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<div>Just as points of information ops did make the offer to balance their dipole against arc 2 on an owl shift last week and the shift leader turned us down. They've also been running with ffb off because as Dennis noted in his email chain with Chris it has
produced some undesirable consequences. (<x>/<y> noise I think...?)</div>
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<div>At the request of the hall A we have occasionally engaged ffb with rf on to set the energy when hall C is off for some reason and then disengaged it (ffb on/operating is where this -1e-4 number came from).</div>
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<div>Alternately, a high forced gain mode on the arc 2 bpms when B/D are at high enough currents [O(0.5 uA combined)] may also be a potential option...</div>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400;">I would defer further discussion to the meeting...</span><br>
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<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400;">Respectfully,</span></div>
<div><span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 16px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400;">Mike</span></div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> BTeam <bteam-bounces@jlab.org> on behalf of Yves Roblin <roblin@jlab.org><br>
<b>Sent:</b> Monday, August 24, 2020 10:21 AM<br>
<b>To:</b> Dennis Turner <dturner@jlab.org>; bteam@jlab.org <bteam@jlab.org><br>
<b>Cc:</b> Christopher Slominski <cjs@jlab.org><br>
<b>Subject:</b> Re: [BTeam] Thoughts on the energy locks</font>
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The BEM determination for Hall A is actually more accurate that ARC1/ARC2. The Hall A arc dipole string is cross-calibrated for energy measurement with the reference dipole and there is no correctors in the Hall A arc. So, yes, this would work. It would have
to be such that when we do this, ARC2 elock is disabled of course. This lock would use the SL (the same zone that ARC2 elock uses) to regulate the energy.
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Of course, with that, you can also dial in whatever energy offset is desired. The one thing we will want to do is make sure the Hall A dipole string is commensurate with the ARC2 string so that when we switch from one to the other we dont move the energy for
the other halls.</div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> BTeam <bteam-bounces@jlab.org> on behalf of Dennis Turner <dturner@jlab.org><br>
<b>Sent:</b> Monday, August 24, 2020 10:12 AM<br>
<b>To:</b> bteam@jlab.org <bteam@jlab.org><br>
<b>Cc:</b> Christopher Slominski <cjs@jlab.org><br>
<b>Subject:</b> [BTeam] Fw: Thoughts on the energy locks</font>
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Here's a discussion between me and Chris Slominski about using the existing energy locks to lock beam energy in Hall A rather than FFB or the Arc2 energy lock. It's yet another option we can explore for energy stability.</div>
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Dennis<br>
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<div id="x_x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> Chris Slominski <cjs@jlab.org><br>
<b>Sent:</b> Monday, August 24, 2020 6:33 AM<br>
<b>To:</b> Dennis Turner <dturner@jlab.org><br>
<b>Subject:</b> Re: Thoughts on the energy locks</font>
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<p style="margin-top:0px; margin-bottom:0px; margin-top:0px; margin-bottom:0px">Any BEM measured section could be the source of energy error. The three sets of controls, LINACs, would only be able to be used once per measurement section. Are we confident the
Hall A energy error estimated by BEM is accurate? This could be done before the end of this run.<br>
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<div class="x_x_x_moz-cite-prefix">On 8/21/2020 10:16 PM, Dennis Turner wrote:<br>
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Hi Chris,</div>
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There was some discussion earlier today about the recent energy drifts in Hall A. They would normally use either the 2A energy lock or Fast Feedback to lock the beam energy in the hall, but FFB has been exhibiting other undesirable effects, and Arc 2 only
has nA beam until Hall C comes back on line. Would it be possible to use the existing arc energy locks to lock the energy in a hall? The existing arc energy locks look at the BEM signals for the arcs, like ARC1:p and ARC2:p. It seems to me that it wouldn't
be terribly difficult to have additional energy locks for the halls that look at the hall BEM readbacks, like HALLA:p for example. I could imagine some logic that would, for example, exclude using the 2A and a hall to lock energy at the same time. What are
your thoughts on this? <br>
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Dennis<br>
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