• P. Gerhard, W.A. Barth, L.A. Dahl, A. Orzhekhovskaya, K. Tinschert, W. Vinzenz, H. Vormann, S.G. Yaramyshev
  GSI, Darmstadt
• A. Schempp, M. Vossberg
  IAP, Frankfurt am Main

The super heavy element research is one of the outstanding projects at GSI. At SHIP* six new elements have been discovered; moreover, nuclear chemical experiments with transactinides were recently performed at TASCA**. This experimental program strongly benefits from high average beam intensities. In the past beam currents were raised significantly by a number of improvements. The present upgrade program comprises the installation of a superconducting (sc) 28 GHz ECR ion source, a new frontend (low energy beam transport and RFQ), and, in the long term, an sc cw Linac. For the short term, the new RFQ will raise the duty factor by a factor of two (50%), limited by the following accelerator only. This bottleneck will be resolved by the applied cw Linac. Beam tests with a newly developed sc CH cavity are scheduled for 2012. The setup of the RFQ as the major upgrade of the 20 year old HLI*** is in progress, the commissioning will be finished in March 2010. Besides a higher duty factor, improved longitudinal beam quality and transmission are expected. This paper reports on the challenging rf and beam commissioning.

* Separator for Heavy Ion Reaction Products
** TransActinide Separator and Chemistry Apparatus
*** High charge state injector, a part the UNILAC

• M. Busch, M. Amberg, F.D. Dziuba, H. Podlech, U. Ratzinger
  IAP, Frankfurt am Main
• W.A. Barth
  GSI, Darmstadt

At the Institute for Applied Physics a superconducting CH-Cavity (Crossbar H-Mode) has been developed. It is the first multi-cell drift tube cavity for the low and medium energy range of proton and ion linacs. A 19 cell, β = 0.1 prototype cavity has been fabricated and tested successfully with a voltage of 5.6 MV corresponding to gradients of 7 MV/m. The construction of a new superconducting 325 MHz 7-gap CH-cavity has started. This cavity has an optimized geometry with respect to tuning possibilities, high power RF coupling, minimized end cell lengths and options for surface preparation. Static tuning is carried out by small niobium cylinders on the girders. Dynamic tuning is performed by a slow bellow tuner driven by a step motor and a fast bellow tuner driven by a piezo. Additional thermal and mechanical simulations have been performed. It is planned to test the cavity with a 10 mA, 11.4 AMeV (β = 0.158) beam delivered by the Unilac at GSI. Another cavity (f = 217 MHz, β = 0.059) is currently under development for the cw Heavy Ion Linac at GSI. It is the first of nine sc CH-Cavities planned for this project covering an energy range from 1.4 to 7.3 AMeV.