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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Joe,
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I’m forwarding this info to the B-Team as there is a parallel effort to ID the source of radiation in the Arcs.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Steve<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Joe Grames <grames@jlab.org>
<br>
<b>Sent:</b> Tuesday, March 10, 2020 1:42 PM<br>
<b>To:</b> Steve Suhring <suhring@jlab.org><br>
<b>Cc:</b> Matthew Poelker <poelker@jlab.org>; Camille Ginsburg <ginsburg@jlab.org>; Ruben Fair <rfair@jlab.org><br>
<b>Subject:</b> Re: heat/activate Gun2 photocathode next week?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">In ~12 hours, we heat/activate/qe scan a photocathode, turn back over to ops. During this time we fix/test/certify the macropulse chassis.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">Hall A is going to ask to rotate the photocathode until we luckily set it's roll just right, that's another 8 hours where halls don't get any beam, also too long for one day's work.
I think it's fair to ask them to explain again why this degree of precision, and re-evaluate if this is necessary to the same degree at this point in the run...<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">I would not change too many things at once....i.e. swap Hall C pulse sooner or later, but need to forecast this. Shukui is standing ready to help LERF run. And, bear in mind
Hall A may ask for another Wien flip too.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-family:"Calibri",sans-serif;color:black">Joe<o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> Steve Suhring <<a href="mailto:suhring@jlab.org">suhring@jlab.org</a>><br>
<b>Sent:</b> Tuesday, March 10, 2020 1:24 PM<br>
<b>To:</b> Joe Grames <<a href="mailto:grames@jlab.org">grames@jlab.org</a>><br>
<b>Cc:</b> Matthew Poelker <<a href="mailto:poelker@jlab.org">poelker@jlab.org</a>>; Camille Ginsburg <<a href="mailto:ginsburg@jlab.org">ginsburg@jlab.org</a>>; Ruben Fair <<a href="mailto:rfair@jlab.org">rfair@jlab.org</a>><br>
<b>Subject:</b> RE: heat/activate Gun2 photocathode next week?</span> <o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi, Joe,
</span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">How much lead time do you need? If something broke and was going to take time, would you be able to respond (during somewhat normal working hours)?</span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">But for a planned heat and activation, can we go with next Tuesday 3/17/20?</span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Do we swap seeds around at that time? B/D for C?<br>
<br>
Steve</span><o:p></o:p></p>
<p class="xmsonormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> </span><o:p></o:p></p>
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<p class="xmsonormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif"> Joe Grames <<a href="mailto:grames@jlab.org">grames@jlab.org</a>>
<br>
<b>Sent:</b> Monday, March 9, 2020 12:29 PM<br>
<b>To:</b> Steve Suhring <<a href="mailto:suhring@jlab.org">suhring@jlab.org</a>>; Camille Ginsburg <<a href="mailto:ginsburg@jlab.org">ginsburg@jlab.org</a>><br>
<b>Cc:</b> Matthew Poelker <<a href="mailto:poelker@jlab.org">poelker@jlab.org</a>><br>
<b>Subject:</b> heat/activate Gun2 photocathode next week?</span><o:p></o:p></p>
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<p class="xmsonormal"> <o:p></o:p></p>
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<p class="xmsonormal">Hi Camille, Steve,<o:p></o:p></p>
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<p class="xmsonormal"> <o:p></o:p></p>
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<p class="xmsonormal">We need to heat/activate the gun2 photocathode to make it until the end of Hall A's program late April, or for that matter anybody's program May 6. Can we schedule this heat/activation for sometime next week, taking advantage of Hall
C being off?<o:p></o:p></p>
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<p class="xmsonormal"> <o:p></o:p></p>
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<p class="xmsonormal">It takes ~12 hours to make a fresh photocathode. During that same time we would complete the modification to the macropulse chassis, to eliminate the sticky button issue completely. We can restore from the same spot on the photocathode,
so minimal injector tuning.<o:p></o:p></p>
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<p class="xmsonormal"> <o:p></o:p></p>
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<p class="xmsonormal">The only caveat is this ... Hall A will ask us to insert the photocathode back into the gun within ~0.5 deg of where it is located today. Their argument, I believe, will be that they are attempting to control a helicity-correlated spot
size asymmetry for which they have not developed a method to measure directly. Luckily, we have some ability to set this angle, but roughly, however, the gun wasn't designed or built for this level of precision, so the only success we've had the couple times
we've done this required groping blindly for ~8 hours until we got lucky. I was okay testing the waters to learn exactly how challenging this would be to better understand a future solution and present risks. My conclusion is the process poses a risk to
running the gun; it adds wear & tear to the internal vacuum component and has potential to reduce the useful QE. During a usual groping session, I move a photocathode in/out of the high voltage chamber ias often as we might do in one year, and during the
long shutdowns. So, I'd like to push back on this step; although I think Hall A will just say it's imperative to their program. We're beginning to look at how to address this long term, e.g. if if Moller or other future parity experiements require setting
the roll of the photocathode to 0.5 deg, or whatever angle, we'll need to have a solution. Presently, we're looking at how to make the photocathode alignment less sensitive to the laser light passing, and we can explore how to rebuild the gun, but that's
for the future.<o:p></o:p></p>
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<p class="xmsonormal"> <o:p></o:p></p>
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<p class="xmsonormal">Joe<o:p></o:p></p>
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<p class="xmsonormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> Dave Mack <<a href="mailto:mack@jlab.org">mack@jlab.org</a>><br>
<b>Sent:</b> Monday, March 9, 2020 11:48 AM<br>
<b>To:</b> Joe Grames <<a href="mailto:grames@jlab.org">grames@jlab.org</a>><br>
<b>Subject:</b> Re: Hall C plans</span> <o:p></o:p></p>
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<p class="xmsonormal"> <o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">Joe,</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">Great idea! The down in Hall C is nominally March 13 (this Fri) to March 20. It would be wonderful for Hall C if you could recesiate or whatever during that time.
</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">After Hall C comes back March 20-ish, the schedule shows more of the same 5 pass, 30 muA , polarized. As far as I know, we get the TBD days and run until May 6. (There may be
a few days of 1 pass, 30 muA at the end when Hall A is off.) </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">Dave
</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black"> Joe Grames <<a href="mailto:grames@jlab.org">grames@jlab.org</a>><br>
<b>Sent:</b> Monday, March 9, 2020 11:34 AM<br>
<b>To:</b> Dave Mack <<a href="mailto:mack@jlab.org">mack@jlab.org</a>><br>
<b>Subject:</b> Hall C plans</span> <o:p></o:p></p>
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<p class="xmsonormal"> <o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">Hi Dave,</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">Can you remind me the approximate dates when Hall C will turn off, then come back?</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">I need to heat/activate the photocathode before May, that's probably as good as any to do this.</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">Are the Hall C beam requirements similar after returning? 5th pass, 30uA, polarized</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black"> </span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">thanks,</span><o:p></o:p></p>
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<p class="xmsonormal"><span style="font-family:"Calibri",sans-serif;color:black">Joe</span><o:p></o:p></p>
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