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Kondo, Yasuhiro; Morishita, Takatoshi; Hasegawa, Kazuo; Naito, Fujio
no journal, ,
The J-PARC RFQ has suffered from instability due to breakdown from the start of routine operation started in 2009. We improved pumping speed, performed baking. In this presentation, a series of improvement to prevent breakdown of the RFQ. The result of recent residual gas analysis is also shown. Additionally, newly fabricating RFQs based on operating experience are presented.
Morishita, Takatoshi; Kondo, Yasuhiro; Hasegawa, Kazuo; Sugimura, Takashi*; Kawamata, Hiroshi*; Naito, Fujio*
no journal, ,
In the J-PARC linac, a new RFQ is designed for higher current (50 mA) operation and we started a fabrication last year. The 3.6m RFQ cavity is divided into three unit tanks in the longitudinal direction. Each unit tank consists of four vanes which are brazed together. To reduce the cost and time required to develop a special formed bite for the vane modulation machining, a numerical controlled machine using a conventional ball-end-mill was adopted for the vane modulation cutting instead of a generally used wheel shaped cutter. To reduce a breakdown risk at the operation, the smoothness is important at the modulation surface. By the ball-end-mill machining, the smoothness is also improved. In addition, the surface is chemically polished after the machining to improve the smoothness.