Relativistic diodes in crossed magnetic fields. Progress report, June 1, 1975--February 15, 1976
The behavior of a cylindrical field emission diode (radial potential approximately 200 kV) was studied in the presence of an externally applied axial magnetic field B less than or equal to 16 kG. Observations made of the space charge-limited electron current (approximately 50 kA) compare favorably with theory which takes into account the presence of both the external axial magnetic field and the azimuthal self-magnetic field generated by current flow in the cathode. At magnetic fields exceeding the critical field necessary for cutoff, small but not insignificant current flows persist. The associated microwave emission suggests that this residual current is being driven by an as-yet-unidentified high-frequency instability. Time-resolved measurements of the diode current and voltage lead to a determination of the expansion velocity of the cathode and anode plasmas. It was found that an external magnetic field of approximately 5 kG suffices to stop plasma motion. This value is in agreement with magnetohydrodynamic computations for a hydrogen plasma having an initial temperature of a few eV. Spectroscopic measurements of the diode plasma have shown that hydrogen is indeed the dominant ion species. Stark broadening of the spectral lines yields their number density.
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge (USA). Research Lab. of Electronics
- DOE Contract Number:
- E(11-1)-2766
- OSTI ID:
- 7145302
- Report Number(s):
- COO-2766-3
- Country of Publication:
- United States
- Language:
- English
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