Plasma cyclotron maser with a magneto-compressional pumping

The capabilities of modern vacuum electronic devices with respect to accumulation of energy in an “active substance” and control of the duration of resultant electromagnetic radiation are constrained by the interaction time of an electron beam with the radiation limited by the beam transit through a resonator. Using non-equilibrium plasma as an active substance opens new possibilities for long-lasting accumulation of energy in a resonator volume with subsequent release of this energy in the form of a short pulse of electromagnetic radiation. Energy may be effectively pumped by a magnetic compression in time resulting in formation of non-equilibrium energetic tails in the electron distribution function. The energy of fast electrons may be released as coherent maser electromagnetic radiation due to development of electron cyclotron (EC) instabilities caused by the anisotropy of the electron distribution function. The radiation frequency is determined by the magnetic field strength at the moment when the instability develops, and therefore can be varied in wide limits. Realization of such modes in a plasma device faces essential difficulties because the accumulation time of energetic electrons exceeds by many orders of magnitude the instability growth times, what causes a premature release of the energy before it is accumulated. These difficulties were partially overcome, where a new mode of generation was proposed being based on excitation of oblique fast extraordinary waves in rarefied plasma. It was found that development of the cyclotron instabilities may be refrained by dense background plasma, what has been confirmed by a laboratory experiment on detecting the cyclotron instabilities on a decay phase of a pulsed ECR discharge in a mirror trap discussed in the present paper, which continues our early work. These results open good prospects for development of a new class of sources of pulsed electromagnetic radiation, in particular, in the terahert- frequency range poorly mastered by classic vacuum electronics devices.