Beam-spot temperature monitoring on the production target at the BigRIPS separator

Since 2007, a water-cooled high-power rotating disk target has been in operation at the in-flight radioactive-isotope beam separator (BigRIPS), RIKEN. The target should withstand a goal beam intensity of 1 particle μA (pμA) 238U-beam at 350 AMeV with a spot size of 1 mm in diameter, resulting in a heat deposit of 22 kW in the target.A beam-spot temperature monitoring system using infrared devices in high-radiation environment was elaborately developed. The beam-spot temperature on a beryllium (Be) fixed target and on a rotating Be and tungsten (W) disk target was measured with the most intense beams presently available at our facility. The heat deposit achieved was 0.6 kW, that is 1/37 of the goal value. At the present beam intensity, the result supports our estimation that a water-cooled rotating disk target of 30 cm diameter can withstand an approximately tenfold beam intensity compared to a water-cooled fixed target.