Study of Microwave Generation Utilizing Double-Stream Instabilities in Anisothropic Media

摘要

The computer results for the two-stream instability in pyrolytic graphite (PG) and bismuth (Bi) have been obtained. The instability frequency for the acoustical mode in the optimum crystalline direction (trigonal) is approximately 500 GHz wavelength = 0.6 mm) at the frequency of maximum growth rate. The current density required at the threshold of the instability is approximately 15 amp/sq mil. For PG, the corresponding frequency and current density requirement in the a-plane is 3 x 13 to the 13th power cps (wavelength = 10 microns) and 35 amp/sq mil. Experiments with PG samples of larger cross-sectional area have been unsuccessful even though the detection system sensitivity has been improved. Further experiments will be concentrated in Bi using an indium antimonide submillimeter detector operating at liquid helium temperature. (Author)