제2회 국제선형충돌가속기(ILC) Workshop 초전도 RF Cavity의 기술 및 ILC 건설에 한국의 참여방안, PAL의 관련 연구소개 손 영욱, 고 인수, 남궁 원 포항가속기연구소, 포항공과대학교 2004. 12. 28-29 포항가속기연구소 Working Group 3: Accelerator Technology

Contents Activities of PAL in SC RF Technology - beam dynamics - cavity design - cryostat design Technical Topics for SC RF Cavity Module Proposal to Contribute ILC in Part of Cold Technology 1/22

Activities of PAL in SC RF 초전도 3rd Harmonic RF cavity의 feasibility study - Beam dynamics 측면에서 필요성 연구 o Beam emittance의 개선으로 인한 빔수명단축을 개선 o Landau damping에 의한 빔안정화 개선 초전도 3rd Harmonic RF cavity의 Prototype 설계 - Cavity shape 선정 및 field 해석 - Prototype 공학설계 초전도 Cavity 제작공정 연구 - 제작공정에 대한 외국사례연구 - 국내 업체의 제작능력 조사 2/22

Activities of PAL in SC RF 초전도 RF cavity 시험용 초저온 용기 설계 선진 연구 Group의 자문 - 일본 KEK 시설견학 (K,Saito Lab.) 및 자문 - 스위스 SLS 시설견학 및 자문 - 독일 BESSY SC cavity 설계자 자문 - 이탈리아 ELETTRA 설계자 자문 3/22

Feasibility Study of SC 3H Cavity for PLS in Beam dynamics Fig. Potential well and longitudinal bunch distribution of PLS Fig. Lifetimes(□) and bunch lengths(●) with 3rd harmonic voltage 4/22

Preliminary Design of SC 3HC for PLS Frequency 1500 MHz Cavity type Elliptical Diameter 19.2 cm Bore diameter 9.0 cm Table. Material Properties PARAMETERS VALUE Material Niobium Critical magnetic field 190 mT Critical temperature 9.2 K Resistivity 1.724x10-9  m Residual resistance 1.077x10-6  Operating temperature 4.5 K Fig. Cavity Geometry 5/22

Preliminary Design of SC 3HC for PLS Table. RF characteristics PARAMETERS VALUE Averaged accelerating field 4.20 MV/m Frequency 1499.99 MHz Stored energy 0.1012 Joules Power dissipation 15.88 W/cavity Quality factor 0.2403E+09 Shunt impedance 243671.03 MOhm/m Rs*Q 258.95  Z*T*T 41505.11 MOhm/m Geometry factor(r/Q) 34.54 Ohm Ratio of peak fields Bmax/Emax 3.32 mT/(MV/m) Peak-to-average ratio Emax/E0 2.84 Fig. Accelerating field 6/22

Conceptual Design of Cryomodule Port for Instruments Super-insulation 30 layers 50 layers LN2 Tube Port for Vacuum Pump Port for RF Instruments GHe Tube LHe Tank (Titanium) Thermal Shield (30K) Thermal Shield (77K) External Vacuum Tank (sus316) SC RF Cavity (Niobium) Beam Tube (SUS 316) Port for Cryogenic Devices 1200 600 Fig. Conceptual scheme of cryomodule for SC cavity 7/22

Conceptual Design of Cryomodule Table. Heat Loads of Cryogenic cooling system HEAT SOURCES VALUE (W) Dissipations in cavity 32 Conduction via warm flange of cryomodule 11 Conduction via feed-through of instruments 8 HOM couplers (or absorber) ? Cryogenic losses in cryogenic supply system 30 Total 81+ ()Total heat load depends on the scheme of HOM power removal and the piping distance between SC cavity and cold box of cryogenic system. The refrigerator, of which capacity is more than 120 Watt, is required with consideration of capacity margin 8/22

Cryostat for Vertical Test TEST PORT LHe TUBE LN2 TUBE GHe TUBE GN2 TUBE He LEVEL N2 LEVEL INSULATION PLUG THERMAL SHIELD (77K) SUPER INSULATING VACUUM VESSEL TEST CRYOSTAT 2030 505 Prototype 3rd harmonic cavity - Nb cavity with 2 volumes - Test cryostat with multi- purpose - Cold test of SC cavity - Design study 9/22

Design of Test Cryostat Parameters Values Helium vessel neck diameter (mm) 505 Liquid helium volume (liter) 170 Liquid nitrogen volume (liter) 190 Working environment temperature (K) helium vessel nitrogen vessel 4.2 77.3 Liquid He consumption rate via cryostat (liter/hr) 0.7 Liquid He consumption rate via current leads (liter/hr) 2.4 Liquid nitrogen consumption rate (liter/hour) Design pressure (Mpa) 0.25 Operation pressure helium vessel (Mpa) nitrogen vessel (Mpa) thermal insulation space (pa) 0.1 <10-6 Cryostat height (mm) 2200 Cryostat diameter (mm) 800 Total weight (Kg) ~300 10/22

Technical Topics for SC RF Cavity Module Superconductivity of Niobium Critical magnetic field Penetration depth, coherence length, G-L parameter, RF critical magnetic field Thermal conductivity RRR measurement Surface resistance in AC application 11/22

Technical Topics for SC RF Cavity Module Design of SC RF Cavity Cavity shape Characteristic parameters of RF cavity Analysis of electromagnetic fields Engineering design Planning fabrication and tests & measurements 12/22

Technical Topics for SC RF Cavity Module Fabrication of SC RF Niobium Cavity Forming (deep drawing, spinning, hydroforming) Coated cavity with Nb film Trimming Correcting machining error Beam tube fabrication Electron Beam Welding (EBW) Bonding technology 13/22

Technical Topics for SC RF Cavity Module Cleaning & Conditioning Mechanical grinding ☞ Centrifugal barrel polishing (CBP) Chemical polishing (CP) Electropolishing (EP) Heat treatment High pressure rinsing with ultra-pure water (HPR) Ultrasonic rinsing Assembly in clean room 14/22

Technical Topics for SC RF Cavity Module Test & Measurements in Vertical Cryostat Theory of RF measurement of SC cavities RF measurement system for vertical test; electronic devices, monitoring sys., controller, etc Cryogenics for cooling RF accessories; pickup/input coupler, RF generator, vacuum devices, etc 15/22

Technical Topics for SC RF Cavity Module Final Cavity Assembly Method with Cleanness Cavity disassembly after vertical test; - preventing large degradation from exposure to air - baking to recover performance - removing indium sealing Assembly in horizontal cryostat 16/22

Technical Topics for SC RF Cavity Module Cryogenics Design of horizontal cryostat for SC cavity modules - horizontal test cryostat - real cryostats for installation Fabrication of horizontal cryostat Test of cryostat performance Assembly cryomodules with SC cavity Design of cryo-plant 17/22

Advanced Technical Issues (Challenges) High gradient SC cavity, Eacc > 45 MV/m - High pure niobium material, RRR~250 - Electropolishing (EP) - High Pressure Water Rinsing (HPR) - Baking (70~140oC) Degradation-free final cavity assembly - Opening vacuum with argon gas - Simple aluminum vacuum sealing Cost-effective cavity production method - Nb/Cu clad seamless cavity - Simplified surface treatment 18/22

Proposal to contribute ILC in part of SC RF Cavity Work Process: Superconducting RF cavity Establishment of technology for high gradient accelerating field, Eacc  35 MV/m - 일본 KEK, 미국 FNAL 등에서 기술개발 주도 - 한국의 PAL, … 등에서 공동참여 및 인력 training Preliminary development of prototype cavity modules - 설계, 제작, 시험 등 KEK, FNAL 등에서 개발 주도 - 한국의 PAL, … 등에서 인력지원 및 training 19/22

Proposal to contribute ILC in part of SC RF Cavity Work Process: Superconducting RF cavity Calculation & design of production cavities - KEK, FNAL 등에서 개발 주도 - 한국의 PAL, … 등과 설계참여 및 training Fabrication, cleaning & conditioning - 국내 제작을 위한 시설확보 (PAL, …, 참여기업) - 제작후 processing을 위한 시설확보 (PAL, 참여기업) - 국내 지분율에 해당하는 cavity제작 (PAL, …, 참여기업) : 9-cell cavity 약 2,000 set 20/22

Proposal to contribute ILC in part of SC RF Cavity Work Process: Superconducting RF cavity Vertical test of 9-cell cavity - Vertical test를 위한 시설확보 (PAL, …) - 9-cell cavity에 대한 상온 및 저온상태에서 시험 (PAL, …) 21/22

Proposal to contribute ILC in part of cold technology Work Process: Cryogenics, Test & Measurement in Cryomodule Assembly of cryomodule with 9-cell cavities - 시험용 horizontal cryostat 설계, 제작 (KBSI, 참여기업) - Test facility 구축 (KBSI, 참여기업) - 양산용 cryostat 설계, 제작 (KBSI, 참여기업) - 9-cell cavity 12 set로 구성된 cryomodule 조립 Test & measurements with horizontal cryomodule - Test & measurements (KBSI) - Data analysis (KBSI, PAL) 22/22

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