Operation status of the J-PARC linac

Ito, Takashi  

The beam operation of the J-PARC (Japan Proton Accelerator Research Complex) linac started in November 2006 and a beam has been delivered to the users since November 2008. During the operation, we have experienced many kinds of troubles, such as the discharge problem of Radio Frequency Quadrupole (RFQ), failure of High Voltage DC power supply (HVDC) for klystron and so on. To solve these troubles one by one, the beam power have been ramped up to 300 kW (beam energy: 181 MeV, peak beam current: 15-20 mA) from a 3 GeV Rapid Cycling Synchrotron (RCS), and we have made the linac operation more stable. The goal of the J-PARC project is to deliver a 1 MW beam from the RCS and a 0.75 MW beam from a 30 GeV Main Ring synchrotron (MR). To achieve the goal, the upgrade of the linac is required: the beam energy upgrade from 181 MeV to 400 MeV and the beam current upgrade from 30 mA to 50 mA. For the energy upgrade, a new accelerator structure, annular-ring coupled structure (ACS) linac, was installed in September 2013 and available for users in February 2014. A front-end, i.e. a new ion source, RFQ and some components between the RFQ and the Drift Tube Linac (DTL), was replaced to increase a peak beam current in August 2014. The user operation with the new front-end linac has started in November this year, and the linac operation is very stable so far.