A pulse-periodic gyroresonant plasma accelerator

Abstract

A plasma electron accelerator based on the gyromagnetic autoresonance effect is described. Electrons of the initially cold internal-injection plasma (a classical ECR discharge) are accelerated in the magnetic field of a magnetic mirror trap under a one-stage effect of the resonant microwave field and an additional pulsed magnetic field. The synchronism in maintaining the resonance conditions is ensured by a smooth increase in the pulsed magnetic field in the course of a microwave pulse. At the moderate values of the input microwave power (up to 2.5 kW) and the steady-state and pulsed magnetic fields (each up to 1 kG), it is possible to obtain stable relativistic plasma bunches, in which the energy of the electron components is a few hundred keV. The measured X-ray bremsstrahlung spectra have features characteristic of the energy distribution of photons, and the high-energy tails are recorded in the region of 600–800 keV. The dependences of the bremsstrahlung characteristics on the experimental conditions—the value of the steady-state magnetic field and the amplitude of the pulsed magnetic field—are investigated. The experimental data are in good agreement in the quantitative sense with the results of the computer simulation and with the earlier studies.