Plasma dynamics during relativistic S-band magnetron operation

Abstract

Results of a time- and space-resolved spectroscopic research studies of an S-band relativistic magnetron generating 1.5×108 W microwave power at f=2950 MHz, powered by a linear induction accelerator (450 kV, 4 kA, 150 ns), are presented. The cathode plasma electron density and temperature were obtained by analyzing Hα and Hβ hydrogen Ballmer series and carbon C II and C III ion spectral lines and the results of collision radiative modeling. It was shown that the microwave generation is accompanied by a significant increase in plasma density and ion temperature, up to ∼5×1016 cm−3 and ∼8 eV, respectively. The plasma electron temperature was found to be ∼8 eV. It was shown that the plasma expansion velocity in the axial direction reaches ∼107 cm/s and does not exceed ∼2×105 cm/s in the radial direction. In addition, it was shown that the plasma is not uniform and consists of separate plasma spots whose number increases during the accelerating pulse. Estimates of the plasma transport parameters and its interaction with microwave radiation are also discussed.