Composition of the power supply system for the JT-60 active beam source and suppression of surge current

An active beam diagnostic method is being adopted for the ion temperature measurement of the JT-60 core plasma. As an active beam source, a 200 keV, 3.5 A, 0.1 sec helium ion beam acceleration system has been developed. Before the installation onto the JT-60, the system was assembled and tested in a test room. After some improvements, rated ion beams were obtained repeatedly. In a present report, the composition of the power supply system is described firstly. Secondly, the countermeasure is given against malfunction of the power supply system due to surge voltage propagation associated with breakdown of the ion source. Further, the modification to reduce surge current for stable ion beam extraction is given along with the comparison between surge measurements and corresponding numerical simulations. Lastly, the numerical simulation of surge propagation is given when the beam line is installed onto the JT-60. (author)