboratories. This news has been welcomed partly because producing any phenomenon in a new way is of scientific interest. But part of the welcome has a more pragmatic flavor: If the large amounts of energy produced in a reactor could be efficiently channeled into a laser, the resulting device might be powerful enough for applications ranging from isotope separation, to laser fusion, to communications in space. These first reports, from Sandia Laboratories in Albuquerque, New Mexico, and from Los Alamos Scientific Laboratory in Los Alamos, New Mexico, indicate that such lasers are in principle possible although as yet far from practical. David McArthur and Philip Tollefsrud (Sandia) described their carbon monoxide laser in the 15 February issue of Applied Physics Letters, and Herbert Helmick (Los Alamos), James Fuller and Richard Schneider (both of the University of Florida, Gainesville) reported lasing from xenon in the 15 March issue of the same journal. Both of these lasers are excited byU235fission fragments that result from irradiating uranium foil with neutrons from a fast‐burst reactor.

ISSN:0031-9228    

DOI:10.1063/1.3068962

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Research on solar cells focusses on finding devices that have the simultaneous promise of high efficiency, long lifetime and low cost. Therefore observers have been excited about the recent development of two new solar cells with efficiencies of 12–13&percent; that might be many times cheaper than silicon cells—if they fulfil their potential to be made by thin‐film techniques. The potential of these two devices for solar‐energy conversion was recognized by Sigurd Wagner and Joseph Shay of Bell Laboratories as they were investigating new materials and components for optical communications systems. One of these cells consists of a thin film of cadmium sulfide deposited on a single‐crystal substrate of indium phosphide.1The other has a cadmium‐sulfide layer on a single‐crystal substrate of copper indium diselenide.2

ISSN:0031-9228    

DOI:10.1063/1.3068963

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Ultraheavy cosmic‐ray nuclei, those with atomic number over thirty, constitute less than about one in107of the relativistic particles that stream through our solar system, yet they promise to lead to a major contribution in our understanding of the complex phenomena of the cosmic‐ray gas that pervades interstellar space. The study of these nuclei should advance our understanding of the sources of cosmic rays as well as of the nature of the physical processes that influence the particles after their acceleration. This work is greatly accelerating with the advent of satellite experiments, such as the Skylab mission pictured in figure 1.

ISSN:0031-9228    

DOI:10.1063/1.3068964

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The rapid development of new technologies over the past decade has greatly expanded the capabilities of relativistic electron beams. While electron beams constitute one of the oldest particle beams available to physicists, the strengths of such beams were limited to a few amperes up to the early 1960's. Since then, however, a new type of accelerator has been developed that permits electron‐beam bursts of many kiloamperes—and even megamperes—to be accelerated to energies of several megavolts. The most recent facility of this type at Cornell University, shown on the cover of this issue ofPHYSICS TODAY, is capable of accelerating a 15‐kA beam of electrons to 5 MeV. Figure 1 shows Aurora, the largest facility of this type presently operating, which is able to accelerate 160‐nanosecond pulses of electron beams of up to 1.6 megamperes to energies as high as 12 MeV.

ISSN:0031-9228    

DOI:10.1063/1.3068965

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

A piece of ordinary glass is a silicate material that did not crystallize when cooled from its liquid state to ambient temperature. Other substances, especially those whose molecules tend to polymerize, can also be cooled to ambient temperatures without crystallization. With metals, however, this could not be done until rather recently, and doing it continuously to make materials of interest to engineering is a very recent development. Metal alloys that can be quenched without crystallization form metallic glasses—solids with unusual, and in some cases outstanding, physical properties. Because their atoms are bound together by long‐range metallic bonding, these glasses are malleable and good electrical conductors (comparable to stainless steels), unlike covalently bonded silicate glasses.

ISSN:0031-9228    

DOI:10.1063/1.3068966

出版商:AIP    

年代:1975

数据来源: AIP