摘要:

Dispersion relations for two‐stream instabilities in electron—hole plasmas in bismuth and pyrolytic graphite have been obtained. The band structure of these anisotropic semimetals has been incorporated into the dispersion relations. These dispersion relations were numerically evaluated for the growth rate and frequency of oscillation for waves propagating in the three principal crystal axes of bismuth and for the wave propagating in thea‐plane of pyrolytic graphite. For the wave propagating along the trigonal axis of bismuth there is one optical branch and one acoustical branch. For the acoustic branch the growth rate exceeds the collision damping at an applied electric field of 7 V/cm. The frequency of oscillation where the growth rate is maximum is 510 GHz, which is in the submillimeter‐wave range (&lgr;≈0.6 mm). For the wave propagating along the binary axis there is an optical branch, a high‐frequency acoustical branch, and a low‐frequency acoustical branch. The high‐frequency branch is damped even for electrons drifting with velocity near the Fermi velocity. The low‐frequency branch exhibits growth but the threshold electric field of 15 V/cm is higher than the field required for the trigonal case. The frequency which corresponds to the peak growth rate for this electric field is 2.3×1012cps, or &lgr; = 130 &mgr;, which falls in the far‐infrared region. Waves propagating along the bisectrix axis of bismuth exhibit anomalous behavior which results in two coupled acoustic modes. The threshold conditions for pyrolytic graphite are less favorable than those for bismuth. The threshold electric field is 160 V/cm which is very much higher than the threshold for bismuth. The frequency of oscillation corresponding to peak growth rate is 3×1013Hz, or &lgr; = 10 &mgr;, which is in the near‐infrared range.

ISSN:0021-8979    

DOI:10.1063/1.1709329

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The general principles and design theory ofp‐njunction detectors with narrow spectral responses are described. These detectors do not require the use of external filters and are capable of maintaining their narrow spectral response over large fields of view. Use of zinc diffusion inn‐type gallium arsenide has produced detectors peaking in the neighborhood of 8850 Å with characteristic bandwidths on the order of 200 Å and quantum efficiencies from 0.2–0.3 electrons per photon. The principle has been experimentally extended to a second material, indium‐arsenide—phosphide, whose composition is tuned to provide a narrow spectral response peaking at 1.06 &mgr;. The experimental results are compared with theoretical predictions.

ISSN:0021-8979    

DOI:10.1063/1.1709330

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Targets of 2024‐T351 aluminum were shocked to approximately 110 kbar and 340 kbar by flyer plates having velocities of 0.12 and 0.32 cm/&mgr;sec, respectively. Free‐surface velocities were determined as a function of target thickness by recording the time of flight across known distances of thin shims which were originally in intimate contact with the surfaces of the samples. The experimental data are believed to be more accurate than any obtained previously. In earlier work it appeared that the free‐surface velocity decreased in a stepwise manner as the target thickness was increased. The new data do not show a stepwise decrease, so the simple elastoplastic relations cannot be used to predict attenuation. Some improvement in the predictions was obtained by using a variable shear modulus. The relation between the shear modulus and the strain was obtained from the results of the attenuation experiments. Further improvement may be obtained by the inclusion of the Bauschinger effect in the calculations. Some data were obtained for annealed 1060 aluminum at 110 kbar. The response of 1060 aluminum appears to differ significantly from that of the hard aluminum.

ISSN:0021-8979    

DOI:10.1063/1.1709331

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709332

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709333

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709334

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709335

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709336

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709337

出版商:AIP    

年代:1967

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1709338

出版商:AIP    

年代:1967

数据来源: AIP