Development of RF-driven negative hydrogen ion source for J-PARC

Ueno, Akira  

In order to achieve the design beam power of 1 MW, a negative hydrogen ion source with a peak beam current of 60 mA within horizontal and vertical 1.5 mmmrad emittances is under development. The beam extraction system is the same with the J-PARC ion source, which is using a lanthanum hexaboride (LaB) filament. The inner diameter of the plasma chamber is enlarged form 100 mm to 120 mm in order to install a water cooled plate attached to the plasma electrode (PE) and a cesium (Cs) injector. The end flange is modified to install the RF-antenna. A rod-filter flange is installed to produce a low-temperature plasma around the PE. For the conditions of the pulsed RF duty of 2.5% (1 ms 25 Hz), the air cooled PE (PE temperature of 120 C) and opening the Cs valve for 4 min/day, a negative hydrogen ion beam with a peak beam current of more than 60 mA within 1.5 mmmrad emittances is successfully produced for more than 100 hours.