To keep the ambitious Super Heavy Element (SHE) physics program at GSI competitive a superconducting (sc) continuous wave (cw) high intensity heavy ion LINAC is currently under progress as a multi-stage R&D program of GSI, HIM and IAP [2]. The baseline linac design consists of a high performance ion source, a new low energy beam transport line, an (cw) upgraded High Charge State Injector (HLI), and a matching line (1.4 MeV/u) which is followed by the new sc-DTL LINAC for post acceleration up to 7.3 MeV/u. In the present design the new cw-heavy ion LINAC comprises constant-beta sc Crossbar-H-mode (CH) cavities operated at 217 MHz. The advantages of the proposed beam dynamics concept applying a constant beta profile are easy manufacturing with minimized costs as well as a straightforward energy variation [6]. An important milestone will be the full performance test of the first CH cavity (Demonstrator), in a horizontal cryo module with beam. An advanced Demonstrator setup comprising a string of cavities and focussing elements is proposed to build from 10 short CH-cavities with 8 gaps. The corresponding simulations and technical layout of the new cw heavy ion LINAC will be presented.

For future experiments with heavy ions near the coulomb barrier within the SHE (super-heavy elements) research project a multi-stage R&D program of GSI, HIM and IAP is currently in progress [1]. It aims at developing a superconducting (sc) continuous wave (cw) LINAC with multiple CH cavities as key components downstream the High Charge Injector (HLI) at GSI (Fig. 1). The beam dynamics concept is based on EQUUS (equidistant multigap structure) constant-β cavities. Advantages of its periodicity are a high simulation accuracy, easy manufacturing and tuning with minimized costs as well as a straightforward energy variation. The next milestone will be a full performance beam test of the first LINAC section, comprising two solenoids and a 15-gap CH cavity inside a cryostat (Demonstrator).

To compete in the production of Super Heavy Elements (SHE) in the future a 7.3 AMeV superconducting (sc) continuous wave (cw) LINAC is planned at GSI. The baseline design consists of 9 sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Currently an advanced cw demonstrator is under design at the Institute for Applied Physics (IAP) at Frankfurt University. The purpose of the advanced demonstrator is to investigate a new concept for the superconducting CH structures. It is based on shorter CH-cavities with 8 equidistant gaps without girders and with stiffening brackets at the front and end cap to reduce pressure sensitivity. One major goal of the advanced demonstrator is to show that the new design leads to higher acceleration gradients and smaller Ep /Ea values. In this contribution first simulation results and technical layouts will be presented.

A new superconducting (sc) continous wave (cw) LINAC at GSI is desired by a broad community of future users. Especially the Super Heavy Elements (SHE) program at GSI and at the Helmholtz Institute Mainz (HIM) benefits highly from such a dedicated machine [1]. A conceptual layout of an sc cw-LINAC was worked out at the Institute for Applied Physics (IAP) at Frankfurt University [2]. Here the key component, an sc Crossbar-H (CH) cavity, was developed recently [3]. The multi-gap cavity is operated at 217 MHz and provides gradients of 5.1 MV/m at a total length of 0.69 m [4]. The first section of the proposed cw-LINAC comprising a sc CH-cavity embedded by two sc solenoids is financed by HIM as a demonstrator. One important milestone of the project is a full performance test with beam of the demonstrator in 2013/14 at the GSI High Charge Injector (HLI). With the demonstrator the srf-technology finds the way to GSI. The tests would be the first of an sc multi-gap structure with heavy ions being an important milestone towards the proposed cw-LINAC. MOTIVATION Since 1981 six new elements, from element 107 to element 112, were discovered at GSI. An important milestone for the successful SHE program at GSI was the commissioning of the High Charge Injector (HLI) in the early nineties. Nevertheless the HLI in combination with the Universal Linear Accelerator (UNILAC) is not a dedicated machine to the SHE-research. In future the UNILAC is designated as an injector for FAIR (Facility for Antiproton and Ion Research). Beam time availability for SHE-research will be decreased due to the limitation of the UNILAC in providing a proper beam for SHE and in fulfilling the requirements for FAIR simultaneously. To keep the SHE program at GSI competitive on a high level, an upgrade program of the HLI was initialized comprising a new 28 GHz ECR source and a new cw capable RFQ [5, 6]. As a result of a long term cost-benefit analysis a standalone sc cw-LINAC in combination with the upgraded HLI is assumed to fit the requirements of SHE at best [1]. Significant higher beam intensities will be provided and lead to an increase of the SHE production rate: The production cross section of element 120 is assumed to be smaller than 0.1 pbarn for instance. With the existing UNILAC a beam time on target of ten weeks for one event is estimated at minimum by experience [7]. The proposed sc cw-LINAC is expected to reduce the beam time by a factor of 20 to 4 days. Figure 1: Draft layout of the future GSI accelerator facility with the integrated cw-LINAC in parallel to the existing UNILAC (Ci = Cavity, Bi = (Re-)Buncher, Si = Solenoid, QT = Quadrupole-Triplet). The cw-LINAC should provide SHE-experiments like SHIP (Separator for Heavy Ion reaction Products) and TASCA (TransActinide Separator and Chemistry Apparatus ) with beam. THIOA05 Proceedings of SRF2011, Chicago, IL USA 646 08 Future projects

The Helmholtzcenter for Heavy Ion research (GSI) is focusing on the Facility of Antiproton and Ion Research (FAIR) strongly. Providing highest energy beams the new facility will offer outstanding research opportunities and discovery potential in future [1]. Nevertheless, regarding the public impact the discovery of new elements is next to the cancer therapy with heavy ions still the flagship of GSI. It is an ongoing process to keep the super heavy element (SHE) program at GSI together with its international collaborations competitive on a high level. Providing high primary beam intensity by a dedicated accelerator is one import part therefore. A cost-benefit analysis has shown, that a superconducting (sc) continuous-wave (cw) linear accelerator (LINAC) in combination with the upgraded GSI High Charge Injectior (HLI) fits the requirements for the GSI SHE program at best [2]. A predicted increase of the beam intensity by a factor of 10 to 20, depending on the ion and charge state, would keep the successful and popular SHE program competitive with remarkable reduced operational costs in comparison with the existing accelerator at GSI. In the following the status of the cw LINAC project is reported and its perspectives are discussed.

The superconducting (sc) continuous wave (cw) LINAC Demonstrator is a collaboration project between GSI, the Helmholtz Institute Mainz (HIM), and the Institute for Applied Physics (IAP) at the Goethe University Frankfurt. The aim is a full performance test of a 217 MHz sc Crossbar H-mode (CH) cavity, which provides gradients of 5.1 MV/m at a total length of 0.69 m. In addition the Demonstrator comprises two 9.3 Tesla sc solenoids. The configuration of a CH-cavity embedded by two sc solenoids is taken from a conceptual layout of a new sc cw LINAC with nine CH-cavities and seven solenoids. Such an accelerator is highly desired by a broad community of users requesting heavy ion beam energies in the Coulomb barrier range. A successful test of such an sc multigap structure is an important milestone towards the proposed cw-LINAC.

The realisation of the first section of a new superconducting (sc) continuous wave (cw) LINAC is planned in 2013. The project is called “cw LINAC Demonstrator” and is financed by the Helmholtz Institute Mainz (HIM). The aim is a “full performance test” at GSI-HLI of a new 217 MHz sc CH-Cavity which is designed by the Institute of Applied Physics (IAP) of the University Frankfurt [1, 2]. According to an engineering study for the cryostat, a frame has been designed to support the cavity embedded by two sc solenoids. A nuclotron -suspension analog to the SIS-100 Magnets for FAIR is used, which nearly prevents the displacement of the components on the frame while cooling down. Another challenge is to reduce the magnetic field of the solenoid from 9.3 T to 50 mT at the cavity within some centimeters by moveable compensation -coils. This and other technical solutions in the cryogenic environment of the Demonstrator are presented. INTRODUCTION Since 1990 the High Charge Injector (HLI) is in service to provide SuperHeavyElement (SHE) experiments (SHIP and TASCA) with beam at GSI. It comprises a 14 GHz ECR, an RFQ, and an IH anti-parallel to the UNILAC. In 2005 an upgrade program for the HLI was defined to make the HLI cw-capable [3, 4]. Straight forward to this injection line the Demonstrator should be assembled for a “full performance test” with beam. In order to use these favourable conditions it is planned to adjust the test environment, with the cryostat, a 3000ltr. Helium reservoir, a radiation protective shield, the beam diagnostics and other supply units in this area (Fig.1). In order to solve the physical, technical, and assembling requirements some solutions are presented to accomplish the components (solenoids, cavity, supporting frame) and keep the needed tolerances. Another challenge is the detection of the displacements of the components while cooling down. Figure 1: The future layout of the GSI accelerator facility with the cw-LINAC Demonstrator integrated in the existing High Charge Injector (HLI). MOPO030 Proceedings of SRF2011, Chicago, IL USA 144 05 Cavity design The Demonstrator comprises two superconducting solenoids and the 217 MHz sc CH-cavity and is the first section of the future sc cw-LINAC, which allows the acceleration of highly charged ions with a charge to mass ratio of 1 to 6 at 1.4 MeV/u from the upgraded HLI. The proposed cw-LINAC is designed with nine sc CH-cavities and seven sc solenoids [5, 6]. CW-LINAC-DEMONSTRATOR

At present, two superconducting (sc) CH cavities are under development at the Institute for Applied Physics (IAP) of Frankfurt University. The construction of a sc 325 MHz CH cavity with 7 cells and an envisaged design gradient of 5 MV/m is almost finished. It is planned to test this cavity with beam at GSI Universal Linear Accelerator (UNILAC), Darmstadt to show its performance as a candidate for the UNILAC upgrade. Furthermore, the 217 MHz CH structure with 15 accelerating cells and a real estate gradient of 5.1 MV/m will be the first cavity of the new sc continuous wave (cw) LINAC at GSI. This proposed cw LINAC is highly requested to fulfil the requirements of nuclear chemistry and especially for a competitive production of new Super Heavy Elements (SHE). To demonstrate the cavity capabilities under a realistic accelerator environment, a full performance test by injecting and accelerating a beam from the GSI High Charge Injector (HLI) is planned in 2013/14. The current status of both sc CH cavities is presented.

The superconducting (sc) CH-structure (Crossbar-Hmode) is a multi-cell drift tube cavity for the low and medium energy range operated in the H21-mode, which has been developed at the Institute for Applied Physics (IAP) of Frankfurt University. With respect to different high power applications two types of superconducting CH-structures (f = 325 MHz, β = 0.16, 7 cells and f = 217 MHz, β = 0.059, 15 cells) are presently under construction and accordingly under development. aspect of the cavity design. Furthermore, several simulations with ANSYS Workbench have been performed to predict the deformation of the cavity walls due to the cavity cool-down, pressure effects and mechanical vibrations. To readjust the fast frequency changes in consequence of the cavity shape deformation, a new concept for the dynamic frequency tuning has been investigated, including a novel type of bellow-tuner.

The search for Super-Heavy Elements (SHE) is one of the frontiers in nuclear physics. By trend the production cross sections decrease significantly for larger proton numbers and heavier nuclei, respectively. To limit the required beam time it is necessary to use the highest available intensity. This prefers cw operation and the use of superconducting cavities. A cw operated superconducting linac using CH-cavities at GSI has been designed. As front end the existing 108 MHz High Charge Injector (HLI) will be used which is presently being upgraded for cw operation. The superconducting part of the linac covers the energy between 1.4 AMeV and 7.3 AMeV. It consists of 9 multicell CH-cavities operated at 217 MHz. Each cavity is optimized for a specific particle velocity but without beta profile. Above 3.5 AMeV the linac is fully energy variable. The first superconducting CH-cavity will be constructed tested with beam delivered by the HLI. The development of the prototypes and the overall design including beam dynamics issues is presented.

Currently the 325 MHz CH-Cavity, which is proposed for beam tests at GSI UNILAC, is under construction. First cryo-tests are determinded for mid-2011. One focus of the new cavity will be the new tuning system consisting of bellow tuners. The design of these bellow tuners is still in progress in order to avoid multipacting scenarios. The chal lenge of this project will be the exact achievement of the goal frequency after all the fabrication steps which have to be planned very thoroughly.