[Prex] [New Logentry] RC status summary 8/28

[jonesdc at jlab.org]

Logentry Text:
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Yesterday we took beam during the day and swing. Our efficiency was rather low especially during the swing collecting about 2.15 C during the day and 1.39 C during swing. Overnight beam was intermittent and trippy and we collected a total of 0.65 C. 

At 5AM the ioc that controls the CHL lost communication resulting in a full crash of the CHL around 7:30 AM. Efforts to restore communication were ongoing as of the 8AM meeting. After communication is restored and the IOC brought back online, the long recovery efforts begin involving getting liquid out of the transfer lines. This usually takes several hours. I don't expect to recover beam before end of day shift, but it is in principle possible.

Shortly before 6AM the RHS Q1 tripped and efforts to restore it were unsuccessful. The tech on call was contacted around 6AM. I talked to Jesse and he said we would need an access to look at the power supply. The hall was taken to controlled access around 8:30 and a full sweep completed within an hour. Jessie contacted Heidi and Jack about getting in to look at the Q1 power supply. 

Jack and Heidi were able to repair the issue with the RQ1 power supply in short order and Jack went on to look at the VDC noisy threshold. He said that he thought he had previously repaired it but found today the actual problem and he believes it should be resolved. Devi and Chandan need to verify that it is indeed resolved and the threshold is now stable.

Jessie ramped down all the quads and septum to low current (50 A) to mitigate any issues arising from cryo due to the CHL work. We will ramp everything back up prior to beam delivery.

Early diagnosis of the SL cryogenic state indicated that we would be down for a day or more due to having to transition the linac from 2K to 4K and that the linac return lines were substantially overflowed with approximately 2,400 liquid liters of helium. Closer looking prompted a more optimistic tone and as of 2 PM they had begun a pump down of the linac and begun refilling with liquid helium. The PD logged that she expects to be returning beam by end of day or early swing.

Issues in ability to deliver stable high current to both Halls C and A are likely to result in a reduced current to Hall A. This news was provided by Thia to the collaboration this morning. We should expect to get somewhere between 110 and 120 muA over the weekend. 

Monday around 8:30 AM we will lose beam for the pass change. I have asked Radcon to support a sweep at 8:30 to take us to restricted access. We will remain in restricted access at least until late day shift Wednesday if not early Thursday at which point we will go back to controlled. Morning RC meetings with the PD have been requested by B. Sawatzky throughout the weekend to keep everyone abreast of any developments in anticipation of the pass change Monday. Due to the fluid and uncertain nature of accelerator scheduling, I am not cancelling shifts next week until the pass change begins. If things go as planned, we will continue taking data until 8:30AM Monday and then take the hall to Restricted access. I don't want the owl crew to have to stay to do this so I still would like to see the Monday day crew come in and take the last 30 minutes of data and then transition the hall to Restricted including ramping down the magnets before leaving. 

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This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/3836381
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