1. Clemente@gsi.deClemente@gsi.de www.linac-world.de Development of the Room Temperature CH-DTL in the frame of the HIPPI-CARE Project Gianluigi Clemente, Ulrich Ratzinger, Holger Podlech, R.Tiede, R.Brodhage, L.Groening GSI, Darmstadt, Germany J.W. Goethe-Universität, Frankfurt am Main, Germany HIPPI ANNUAL Meeting, CERN, GENEVA October 29 th, 2008

2. Clemente@gsi.deClemente@gsi.de www.linac-world.de Topic  The Room Temperature CH-DTL in the Frame of HIPPI  RF Properties  Past activities  Status of the Coupled CH-DTL: Model and Prototype  Future Plans

3. Clemente@gsi.deClemente@gsi.de www.linac-world.de GOAL OF THE PROJECT  For the GSI linac, with a final energy of approximately 70 MeV, the “KONUS” beam dynamics is foreseen with the use of H-mode structures over all the range of energies. Low power model cavities have to be built and measured, and a prototype 352 MHz CH cavity is proposed to be built and tested in a high power test stand at GSI or at CERN. ⇒  Construction of a cold model  Construction of a warm RF model  Construction of the first "FAIR" Prototype  Investigation of the KONUS beam dynamics for a multi MeV Linac ORIGINAL PLAN in Early 2004

4. Clemente@gsi.deClemente@gsi.de www.linac-world.de Why CH? Highest Shunt impedance at low-medium beta profile Existing H-Mode provided the highest accelerating gradient in those range of energy (10.5 MV/m at Cern linac 3) High Resistance against electric breakdown (K l > 5 at Cern Linac 3) Compact structure Mechanical Robustness Reduced number of focusing elements Easy to be cooled

5. Clemente@gsi.deClemente@gsi.de www.linac-world.de First Model 8 cells,β /2=45mm, total inner length 600 mm Original Idea based on "Press-fit technique" Copper Copper Plated Stainless Steel During the R&D development it was decided to build directly a warm model which could stand high RF level

6. Clemente@gsi.deClemente@gsi.de www.linac-world.de Tuning the end cells The end half drift tube can host magnetic lens and a diagnostics device Magnetic Tuning of the end cell 7

7. Clemente@gsi.deClemente@gsi.de www.linac-world.de Tuning concept Final tuning is obtained by changing the Gap/Length along the cavity axis Capacitive Tuning 8

8. Clemente@gsi.deClemente@gsi.de www.linac-world.de The first CH-DTL C ooling system: 8 water pipes (2 per quadrant) on the outer tank Hollow stems with own water connection 6 Copper plating: Successfully performed at the GSI galvanic workshop, average thickness: 40 μm Welding: Stems welded from inside, leak test successful Construction of the first room temperature CH-DTL

9. Clemente@gsi.deClemente@gsi.de www.linac-world.de The first CH-DTL: Results Main Results: Reliability of CH-DTL design in terms of mechanical construction, welding, and Copper Plating Measured Q 0 = 13000 (95 % of the ideal MWS Value) Measured Frequency 340 MHz ( 338.6 MHz Simulated ) Test at 2 kW CW: no multipacting observed, stability of cavity’s temperature during long test operation ⇒ Proof of efficiency for the cooling system Observed Problems: Deformation of the drift tubes during the welding process: Press-fit technique no longer used

10. Clemente@gsi.deClemente@gsi.de www.linac-world.de Application to FAIR  After LINAC 06 it was decided to feed the FAIR Proton Injector with the klystrons developed for JPARC : Frequency: 352 MhZ ⇒ 325.244 (3 times the UNILAC DTL frequency) Power: 13 klystrons, 0.8 MW ⇒ 7 klystron, 2.5 MW  A coupled structure results to be the best choice to match the linac with such a high power. No coupled H-Mode structure ever built up to now A current flow like this would create the desired coupling

11. Clemente@gsi.deClemente@gsi.de www.linac-world.de  The coupling concept was tested simulating CH resonators identical to the test model (8 gaps each with an intertank section of length 5 βλ)  Evidence of the coupling and of a parasite mode! The Coupled CH 0 Mode π / 2 Mode

12. Clemente@gsi.deClemente@gsi.de www.linac-world.de FAIR Coupled Resonator No 2  27 gaps including beta profile (generated by LORASR) (13+14)  Energy Range: 11.7-24.3 MeV (β :0.15-0.22)  Frequency: 325.2 MHz  Q_ 0 : 15300  Bandwidth ~ 21.2 kHz  K ~ 0.5 %  K l : 2.0  ZT 2 : 60 MΩ/m  RF LOSSES: 1.37 MW  Beam Loading: 882 kW (at 70 mA, 35 required for the injection into the SIS 18)  Total Power: 2.25 MW

13. Clemente@gsi.deClemente@gsi.de www.linac-world.de Scaled Model Position of mobile tuners Aluminium Brass

14. Clemente@gsi.deClemente@gsi.de www.linac-world.de Stems without drift tubes: drift tubes can be exchanged for final tuning where needed (change of the gap/length ratio) Scaled Model 1:2

15. Clemente@gsi.deClemente@gsi.de www.linac-world.de Scaled Model 1:2 First frequency Measurements in good agreement with simulations Next H-Mode Harmonic (F m – F s )/ F s = 0.25% K m =0.56 (0.5 simulated)

16. Clemente@gsi.deClemente@gsi.de www.linac-world.de Field Distribution SIMULATED WITH MWS MEASURED !

17. Clemente@gsi.deClemente@gsi.de www.linac-world.de Prototype: Technical Drawing

18. Clemente@gsi.deClemente@gsi.de www.linac-world.de Prototype: Technical Drawing

19. Clemente@gsi.deClemente@gsi.de www.linac-world.de Prototype: Technical Drawings Coupling Section Section between two coupled structures

20. Clemente@gsi.deClemente@gsi.de www.linac-world.de Outlook and Next Step  An improved low level RF test bench has been built at IAP in the frame of a degree thesis (R.Brodhage)  Final Assessment of the coupled model is in progress  Production of the real prototype is expected for 2009  Full Power test at 2.5 MW will be performed at the new test stand at GSI

21. Clemente@gsi.deClemente@gsi.de www.linac-world.de HIPPI Schedule  The original schedule foresaw the construction of a "cold model" to test the mechanical properties of the CH and a "full power" Prototype.  IAP delivered a high power prototype and developed the concept of coupled H-mode structure to exploit the 2.5 MW rf power provided by commercial amplifiers  However, this complex cavity is of course by far off the cost frame of our HIPPI engagement. So, we think, that the two models produced during HIPPI including the RF investigations are covering the volume of CH-DTL development promised at the beginning quite well.