Conceptual Cryomodule Design for the CW HElmholtz LInear ACcelerator at GSI F. Dziuba1,2,4 K. Aulenbacher1,2,4, W. Barth1,2, M. Basten3, C. Burandt1,2, M. Busch3, V. Gettmann1,2, M. Heilmann2, T. Kürzeder1,2, S. Lauber1,2, J. List1,2 , M. Miski-Oglu1, H.Podlech3, A. Schnase2, M. Schwarz3, S.Yaramyshev2 1HIM, Helmholtz Institute Mainz, Mainz, Germany 2GSI Helmholtzzentrum, Darmstadt, Germany 3IAP, Goethe Univ. Frankfurt, Frankfurt, Germany 4KPH, Johannes Gutenberg Univ., Mainz, Germany

Superconducting cw HELIAC Recent layout of the future superconducting cw HELIAC Layout properties Multigap CH cavities Cavities with short lengths (<1m) and small transverse dimensions (<0.5 m) Modular construction with 4 cryomodules Each containing 3 CH cavities, 1 buncher, 2 solenoids Ea= 5.5 MV/m enables compact linac design First step Demonstrator project

Design of the Demonstrator Cryomodule Design properties Universally design, multi-use Magnetic shield coupled to 300 K Support frame located within thermal shield Various flanges for power couplers, tuners, electrical feedthroughs etc. LHe provided by 250 l dewars Transversal tolerance during cool down ± 0.1 mm Several fiducials for component alignment LN2 reservoir (50 l) LHe reservoir (100 l) Layout of the horizontal demonstrator cryomodule Superconducting 9 T solenoids Support frame 217 MHz CH cavity 2.2 m DEMONSTRATOR CRYOMODULE Inner length mm 2200 Inner diameter 1120 Material vessel Aluminum Insulating vacuum mbar < 1·10-5 Max. system pressure bar < 0.5 Operating temperature K 4.2 Temperature thermal shield 77 Max. static losses (stand by) W < 5

Support Frame & Alignment suspended on outer vessel Tuners Nuclotron suspension CH cavity and two solenoids mounted in the support frame Power coupler Alignment of all components to each other ⇾ common component axis Transfer of common component axis to support frame ⇾ string integration Transfer of frame axis to cryomodule ⇾ vessel closing Alignment of cryomodule axis to beam line

Assembly of Cold String at GSI Successfully tested with beam! Clean room at GSI Outer part: ISO6 Inner part: ISO4 Integration into Cryostat

Next Step: Standard Cryomodule Layout New cryomodule layout optimized for the cw HELIAC requirements Cryomodule containing 3 CH cavities , 1 buncher cavity and 2 solenoids Operated at 4.2 K, required cooling power 60 W (total) Each component equipped with own He jacket and magnetic shield LHe supplied by the 700 W GSI cryo plant

Design features & improvements New Cryomodule Layout Design features & improvements 4 rectangular service doors On site alignment of each component to the beam line with a laser tracker Assembly of RF power couplers and solenoid current leads through the doors Nuclotron suspension of single components Segmented support frame, mechanically and thermally coupled to outer tank (300 K) Thermal shield inside of support frame Segmented frame standing on dedicated points of the bottom of the cryostat Deformations of outer vessel during evacuation do not affect the position of the frame Trans. position of each component will be preserved within ± 0.1 mm during cool down One of the main improvements…

New Cryomodule Layout Already ordered, expected delivery in 04/2020 Built by Cryoworld, Advanced Cryogenic, Netherlands Size of order: 520k€ CRYOMODULE CM1 Inner length mm 4500 Inner diameter 1500 Material vessel Stainless steel 1.4404 Insulating vacuum mbar < 1·10-6 Max. system pressure bar < 0.5 Operating temperature K 4.2 Temperature thermal shield 40 Max. static losses (stand by) W < 5

Assembly Procedure: Step 1 CH0 B1 CH2 CH1 S1 S2 Step 1: Inside the clean room the cold string is mounted on a rail system All components will be connected with bellows Their relative position to each other is fixed with bolts Cold string is terminated with gate valves and evacuated Rail guided support system

Assembly Procedure: Step 2 Mounting rack Segmented frame (top part) Step 2: Cold string is moved along the rail system outside the clean room Top part of segmented frame is assembled to the mounting rack Rough alignment of the cold string with the segmented frame

Assembly Procedure: Step 3 Suspension of individual components into the segmented frame Removal of rail guided supports Assembly of He distribution piping

Assembly Procedure: Step 4 Bottom of segmented frame is connected to the top part Remaining nuclotron suspensions will be assembled Alignment of single components Thermal shield is closed except door regions Segmented frame (bottom part)

Assembly Procedure: Step 5 Frame is shifted into the cryostat using an internal rail system Internal rail system is locked Assembly of warm parts of the power couplers Final alignment of components with laser tracker Closing of remaining thermal shield and outer vessel

Thank you very much for your attention! Acknowledgements Thank you very much for your attention! Improvments, comments, concerns and doubts are welcome! Collaboration partners GSI / HIM KPH - Johannes Gutenberg University Mainz IAP - Goethe University Frankfurt

Backup Slides

Layout of the horizontal demonstrator cryomodule Things to Optimize LN2 reservoir (50 l) Things to optimize Assembly procedure of components into the support frame regarding longer cold strings Individual alignment of components after integration of cold string into cryostat not possible Alignment of components in longer cold strings is difficult due to deformations No convenient access for assembly & maintenance (power coupler, connection of He exhaust etc.) Vessel made from stainless steal instead of aluminium ⇾ abrasion, dust, durability Nuclotron suspension is reliable within required tolerances of ± 0.1 mm! LHe reservoir (100 l) Layout of the horizontal demonstrator cryomodule Superconducting 9 T solenoids Support frame 217 MHz CH cavity 2.2 m

RF Design of the Demonstrator Cavity CH0 (based on beam dynamic design by S. Mineav 2009) Inclined stem Helium vessel Static tuner Dynamic tuner Preparation ports 3rd superconducting CH cavity developed at IAP Manufacturered at Research Instruments Most complex superconducting cavity ever been built Bulk Niobium (RRR 300) from Tokyo Denkai

PhD thesis of M. Basten, IAP, Frankfurt University Short CH Cavity Design Design parameters of short CH cavities CH1 & CH2    0.069 Frequency MHz 216.816 Cell number # 8 Length (βλ-definition) mm 381.6 Cavity diameter (outer) 400 Cell length 47.7 Aperture diameter 30 Dynamic bellow tuner 2 Wall thickness 3-4 Accelerating gradient df/dp MV/m Hz/mbar 5.5 -13 Ep/Ea 5.2 Bp/Ea mT/(MV/m) <10 G Ω 50 Ra/Q0 1070 PhD thesis of M. Basten, IAP, Frankfurt University CH1 w/o He vessel has been already RF tested at 4 K @ IAP

Cavity Tuning Rotation axis Main properties of the tuning system: Stepping motor Piezo actuator Bellow tuner Lever Spindle Main properties of the tuning system: Enables slow & fast frequency adjustment Capacitive bellow tuner Max. mechanical displacement ±1 mm (≈ ±60 kHz) Required force < 800 N Lever with pivot point ratio ≈ 2:1 Gear reduction ratio 50:1 Piezo actuator ‚connected in series‘ with slow tuning unit Required displacement of piezo ±4 µm (≈ ±240 Hz) PhD thesis of M. Amberg, 2015 KPH, Mainz University 50 mm

Coupler design based on the work of S. Kazakov, Fermilab High Power Coupler Outer conductor 3 1/8‘‘ Bellow Diagnosis port 502.6 mm Warm part Inner conductor Cold part 300 K Warm window 70 K Cold window 4 K Coupler design based on the work of S. Kazakov, Fermilab Coaxial antenna setup (inner conductor made from copper) Capacitive coupling of RF power Devided into cold & warm part by 2 ceramic windows (Al2O3), TiN coated 5 kW cw operation, cold window connected to LN2 supply 216.816 MHz operation frequency with 33 MHz bandwidth

HLI provides Ar11+, Ar9+, Ar6+, He2+ @ 1.4 MeV/u Matching Line – Demonstrator HLI provides Ar11+, Ar9+, Ar6+, He2+ @ 1.4 MeV/u HLI 1,4 MeV/u R2 x | y cw Demonstrator R1 T P G BSM Mob EMI QT QD QT: Quadrupol triplet R: Re-Buncher (QWR) QD: Quadrupole doublet x|y: Steering magnets G: Profile Grid T: Beam current transformers for transmission measurement P: Phase probes for TOF measurement BSM: Bunch shape monitor (Feschenko monitor) EMI: Slit-Grid emittance measurement device

Timeline Funding of CM1 for the HELIAC 02/2015 Ordering of CH cavities CH1 & CH2 Tendering of CM1, solenoids S1 & S2, buncher cavity B1 Delivery of CH1 & CH2 Delivery of CM1, S1, S2 , B1 and assembly @ HIM 4K test of fully equipped cryomodule CM1 @ GSI Beam test @ GSI 02/2015 09/2016 10/2018 02/2019 04/2020 09/2020 10/2020