Upgrading the Heidelberg MP-Tandem Postaccelerator Combination

The Heidelberg Tandem Postaccelerator Combination is undergoing a stepwise upgrading program intended to further considerably extend its mass and energy range as well as to increase the available intensity of heavy ion beams. In a first step in 1982 a resonator module of four newly developed ß = 0.12 spiral-splitring resonators had been added to the high energy end of the linear accelerator. These resonators deliver rf-voltages of 0.5 MV (CW) and 1.0 MV (df = 0.25) each, increasing the effective acceleration voltage of the booster to 22.5 MV. To improve the performance of the accelerator system for heaviest projectiles two extensions are under construction. A 3 MV negative ion injector based on a reconstructed single ended pelletron accelerator is nearing completion. It is designed to facilitate the injection of well isotope separated low emittance beams of the highest masses into the low acceptance acceleration tubes of the MP-Tandem, thus reducing beam loading and allowing for considerably higher intensities of beams like 197Au, 208Pb, and 238U. Later on a module of four 6 = 0.04-spiral-splitring resonators will be installed in front of the linac to match the velocity of heavy ions like 238U to the presently operating machine.