1. LCLS-II HE R&D ongoing results
Background to recipe development
Results - 2 of 12 test
Ari Palczewski
Monday, April 22, 2019

2. Background JLab LCLC-II HE R&D recipe
800°C 3N60 EP5/10/?
This recipe (2N60 in 2015) showed one cavity quenching above 31MV/m with a reasonable Q0 for the material.
This recipe should be tried on multiple cavities with multiple doping to verify statistics or abort, i.e. is this recipe actually good.
Goal ~ 21MV/m with Quench field >30MV/m on good flux expelling material
JLab LCLC-II HE R&D plan – 12 tests
Heat treat three cavities (3N60) at a time in furnace, and perform a 5 micron EP on each, test
perform additional 5 micron EP, test
Break point – good or bad or ?
If good i.e they all meet the goal, reset all cavities and redo study for statistics
If gradient bad but Q0 still good, 5 more micron EP and then evaluate
If gradient and Q0 unacceptable, abort plan and reformulate

3. Background JLab LCLC-II HE R&D cavities
Three prequalified single cell cavities need for the study
All cavities must have gradient close to 24MV/m with a ~3.5e10
SC-04, SC-07 and SC-08 made by RI for LCLS_II TD material batch qualification selected.
All cavities quenched between 23 and 26MV/m.
All cavities showed at least 80% flux 5K gradient across the cavity except SC-07 which only shows 70% and does not level out – next slide
All cavities received additional 900°C 3Hr heat treatment and then 50 micron EP reset. – ready for the study

4. Flux expulsion baseline cavities

5. SC-08 results – Quench @ 36MV/m

6. SC-08 results – Quench @ 36MV/m cont.

7. Sc-07 results – quench @ 16.5MV/m
Modern SRF cavity assembly and practices