Theoretical Study of a Plasma-Filled Relativistic Cerenkov Generator With Coaxial Slow-Wave Structure
The linear and nonlinear theory of a plasma-filled relativistic Cherenkov generator with coaxial slow-wave structure (SWS) is developed. Linear analysis includes the space-charge limiting current, dispersion relations, dispersion curves, and coupling impedance. In nonlinear theory, the electron beam space-charge effect, nonsynchronous interaction, and complex reflection coefficients of the electromagnetic wave at the boundaries of the SWS are taken into account. With the assumption of quasi steady state, the self-consistent equations are numerically calculated using the fourth-order Runge-Kutta method. The effects of the relative phase between inner and outer corrugations, phase and amplitude of the complex reflection coefficient at the boundaries of the SWS, and plasma density on device efficiency are discussed. Efficiencies of up to 37% without plasma and about 50% with plasma density of np = 3-7 times 1011 cm-3 are obtained.
Experimental study of a plasma-filled backward wave oscillator
We present experimental studies of a plasma-filled X-band backward wave oscillator (BWO). Depending on the background gas pressure, microwave frequency upshifts of up to 1 GHz appeared along with an enhancement by a factor of 7 in the total microwave power emission. The bandwidth of the microwave emission increased from ≤0.5 GHz to 2 GHz when the BWO was working at the RF power enhancement pressure region. The RF power enhancement appeared over a much wider pressure range in a high beam current case (10-100 mT for 3 kA) as compared to a lower beam case (80-115 mT for 1.6 kA). The plasma-filled BWO has higher power output compared to the vacuum BWO over a broader region of magnetic guide field strength. Trivelpiece-Gould modes (T-G modes) are observed with frequencies up to the background plasma frequency in a plasma-filled BWO. Mode competition between the Trivelpiece-Gould modes and the X-band TM01 mode prevailed when the background plasma density was below 6×1011 cm-3. At a critical background plasma density of ncr≅8×1011 cm-3 power enhancement appeared in both X-band and the T-G modes, with mode collaboration. Power enhancement of the S-band in this mode collaboration region reached up to 8 dB. Electric fields measured by Stark-effect method were as high as 34 kV/cm while BWO power level was 80 MW. These electric fields lasted throughout the high power microwave pulse.
The effect of continuous exposure to low frequency electric fields on three generations of mice: A pilot study
Mice were allowed to mate, gestate, deliver and rear their offspring for 3 successive generations while being continuously exposed to 60 Hz electric fields. Mice exposed to vertical electric fields exhibited decreased body weights at 35 days postpartum and increased mortality, rates for 3 successive generations. Mice exposed to horizontal electric fields exhibited decreased body weights for 2 successive generations.