RF plasma source for heavy ion beam charge neutralization

Highly ionized plasmas are being used as a medium for charge neutralizing heavy ion beams in order to focus the ion beam to a small spot size. A radio frequency (RF) plasma source has been built at the Princeton Plasma Physics Laboratory (PPPL) in support of the joint Neutralized Transport Experiment (NTX) at the Lawrence Berkeley National Laboratory (LBNL) to study ion beam neutralization with plasma. The goal is to operate the source at pressures ∼ 10 ^-5 Torr at full ionization. The initial operation of the source has been at pressures of 10 ^-4 - 10 ^-1 Torr and electron densities in the range of 10 ⁸ - 10 ¹¹ cm ^-3. Recently, pulsed operation of the source has enabled operation at pressures in the 10 ^-6 Torr range with densities of 10 ¹¹ cm ^-3. Near 100% ionization has been achieved. The source has been integrated with the NTX facility and experiments have begun.