High power DC and ns-pulsed 2 MV accelerator for light ions

Abstract

High Voltage Engineering developed, built, and tested a unique 2 MV single-ended accelerator (SingletronTM) for light ions. The system combines a beam current of up to 2 mA for protons and helium in direct-current mode with nanosecond-pulsing capability. Compared to other chopper-buncher applications with Tandem accelerators, the single-ended accelerator increases the charge per bunch by about a factor of 8. The all-solid-state Singletron 2 MV power supplyTM supports high-current operation and features a large dynamic range of the terminal voltage and good transient performance to support the high-current operation. The terminal accommodates an in-house developed 2.45 GHz electron cyclotron resonance ion source and a chopping-bunching system. The latter features phase-locked loop stabilization and temperature compensation of the excitation voltage and its phase. The chopping bunching system further features the selection of hydrogen, deuterium, and helium as well as a pulse repetition rate, ranging from 125 kHz to 4 MHz, that are fully computer controlled. In the testing phase, the system demonstrated smooth operation for 2 mA proton and helium beams at terminal voltages from 0.5 to 2.0 MV, and somewhat reduced current at a voltage down to 250 kV. In pulsing mode, pulses with a full width at half maximum of 2.0 ns reached a peak current of ∼10 and ∼5.0 mA for protons and helium, respectively. This is equivalent to a pulse charge of about 20 and 10 pC. Applications range from various fields requiring direct current at multi-mA levels and MV light ions, including nuclear astrophysics research, boron neutron capture therapy, and deep implantation for semiconductor applications.