Cryostat & LHC Tunnel Slava Yakovlev on behalf of the FNAL team: Nikolay Solyak, Tom Peterson, Ivan Gonin, and Timergali Khabibouline The 6 th LHC-CC webex meeting, Dec 09, 2008

SBIR proposals have been submitted (AES) on 1)Cryostat design; 2)Tuner design. Possible CC design for phase I Cryostat location Using LHC 400 MHz cavity cryostat –problems? SBIR phase-I proposal for CC cryostat Helium Temperature 1.8K vs. 4.6K LHC requirement for cryostat/cavity

LHC IP4 location (RF) CC location CC location (second beam)

Global Option Location: P4 at (staged) ACN location

CM Layout (400 MHz cavity) 1496 mm 1130 mm

Sub-unit for one 400 MHz cavity Side view Top view WG Variable input coupler Narrow band HOM coupler Broad band HOM coupler Needs 2 cavities (2 units) Port locations are different

Flange ports Cover plates Easy access for cavity assembly inside cryostat Cryostat frame

Cavity Support / Alignment Top View Side View Horizontal Vertical Longitudinal

Problems with using of LHC cryostat Port locations do not fit present CC design Cryogenic ports do not fit as well (?) 2K option is not possible (shielding, cryosystem). Need redesign: support system, alignment, tuner (hopefully partial), … Needs at least 2 sub-units and 2 end-cups  not available. New order is costly  cryostat has complex design and expensive in production. New design probably is more preferable option –SBIR phase-I proposal with AES are submitted

New design constrains Most constrains are defined by CERN requirements and safety regulations (see talk of J. Tückmantel “LHC Integration of a Crab Cavity” an CC mini workshop, CERN, Aug. 21,2008) –CERN Standards –Compatibility –Safety, –Materials for CM and components –Cryogenic and protection from accidents –Vacuum, bake-out, –Radiation –RF components, cables etc. –Alignment –Transportation –Other

Questions: Operating temperature: 1.8  K versus 4.6  K. 1.8  K problems: 1.The additional 1.8 K load on the LHC cryogenic system. 2. A more complicated connection to the cryogenic transfer line (QRL) 3. Possible need for better shielding to reduce heat load. Need to be investigated – robust cavity design, helium input, fast valves, etc.

4.6  K problems: Neither magnetic shield no a heat shield are necessary ! 1. Higher losses in the cavity. 2. Microphonics from boiling. 3. Possible helium pressure fluctuation from the 20 K return line. 4. Possible helium pressure spike from the 20 K return line caused by a magnet quench. 5. Lower maximum field gradient. Need to be investigated – cavity design, available place for them. While both cryogenic supply systems are available within the LHC environment, the decision of cavity operating temperature may in part depend on the physical availability of the cryogenics nearby the crab cavity installation in the LHC tunnel.

1.8 Kelvin cooling. Figure shows a cooling scheme drawing 5 K, 3 bar helium from the transfer line and in a manner similar to that used to cool the magnets to generate 1.8° K saturated helium. Some relief valve and/or rupture disk overpressure protection must be provided for the helium vessel, which is shown connected to a 300° K line or, optionally, the 20° K line. The connection to the 20° K line via a relief valve is may not be desirable due to the potential for leaks back into the low pressure helium vessel during operation. Appropriate solutions to these issues will need to be worked out.

4.6 Kelvin cooling. The 4.6° Kelvin cooling concept, shown in figure, is actually quite similar to that for 1.8° K, except that the helium returns to the 20° K, 1.3 bar line. Since this line also serves as the magnet quench header and can go to 20 bar pressure, a back pressure control valve must be included to prevent pressurizing the SRF helium vessel from this line. An additional helium vessel relief valve to a lower pressure collection line, here shown as the 300° K, 1 bar line would also be needed.

SNS experience (805 MHz, pulse regime)

FNAL CRAB CAVITY WITH QUARTEWAVE COUPLERS (alternative compact design) LOM Couplers HOM and FP Couplers Notch-filter for 800 MHz

2D optimization L gap a b R cavity R ap A B FIXED: R cavity =175mm R ap =60mm a, b, A, B, L gap are optimized. H s /H eff L gap, mm

V * ┴, MV 2.5 Bpeak, mT 77.4 Epeak MV/m 31.7 R ┴ /Q, Ohms 52.5 * V ┴ = Δp ┴ c/e a 50 b 60 A 50 B 45 L gap 125 D1/D2 294/350 Dimensions (in mm) and main parameters of FNAL Crab cavity D1 D2 F, MHzQR/Q, Ohm RESULTS OF FIRST 3D OPTIMIZATION Monopole modes P<2kW P=2.5 kW