1. Accelerator / Elliptical Cavities Cryomodules
Pierre BOSLAND, CEA Saclay
External WP5 leader
Christine Darve,
ESS deputy WP leader
April 21, 2015

2. Elliptical Cryomodules Overview
MEDIUM-β
HIGH-β β
0.67
0.86
# CM 9 21
Cav. /CM 4
# Cav. 36 84
CM L [m]
6.584
Sector L [m] 77
179
Elliptical cavities Cryomodules
Medium-b and high-b
Proton Beam
Annual Review 23rd April 2015

3. Schedule

4. Technical performances
The level-4 requirements for the medium and high beta cryomodules are listed in the DOORS management system (Dynamic Object-Oriented Requirements System).
Conformance of the design with these requirements has been presented at a-TAC (October 2013).
Selected requirements:
Frequency: 704,42 MHz
Nb superconducting cavities at 2K:
medium beta cavities: 6 cell at bgeo =0,67
high beta cavities: 5 cell at bgeo =0,86
Nominal accelerating gradients Eacc corresponding to 45MV/m peak field :
16,7MV/m : medium beta cavities
19,9MV/m : high beta cavities
Max RF power dissipation at nominal gradient corresponding to Q0=59 (RF duty cycle: 4,7%):
Medium beta cavities: 4,9W
High beta cavities: 6,5W
Maximum RF peak power: 1,1MW
No HOM coupler: All higher order modes (HOMs) shall be at least 5 MHz away from integer multiples of the beam-bunching frequency (352.21 MHz) for any HOMs whose resonant frequencies are below the cut-off frequency of the beam-pipe.”

5. Selected technologies
Similar to CEBAF/SNS cryomodule concept with 4 cavities per cryomodule
Common design for medium (6 cells) and high beta (5 cells) cavities
Regulation He valve
Vacuum valve
Thermal shielding
Alignement fiducial
Jumper connection
Magnetic shielding
Spaceframe support
Heat exchanger
Diphasic He pipe
Proton Beam
Cavity with Helium tank
Intercavities belows
Power coupler
Cold to warm transition
Annual Review 23rd April 2015

6. Selected technologies
Segmented cryomodules
6,6 m long - beam gate valves
4 cavities
Power couplers located below the cavities
Space frame holding the cavity string
Superconducting elliptical cavities :
Bulk niobium
Stiff cavities to reduce the Lorentz force detuning
No HOM couplers
RF power coupler:
HIPPI type coupler tested up to 1,2MW at 10% DC and pulse length of 2ms
New door knob equiped with a bias system and RF trap
Tuner
HIPPI tuner modified with a second piezo stack for reliability improvement

7. Compliance with European PED 97/23/EC
Cryo pipes designed to reduce the overpressure in case of beam vacuum failure
TUV Nord analysis report:
The elliptical cryomodules are classified according to PED article 3.3
2 F=100 bursting disks at each extremity
continuous diphasic pipe F=100 with large curvatures
Volumes of the helium circuits and vessels < 50 l
1,431 bars< Working pressure
Ps = 1,9 bars
Annual Review 23rd April 2015

8. Protypes with HOM ports for RF measurement
Integration and Verification
Two high beta prototype cavities
P01 - E. ZANON
P02 - RI
Protypes with HOM ports for RF measurement
Both prototype cavities met the ESS requirements after the first test: very encouraging results!
Slight degradation of performances after thermal treatment for hydrogen removing (pollution)
Annual Review 23rd April 2015

9. Calculated with measured shape (HFSS)
Dangerous Higher Order Mode close to MHz
Both high beta prototype cavities are not conform with the ESS HOM Requirement
Reminder: « All higher order modes (HOMs) shall be at least 5 MHz away from integer multiples of the beam-bunching frequency (352.21 MHz) for any HOMs whose resonant frequencies are below the cut-off frequency of the beam-pipe.”
3D measurements of the cavity shape have been performed
Shape reconstructed in the simulation software HFSS
Slater coefficient analysis which represents frequency sensitivity to volume changes:
Design
(at 300K)
Measured on ESS086-P01
Calculated with measured shape (HFSS)
Measured on ESS086-P02
1403.8
1406.8
704 MHz
1421,32 MHz
On P01 cavity (from ZANON), a strong internal shape deviation in this dome region (more than 1 mm instead of 0.3 mm) explains very well the frequency decrease of the two dangerous HOM
Study under progress on P02 cavity (from RI)
Cells reshaping has to be implemented in the fabrication process of future cavities
Annual Review 23rd April 2015

10. Integration and Verification
Fundamental power coupler
HIPPI power coupler (KEK-type window) tested to 1.2 MW, 10% Duty factor at Saclay
Test of the HIPPI power coupler on the HIPPI cavity at 1.8 K, full reflection
New design of the doorknob waveguide transition including a HV bias capacitor with RF trap

11. Integration and Verification
Study of the assembling tooling in clean room finalized
Training in the new clean room for assembling a HIPPI coupler with the tooling used for the ESS coupler.
XFEL cavity string assembly at Saclay.
The ESS cryomodules will be assembled in this large clean room.
The new “ESS” clean room for the prototype ESS elliptical cryomodules ECCTD is now in operation.at Saclay.
Annual Review 23rd April 2015

12. Framework of the cryomodules development and production
Two prototype cryomodules:
medium beta: M-ECCTD <= FR-SW agreement
High beta: H-ECCTD <= CEA FR In Kind Contribution
Production of cavities of the series with RF tests:
medium beta cavities <= LASA - IT In Kind Contribution
High beta cavities <= STFC - UK In Kind Contribution
Production of all other components: <= CEA FR In Kind Contribution
(including coupler production with RF power processing)
Cryomodule assembling : <= CEA FR In Kind Contribution
(XFEL assembly infrastructure)
RF power tests of the cryomodules <= ESS Lund
Annual Review 23rd April 2015

13. Organization at CEA SaclayWP
Cryomodules
de série
P. Bosland/XXX
Tests IPHI
B. Pottin
Diagnostics
F. Sénée
Contrôle
Commande
F. Gougnaud
ACCSYS WP3
ACCSYS WP5
Projet ESS / IRFU
CdP: P. Bosland
Adjoint: A. Daël
Project Office
planning: X. Hanus
ressources: L. Lecourt
secrétaire: XX
Cellule Qualité
A Bruniquel
C. Cloué
Sécurité
O. Kuster
Management :
Coordination C.
Collaboration C.
In Kind Review C.
ACCSYS WP 3
ACCSYS WP 5
ACCSYS WP 7
ICS WP 6
ICS WP 10
ICS WP 6 / 10
Bunker 352 MHz
JP. Charrier
ESS - AB
ESS - IRFU
Technique :
Technical
Board
Responsables
Scientifiques
G. Devanz
D. Uriot
O. Piquet
Test
injecteur
M-ECCTD
IKC
H-ECCTD
WP ECCTD
F. Peauger
Design RFQ
RFQ
WP RFQ
ACCSYS WP7
IRFU reorganization on the 1rst of June 2015:
Florence Ardellier: Project Manager
Pierre Bosland : Scientific Director
1st April 2015
TAC11

14. Budget and cost-book

15. Major Procurements Main procurements for M-ECCTD launched:
6 cavities
6 power couplers
Vacuum vessel
Toolings
Clean room
Cryogenic lines and RF wave guides for RF power test stand ….
H-ECCTD: Niobium and fabrication of the high beta cavities
Cryomodules of the series:
Niobium for the elliptical cavities (see LASA and STFC presentation)
RF power source for RF conditionning of the couplers of the series
RF power couplers
Cryostat components
Industrial cryomodule assembly
Annual Review 23rd April 2015

16. Top risks
Some comments and recommendations for the TAC 1st April 2015:
The success oriented schedule presented leaves almost(?) no room for iteration of any of the sub-components or the module itself. Thus an extremely careful self-assessment of technical risks is to be made.
there will be no feedback from first cryomodule power testing on the assembly of the following cryomodules, and this is a serious concern
The IKC concept for the cryo module and its‘ components requires precisely defined interfaces. Include in all IK negotiations aspects for technical, logistical and contractual issues.
Regarding manufacturing geometry accuracy, analysis should be performed to determine the geometric tolerance to escape the HOMs from the harmonics with a minimum spacing of 5 MHz
(=> Analysis started and in progress)
Annual Review 23rd April 2015

17. Next Six Months
Follow up of the component production for the M-ECCTD prototype cryomodule
Test the first medium beta prototype cavity
Test the first prototype power coupler
Complete and test of the cryogenic line of the RF power test stand at Saclay
Development of the Control/command system of the RF power test stand at Saclay
Prepare the assembling area of the M-ECCTD outside the clean room
Organize and prepare all the In Kind activities at Saclay for the production of the cryomodules of the series

18. Elliptical cavity cryomodules Summary
The design of the elliptical cavities and cryomodules complies with the ESS requirements.
The prototype cryomodules M-ECCTD and H-ECCTD will validate the design. 
The preliminary planning for the design/prototyping and for the production of the elliptical cryomodules has been proposed in compliance with the RFI dates.
This planning is success oriented with major risks identified 
The coordination between the In-Kind partners has to be quickly placed to start the work as soon as possible:
Coordination between CEA, CNRS, INFN, STFC and ESS
ESS has to establish a "partnership with INFN and STFC, which will permit to make use of the best European competences in the field of SRF".