H-ECCTD KICK-OFF DESCRIPTION AND CHALLENGES 16/03/2016 F. PEAUGER

ELLIPTICAL SUPERCONDUCTING CAVITIES CRYOMODULES Cryoline Valve box Elliptical cavity cryomodule Proton Beam Quadrupole Highest priority in 2016 H-ECCTD purpose: -Qualify the « high beta technology » -Prepare the series procurements -Prepare industrial subcontractor for the assembly -Test a transport to Lund -Could be used as a spare cryomodule in the tunnel H-ECCTD purpose: -Qualify the « high beta technology » -Prepare the series procurements -Prepare industrial subcontractor for the assembly -Test a transport to Lund -Could be used as a spare cryomodule in the tunnel

MAIN FEATURES OF THE H-ECCTD CRYOMODULE  Four superconducting cavities 5 cells at MHz -  =0.86  E acc max = 19.9 MV/m, Q 0 > (6.5 W RF losses per cavity)  Power coupler: 1.1 MW max  Slow tuning system: ± 300 kHz  Fast tuning system (LFD) : 1+1 piezo, ± 1 kHz  Cavity cooling: LHe at 2 K  Coupler cooling: SHe at 4.5 K, 3 bars  Thermal shielding cooling: LHe 50 K  Overall length: 6584 mm from flange to flange  Thermal losses: Static losses at 50 K: 46.2 W Static losses at 2 K: 12.2 W Dynamic losses at 2 K: 27.6 W  Four superconducting cavities 5 cells at MHz -  =0.86  E acc max = 19.9 MV/m, Q 0 > (6.5 W RF losses per cavity)  Power coupler: 1.1 MW max  Slow tuning system: ± 300 kHz  Fast tuning system (LFD) : 1+1 piezo, ± 1 kHz  Cavity cooling: LHe at 2 K  Coupler cooling: SHe at 4.5 K, 3 bars  Thermal shielding cooling: LHe 50 K  Overall length: 6584 mm from flange to flange  Thermal losses: Static losses at 50 K: 46.2 W Static losses at 2 K: 12.2 W Dynamic losses at 2 K: 27.6 W These parameters are only objective values for the H-ECCTD, based on ESS requirements, not formal acceptance criteria

HISTORIC OF THE PROJECT  Technical annex Early-kind signed in June 2015, based on the re-use of the M-ECCTD vacuum vessel and components  Autumn 2015: change request from ESS to fabricate a second vacuum vessel  New costing taking into account this change, sent to ESS the 1 st of Dec  « Change request » validated recently at ESS for the cost increase  Technical annex Early-kind signed in June 2015, based on the re-use of the M-ECCTD vacuum vessel and components  Autumn 2015: change request from ESS to fabricate a second vacuum vessel  New costing taking into account this change, sent to ESS the 1 st of Dec  « Change request » validated recently at ESS for the cost increase  This project is now included in the « schedule 1.10 » of the In-kind agreements

MAIN TASKS FOR THE H-ECCTD CRYOMODULE Objective: full realization and test of a technological demonstrator cryomodule with high beta elliptical cavities 1. Redesign phase following the manufacture, assembly of the M-ECCTD 2. Redesign phase following the changes of interfaces of the vacuum vessel 3. Procurement 5 high beta cavities, RF tuning, surface preparation (including chemical treatment, clean room assembly and heat treatment) and vertical tests 4. Partial procurement, assembly and RF conditioning of 3 pairs of power couplers 5. Procurement of vacuum vessel and cryomodule components 6. Modify or change if necessary some cryomodule assembly tools 7. Assembly of the cavity string in clean room 8. Assembly and cryostating outside the clean room 9. High power tests at CEA Saclay 10. Preparation for shipment to ESS - Lund. Transportation is within the responsibility of ESS 11. Delivery of the documentation associated with the project Objective: full realization and test of a technological demonstrator cryomodule with high beta elliptical cavities 1. Redesign phase following the manufacture, assembly of the M-ECCTD 2. Redesign phase following the changes of interfaces of the vacuum vessel 3. Procurement 5 high beta cavities, RF tuning, surface preparation (including chemical treatment, clean room assembly and heat treatment) and vertical tests 4. Partial procurement, assembly and RF conditioning of 3 pairs of power couplers 5. Procurement of vacuum vessel and cryomodule components 6. Modify or change if necessary some cryomodule assembly tools 7. Assembly of the cavity string in clean room 8. Assembly and cryostating outside the clean room 9. High power tests at CEA Saclay 10. Preparation for shipment to ESS - Lund. Transportation is within the responsibility of ESS 11. Delivery of the documentation associated with the project

PROJECT ORGANISATION AND COLLABORATIONS  The H-ECCTD project is a bilateral agreement between ESS and CEA  IPN Orsay (Gilles Olivier) will be involved for expertise for CEA : Cryostat components design update and mechanical drawings update Cryostat components fabrication experience There is no direct participation of INFN and STFC in this project. This collaboration is included in another agreement (Schedule #1.3)  The H-ECCTD project is a bilateral agreement between ESS and CEA  IPN Orsay (Gilles Olivier) will be involved for expertise for CEA : Cryostat components design update and mechanical drawings update Cryostat components fabrication experience There is no direct participation of INFN and STFC in this project. This collaboration is included in another agreement (Schedule #1.3) ESS CEA IPNO H-ECCTD project

TECHNICAL CHALLENGES

TECHNICAL CHALLENGE #1: CAVITIES Accelerating mode frequency HOM frequencies Cavity length Cavity fabrication: Cavity performances:  Accelerating Gradient and Q0: o surface field distribution o chemical etching quality o High pressure rinsing process o Assembly process in clean room  3 targets at the same time (dumbbell trimming and shaping)

 Both prototype cavities already met the ESS requirements after the first test: → Very encouraging results  Slight degradation of the performances after thermal (pollution?) TECHNICAL CHALLENGE #1: CAVITIES Vertical test results of the 2 first prototypes at 2K

From JL. Biarotte, SLHIPP-4 meeting 2014 Graph cryomodules xfel SNS β 0.61: 10.2MV/m SNS β 0.81: 15.8MV/m SPL β 1.0: 25MV/m SPL β 0.65: 19MV/m ESS β 0.67: 16.7MV/m ESS β 0.86: 19.9 MV/m MYRRHA nom β 0.65: 11MV/m PIP-II β 0.9: 17.0MV/m MYRRHA nom β 0.5: 8.2MV/m PIP-II β 0.61: 16.6MV/m SNS  0.61 SNS  0.81 SNS performances The specification of 19.9 MV/m stays very challenging compared to SNS performances TECHNICAL CHALLENGES #1: CAVITIES ESS  0.86 SPL  1 SPL  0.65 (IPN)

TECHNICAL CHALLENGES #1: CAVITIES The 5 H-ECCTD cavities will have the same RF design as the two high beta prototypes already built within the French-Swedish agreement H-ECCTD Cavity design: ESS086 design The niobium thickness reduction (3.6 mm instead 4.2 mm) and the removal of HOM ports will be the only changes in the mechanical design. This RF and mechanical design will be also used by STFC for the series cavities Lessons learned from the Q0 degradation due to the heat treatment (change of Hydrogen degassing furnace) and the HOM issue (reshaping process) will be considered for the H-ECCTD project

TECHNICAL CHALLENGES #2: POWER COUPLERS The peak power of 1.1 MW at a long pulse of 3.6 ms is a real challenge The same power coupler design is used for the MB and HB cryomodules, except for the external coupling factor Qx (only 3.15 mm difference for the external conductor length – see next slide) The first pair of power couplers will be RF conditioning and test will occur in April/May 2016 for the M-ECCTD cryomodule. Even if the Medium beta cryomodules requires only 864 kW max., at least one pair will be tested at 1.1 MW in This is the maximum RF power that can reasonably be acheived with our actual klystron and modulator A new 1.5 MW klystron procurement is in progress rigth now and should be available within 18 months for the H-ECCTD project for evaluation of possible margins

Procedure to evaluate the antenna length * HFSS simulation to determine the distance cavity axis –antenna tip + curve interpolation : dist=61.26mm for the medium  cavity, dist= 64.41mm for the high  cavity * Taking into account the seals (compression) and thermal expansion of the double wall tube (stainless steel 316L) TECHNICAL CHALLENGES #2: POWER COUPLERS High beta Medium beta HFSS model of the high  cavity and the coupler HFSS model of the medium  cavity and coupler ESS should confirm the Coupling factor of Qx = 7.6 e 9 as soon as possible to adjust the external conductor length Qx

TECHNICAL CHALLENGES #3: CAVITY PACKAGE The high power test of a “ESS high beta elliptical cavity package” composed of a cavity, a power coupler, a tuning system and a magnetic shielding is an important validation step and has not been performed yet This test will be done on MB cavities inside the M-ECCTD cryomodule However, the mechanical behavior of the MB and HB are quite different (stiffness, LFD coef., pressure sensitivity) and a high power test at Eacc=19.9 MV/m on a HB cavity is mandatory before launching the series Medium beta High beta Niobium thicknessmm43.6 Cavity stiffner radiusmm7084 Tank thicknessmm55 Lorentz Force Detuning coef. K L fixed ends Hz/(MV/m)²) Lorentz Force Detuning coef. K L free ends Hz/(MV/m)² Cavity stiffnesskN/mm Tuning sensitivity  f/  z kHz/mm max VM stress /1mm elongationMPa25 Pressure sensitivity K P fixed ends Hz/mbar23.084,85 Pressure sensitivity K P free endsHz/mbar max VM stress /1bar fixedMPa max VM stress /1bar freeMPa31.415

OTHER TECHNICAL CHALLENGES #4: COLLECTIVE EFFECTS Check interferences between the 4 cavities due to mechanical vibrations #5: CRYOGENIC BEHAVIOR Check the static and dynamic losses Check the cooling stability #6: CAVITY ALIGNMENT Before and after cool-down #7: CRYOMODULE INSTRUMENTATION Verify the operation of the vacuum valves, cryogenics control valves, heaters, level sensors, vacuum gauges #8: ASSEMBLY PROCEDURE Optimize the process