PIP-II WORKSHOP CEA COUPLERS G. Devanz
EU PROGRAMME CARE-HIPPI The developpement of the 1MW 704 MHz FPC started with EU R&D programme CARE directed towards high power pulsed proton accelerators with 10% duty cycle KEK-B, SNS type coupler doorknob (air) vacuum gauge electropolished water cooled inner conductor water cooled RF window Coaxial coupler cryostat flange • 100 mm diameter 50 W • He cooled outer conductor G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 2
CARE-HIPPI FPC PROTOTYPES Built one pair of FPC in industry (one for each of the 3 main compenents), except Cu film done by CERN G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 3
HIPPI PERFORMANCE ON TEST STANDS AND HORIZONTAL TEST CRYOMODULE TW on conditioning test stand Test of the HIPPI power coupler on the HIPPI cavity at 1 pair tested up to 1.2 MW, 10% 1.8 K, full reflection duty factor This coupler achieves 120 kW average power on test bench and on SRF cavity G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 4
HIPPI conclusion ( from WWFPC-2015) What we tested that generally cause worries : • Assembly on the cavity from the top in the clean room. No particle counting was performed in the 2009 assemblies but FE was not enhanced on the two test SRF cavities • Massive antenna resting for years in horizontal position : no deflection observed • More recently a new clean room test assembly of 1 HIPPI coupler was carried out in the new ISO5 clean room succesfully with particle counting • The coupling waveguide aspect indicates it may have been the most difficult part to condition (Cu particulates were present inside) G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 G. Devanz – WWFPC 2015 5
ESS ELLIPTICAL CRYOMODULES Designed by CEA-Saclay/IRFU and CNRS/IPNO • Freq = 704.42 MHz • Pmax = 1.1 MW , RF pulses at 14 Hz • Beam pulses duration = 2.86 ms, • minimum required RF pulse length = 3.1 ms 1.1MW Medium and high beta differ only by the cavity length and number of cells G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 6
ESS FPC – DERIVED FROM HIPPI • Minor changes for window and double wall tube • New doorknob with 10 kV HV biasing capability • Less demanding power-wise (10%DC-> 5%DC) Electrical specifications RF frequency 704.42MHz Repetition frequency 14 Hz Forward RF power 1.1 MW He 500 μs RF pulse width in full cooling reflection (all phases) CM insulation RF pulse width in 3.6 ms vacuum travelling waves Bias Voltage limits ±10 kV air Alumina disk Rect. WG port Water cooling G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018
WINDOW RF PROPERTIES Parameters Value E field distribution Pforward= 1.1 MW • RF simulations Dielectric losses (travelling 10 W wave) Dielectric losses (full 29.4 W reflection) RF losses for external 1.2 W choke (travelling wave) RF losses for external 1.4 W choke (full reflection) RF losses for internal choke 6.1 W (travelling wave) RF losses for internal choke 6.8 W (full reflection) Very wide bandwidth Frequency (GHz) Same design used for 352MHz RFQ Bandwidth at -55dB 94 MHz (753-659) window S 11 (dB) -55 external choke Port 1 ceramic Air/vacuum Simulation model r =9.5 Port 2 r =9.3 r =9.4 r =9.6 r =9.7 G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 8 Internal choke
DOUBLE WALL TUBE • Stainless steel 316L • Cooling circuit manufactured with the shrink-fitting method Copper coating with 10µm(-3/+2µm) thickness and RRR [20;40] • 320 mandrel 300 Kelvin, Watt/m 2 .K 280 260 Heat Flux at 2K = 1 watt 240 Helium Mass Flow = 2.31 10 -5 Kg/s 220 200 180 160 140 cover 120 100 80 Wall Temperature 60 Helium Temperature 40 Heat transfer coefficient 20 Swagelok connector m 0 0.000 0.025 0.050 0.075 0.100 0.125 0.150 0.175 0.200 0.225 Design temperature profile He cooling circuit based on 3 spiral channels Copper coating inside the tube G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 9
DOORKNOB TRANSITION • PEEK Insulation able to provide 10kV insulation Actual measured breakdown voltage ≥ 18kV) • Coaxial waveguide Port for arc detection Inner conductor knob Insulation Waveguide WR1150 High voltage port Water cooling G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 10
COOLING • Estimation of the power dissipated by the coupler For 1.1 MW peak, duty cycle 5% -RF power dissipation of the antenna: in travelling wave 58W in standing wave 94W -RF power dissipation of the ceramic (tan d =3 10 -4 ) in travelling wave 9.3W • Cooling of the antenna in standing wave 40W (worst case) 154.84mm 310.55mm Complementary antenna (L ant ) Estimation of the water flow HFSS simulated length=356mm D T Internal chokes 2 l/min 0.97° 55.75mm 476.1mm 2.5 l/min 0.78° 3 l/min 0.65° HFSS limit During the conditioning: for =2.4l/min 466.28mm 450.39mm T water input=25.6°C T water output=26.2 ° C G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 11
THERMO-MECHANICAL SIMULATIONS • Steady state in TW 120kW avg power (HIPPI test case) HIPPI test case 2.5 x the ESS average RF power RF PEAK POWER 1.2 (MW) pressure, convection for air and water are modeled Duty cycle (%) 10 RF dissipations Regime TW To + 2K s V.M. D T vacuum ambiant air To air G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 12
CONDITIONING CAVITY • Lesson learned from HIPPI previous design (copper coated welded SS cavity) and E. Montesinos dismountable cavity, we tried to simplify a step further by not having any copper layer. • Thermal design with margins showed fin heat exchangers and fan system were required. • In use, the box was operated with good thermal stability with only air circulation on the cover plate (air channels) • Pumping port and port for arc detection • Aluminum wire used as seal between cover and bottom for vacuum tightness Pumping port Arc detection port Cover with air Box channels bottom G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 13
COUPLER CLEAN ASSEMBLY Double wall window Coupling Cavity Assembly has been performed in tube three different clean areas: Outside Us+tikopur Antenna Deox Us+tikopur • ISO5 of clean T310+rinsing For new cavities/Belimed • ISO4 room washing machine for • Clean booth conditioned cavities without any noticeable change in De-oxidation Ethanol cleaning conditioning time RBS T310 of ports, outer shell rinsing Top gun+Particle counter on all cavuum components Clean drying drying room Top Top gun+particle Particle free pumping and gun+particle counter venting systems counter G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 14
NEW CONDITIONING INFRASTRUCTURE • 2 klystrons – existing CPI klystron + cea modulator upgraded to 1.2MW 3.6ms pulses – Additional 1.6 MW Thales klystron+modulator (not yet operational) • 2 FPC pairs can be conditioned in parallel Baking • 2 conditioning systems w oven EPICS control/DAQ/ hardware interlocks • 2 Baking ovens with N2 atmosphere G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 15 1.6 MW kly.
DEDICATED RF CONDITIONING AREA • Line1 : CPI 1.2MW klystron • Line2 Thales 1.6 MW klystron (HVPS to be delivered) New N 2 atmosphere 170°C baking current setup baking oven Back-to-back configuration Standing wave setup G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 16
CAVITY STRING WITH PROTOTYPE FPCS 3 CEA cavities ESS M-ECCTD cavity string in Saclay clean room Jan. 2017 1 LASA CAVITY March 2017 G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 17
CONDITIONING SEQUENCE ::TW EXAMPLE pressure RF power 1Hz 14 Hz No bias during conditioning G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 18 Typical conditioning time 45-100hrs
Max. E-field on both ceramics 3600µs,14Hz 3000µs,14Hz 2500µs,14Hz | PAGE 19 1500µs,14Hz 800µs,14Hz 500µs,14Hz CONDITIONING SEQUENCE :: STANDING WAVE G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 500µs,4Hz 500µs,1Hz 300µs,1Hz 100µs,1Hz 3600µs,14Hz 2500µs,14Hz 800µs,14Hz 500µs,14Hz Min. E-field on both ceramics 500µs,14Hz 500µs,8Hz 500µs,4Hz EXAMPLE 500µs,2Hz 500µs,1Hz 400µs,1Hz 300µs,1Hz 200µs, 1Hz 100µs,1Hz 50µs,1Hz
ESS COUPLER EXPECTED RF PERFORMANCE FOR SITE ACCEPTANCE • Reach the peak power of 1.2 MW, 3.6 ms pulses at 14 Hz TW in less than 120 hrs with applied RF • Sustained application of max. power for 1 hour • Full reflection – up 1.2 MW for 500 m s pulses at 14 Hz – Up to 300 kW for 3.6 ms pulses at 14 Hz • 2 most arcing-prone short-circuit positions • 4 other short circuit positions • No time limit G. Devanz CEA-Saclay PIP-II Workshop| june 26 2018 | PAGE 20
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