9-cell Vender Qualification test for LCLS-II Fulfillment of contract Phase 1 - RF tests and flux expulsion measurements Ari D. Palczewski, SRF Scientist Jefferson Lab, USA 2/25/2016 - Contract data and slide courtesy of Frank M. High Q0 working group MOBA07

Outline Venders and Phase 1 contract requirements 9 cell RF results Surface resistance fitting to verify doping Flux expulsion measurements – initial results and why this may be a important factor being overlooked in Phase 1

DoE Subcontract Awardees for Cavity Fabrication (contracts executed 5/29/2015) – Same as X-FEL venders Ettore Zanon, S.p.A. Schio, Italy RI Research Instruments GmbH Bergisch-Gladbach, Germany

Phase I – Vendor Qualification (VQ) N-doping is part of the usual high-temperature vacuum furnace degassing of cavities, vendors already own furnaces What is required by vendors to complete VQ ? Upgrade of furnace hardware and software controls to perform N-doping in compliance with specifications defined by the project Vendors need to strictly adhere to N-doping recipe (‘N2A6 EP 5 μm’) – EP final temperature is controlled below 25C JLab verifies process parameters after N-doping Vendors need to demonstrate successful N-doping ( RF results) on 2 cavities in a row Step Temperature (°C) Duration N-Pressure(mTorr) H degassing 800 ± 10 180 ± 5 min N-Doping 2 min ± 6 sec 26 ± 4 Soak Period (‘Annealing’) 6 min ± 6 sec

Phase I – Vendor Qualification (VQ) ‘Dummy’ Cavities for risk mitigation prior N-doping of VQ cavities Dummy cavities are used to demonstrate proper N-injection and automated N pressure control Each vendor will N-dope 1 dummy prior to VQ cavity Dummy cavities will not be RF tested Dummy cavities are 9-cell TESLA-type cavities with total surface area similar to LCLS-II cavity

Qualification Cavity sent to JLab under vacuum Cavities are undressed (no HV) Cavities do not have HOM couplers JLab will test at 2.0k 1.8k and 1.6K to “extract” doping amount from RF tests Passing unconditionally 3.0e10 @ 18MV/m no field emission – i.e. goal Passing any other way - contract states Jlab will decide if doping/EP was correct and can pass without meeting goal if other issues arise. 2 cavities must pass in a row to qualify vender

9 cell test results Zanon passes phase 1 Unconditionally RI phase 1 was under discussion, now passed (see fitting next)

Surface resistance fitting example 1.6K 1.8K 2.0K

Fitting from Q vs. Eacc – Temperature dependant “A” to qualify doping The extraction of “A: allows verification of doping

Fitting from Q vs. Eacc – “Temperature Independent”

Cavity history – none standard, RI023 closest TB9AES014 ATI Wah Chang material Looks like ~12 hours at 800C Total material removal ~ 250-300 microns Was doped once before Zanon doped by accident – only 40 microns removed after doping TB9AES023 Cavity fully re-crystallized Cavity had bulk EP, CBP and unknown amount of furnace treatments Most likely >400 microns removed Doped @ Cornel 800c 5h N20A0 @ 40torr At least 8 hours in furnace @ 800C TB9AES025 Heat treated at Cornell ~ 3 Days in furnace @ 850C+3hr JLab 800c, ~ 250 microns total removal TB9RI023 ~ 250 microns removal time in furnace 7 hours @ 800c

Measuring Flux Expulsion During Transition Poor expulsion: BSC/BNC ~ 1.1 Good expulsion: BSC/BNC ~ 1.6 Sam Posen | TTC Meeting, SLAC, 2015 – strong material and history dependence on flux expulsion

Flux expulsion ratio – base temperature to 4k The data is from averaging the three magnetometers and the iris to iris temperature when the equator was at 9.25K.

RF results – TB9AES014

RF results – TB9AES023

RF results – TB9RI023

Final thoughts In my opinion both venders are fully qualified to move to phase II It is clear to me that both venders will be able to “dope” cavities during production using the standard recipe without issue It is unclear to me how good the vender doped cavities will be because of the material used in production is not like any used during the R&D phase or vender qualification phase.

Backup

Phase I – Vendor Qualification (VQ) E. ZANON: Dummy cavity N-doping completed (9th October) We expect N-doping of 1st VQ cavity mid/end October 2nd VQ cavity scheduled for end October/early November RI: Dummy cavity N-doping scheduled for 14th October 1st VQ cavity scheduled for 26th October, 2nd VQ cavity early November Results: • N2 injection sequence executed correctly • Pressure range inside required limits, i.e. 26 mTorr ±15% N2 A6 1st furnace N-doping with dummy cavity at E. ZANON (October 2015)