<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Dear Colleagues,<div class=""><br class=""></div><div class="">The accelerator will go down on Wednesday 20 April for RF recovery, beam studies and then a Hall A pass change. Hall D will take access at the same time to look at the Collimator limits switch issue, move the Active Collimator to the 5 mm hole, remove the shilding plate on the TRD and do some work in preparation for raising the solenoid magnet current. There will also be work done on the Fast Shutdown system. Please let me know if you need to do any other work in the Hall. The plan is to raise the magnet current from 1200 A to 1350 A on Thursday.</div><div class=""><br class=""></div><div class="">The goniometer also has some issues with its limit switches on some axes, but we will not attempt to diagnose or repair these until after the run ends. These failures are consistent with radiation damage to the switches. One hypothesis for the source of the radiation is the 0.1-1.0 nA of Hall A beam in the Tagger Hall which may hit the thick goniometer frame when we retract the goniometer or the hit the mounting brackets when change from one target to another within the goniometer. Therefore, in future, when changing targets we will not only ask for no beam but also ask for our slit to be closed.</div><div class=""><br class=""><div class="">
<div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Best,<br class="">Mark Macrae Dalton</div><div style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""></div><br class="Apple-interchange-newline">
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