Advance on High Power Couplers for SC Accelerators

Transcription

1 Advance on High Power Couplers for SC Accelerators Eiji Kako (KEK, Japan) IAS conference at Hong Kong for High Energy Physics, 2017, January 23th Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 1

2 OUTLINE Introduction of high power couplers Essential technical issues on couplers High power couplers for CEPC Summary Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 2

3 OUTLINE Introduction of high power couplers Essential technical issues on couplers High power couplers for CEPC Summary Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 3

4 Essential Consideration for Input Couplers 1. Input coupler is one of the most critical component of an SRF system. 2. Design of an input coupler strongly depends on a cryomodule structure. RF power capability : ( P RF = I beam * V acc * cosφ ) Coupler type : coaxial or waveguide Ceramics window type : disk or cylindrical Number of windows : single or double Coupling with cavity : fixed or adjustable Cooling method : air, He-gas, N 2 -gas or water Bias voltage : useful or needless Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 4

5 Important Technical Issues for Input Couplers Ceramics window : material, purity Metalizing of ceramics Copper plating : thickness, RRR, adhesion, pits, uniformity TiN coating : thickness, uniformity Joining by Brazing Welding by TIG, Laser, E-beam RF properties Thermal characteristics Mechanical analysis Multipacting simulation Cleaning procedure Assembly in clean room Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 5

6 From coupler design to beam operation RF measurement Design/Calculation Fabrication Cleaning/Assembly Pumping/Baking Conditioning at test stand Cavity string assembly in clean room Conditioning at RT in cryomodule High power test at LT and, then operation with beam Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 6

7 Discussion topics for high power couplers - Design: maximum power per coupler, multi-coupler per cavity. - Construction: choice of material and techniques of construction, coating method. - Series production: fabrication, cleaning, handling and assembly. - Series production by industrials: modification of the processes, industrial alternative proposals,... - Cleaning and assembly: which clean room is really needed, for FPC alone, for FPC onto cavity. - Tests: prototype processes versus series processes, RF test boxes, amplifiers for tests. - Statistics: couplers operated in accelerators. - Diagnostics: during R&D and prototyping, diagnostics during operation in accelerators. - Degradation: characteristic over time of beam operation Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 7

8 TRISTAN-type High Power Input Couplers 704 MHz HIPPI Input Coupler (CEA) 805 MHz SNS Input Coupler (ORNL) Original design : 508 MHz TRISTAN Input Coupler S. Noguchi, E. Kako, K. Kubo (4 th SRF-WS, 1989 ) 508 MHz KEKB Input Coupler 1300 MHz cerl Injector (KEK) Input Coupler (KEK) 972 MHz ADS Input Coupler (KEK) Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 8

9 High Power Performance of TRISTAN-type Couplers Facility Frequency Window type Coupling TRISTAN /KEK 508 MHz Coax. Disk Fixed KEKB /KEK 508 MHz Coax. Disk Fixed HIPPI /CEA 704 MHz Coax. Disk Fixed SNS /ORNL 805 MHz Coax. Disk Fixed ADS /KEK-JAERI 972 MHz Coax. Disk Fixed cerl-inj. /KEK 1300 MHz Coax. Disk Fixed Maximum RF Power Test-stand, Operation, 200 kw, CW 70 kw, CW Test-stand, 800 kw, CW Operation, 380 kw, CW Test-stand, 1.2 MW, pulse (10% duty) Test-stand, 2 MW, pulse Operation, 350 kw, pulse Test-stand, 2 MW, pulse Operation, 350 kw, pulse Test-stand, Operation, 40 kw, CW 10 kw, CW All of these RF windows were fabricated by Toshiba-ED company. Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan. 23 9

10 OUTLINE Introduction of high power couplers Essential technical issues on couplers High power couplers for CEPC Summary Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

11 About 30 years ago in TRISTAN at KEK 508MHz, CW 50kW Input coupler with one warm window and water cooling (at test stand, 1988 ) In the initial stage, no TiN coating no Arc sensor Importance of TiN coating and Interlock system Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

12 RF conditioning at test stand for 1.3 GHz CW input couplers after 100 kw CW conditioning Excessive heat-up Inner conductor Cu-bellows Cu-tube Outer conductor Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

13 1.3 GHz CW Input Couplers for cerl Injector Cryomodule Droplet of water on ceramic during cool-down Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

14 Quality control of Cu-plating : projection Test piece with smooth surface Test piece with micro-projections Micro-projection (φ100µm) were formed after brazing at 800 o C. The cause was organic carbon contamination in an old solution. Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

15 RF window troubles in recent coupler development Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

16 Cu-plating troubles in recent coupler developments Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

17 OUTLINE Introduction of high power couplers Essential technical issues on couplers High power couplers for CEPC Summary Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

18 CEPC SRF hardware specification Hardware Qualification Normal Operation Max. Operation 650 MHz 2-cell Cavity VT 22 MV/m HT 20 MV/m 16 MV/m 20 MV/m 1.3 GHz 9-cell Cavity VT 25 MV/m 20 MV/m 23 MV/m 650 MHz Input Coupler 1.3 GHz Input Coupler HPT 300 kw sw < 254 kw 280 kw HPT 20 kw peak, 4 kw avr. < 15 kw peak 18 kw peak 650 MHz HOM Coupler HPT 1 kw < 0.2 kw 1 kw 650 MHz HOM Absorber 650 MHz Cryomodule (six 2-cell cavities) Tuner (MR & Booster) LLRF (MR & Booster) HPT 5 kw < 2 kw 5 kw static loss 5 2 K tuning range / resolution 400kHz/1Hz amp & phase stability 0.1%, 0.1 deg static loss 8 2 K static loss 10 2 K 200 khz / 1 Hz 400 khz / 1 Hz amp & phase stability 1%, 1 deg amp & phase stability 0.1%, 0.1 deg by J. Zhai (IHEP) Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

19 650 MHz 2-cell cavity for CEPC Parameters Value Riris (mm) 78 Alpha (deg) 3.22 A (mm) 94.4 B (mm) 94.4 a (mm) b (mm) L (mm) D (mm) k 2.86% R/Q (Ω) 213 G (Ω) 284 Ep/Eacc 2.4 Bp/Eacc [mt/(mv/m)] 4.2 k loss (total) [V/pC] Cut-off frequency of beam tube (MHz) 0.81 (bunch length 4 mm) TE11:1126 TM01:1471 by J. Zhai (IHEP) Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

20 by J. Zhai (IHEP) CEPC 650 MHz Cryomodule Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

21 Recent new development of high power couplers cerl Injector Cryomodule (KEK) by E. Kako (KEK) berlinpro Booster Cryomodule (HZB) by A. Neumann (HZB) Under beam operation Under construction 1.3 GHz, CW 100 kw Coupler 1.3 GHz, CW 120 kw Coupler Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

22 Coupler specification of SC cavities for CEPC Machine Parameters CEPC CEPC Beam Energy 120 GeV 6 -> 120 GeV Beam Current 16.9 ma 0.9 ma Circumference 55 km 55 km Total RF Voltage 3.5 GV 0.2 -> 5.2 GV Coupler Parameters Collider Ring Booster Ring RF Frequency 650 MHz 1300 MHz Accelerating Gradient 16 MV/m 20 MV/m Cavity Effective Length 0.46 m (2-cell) 1.04 m (9-cell) Required RF Power CW, 210 kw Peak, 20 kw Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

23 CEPC high power coupler 650 MHz coupler 300 kw CW, assemble with cavity in class 10 cleanroom, inner conductor water cooling, outer conductor He gas cooling, fixed or variable coupling. 1.3 GHz coupler 20 kw peak, 4 kw average, no cooling, variable coupling. by J. Zhai (IHEP) Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

24 SUMMARY Development of high power couplers is always challenging work. Many technical issues to be solved are still existing in highly reliable couplers for a stable beam operation. RF conditioning of prototype couplers at the test stand for CEPC should be started in an early stage. KEK will join and cooperate on R&D of high power couplers for CEPC. Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan

25 Thank you for your attention. Eiji KAKO (KEK, Japan) IAS at Hong Kong, 2017 Jan