# Presentation: 490270

## Plans for SSR1-01, 5-15-08

- Hasan Padamsee was at Fermilab for an accelerator review, and we talked with him about the completed tests of the SSR1-01 in the VTS and plans for a test in the near future (before a high temperature bake):
**Previous VTS tests:**
- Mid-range Eacc (2 to 10 MV/m): No evidence for non-multipacting x-rays, and the Q drop is possibly (probably?) due to hydrogen (Q disease).
- High Eacc (10 to 13.4 MV/m): x-ray evidence beyond multipacting indicates the likelihood of field emission.  The Q drop here may be due to Q disease, field emission, or a combination.
- Condensates due to "bad" vacuum could definitely have exacerbated the multipacting problem.

## Next VTS test (wish list):

- The evidence for field emission at high field indicates that another HPR may help reduce particulates.
- Whether or not we can do the HPR, the 120C bake for 48 hours should definitely be done in order to improve the vacuum and reduce condensates.
- The new VTS vacuum system should also help with the condensates.
- Hasan said that two interesting tests can be made for Q disease.  The first test is to minimize hydride formation by passing as quickly as possible between 200K and ~70K.  He hopes we could do this in 1/2 hour to 1 hour.  We did not know how fast we went through this region in the previous tests and should check with Joe Ozelis.  In practice one should cool down at a normal rate to 200K before starting the fast phase.  The second test is to purposely sit at 150K for 4 to 6 hours in order to produce an enormous Q drop (if Q disease is really present).  We thought we should do the second test after the first test.
- Ivan Gonin asked how high we can likely go if things are optimized.  Hassan said that a BCP'd cavity can likely reach a surface magnetic field of 80 mT (Eacc ~ 16 MV/m for the SSR1) before hitting the high field Q slope.  I asked if the 120C bake would help reduce the high field Q slope, and Hassan said that this is unlikely if the surface is rough (I believe that the SSR1-01 surface is "rough").

## Questions I asked Mike Kelly (ANL):

- I think that the HPR can be improved with the addition of the trunion, which was not available before, but it is now.  Also, with less overhead due to people entering the clean area to turn the cavity, I think the actual "water" time can be increased from 2 to 4 hours (a number that Joe Ozelis said is more common for cavities of this size at Jlab).  Giorgio Apollinari said that Dan Assel could be made available to help set up and perform the HPR.  Would this be possible toward the end of May?  I know it would take some of Scott's and Mark's time to do the HPR (possibly Dan and I could be "trained" to help), and it would take some of your time to install the clean flanges.
- We are making future plans for the expected 600C bake.  Tug recommended a company in Des Plaines with a suitable vacuum furnace.  I believe you mentioned that ANL has a suitable furnace, and this would be more convenient since the bake needs to be followed by the light BCP and HPR.  Would it be possible to check into the cost and availability of using the furnace at ANL?
- I am starting to think about the plumbing required to add acid outlets near the top and bottom of the cavity.  Do you have an estimate of the viscosity of the 1:1:2 mix?

## SSR1-01 vacuum test and contacts concerning 120C bake:

- Brian Smith is presently testing how the vacuum degrades in the SSR1-01 when it just sits on the shelf.  Previously we saw a large degradation in vacuum before and after tests in the VTS, but was this just due to normal out gassing?
- Bob Webber and I have touched base with people who will do the 120C bake at NWA.  This oven becomes available after May 20.  Summary by Ron Kellet:  The specifics are; 120C bake for 48 hours.  Ramp up rate is not important.  The Niobium cavity is robust compared to the 9 cell cavities, so it can be handed without concern of structurally damaging it.  There is no need to find out what the ultimate pressure is, therefore, do not use an IP during the bake.  Particle free inside the cavity is important, so the connection and removal of the turbo must be made in the clean room, along with all particle free practices.  They are trying to get Argonne to do a high pressure internal rinse before we bake the cavity, Bob thinks sometime near May 20th.

## Bob Webber’s enquiry into getting BCP help from Mike Foley’s group:

- I spoke with Mike Foley today about the possibility of Alan Rowe and Wade Muranyi helping to do some HINS cavity BCP work at Argonne. Mike indicated that this could quite likely be arranged with sufficient planning. I suggested that the help would not be needed before ~July, i.e. after seeing results from a June VTS test. Mike hopes the 3.9 work which has been consuming their time is completed by then.  Anyway this looks like it might be a realistic avenue for some qualified BCP help.