[Halld] Run and hurricane preparation update, and shifts cancelled until 09/19

[Alexandre Deur]

Dear Collaborators,

Accelerator is making preparations for the coming Hurricane Florence, with the linacs being brought to 4K, one of the CHL turned off, provision of N2 and He, and room in the accelerator to save some of He in case of power failure. On our side, we are also powering down the equipment and raising the vacuum in the Hall D beam pipe in order to prevent damage to our vacuum windows in case of vacuum failure. Elton and Tim are overseeing the shutdown procedure. Please, see with them if you need further information.

If CEBAF has no loss of power/cryogen until the storm is over, and if the repairs that were done to the accelerator have fixed the obstruction problem that have so far precluded beam delivery, the earliest the accelerator could be ready with physics beam would be an optimistic Wednesday next week (09/19/2018). Consequently, shifts are cancelled until then (09/19 8am). Given that and the coming of the hurricane, we will also cancel the RC meetings this week. The next one will be Monday, Sept 17th, 8:45am, weather permitting. I'll update you if any important information arises meanwhile.

Another news from the accelerator is that they found multiple vacuum leaks in some of the U-tubes, due to radiation damage to sealing o-rings. These systems are independent vacuum systems (that should be at 10^-5 Torr but were found at 0.1 to 1 Torr) so this problem is unrelated to the insulating vacuum problem found last week, and to the beam tube vacuum problem that prevented beam delivery. At the moment, it is suspected that the insulating vacuum problem comes from a leak at a connector level, while the presumed ice ball in the beam pipe may not be due to a leak but to a fault in the installation of the ex-FEL module during the summer. 

Finally, flood gates are being installed in various places at JLab, including the Hall D tagger and counting room. They will prevent access to these areas, although flood gates for the personnel accesses will be place as late as possible so that we can finish the shutdown process. Please see with Tim or Elton if you need to access Hall D, the tagger area of the counting room.

Best regards,

Alexandre Deur