Latest Design of ILC RDR A Primary Cost

Latest Design of ILC（RDR)

A Primary Cost Driver for ILC -- Superconducting RF Technology • 1. 3 GHz technology developed by TESLA Collaboration, R&D from 1992 to reduce the cost per Me. V by a factor of 20 from current SCRF installations (CEBAF). • Increased the operating accelerating gradient by a factor of 5 : ~5 MV/m to ~25 MV/m, Reduced the cost per meter by a factor of four for large-scale production. • TESLA cavity R&D based on CERN, CEBAF (JLAB), Cornell University. KEK, Saclay and Wuppertal. • Basic element of the technology is a nine-cell 1. 3 GHz niobium cavity. • Approximately 160 of these cavities have been fabricated by industry as part of R&D program at DESY.

Principle of 50 MV/m Cavity shape designs with low Hp/Eacc TTF: TESLA shape Reentrant (RE): Cornell Univ. Low Loss(LL): JLAB/DESY IchiroｰSingle(IS): KEK TESLA LL RE IS Diameter [mm] 70 60 66 61 Ep/Eacc 2. 0 2. 36 2. 21 2. 02 Hp/Eacc [Oe/MV/m] 42. 6 36. 1 37. 6 35. 6 R/Q [W] 113. 8 133. 7 126. 8 138 G[W] 271 284 277 285 Eacc max 41. 1 48. 5 46. 5 49. 2

ICHIRO Cavity . Goal： 51 MV/m

Fabricated Six ICHIRO Single Cells Deep-drawn Nb cups • Electron Beam Welding (EBW) • Both KEK in-house machine and industrial machine were used • Six IS cavities were fabricated (IS#2, #3, #4, #5, #6, #7). • Series of tests done to optimize KEK surface treatment.

Centrifugal Barrel Polishing (CBP) Mechanical Grinding Stones and water KEK CBP • Rough stones + water : 4 hours x 3 times • Removal thickness = 25 μm x 3 = 75 μm • Fine stones + water : 4 hours x 3 times • Removal thickness = 20 μm x 3 = 60 μm Rough stones Fine stones • Total removal thickness = 135 μm.

Light Chemical Polishing • Light Chemical Polishing (CP) HF(46%) : HNO 3(60%) : H 3 PO 4(85%) 1 : 1 in volume • CP for 1 minute at 25 OC. • Removal thickness = 10 μm. • Prepare smooth surface before EP. Annealing - Degassing • Annealing/Degassing in furnace 750 OC for 3 hours • Degassing of hydrogen important. • Temperature and time optimized for cavity softness and cost.

Measurement of and Unloaded Q-value Measure time constant for cavity to “ringing down” when RF switched off Accelerating Field Geometric Factor

Schematic of Experimental Setup 1. 9 K LHe Cavity in Cryostat Signal Generator Phase Locked Loop Q of Cavity is very large Power Meters

Re-Entrant Cavity - Best Eacc = 59 MV/m • Manufactured @ Cornell • Surface preparation at KEK • Vertical test @ Cornell

International Collaborations （ILC WG 5 -Asia） Korea, Pusan Univ: CHO (student) stayed in Mar 2005 IHEP: Shi Hua (engineer) stayed Feb - Mar 2005 Korea, CHEP, Kyungpook Univ. : Prof. Hyoung Suk KIM stayed Jan-Mar 2006 Korea, PAL: Y. uk SOHN 　 stayed Mar – Aug 2005 (WG 5 Korea convener) IHEP: GE Mingqi (student) stayed Jan– Mar 2006 Canada, Toronto Univ: Prof. Robert ORR stays from Aug 2005 for 1 year LNL-INFN: Giullia LANZA (student) stays Jan – Mar 2006.