ESS SC cavities development G. Devanz TTC meeting, march 1st 2011, Milano

5MW proton beam (50 mA) pulsed operation 20 Hz, 2 ms upgrades 7.5 MW (15 MW) by increasing the beam current : 50 mA, 75 mA,… EUROPEAN SPALLATION SOURCE

WP 4 and 5 for spoke and elliptical cavities in the design update phase

Spoke resonators double spoke resonators frequency = MHz beta = 0.53 Challenges: High gradients ( 8 MV/m ) High peak power couplers (~ 400 kW nominal) Pulsed operation Series production of spoke cavities (real 3D geometry and performance reproducibility) Open questions : HOM Operation T° (2K or 4K) Cryomodule type …

Spoke resonators About 15 spoke resonators (SSR, DSR, TSR) have been constructed and tested worldwide. IPN Orsay Triple (G. Olry)

Main contributors for prototypes CNRS/IN2P3/IPN Orsay (France): cavities (2 prototypes), couplers ( 2proto types), tuners, cryomodule, preparation and test facility, WP coordination ESS BILBAO/TEKNIKER (Spain): cavities, tuners, engineering design (mechanical, RF) JLAB (USA) : Discussion in progress for a plug- compatible cavity design and prototype, independent cryomodule design

Elliptical cavities betaEacc VT (MV/m) Eacc Linac (MV/m) cell cavities frequency = MHz two beta families gradient specifications: Challenges: Obtain reproducible cavity performance High peak power couplers (900 kW nominal, max. 1.2 MW) Open points : Cryomodule architecture : X-FEL type or SNS type equivalent to warm/SC focusing choice or beam instrumentation choice (beam profile monitors) Cavity processing (combination of BCP/EP?)

High beta (0.86) 704 MHz 5-cell cavities, 2 prototypes HOM couplers 1 MW power couplers, 2 prototypes Magnetic shielding Combined fast/slow tuner ESS design and prototyping activities at CEA-Saclay Design update ( ) 6 high beta (0.86) 704 MHz 5-cell cavities with HOM couplers, tuner, magnetic shielding, power coupler Fabrication, preparation conditioning and test of all elements P2B ( ) RF Conceptual design of the cavity

Cavity geometry and peak fields [ Pierini, HPSL Workshop ] current status of ESS b=0.86 (conceptual RF design) Ep/Eacc=2.3, Hp/Eacc = 4.3 mT/(MV/m)

Peak field performances [ Pierini, HPSL Workshop ] ESS beta=0.86

704 MHz 5-cell cavities and existing components SPL /Eucard beta=1 - Saclay design with Ti He vessel - CERN modified design with SS tank All at the manufacturing stage Saclay tuner for 704 MHz cavities tested on a beta cell cavity in horizontal cryostat, pulsed mode 50Hz 2ms INFN beta cell cavity with blade tuner tested next week in horizontal cryostat with high power

LFD compensation LDF compensation on the Saclay beta= MHz 5-cell cavity with the piezo tuner (Saclay-IV) Eacc = 13 MV/m. RF pulses 2 ms 50 Hz. Static KL=-3.8 Hz/(MV/m)² Piezo offPiezo on Phase excursion on flat top+/- 25 deg.+/- 8 deg. Amplitude variation on flat top45%1.4% Good repeatability although mechanical modes have no time to decay between successive RF pulses (10 pulses recorded with CERN LLRF crate)

704 MHz 1 MW fundamental power coupler DesignConditioning Cavity 1.8 K Cryholab (  =0.47) Peak power (kW) in TW , 2 ms 50 Hz- Peak power (kW) in SW , 1 ms, 0.31 Hz1000, 2 ms 50 Hz, cavity off resonance TW conditioning Fully reflected on the cavity at 4 K & 1.8K Proposal to upgrade Saclay existing 1 MW test stand to 2 MW to mainly test FPCs at higher power

More components CEA-CNRS 704 MHz beta cell cavity for CW proton linacs. Now a new derived design from IPN-Orsay for Eucard/SPL with rings for pulsed operation, to be tested in 2012 … And all 90+ SNS cavities and power couplers, upcoming Project-X cavity prototypes at FNAL Progress on proton SC cavities in the EU initiated from waste managment (90’s), ADS studies and continued thanks to successive EU R&D programs focussed on pulsed proton injectors: CARE-HIPPI, SLHC-PP and Eucard

Collaboration on ESS elliptical cavities CEA-Saclay : high beta cavities, power couplers, tuners ESS-AB : cryomodule and cryogenics Lund-U : medium beta cavities Rostock : HOM (RF WP8) RHUL : HOM, complex RF and multipacting simulations (RF WP8) CERN : 704 MHz test area, 4-cavity cryomodule test (beta=1 cavities) Upsala : Fully equiped test stand with horizontal cryostat Jlab and DESY : On going discussions for cryomodule conceptual design comparisons