1. 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

2. 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

3. 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

4. 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

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

6. 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

7. 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…

8. 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
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

9. 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

10. 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

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

12. 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)

13. 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

14. 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

15. Backup Slides

16. 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

17. 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

18. PhD thesis of M. Basten, IAP, Frankfurt University
Short CH Cavity Design
Design parameters of short CH cavities CH1 & CH2 
0.069
Frequency
MHz
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 IAP

19. 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

20. 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
MHz operation frequency with 33 MHz bandwidth

21. HLI provides Ar11+, Ar9+, Ar6+, He2+ @ 1.4 MeV/u
Matching Line – Demonstrator
HLI provides Ar11+, Ar9+, Ar6+, He @ 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

22. 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 HIM
4K test of fully equipped cryomodule GSI
Beam GSI
02/2015
09/2016
10/2018
02/2019
04/2020
09/2020
10/2020