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Hi Jay:</div>
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I just want to add that the date April 1-4 may not be when we schedule to change our cells. The cell typically last a month, and changing it too early or too late is not practical for the running of A1n/d2n. And if we don't change the cell then we will lose
3 days of beam time. <br>
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Is your proposed date Apr 1-4 flexible to some extent? <br>
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Thanks,</div>
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Xiaochao<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Jay Benesch <benesch@jlab.org><br>
<b>Sent:</b> Friday, January 31, 2020 4:55 PM<br>
<b>To:</b> BTeam <bteam@jlab.org><br>
<b>Cc:</b> Cynthia (Thia) Keppel <keppel@jlab.org>; Garth Huber <Garth.Huber@uregina.ca>; Jian-Ping Chen <jpchen@jlab.org>; Gordon D. Cates <cates@virginia.edu>; Brad Sawatzky <brads@jlab.org>; Xiaochao Zheng <xiaochao@jlab.org>; Paschke, Kent Dieter (kdp2c)
<paschke@virginia.edu><br>
<b>Subject:</b> higher linac current capability</font>
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<div class="PlainText">Colleagues,<br>
<br>
It is proposed to test whether the C100s can support 800 uA so CEBAF can <br>
complete the approved physics program (sans SoLID) this decade. MOLLER <br>
has requested 80 uA fifth pass, leaving little or no beam current for <br>
Hall C with 450 uA limit. lem suggests that the linacs can _now_ <br>
support 800 uA at 1000 MeV/linac. BBU instability is a concern because <br>
the HOM damping in the C100s is poor. A test is warranted. If BBU is <br>
not an issue, relatively inexpensive changes (H wall stub tuners) should <br>
be able to better match C100 and C75 cavities to klystrons at the higher <br>
current. If BBU is an issue, linac optics changes might help.<br>
<br>
CREX contingency runs Friday 3/27 to Saturday 4/4. It is proposed that <br>
Ops "banks" beam studies time for most of February and March, totalling <br>
96 hours. The test could then be scheduled Wednesday April 1 to <br>
Saturday April 4. This would interrupt Halls B/C/D but has long term <br>
benefit to C. a1n/d2n could schedule their last target change during <br>
CEBAF setup. 45 uA five pass to C (carbon target) and 115 uA fifth pass <br>
to A (carbon) would then put 800 uA in the linacs. Wien assumed left as <br>
is so little polarization to B and C during the run but easy restore.<br>
<br>
Two energy options present:<br>
<br>
990 MeV, 100 MeV below design, provides a stringent BBU test at an <br>
energy within expected range for high current experiments.<br>
<br>
930 MeV setup is available in allsaves from December 2018. Fifth pass <br>
to A, second pass to C, 40 uA max during allsave. Perhaps too stringent <br>
a test, given BBU scaling inversely with energy.<br>
<br>
I attach a spreadsheet which has beam property measurements made during <br>
the Nov. 2018 930 MeV setup. These may be compared to the ones made a <br>
year later with improved procedures.<br>
<br>
Comments? Shall we discuss it Tuesday February 4?<br>
<br>
Jay<br>
<br>
DOE documents allowing 2000 kW beam in CEBAF<br>
<br>
Environmental Assessment Determination (8 pages)<br>
<a href="https://jlabdoc.jlab.org/docushare/dsweb/Get/Document-50496/EA%20Determination%20-%20Proposed%20Upgrade%20&%20Operation%20of%20CEBAF%20&%20FEL%20Accelerators%202004%2010-Year%20Plan.pdf">https://jlabdoc.jlab.org/docushare/dsweb/Get/Document-50496/EA%20Determination%20-%20Proposed%20Upgrade%20&%20Operation%20of%20CEBAF%20&%20FEL%20Accelerators%202004%2010-Year%20Plan.pdf</a><br>
<br>
Environmental Assessment (395 pages)<br>
<a href="https://jlabdoc.jlab.org/docushare/dsweb/Get/Document-15071/EA-1534!.pdf">https://jlabdoc.jlab.org/docushare/dsweb/Get/Document-15071/EA-1534!.pdf</a><br>
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