Spoke Cryomodules (WP4)

Guillaume OLRY(CNRS/IPN Orsay)

WP4 Deputy Leader

www.europeanspallationsource.seApril 21, 2015

Spoke Cryomodule Activities : Executive summary

• IPN Orsay is taking in charge the design of the ESS spoke cryomodules. The design activity is 95% achieved, only details of the cryomodule are still being studied.

• WP4 is in the design validation phase: prototypes of all sub-components have been (or close to be) fabricated and are under test to have an experimental validation of their performances before starting series productions.

• Results obtained so far are extremely positives: the 3 cavity prototypes performed well above specifications.

• The activities are conforming to the original planning: intermediate tests/validation allow to start series production before the final experimental validation (which is the test at Uppsala University of the prototype spoke cryomodule). 2

Schedule: the main blocks

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• Main objective: deliver to ESS the last (#13) spoke cryomodule for Xmas 2018

Schedule: the 3 critical validation steps

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Several test results are validation of components ability to perform as required by ESS and thus are mandatory before launching series production:• Cavity test in vertical cryostat (achieve 9MV/m and nominal Qo)

Required prior tendering for niobium production for series (March 2015) i.e. one successful test to be achieved in February 2015 at the latest

• Cavity with coupler test in HNOSS (RF coupling successful, achieve 9MV/m and CTS) The test requires around 100 kW of RF power Required prior tendering for the Spoke cavities mass production (Feb. 2016) i.e. one successful test to be achieved in Dec 2015 at the latest

• Prototype cryomodule test (validate cryo, assembly, overall results) Required prior tendering for the series production of spoke cryomodules (July

2016) i.e. one successful test to be achieved in June 2016 at the latest

Schedule: the 3 critical validation steps

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Go/NoGo #3: Successful test of the spoke

prototype cryomodule

Go/NoGo #1: Successful test of a cavity

in vertical cryostat

Go/NoGo #2: Successful test of a

cavity+coupler in HNOSS

The 3 VT have been achieved in

March 2015

Planned for summer 2015

Planned to start in Déc 2015

Done !On time

i.e. a 5 months margin

Spoke cryomodule requirements & technical performances

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Section Cavity b Total number of Modules

Cavity frequency

# Cavity per module

# Cavity per section

Section length

Spoke 0.50 13 352.21 MHz 2 26 56 m

IPN Orsay is responsible for the design, production and delivery of the 13 spoke cryomodules and associated cold distribution system for ESS.

The IPNO task includes all activities linked to the design, prototyping, series production, preparation, assembly and then testing of the spoke cryomodule components (cavities, power couplers, cold tuning systems, cryostat). The 13 cryomodule validation tests at nominal RF power will be done by the Uppsala University team, already strongly involved in the project, in their newly built and operational FREIA facility.

Spoke Cryomodule Technical performances

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Power Coupler

Cold Tuning System

• Ceramic disk, 100 mm diameter• 400 kW peak power (330 kW nominal)• Antenna & window water cooling• Outer conductor cooled with LHe• Doorknob transition from coaxial to ½ height WR2300 waveguide

• Slow tuner (stepper motor): Max tuner stroke: 1.28 mm Max tuning range: ~ 170 kHz Tuning resolution: 1.1 Hz• Fast tuning by 2 piezo-actuators Noliac 50x10x10 or PI 36x10x10 mm Applied voltage up to +/- 120 V Estimated tuning range at 2K: 800 Hz

Double Spoke SRF Cavities

• Double spoke cavity (3-gaps), 352.2 MHz, b=0.50• Goal: Eacc = 9 MV/m [Bp= 72 mT ; Ep = 39 MV/m]• 4 mm (nominal) Niobium thickness• Titanium Helium tank, Ti stiffeners• Lorentz detuning coeff. : -4.4 Hz/(MV/m)2

• Tuning sentivity Df/Dz = 128 kHz/mm

Spoke cavities: design & prototype performances 1/2

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DOUBLE-SPOKE CAVITY

Frequency [MHz] 352.21

Beta_optimum 0.50

Operating gradient [MV/m] 9.0

Temperature (K) 2

Bpk [mT] 61

Epk [MV/m] 38

G [Ohm] 133

r/Q [Ohm] 427

Lacc (=beta optimal x nb of gaps x λ /2) [m]

0.639

Bpk/Eacc [mT/MV/m] 6.8

Epk/Eacc 4.3

P max [kW] 3353 spoke cavity prototypes have been fabricated and tested in vertical cryostat: #1 fabricated by SDMS (Fr), #2 and #3 fabricated by ZANON (It)Niobium is from Tokyo Denkai (Japan)

ZA 02Giulietta

ZA 01Romea

SD 01Germaine

Spoke cavities: design & prototype performances 2/2

Spoke cavity prototype test results (Jan. – March 2015):• Excellent performances, well within specifications (both on Eacc & Qo)

• Eacc max=15.1 MV/m achieved with Giulietta• Several MP barriers, but quite easily processed• Best Qo is > 1010 at low field• Strong FE at max gradient• Limitations on all 3 cavities is cooling capacity (unstable conditions, cavity in vertical position)

Spoke cryomodules: design & prototype fabrication 2/2

Prototype fabrication: power couplers, CTS

Cold Tuning System: 2 units fabricated and tested, 2 more under production

Power coupler conditioning bench: all parts realized, dry assembly done.Now in clean room for preparation

Power Coupler: 2 units achieved and received, 2 others in final production step

Power coupler parts: double wall external conductor and doorknob: fabricated

Spoke cryomodules: design & prototype fabrication 2/2

Prototype cryomodule fabrication: all “big” parts fabricatedSpoke cryomodule vacuum vessel:

Fabrication achieved (FAT done)

Spoke valve box: detailed design in progress, procurement for heat exchanger and cryo valves is ongoing

Cold/warm transition

Inter-cavity belows

Gate valves

Cryomodule support

S. Bousson

WP leader

G. Olry

Spoke cavities

E. Rampnoux

Power Coupler

P. Duthil

Cryomodule

N. Gandolfo

CTS

D. Reynet

System Engineer

V. Laurencier

Project Assistant

V. Poux

Quality Engineer

Organization at IPN Orsay for ESS

• In 2014: 26 persons involved in ESS WP4, for a total of 7.5 FTEs

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Design OfficeS. Brault, J. Dault, S. Blivet

Cavity & cryomodule preparation & testsP. Szott, R. Martret, A. Stephen, L. Renard, F.

Chatelet, G. Michel, C. Joly, M. Pierens…

Simulation/modeling: P. Duchesne

P. Duthil/M. Pierens

Valve Box

Major Procurements (1/2)

1. Niobium procurement & lead time• Scheduled between March 2015 and Sept. 2016 - Cost estimated to ~ 2.2 M€• Several suppliers worldwide (Niobium for prototypes is from Tokyo Denkai)• Order all niobium for spokes in one single procurement• Supplier strategy: only 1 (for the ~ 4 tons of Nb)• Spare strategy: niobium equivalent to 1 more cavity.

2. Spoke cavities procurement & lead time• Scheduled between Feb. 2016 and Feb. 2018 - Cost estimated to ~ 4.2 M€• Several companies worldwide, 3 in Europe – Prototypes: SDMS (Fr) & Zanon (It)• Order the 26 spoke cavities in one single procurement• Supplier strategy: only 1 – it’s cost effective & less required work for fabrication follow-up

(2 contractors is of course possible, but no clear advantages, not necessary for schedule reasons for instance)

• Spare strategy: no spare (ESS guideline), but with option for 1 spare• Allocated production lead time will allow 2 phases:

- a pre-production (4 units) to check production processes and quality, constituting a Go/NoGo for phase 2.

- a series production for the remaining 22 units

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Major Procurements (2/2)

3. Spoke power couplers procurement & lead time• Scheduled between May 2016 and February 2018 - Cost estimate: ~ 1.1 M€• Several companies worldwide & Europe – Prototypes: SCT (Fr) and PMB (Fr)• Order the 26 power couplers in one single procurement, to a single supplier• Spare strategy: no spare (ESS guideline), but with option for 1 or 2 spares• Allocated production lead time will allow 2 phases:

- a pre-production (2 to 4 units) to check production processes and quality, constituting a Go/NoGo for phase 2.

- a series production for the remaining (22 or 24)

4. Spoke cold tuning systems procurement & lead time• Scheduled between June 2016 and Dec. 2017 - Cost estimate: ~ 0.5 M€

5. Cryomodule parts procurement/assembly & lead time• Scheduled between July 2016 and Dec. 2017 - Cost estimate: ~ 4.0 M€

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Top 3 risks for the spoke cryomodules

• #1 (Main risk): success-oriented schedule: no room for a failure – Typically: a cavity VT failure, a cryomodule assembly failure implying a partial or

full disassembly/re-assembly of a cryomodule.– Mitigation: anticipate as much as possible the series production, to give schedule

margin during series production, without taking additional risk: this is the followed scenario with the intermediate validation tests.

• #2: No spare: neither for sub-components nor for a complete module– A failure during production of a sub-component, or a lower performing

component (cavity, power coupler, cryomodule...).– Mitigation: integrate options in procurement for additional production (1 or 2

spares) and use whenever possible the prototype cryomodule parts.• #3: Failure of a test/preparation facility: RF source, vertical cryostat,...

– Cavity, coupler or cryomodule tests and preparations rely on heavy infrastructure that might have failures

– Mitigation: have fallback solutions: for RF, several sources will be available at UU (FREIA) and 1 at IPNO; for cryo test, 2 VC will be available at IPNO,...

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The Main milestones for the next six months

• Conditioning of the 2 sets of power coupler pairs• Develop and validate several cavity procedures:• Baking at 120 °C (expected benefit on Qo and field

emission / multipacting)• Cavity H degassing at 550 °C to cure from Q-disease• Cavity venting procedure without inducing particle

contamination

• Achieve the valve box design and start fabrication of the prototype, compatible with operation in FREIA

• Achieve preparation and assembly of the spoke cryomodule for Dec. 2015

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Summary

• All 3 cavity prototypes already tested in VT and showed excellent performances, with important margins w.r.t. specifications, thus validating the cavity RF design.

• Design of all components for the spoke cryomodule is 95 % achieved, including assembly tooling.

• Fabrication of the spoke cryomodule prototype and cavity package is well advanced, close to completion; the prototype cryomodule should be assembled and ready for test in Dec. 2015.

• An optimized schedule allows to start series production (first item: Niobium) without waiting for the prototype cryomodule test, thanks to the involvement of Uppsala University.

• The actual schedule allows us to deliver the last spoke cryomodule to ESS on time (Dec. 2018), with realistic time allocated for the different activities…but only little margin exists for potential failures.

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