1. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 Task SIS18-1: h=2 Cavity P. Hülsmann GSI, Gesellschaft für Schwerionenforschung mbH Planckstraße 1 D-64291 Darmstadt EU-FP6 Annual Report Meeting, October 11, 2007

2. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 Task SIS18-1: h=2 Cavity 1)Requirements 2)Technical Description 3)Organizational Issues 4)General Strategy for Construction Content

3. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 Objectives Development of new RF accelerating cavity based on the novel magnetic alloy materials (MA-materials) for operation at harmonic number h=2 (f = 0.43 to 2.7 MHZ) to provide the necessary accelerating voltage for SIS18 injector operation with high intensity heavy ion beams in a fast operation mode with three cycles per second. Presently the SIS18 rf – system operates at the fourth harmonic. At the end of the SIS18 upgrade program the harmonic number two system will replace one of the old cavities in order to enable a double harmonic rf operation with the remaining cavity. It is important to point out that the existing SIS18 rf system does not provide enough bucket area in order to accelerate intense bunches in the 3 Hz SIS12 mode. 1) Requirements Task SIS18-1: h=2 Cavity

4. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 Due to the many insertions which were additionally implemented into the synchrotron ring SIS12/18 in the meantime, the available length in SIS12/18 for one cavity is very short. Due to technical reasons the required length for three cavity units have been enlarged from 3,4 m to 3,8 m. It turned out that a beam pipe equipped with 6 ceramic gaps could not be mounted as a whole, it needs two additional flanges to divide it into three parts. The gap voltage requirement with a bucket filling of 2/3 with space charge compensation and under beam loading is 40 kV in the frequency region of 0,43-1,6 MHz (11.4 – 200 MeV/u). In order to leave a safety margin we demand a total voltage of not less than 50 kV, of course without beam. It was carefully proved that the required length for a ferrite- system will be more than 7 m. 1) Requirements Task SIS18-1: h=2 Cavity

5. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 Task SIS18-1: h=2 Cavity 2) Technical Description: Cavity and power amplifier Fig. 1,2: One cavity unit consists of two ceramic gaps and four short stacks of three Finemet FT3M ring cores from Hitachi. The stacks of cores are covered by pressure resistant stainless steel tanks which are closed at the gap-side by strong plates made of fiber-reinforced resin. The ring cores are cooled by mineral- or silicon oil which flows between adjacent cores. Two core stacks are connected in parallel respectively by a busbar which is directly connected to the gaps. RF-power is fed into the cavity via the busbars.

6. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 2) Technical Description: Cavity and power amplifier Task SIS18-1: h=2 Cavity Fig. 3: Three cavity units connected to their power amplifiers. Each power amplifier consists of two vacuum tubes (probably RS 2042 SK, 300 kW) operating in push pull mode on one cavity unit. On top of the tubes the choke coils and the coupling capacitors are located. The power amplifier resides directly in front of the cavity in order to avoid transmission lines or additional capacitive loads which would decrease the bandwith.

7. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 2) Technical Description: Cavity and power amplifier Task SIS18-1: h=2 Cavity

8. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 2) Technical Description: Cavity and power amplifier Task SIS18-1: h=2 Cavity

9. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 Fig. 4: Up to now we have identified two possible places of installation. One is located in period 1 as indicated top right (red circle) in the drawing, the other is located in period 7 (blue circle). The discussions about the cavity location is ongoing. From our point of view the location in period 7 is advantageous compared to period 1. Reasons for that are: During beam time one needs access to the oil- and water pumps and the heat exchanger, in order to service the system. Therefore pumps and heat exchanger should be located in the transfer hall just to avoid an expensive modification of the ring tunnel. For installation in period 1 one needs more than 100 m of oil-pipeline back and forth and this needs additional pressure for balancing the pressure loss caused by the pipeline, heat exchanger and equalising tank. This leads to a pressure of nearly 300 kPa The cavity can survive 300 kP at maximum 3) Technical Description: One possible place of installation Task SIS18-1: h=2 Cavity

10. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 2) Technical Description: Location preferred Task SIS18-1: h=2 Cavity Fig. 5: The most promising location for the rf-system. Oil and water pipelines are very short since the location is very near to the tranfer hall. At this location the roof of the tunnel can be removed. But anyway some additional discussion is needed to insure that the location is available (Exciter, corrector magnet). Just behind the cavity the FRS-target area is located. Clarification with the FRS-collegues is necessary.

11. Peter Hülsmann, GSI RF-Group, Email: P.Huelsmann@gsi.de, Tel: +49 6159 71 2066 Task SIS18-1: h=2 Cavity Organisational risks: Tough time schedule due to FAIR-overall planning Technical risks: Reliability The cavity (3 units) will be build and delivered by HITACHI A final technical specification of the cavity is up to now not available since the location in the ring tunnel could not be fixed and a detailed document of all operational cycles (bucket filling, space charge influence) is not available. The discussion is ongoing whether HITACHI will also deliver the power amplifiers or not. The supply units will be subject of an European tender. The specification for the supply units is now available (parameters subject to change). GSI is concentrating mainly on system implementation and therefore will provide the rf control system for single- and double harmonic operation. Furthermore GSI will deliver the choke coils for the power amplifiers (since HITACHI has refused to deliver those) and last but not least GSI will deliver the oil cooling system. 4) General strategy for construction, risks