Further Investigations for a Superconducting cw-LINAC at GSI

For superconducting (sc) accelerator sections operating at low and medium beam energies very compact accelerating-focusing structures are strongly required, as well as short focusing periods, high accelerating gradients and very short drift spaces. The Facility for Antiproton and Ion Research (FAIR) is going to use heavy ion beams with extremely high peak current from UNiversal Linear ACcelerator (UNILAC) and the synchrotron SIS18 as an injector for the SIS100. To keep the GSI-Super Heavy Element program competitive on a high level and even beyond, a standalone sc continuous wave LINAC in combination with the upgraded GSI High Charge State injector is envisaged. In preparation for this, testing of the first LINAC section (financed by HIM and GSI) as a demonstration of the capability of 216 MHz multi gap Crossbar H-structures (CH) is still ongoing, while an accelerating gradient of 9.6 MV/m (4K) at a sufficient quality factor has been already reached in a horizontal cryostat. As a final R&D step towards an entire LINAC three advanced cryo modules, each comprising two short CH cavities, should be built until 2019, serving for first user experiments at the coulomb barrier.