ISSN:0031-9228    

DOI:10.1063/1.2998950

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2998912

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2998913

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

In a year full of surprises in high‐energy physics, an experiment at the SPEAR colliding‐electron‐beam facility has uncovered yet another unexpected phenomenon: A significant number of events have been seen in which an electron and positron collide and produce one electron and one muon plus some missing energy. The experimenters can find no conventional explanation for this anomalous production of leptons and postulate that this reaction could proceed through the production of a pair of new particles. Each of the U particles, as they have been tentatively called, would then decay into an electron or a muon plus one or two neutrinos.

ISSN:0031-9228    

DOI:10.1063/1.2998915

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

The 2XIIB mirror device at Lawrence Livermore Laboratory has produced plasma temperatures of 10–14 keV, more than four times higher than temperatures reached in an earlier version of the device. Simultaneous with this achievement of reactor‐level temperatures in a dense plasma was a tenfold increase in plasma confinement time, to about five milliseconds. Although these new results are not being taken to mean that magnetic‐mirror confinement has suddenly become the favorite for producing a practical fusion reactor, they do show that the plasma produced in such a device continues to follow classical energy scaling at high temperatures. Confinement time, that is, does increase with energy, indicating that most of the plasma losses are caused by collision between plasma particles rather than by the more serious effects of internal instabilities. Moreover, notes Frederic Coensgen, leader of the California experimental group, the temperature reached was just that predicted two‐and‐one half years ago, and success was achieved within the predicted time and for the predicted cost. Other members of the experimental team are Thomas Simonen, William Cummins, Grant Logan, Arthur Molvik, William Nexsen Jr, Barry Stallard and William Turner.

ISSN:0031-9228    

DOI:10.1063/1.2998916

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

An accident that occurred at Bell Laboratories in 1925 started Clinton Davisson and Lester Germer on an historical series of experiments. While studying the backscattering of slow electrons from a polycrystalline nickel target, they observed that the angular distribution of the electrons changed completely when the surface was inadvertently oxidized at a high temperature. The consequent study of diffraction phenomena in electrons scattered from the (111) face of a nickel crystal confirmed the de Broglie hypothesis of the wave nature of electrons. But Davisson and Germer also predicted that this type of experiment would provide a valuable approach to the important problem of defining the precise position of atoms in the surfaces of crystalline solids. This suggestion has been pursued diligently by scientists both in the US and abroad. Now, fifty years after Davisson and Germer demonstrated the coherent scattering of electrons by a crystalline solid, the goal of studying surface structure with this technique is becoming a reality. In this article we will discuss some of the major advances of the past few years that are making this achievement possible.

ISSN:0031-9228    

DOI:10.1063/1.2998917

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

When the alarm was sounded last year that the ubiquitous fluorocarbon‐propelled spray cans might be responsible for slowly removing Earth's protective ozone shield, reaction was widespread. Environmentalists urged an immediate ban, legislators held hearings and introduced legislation, government‐sponsored study committees were formed, fluorocarbon‐based industries defended their products and urged more definitive research (which they began to support in part). The concern, of course, is that the ozone layer shields life on Earth from harmful ultraviolet radiation. Much relevant research was already underway, sponsored by the Federal government, and by now workers in such disparate fields as atmospheric science, chemistry, physics and astronomy are working to answer the question, “Are the fluorocarbons depleting the ozone, and if so, how badly?”

ISSN:0031-9228    

DOI:10.1063/1.2998918

出版商:AIP    

年代:1975

数据来源: AIP

摘要:

Historic Boston will be the site of the annual meeting of the Optical Society of America, to be held at the Sheraton Boston Hotel on 21–24 October. Eleven symposia held throughout the four‐day meeting will cover topics as diverse as molecular spectroscopy, laser speckle and visual perception.

ISSN:0031-9228    

DOI:10.1063/1.2998919

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2998920

出版商:AIP    

年代:1975

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2998921

出版商:AIP    

年代:1975

数据来源: AIP