1. 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

2. 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

3. 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

4. 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

5. 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

6. 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 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

7. 9 cell test results Zanon passes phase 1 Unconditionally
RI phase 1 was under discussion, now passed (see fitting next)

8. Surface resistance fitting example
1.6K
1.8K
2.0K

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

10. Fitting from Q vs. Eacc – “Temperature Independent”

11. Cavity history – none standard, RI023 closest
TB9AES014
ATI Wah Chang material
Looks like ~12 hours at 800C
Total material removal ~ 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
Cornel 800c 5h 40torr
At least 8 hours in 800C
TB9AES025
Heat treated at Cornell ~ 3 Days in 850C+3hr JLab 800c,
~ 250 microns total removal
TB9RI023
~ 250 microns removal
time in furnace 7 800c

12. 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

13. 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.

14. RF results – TB9AES014

15. RF results – TB9AES023

16. RF results – TB9RI023

17. 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.

18. Backup

19. 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)