[email protected]@gsi.de Development of the Room Temperature CH-DTL in the frame of the...
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[email protected] 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
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Transcript of [email protected]@gsi.de Development of the Room Temperature CH-DTL in the frame of the...
[email protected] 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, GermanyJ.W. Goethe-Universität, Frankfurt am Main, Germany
HIPPI ANNUAL Meeting, CERN, GENEVA
October 29th, 2008
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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
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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
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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
(Kl > 5 at Cern Linac 3)
Compact structure
Mechanical Robustness
Reduced number of focusing elements
Easy to be cooled
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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
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Tuning the end cells
Bt
dlE
The end half drift tube can host magnetic lens and a diagnostics device
Magnetic Tuning of the end cell
7
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Tuning concept
Final tuning is obtained by changing the Gap/Length along the cavity axis
Capacitive Tuning
8
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The first CH-DTL
Cooling 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
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The first CH-DTL: Results
Main Results:
• Reliability of CH-DTL design in terms of mechanical construction, welding, and Copper Plating
• Measured Q0= 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
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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
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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
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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 % Kl: 2.0
ZT2: 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
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Stems without drift tubes: drift tubes can be exchanged for final tuning where needed (change of the gap/length ratio)
Scaled Model 1:2
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Scaled Model 1:2
First frequency Measurements in good agreement with simulations
Next H-Mode Harmonic
(Fm – F s)/ F s = 0.25% Km=0.56 (0.5 simulated)
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Prototype: Technical Drawings
Coupling SectionSection between two coupled structures
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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
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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.
