<html><body><div style="font-family: trebuchet ms,sans-serif; font-size: 12pt; color: #000000"><div>Arne,</div><div><br data-mce-bogus="1"></div><div>Not good news on the cryo front. I wondered why we were in restricted.</div><div><br data-mce-bogus="1"></div><div>Nothing comes to mind for RF issues at 6 GeV. Presently pass 2 IOT is bypassed, but if it's required it can unbypassed.</div><div><br>Rick</div><div><br></div><hr id="zwchr" data-marker="__DIVIDER__"><div data-marker="__HEADERS__"><b>From: </b>"Arne Freyberger" <freyberg@jlab.org><br><b>To: </b>"Matt Bickley" <bickley@jlab.org>, "Steve Suhring" <suhring@jlab.org>, "Paul Vasilauskis" <vasilaus@jlab.org>, "Theo Larrieu" <theo@jlab.org>, "Anthony Cuffe" <cuffe@jlab.org>, "Ron Lauze" <lauze@jlab.org>, "Randy Michaud" <rmichaud@jlab.org>, "Pam Kjeldsen" <kjeldsen@jlab.org>, "Reza Kazimi" <kazimi@jlab.org>, "Arne Freyberger" <freyberg@jlab.org>, "Ken Baggett" <baggett@jlab.org>, "Matt Bickley" <bickley@jlab.org>, "Randy Michaud" <rmichaud@jlab.org>, "Pam Kjeldsen" <kjeldsen@jlab.org>, "Steve Suhring" <suhring@jlab.org>, "Theo Larrieu" <theo@jlab.org>, "Reza Kazimi" <kazimi@jlab.org>, "Anthony Cuffe" <cuffe@jlab.org>, "Ron Lauze" <lauze@jlab.org>, "Andrew Kimber" <kimber@jlab.org>, "Omar Garza" <garza@jlab.org>, "Nelson, Rick" <nelson@jlab.org>, "Arne Freyberger" <freyberg@jlab.org>, "Dan Sexton" <dsexton@jlab.org>, bteam@jlab.org<br><b>Sent: </b>Saturday, March 28, 2015 1:29:24 PM<br><b>Subject: </b>Fwd: CEBAF/Cryo Status<br></div><div><br></div><div data-marker="__QUOTED_TEXT__">Time to start thinking about a 6GeV program. What are the issues?
Shunts? What else?<br>
<br>
Arne<br>
<div class="moz-forward-container"><br>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Subject:
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<td>CEBAF/Cryo Status</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Date: </th>
<td>Sat, 28 Mar 2015 13:26:22 -0400</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">From: </th>
<td>Arne Freyberger <a class="moz-txt-link-rfc2396E" href="mailto:freyberg@jlab.org" target="_blank"><freyberg@jlab.org></a></td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">To: </th>
<td>Hugh Montgomery <a class="moz-txt-link-rfc2396E" href="mailto:mont@jlab.org" target="_blank"><mont@jlab.org></a>, mike dallas
<a class="moz-txt-link-rfc2396E" href="mailto:mdallas@jlab.org" target="_blank"><mdallas@jlab.org></a>, Bob McKeown
<a class="moz-txt-link-rfc2396E" href="mailto:bmck@jlab.org" target="_blank"><bmck@jlab.org></a>, Andrew Hutton
<a class="moz-txt-link-rfc2396E" href="mailto:Andrew@jlab.org" target="_blank"><Andrew@jlab.org></a>, Fulvia Pilat
<a class="moz-txt-link-rfc2396E" href="mailto:pilat@jlab.org" target="_blank"><pilat@jlab.org></a>, rode >> Claus Rode
<a class="moz-txt-link-rfc2396E" href="mailto:rode@jlab.org" target="_blank"><rode@jlab.org></a>, Allison Lung <a class="moz-txt-link-rfc2396E" href="mailto:lung@jlab.org" target="_blank"><lung@jlab.org></a>,
Leigh Harwood <a class="moz-txt-link-rfc2396E" href="mailto:harwood@jlab.org" target="_blank"><harwood@jlab.org></a>, Rolf Ent
<a class="moz-txt-link-rfc2396E" href="mailto:ent@jlab.org" target="_blank"><ent@jlab.org></a>, rossi patrizia
<a class="moz-txt-link-rfc2396E" href="mailto:rossi@jlab.org" target="_blank"><rossi@jlab.org></a>, Mary Logue <a class="moz-txt-link-rfc2396E" href="mailto:logue@jlab.org" target="_blank"><logue@jlab.org></a>,
Bob May <a class="moz-txt-link-rfc2396E" href="mailto:may@jlab.org" target="_blank"><may@jlab.org></a>, Will Oren
<a class="moz-txt-link-rfc2396E" href="mailto:oren@jlab.org" target="_blank"><oren@jlab.org></a>, Tim Michalski
<a class="moz-txt-link-rfc2396E" href="mailto:michalsk@jlab.org" target="_blank"><michalsk@jlab.org></a>, Rusty Sprouse
<a class="moz-txt-link-rfc2396E" href="mailto:sprouse@jlab.org" target="_blank"><sprouse@jlab.org></a>, Rolf Ent <a class="moz-txt-link-rfc2396E" href="mailto:ent@jlab.org" target="_blank"><ent@jlab.org></a>,
rossi patrizia <a class="moz-txt-link-rfc2396E" href="mailto:rossi@jlab.org" target="_blank"><rossi@jlab.org></a>, 'Javier Gomez'
<a class="moz-txt-link-rfc2396E" href="mailto:gomez@jlab.org" target="_blank"><gomez@jlab.org></a>, Cynthia Keppel
<a class="moz-txt-link-rfc2396E" href="mailto:keppel@jlab.org" target="_blank"><keppel@jlab.org></a>, Volker Burkert
<a class="moz-txt-link-rfc2396E" href="mailto:burkert@jlab.org" target="_blank"><burkert@jlab.org></a>, Eugene Chudakov
<a class="moz-txt-link-rfc2396E" href="mailto:gen@jlab.org" target="_blank"><gen@jlab.org></a></td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">CC: </th>
<td>Jonathan Creel <a class="moz-txt-link-rfc2396E" href="mailto:creel@jlab.org" target="_blank"><creel@jlab.org></a></td>
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<br>
<br>
This is a summary email from Arne and Jonathan.<br>
<br>
Cryo recovery efforts since the power outage Wednesday have not
converged.<br>
<br>
<b>CHL2->SCN->NorthLinac</b>: has gone through several 2K
pumpdowns only to trip an hour or so after achieving 2K. The
CHL2->SCN hardware is in working order. Analysis indicates the
cause of these trips appears to be contamination plugging across
the 2K to 4K heat exchanger in the bottom of the SCN cold box.
This is forcing them them to operate at or near their surge
curves. This problem coupled with the previous contamination
problem with SCN cold compressor 2 seems to indicate that we had a
significant amount of contamination enter the system or move in
the system during the multi-hour power outage. The SCN must be
warmed up and decontaminated in order to support any 2K operation.<br>
<br>
<b>CHL1->SCM->SouthLinac:</b> has not been able to pump
down to 2K. Evidence is mounting that there is a likely physical
problem with cold compressor #4 (CC4) in the SCM. CC4 went
through an unusual trip during the first pump down attempt after
the power outage, the controller responding as it should but the
hardware ramped from 500Hz to 0Hz in a very abrupt fashion. The
magnetic bearings for CC4 will no longer levitate the compressor
wheel. The coils are drawing maximum current but the internal
hardware is not moving. The coil resistances appear normal. The
CC4 and CC5 mag bearing control cables were switched during
trouble shooting. Either mag bearing cabinet can successfully
levitate CC5 but neither mag bearing cabinet can successfully
levitate CC4. This leads to the conclusion that there is likely
something physically wrong with CC4. This is a single point of
failure; CC4 can not be by-passed. The SCM must be disconnected
and warmed up in order to access the compressor to determine what
happened and carry out any repairs. Cryo is performing some final
checks on CC4 and developing plans for an SCM warm up which could
last several weeks to months in duration. <br>
<br>
<b>Short Term:</b> No beam operations this weekend and probably
for the next week or two. Cryo will continue to assess the CC4
problem. Cryo is formulating plans this weekend which they will
review with Ops on Monday morning to formulate a revised schedule.<br>
<br>
<b>Long Term (Plan B):</b> There are options on the table if
CHL1->SCM is not available. These options include, but there
may be others:<br>
<ol>
<li>Configuring both CEBAF LINACS to 2K on CHL2->SCN and
establishing a 5-6GeV CEBAF. Hall-A has some 2GeV data and
HPS data can be accommodated by this configuration, Hall-D
could do some commissioning activities with a 6GeV beam.<br>
</li>
<li>Extending the run well beyond the May 4th scheduled end
date, this will result in a tremendous amount of UIM/CHL2 and
other contractual changes. But it would retain the physics
weeks. <br>
</li>
</ol>
<p><br>
Arne and Jonathan<br>
</p>
<pre class="moz-signature">--
Arne Freyberger
Director of Accelerator Operations
Jefferson Lab
12000 Jefferson Avenue Cell: (757) 876-6289
Postal Suite 19 Email: <a class="moz-txt-link-abbreviated" href="mailto:freyberg@jlab.org" target="_blank">freyberg@jlab.org</a>
Newport News, VA 23606 </pre>
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