Short pulse ECR ion sources of multicharged ions

Summary form only given. Present work is devoted to demonstration of possibility of short pulsed (<; 100 μs) multicharged ion beams formation by ECR ion source sustained by millimetre waves. Such investigations were stimulated by “Beta Beam” project. The possibility of quasi-stationary generation of short pulsed beams under conditions of quasi-gasdynamic plasma confinement was shown in recent experiments. Later another way of such beams creation based on "Preglow" effect was proposed. The effect was discovered at LPSC on PHOENIX ion source using 18 GHz radiation for plasma heating and later was studied at different laboratories in a frequency range from 14 to 28 GHz. As a continuation of previous research at 14, 18 and 28 GHz at present work results of experimental and theoretical "Preglow" effect investigations at SMIS 37 setup with 37,5 GHz MW plasma heating are reported. Generation of "Preglow" peak with duration about 30 μs was shown. Received dependencies of the "Preglow" parameters are in good correspondence with results of numerical simulations. In frames of "Preglow" experimental investigations another regime of short pulses generation was discovered while shortening of MW duration. It was demonstrated that in the case when duration of MW pulse is less then formation time of "Preglow" peak, realization of a regime when ion current is negligible during MW pulse and intense multicharged ions flux appears only when MW ends could be possible. Such pulses after the end of MW were called "micropulses"2. In present work generation of micropulses was observed in experiments with ECR discharge stimulated by gyrotron radiation @ 37.5GHz, 100 kW. In present work it was shown that intensity of such micropulse could be higher than intensity of "Preglow" peak at the same conditions but with longer MW pulse. The generation of micropulses of nitrogen and argon multicharged ions with current of a few mA and length about 30 μs afte- MW pulse with duration of 30-100 μs was demonstrated. The low level of impurities, high current density and rather high average charge make possible to consider such micropulse regime as perspective way for creation of a short pulsed ion source.