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

2. 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

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

4. Spoke resonators double spoke resonators frequency = 352.21 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 …

5. Spoke resonators About 15 spoke resonators (SSR, DSR, TSR) have been constructed and tested worldwide. IPN Orsay Triple 352 0.3 4.1 9.1 (G. Olry)

6. 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

7. Elliptical cavities betaEacc VT (MV/m) Eacc Linac (MV/m) 0.651715 0.862018 5-cell cavities frequency = 704.42 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?)

8. 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 (2011-2012) 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 (2013-216) RF Conceptual design of the cavity

9. 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)

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

11. 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 0.47 5-cell cavity in horizontal cryostat, pulsed mode 50Hz 2ms INFN beta 0.47 5-cell cavity with blade tuner tested next week in horizontal cryostat with high power

12. LFD compensation LDF compensation on the Saclay beta=0.47 704 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)

13. 704 MHz 1 MW fundamental power coupler DesignConditioning Cavity 1.8 K Cryholab (  =0.47) Peak power (kW) in TW10001200, 2 ms 50 Hz- Peak power (kW) in SW1000940, 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

14. More components CEA-CNRS 704 MHz beta 0.65 5-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

15. 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