ISSN:0031-9228    

DOI:10.1063/1.2995440

出版商:AIP    

年代:1979

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2995398

出版商:AIP    

年代:1979

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2995400

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The University of Rochester is now operating a National Users Laser Facility. Last October the first stage of the 30‐terawatt Omega system, which uses neodymium glass, began experiments. This stage, known as Zeta, has six beams and delivers 3–4 TW peak power. In December the second stage, with 24 beams and 12–16 TW peak power, is expected to operate. Construction has been supported by DOE. The last stage, still not funded, is planned to reach 30–40 TW peak power (energy of 10 kJ) by the addition of 24 active‐mirror booster systems. The pulse shape can be tailored, with the total pulse length between 0.05 and 1 nanosec.

ISSN:0031-9228    

DOI:10.1063/1.2995402

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

For several summers, a group of physicists, astrophysicists and oceanographers interested in using the oceans to detect ultrahigh‐energy cosmic‐ray neutrinos have been meeting to exchange ideas. Their interest arises because clean seawater could provide the massive detector needed to observe low fluxes of weakly interacting, deeply penetrating neutrinos (PHYSICS TODAY, April 1976, page 18). The detector volume, about one cubic kilometer, located 5 km or so underwater, would avoid gross interference from ordinary cosmic rays. Organized asDUMAND(Deep Underseas Muon and Neutrino Detector), the group has been formulating the questions that would need to be answered in any feasibility study of the project. The most recent workshop took place 24 July–1 September at the Scripps Institution of Oceanography, La Jolla, with about 90 participants from the US, the Federal Republic of Germany, Japan and the Soviet Union.

ISSN:0031-9228    

DOI:10.1063/1.2995403

出版商:AIP    

年代:1979

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2995405

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A new method of detecting radioactive isotopes promises to have a revolutionary impact on the field of radioisotope dating. The technique, which was developed over the past two and a half years, consists of counting individual atoms of radioactive isotopes that have been ionized, accelerated to high energies, and then selected and identified. By detecting all—or a substantial fraction—of the atoms in the beam, this method has much greater sensitivity than the standard method, which detects only the tiny fraction of the atoms that decay during the counting period. The new “direct detection” method therefore will allow one to use much smaller samples and to measure much greater ages than the older “decay detection” method.

ISSN:0031-9228    

DOI:10.1063/1.2995406

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

All those who wear Polaroid sunglasses are familiar with the polarization of light by reflection, a phenomenon first investigated by Etienne Malus in 1808 when he looked through a calcite crystal at the light reflected from the windows of the Palais Luxembourg. In 1921 Otto Stern and Walther Gerlach demonstrated the spin polarization of atomic beams in magnetic field gradients, and their methods are now in fairly widespread use.

ISSN:0031-9228    

DOI:10.1063/1.2995407

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

In late December 1877 James E. Keeler appeared at Johns Hopkins University to begin his studies in physics and astronomy. He was a “raw country boy” from Florida, without benefit of a high‐school education. Twenty years later, an outstanding astronomer, he was appointed Director of Lick Observatory, the best‐known research institution of that era. Two years later he died unexpectedly of a stroke. Keeler had a brilliant career in astronomy and was, with his younger friend George Ellery Hale, one of the great American pioneers of the new science of astrophysics. His observational discoveries are described in every astronomical textbook today, although often his name is not mentioned, and the research techniques that he developed and the problems that he studied still form the basis of much of modern‐day astrophysics. The portrait on the opposite page shows him at the height of his career.

ISSN:0031-9228    

DOI:10.1063/1.2995408

出版商:AIP    

年代:1979

数据来源: AIP

ISSN:0031-9228    

DOI:10.1063/1.2995409

出版商:AIP    

年代:1979

数据来源: AIP