H^- extraction from electron-cyclotron-resonance-driven multicusp volume source operated in pulsed mode

H2 microwave (2.45 GHz) pulsed plasma is produced from seven elementary electron cyclotron resonance sources installed into the magnetic multipole chamber "Camembert III" (École Polytechnique-Palaiseau) from which H- extraction takes place. The negative-ion and electron extracted currents are studied through electrical measurements and the plasma parameters by means of electrostatic probe under various experimental conditions. The role of the plasma electrode bias and the discharge duty cycle in the extraction process is emphasized. The gas breakdown at the beginning of every pulse gives rise to variations of the plasma characteristic parameters in comparison with those established at the later time of the pulse, where the electron temperature, the plasma potential, and the floating potential converge to the values obtained for a continuous plasma. The electron density is significantly enhanced in the pulsed mode.