Status of the Japan Proton Accelerator Research ComplexH−ion source

Abstract

A cesium-free H À ion source driven by a LaB 6 filament is being operated for the beam commissioning of the accelerators at Japan Proton Accelerator Research Complex (J-PARC). The beam commissioning started in November 2006. As of June 2008, there have been 17 beam commissioning runs. The duration of each run was approximately 4-5 weeks. In these runs, the ion source has succeeded in providing beam to the J-PARC accelerators for 2720 hours. The interruption time due to the failure of the ion source is only approximately 50 hours. The availability of the ion source is calculated to be 98%. Since the fluctuation of the beam current is small, tuning the beam current once a day is sufficient to maintain the beam current within the error of a few percent. Recently, the ion source succeeded in producing the beam current of 36 mA with a flattop pulse width of 500 s and a repetition rate of 25 Hz as required for the first stage of J-PARC.

Operation Status of the J-PARC Ion Source

“…Cesium is not used. The basic structure of the ion source has not been changed since the operation was started [1]. The ion source consists of a plasma chamber, a beam extractor and a large vacuum chamber with two turbo molecular pumps (TMPs) of 1500 l/s for differential pumping.…”

Operation Status of the J-PARC Negative Hydrogen Ion Source

“…The extraction and acceleration gap length are 3.0 mm and 12.0 mm, respectively. The acceleration gap length is optimized to obtain maximum beam transmission rate through the RFQ [7]. The PE is fabricated by boring a 45 degree tapered hole with a diameter of 9 mm on a molybdenum plate with a thickness of 16 mm.…”

“…At present, the H -ion current from the ion source is routinely restricted approximately 16 mA for the stable operation of the RFQ which has serious discharge problem from September 2008 [8], although the ion source is capable of producing an H -ion current of more than 30 mA [7]. The H -ion current is tuned by changing the arc power.…”

Path to 1-MW at J-PARC Rapid Cycling Synchrotron

“…The front-end system consists of a new ion source, new Radio Frequency Quadrupole (RFQ), and some parts of a beam transport line between the new ion source and new RFQ. A cesium-free negative hydrogen ion source driven with a lanthanum hexaboride filament had been used since the Linac operation began in 2006 [30]. Although it satisfied the initial stage requirement of 30mA in J-PARC, it was proven that this current level did not increase by cesiation.…”