Observation of ultrahigh-energy electrons by resonance absorption of high-power microwaves in a pulsed plasma - art. no. 016403

The interaction of high power microwave with collisionless unmagnetized pla sma is studied. Investigation on the generation of superthermal electrons n ear the critical layer, by the resonance absorption phenomenon, is extended to very high microwave power levels (eta = E-0(2)/4 pin(e)kT(e) approximat e to 0.3). Here E-0, n(e), and T-e are the vacuum electric field, electron density, and electron temperature, respectively. Successive generation of e lectron bunches having maximum energy of about 2 keV, due to nonlinear wave breaking, is observed. The electron energy epsilon scales as a function of the incident microwave power P, according to epsilon proportional to P-0.5 to 250 kW. The two-dimensional spatial distribution of high energy electro ns reveals that they are generated near the critical layer. However, the lo wer energy component is again produced in the subcritical density region in dicating the possibility of other electron heating mechanisms.