Speaker
Description
A prototype radio frequency (RF) negative hydrogen ion source is under developing in the national fusion research institute (NFRI) in pursuing of the negative ion beam extraction of 200 keV, 0.5 A. The machine has extracted negative hydrogen ion beam since 2018, and recently two major upgrades have been implemented. The first upgrade is in the inductively coupled plasma (ICP) source. The ICP antenna is modified to supply a maximized RF current at the LC resonance frequency by installing additional capacitors. The RF power supply delivers 50 kW of RF power by active control of the RF frequency. A tungsten filament provides seed electrons just before the RF power is applied, and the plasma is generated by the RF power supply within 200 us. The second upgrade is in the series of the stackable high voltage power supplies. The output of the power supply is 20 kV / 1 A, and each power supply is floated and powered by batteries. So far, stacking is successfully applied to two modules, and will be extended. In this presentation, the details of the above upgrades and beam extraction result will be shown. In the near future, more upgrades will be followed: the plasma grid heater using hot oil circulation system will be used for Cs conditioning, and diagnostics using triple probe, CR based OES, and laser photo-detachment will be prepared.
