[Cuga] Update to the experiment schedule - a message from R. Ent/A. Freyberger for the NPES committee

[Jodi Patient]

As you know we’re in the midst of CEBAF recovery/restart.  We’re having problems with one cryomodule (1L20) essentially delivering no useful gradient due to field emission.  This is an original CEBAF C20 module that was worked on over the down period to replace aging warm rf windows – a relatively routine operation, that was uneventful.   The excessive field emission suggests particulate contamination of the surface.  We are exploring all avenues to identify root cause.



 After working on this crymodule for the last few days we have made the decision to pursue helium processing in order to recover gradient in this module.  This process has been successful in the past in recovering gradient from field emission-dominated cavities. We intend to also helium process module 1L07 at the same time to improve its performance.



To that end, our plan is to delay the scheduled physics start by one week from 1/30/19 (published schedule) to 2/7/19.  This will allow sufficient time to carry out the helium processing activities to try to recover gradient to reach the ~2100 MeV/pass that we want for this run (with acceptable trip rates).

We intent to keep the length of the winter/spring run constant - i.e. continue running until April 15, 2019 at 7:00 AM. The length of the April - June down must also stay constant to meet installation work already scheduled by Facilities. This requires then
starting the summer run one week later than shown in the schedule - i.e. the summer run will start June 17. The length of the summer run period will remain as scheduled - i.e. the summer run will end one week later than shown on the schedule (August 19, 2019). The Fall run will start as shown on the schedule (physics starting November 1, 2019). We will update the posted schedule shortly.


Stuart Henderson | Director | Thomas Jefferson National Accelerator Facility
Office:  757.269.7552 | Email:  stuart at jlab.org<mailto:stuart at jlab.org>

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/cuga/attachments/20190125/ef2b2e63/attachment.html>