摘要:

The influence of solute oxygen and nitrogen on the magnetic breakdown and residual losses of superconducting niobium cavities was investigated experimentally by exposing the cavities to these gases at pressures up to 10−5Torr during the heat treatment at 2100 K. We have collected evidence that the oxygen exposure increases the residual losses and, at bulk concentrations of about 0.1 at.%, the breakdown field is substantially lowered. Penetration depth measurements seem to indicate high values of the Ginzburg‐Landau parameter &kgr; ≈ 4.4 in the surface sheath which could explain the low rf breakdown observed.

ISSN:0021-8979    

DOI:10.1063/1.1662915

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A simple theory of the superconducting single‐junction interferometer (ac Squid) becomes possible if the critical current of the single junction is small relative to &PHgr;0/LR, where &PHgr;0=h/2eis one flux quantum andLRis the inductance of the interferometer loop. This theory predicts a magnetic flux sensitivity which has the same dependence on interferometer parameters as the existing theories for higher critical currents. In contrast to those theories, however, the present theory predicts that the maximum flux sensitivity will be achievedoff resonance. Theoretical predictions for comparison with experiment are displayed as a function of the normalized difference between the operating frequency &ohgr; and the resonant frequency &ohgr;0.

ISSN:0021-8979    

DOI:10.1063/1.1662916

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The ratio of maximum radial field to maximum axial field has been calculated numerically for axisymmetric solenoids of rectangular cross section and constant current density over a wide range of coil configurations. It is also shown that for a certain range of coil shapes the maximum modulus of the magnetic field occurs on the end faces of the windings. These considerations are pertinent in the design of superconducting magnets for two reasons: (i) Many superconductors have lower critical current in a field normal to the wide surface than in a field parallel to the surface, and (ii) large radial fields can cause catastrophic flux jumps.

ISSN:0021-8979    

DOI:10.1063/1.1662917

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

When the signal in an x‐ray image system is formed by integrating the scintillation pulses rather than by counting them, the signal‐to‐noise ratio is reduced by a factor which depends on the shape of the pulse‐height distribution. The signal‐to‐noise ratio cannot be related directly to either quantum absorption or energy absorption, and a new quantity called noise‐equivalent absorption is defined which bears a simple relationship to the signal‐to‐noise ratio. Quantum, energy, and noise‐equivalent absorption are calculated as a function of thickness and x‐ray energy for CsI, Gd2O2S, LaOBr, Zn0.6Cd0.4S, and CaWO4.

ISSN:0021-8979    

DOI:10.1063/1.1662918

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Approximate results are given for the time required to melt a film on a thick substrate if the time dependence of the film temperature is known up to the melting point. Results for temperature versus time are given for a uniformly heated film and for a film heated by very strongly absorbed light incident either from the free surface or through the substrate. The calculations assume one‐dimensional heat flow, but a simple model with radial heat flow is treated in the Appendix.

ISSN:0021-8979    

DOI:10.1063/1.1662919

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

It has been shown that magnetic filters can be constructed that will extract micron‐sized paramagnetic particles from a fluid passing through the filter. The purpose of this paper is to examine the filtering process, to calculate the performance of filters, and finally to consider application of magnetic filtering to the rapid treatment of sewage.

ISSN:0021-8979    

DOI:10.1063/1.1662920

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The dependence of excess carrier lifetimes on the photoinjected carrier densities has been investigated for Cr‐doped GaAs at 300 and 80°K, using photomagnetoelectric (PME) and photoconductive (PC) methods. The result shows three distinct injection ranges covering five orders of magnitude change in photoconductance. The lifetimes are constant at low and high injection ranges while showing injection dependence at intermediate injection range. A theory is given to explain the observed results.

ISSN:0021-8979    

DOI:10.1063/1.1662921

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An expression is derived for the electron density distribution in a weakly ionized plasma afterglow. The case for which the ionization is symmetrically localized about the center of the chamber is considered. It is shown that localization causes the existence of higher‐order modes of decay to be present in the afterglow.

ISSN:0021-8979    

DOI:10.1063/1.1662922

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

We have measured the cubic and growth‐induced uniaxial anisotropies of two series of bulk flux‐grown garnets, Gd3−xEuxFe5O12and Y3−xSmxFe5O12, at room temperature. In both series, the cubic anisotropy is approximately a linear function of composition between the end members, while the uniaxial anisotropy varies quadratically with composition.

ISSN:0021-8979    

DOI:10.1063/1.1662923

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The lateral spread of implanted31P and11B ions into Si has been measured using ion implantation at oblique incidence and theC‐Vmethod. Standard deviations of the lateral spread are 570 and 825 Å for 145‐keV and 260‐keV31P ions, respectively, and 725 and 1100 Å for 80‐keV and 150‐keV11B ions, respectively. These results are in good agreement with the theoretical values in the literature.

ISSN:0021-8979    

DOI:10.1063/1.1662924

出版商:AIP    

年代:1973

数据来源: AIP