Experimental plasma maser as a broadband noise amplifier. I. Long pulse

Operated in the noise amplification regime, a plasma maser underwent a series of experiments. The pulse duration was 50ns, the suppression of feedback was provided by microwave absorbers, transition from the noise amplification to a self-oscillation regime was demonstrated, and the maximum power of 10MW with the efficiency of 3% was measured. For different plasma concentrations, the linear amplification rate was ranging from 0.1 to 0.2cm(-1). The frequency band of an emission pulse was 3-15GHz, and the noise spectrum was stable during the pulse. The experiment provided the guidelines for further development, which are in the pulse duration reduction for abandoning the microwave absorber. The short-pulse plasma maser should be similar to 35cm long with the pulse duration<4ns. It will have more power and efficiency, a pulse spectrum width of 3GHz, and tunable frequency band overlapping 3-14GHz with the rise of plasma concentration.