High-power rotating wheel targets at RIKEN

Two kinds of rotating wheel targets for high-power heavy ion reaction have been developed. One is a thick disk target with water-cooling being developed for the in-flight RI beam separator (BigRIPS). An in-beam test was performed using 40Ar beam at 24 AMeV, 1.9 particle μA, with the beam spot size 3 mm in diameter, resulting 0.25 GW/m2 beam power stopped at the surface of carbon disk 2 mm in thickness and 260 mm in diameter. It performed stably without melting. A simulation study has been developed and its possibility for the use of BigRIPS is discussed. The second is a thin target foil mounted on a wheel disk which rotates in He cooling gas of 13.32–133.2 Pa. Its main use is in fusion reactions to search for super-heavy elements by using the gas-filled recoil separator (GARIS). A typical foil is Pb or Bi of 200–300 μg/cm2 in thickness evaporated onto a carbon backing foil of 30 μg/cm2 thickness, and covered by evaporated carbon of 10 μg/cm2 thickness. It can withstand long use under high-intensity 64Ni beam at 311 MeV, and 0.5 particle μA.