Heavy Ion Acceleration at the Heidelberg Tandem Postaccelerator Combination

At the MPI für Kernphysik the range of heavy ions available with energy higher than 5 MeV/N has been extended to masses of about A=100 by combining the upgraded 13 MV MP-Tandem with a normal conducting RF-linac consisting of 32 independently phased spiral resonators. A first part of the linac of 10 resonators had already been operated between 1977 and 1979 with maximum effective voltages of 3.3 MV (CW) and 5.5 MV (pulse mode). After completion the extended booster now yields 9.7 MV in CW mode and 18.5 MV in pulse mode (duty factor 0.25). The high flexibility of the booster guaranteed by the independent phasing principle allows operation of the machine in the mass range of A=10 to A=100 with nearly constant acceleration voltage and with almost negligible set up times due to the flexible computer control. The maximum energies obtained so far are for some ions: 164 MeV 12C, 332 MeV 32S, 337 MeV 35Cl, 476 MeV 79Br and 511 MeV 127J. The tandemlike beam quality of the Tandem Booster combination (radial emittance < 2 II mm mrad, energy resolution < 10-3 (with debuncher)) and the available beam pulse width of less than 100 ps are an important contribution to the heavy ion nuclear and atomic physics experiments at MPI since March 1980. The overall availability of the postaccelerator together with the MP Tandem was above 80% of the scheduled user beam time.