1. LASA Medium-β Cavity Progress Update Paolo Michelato 2 nd ESS Collaboration Meeting - SRF Elliptical Cavities 15 th December 2015

2. Summary Nb material: LG and FG, defects. Interfaces, mechanical constrains, tolerances, boundaries condition, etc for cavities and tank Frames for cavity handling QA / QC and Quality control strategy

3. Nb LG and FG for prototypes Nb LG (diam. 480 mm), from CBMM arrived in Europe, sliced at Heraeus Hanau. RRR: about 300 Next steps BCP (a few  m) and heat treatment for dehydrogenation and stress release at EZ Dies preparation Deep drawing test Order for FG material for LG cavity prototype (tubes, stiffening) and for FG cavity prototype (sheets, tubes, stiffening) for the second medium beta is under way.

4. Nb defects Still open the question of defects? XFEL statistics: between 0.6% and 2% (company dependent) for a XFEL sheet (265 x 265 mm 2 ). “Propagation” of defects probability for ESS? Linear? Sheets would be around 500 x 500 mm 2. Surface ratio: about 3.2 Expected defects ratio for ESS? Scanning needed? All defects seen with eddy current are dangerous? The BCP treatment reduce the risk: it would corrode and remove “easily” defects with respect to EP Acceptable?

5. Mechanical construction, interfaces and plug compatibility LASA plug compatible design needs for a full clarification of interfaces requirements. Interfaces must be clarified: definitions, dimensions, tolerances, maximum misalignments, etc. to ensure the cavities acceptance and their installation in the cryomodule. Present CEA cavity design should be updated and improved to be ready for series production. E.G. for cavity length (XFEL +/- 3 mm), definition of reference surfaces, flange tolerances, alignments, etc. These activities already started after the Interface Meeting at LASA of November 2 – 3 and it is in progress.

6. Tank design Present CEA tank design doesn’t permit the adjustment of the tank length with respect to the cavity length. Tank is “custom-made” and adapted to the cavity. Present tank design makes quite hard the extraction of the cavity from the tank: from EXFEL experience some cavities could need a further etching and therefore a cavity retuning for field flatness restoring. The suggestion, coming from the past experience, is to insert an L structure sliding join on the tank: this will permit the adjustment of the tank length (one tank design for all cavities) and an easier removal of the tank and the installation of a new one after retreatment.

7. Tank design Implication of the presence of the join on the cavity installation in the module are under investigation by CEA (fixed point, tie rods distances and connections to the cryomodule frame, position of the sliding part w.r.t. coupler, etc)

8. Frames for cavity movement, support, cold test CEA frames will be used for medium beta cavity support, handling, movement, cold test, transportation. Same interaxis distance of rods for naked cavity and cavity with tank Rods: Titanium Verification of compatibility at the industry (cleaning, rinsing, BCP, HPR) under way.

9. Quality Control strategy Based on our experience for XFEL cavity production 400 + 400 cavities (1.3GHz) fully produced at the industry + 10 + 10 cavities (3.9 GHz) produced at the industry (assembly of cavities ancillaries and last HPRs done at LASA), test done at LASA For the 32 medium beta cavities for ESS: Companies are responsible for QA/QC Companies hand over required info to the Contractor (INFN) INFN Team of experts (mechanical, RF, treatments, vacuum, etc.) check and approve documents (“external” QC, process control) “on-line” check of production quality (feedback to the Companies) Only if requirements are fulfilled, the cavity go on with production (Acceptance levels overcome) Non Conformities: If the required property of a component is not provided, a nonconformity report is emitted by the Company and further action are discussed and approved by the contractor: acceptance or quarantine Check list for any outcoming / incoming steps INFN supervise the Quality Control by: Periodic Visit at the companies, scheduled meetings, actions of experts in case of problems.

10. QA / QC: How it will work (ESS) (Data Transfer, Flow of documents and data between INFN and Industry) Industry QC: responsibility of the Company; 3 acceptance levels to overcome Flow of documents for the «external» QC (LASA) INFN Check of all documents (parameters/process); experts do the check and acceptance; Prompt feedback to the Industry LevelCavity status Needed documentsIf Level reached One “Naked” cavity after fabrication Mechanical Fabrication documents Proceed to Level Two workflow Two Cavity after surface treatments Treatment documents Proceed to Level Three workflow Three Cavity integration and last treatments Integration and last treatment documents Integrated cavity ready to be RF tested Managing of documents/ database Industry must be released for each Al before going on with production NCR must be emitted and repair action approved by INFN

11. Flow of cavities INTERNAL Managing System Quality Control Industry Cold RF test Q 0 vs. Eacc CEA STRING ASSEMBLY CAVITY with TANK MODULE ESS

12. QC / QA:How it will work (ESS) (Data Transfer, Flow of documents and data) Cavity production data INTERNAL Managing System Quality Control INFNIndustry INFN Managing system Database (parameter analysis) INFN Experts Check Cold RF test Q 0 vs. Eacc CEA STRING ASSEMBLY CAVITY with TANK Documents for cold RF test acceptance Documents for full equipped cavity acceptance (for string assembly) MODULE ESS (approval) NCR

13. Clean Room (ISO7) Clean Room (ISO4) Example: ESS Prototype Cavities Treatment Flow