Operation of a cw rf driven ion source with hydrogen and deuterium gas (abstract)

We will describe the operation of a cw rf driven multicusp ion source designed for extraction of high current hydrogen and deuterium beams. The source is driven at 2 MHz by a 2.5 turn induction antenna immersed in the plasma. Bare stainless‐steel and porcelain‐coated Cu antennas have been used. The plasma load is matched to the rf generator by a variable tap N:1 transformer isolated to 46 kV, and an LC network on the secondary. With H2 gas the source can be operated at pressures between 5 and 60 mT with power reflection coefficients <0.01. The extracted ion current density with a porcelain‐coated antenna is approximately given by 35 mA/cm2/kW with an 80 G dipole filter field for input powers from 3.5 to 6.6 kW. The current density remained constant for operation with a 6 and an 8 mm aperture. The source has been operated for 260 h at 3.6 kW with a single‐porcelain‐coated antenna. Mass spectrometer measurements of the extracted beam at this power show a species mix for H+:H+2:H+3:OH+ of 0.49: 0.04: 0.42: 0...