Steady-State Orbitron Emissions
The Orbitron maser has been operated at a pressure of 2 × 10-6 in the steady state. Electrons are supplied to the device by an oxide-coated tungsten cathode placed inside the cylindrical cavity. The plasma-free emission corresponded to harmonically related steady-state narrow lines. The fundamental (lowest frequency) line corresponds to a resonance in the cavity system, which could be observed with a grid-dip meter.
Electron density and temperature in the pulsed-orbitron-maser glow discharge
In order to better understand the pulsed-glow discharge that provides the feed electrons for a pulsed-orbitron maser, the authors report using penetrating microwave beams and radially inserted Langmuir probes to make bulk and radial measurements of the number density in the plasma. The Langmuir probe was also used to measure the electron temperature across the plasma radius, and to investigate the effects of an externally applied magnetic field on the RF output of the orbitron. It was found that the emitted frequency is apparently not related to the electron plasma frequency by any simple linear relationship, and that an externally imposed magnetic field of as little as 70 G is required to kill the instability. >
Resistive wall effect on the stability of planar relativistic Brillouin flow
Previous treatments of relativistic Brillouin flow stability are extended to the case of nonzero anode resistivity, for the case of wave propagation across the equilibrium magnetic field. It is found that transverse magnetic (TM) waves are unstable at frequencies below the equilibrium cyclotron frequency, unlike the case for a perfectly conducting anode. Transverse electric (TE) waves, always oscillatory in the case of a perfectly conducting anode, are damped; an explicit expression for the damping rate, valid for large conductivities, is given.