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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Alex, and All,</span></div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Regarding the highlighted comment in the minutes:</span></div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">and, following that:</span></div>
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<p style="margin-top: 0px; margin-bottom: 0px;"><span style="letter-spacing: 0.2pt; font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">"<i>Oliver was making the point about transmission. Not aware if the explanation has been
written down and presented. He’d like to know if it’s written down.</i>"</span></p>
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A possible explanation has been written down, yes:</div>
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A possible cause for the bad beam transmission is explained in my speech at May 25, 26, 2022's CBETA advisory committee. My slides are attached here.</div>
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Namely: A 180deg y-rotation of a combiner dipole is enough to jeopardize the optics (this is shown in slide 4) and thus beam transmission. The on-line model was using matrix transport but the problem cannot be seen with matrix transport, it requires using
field maps (that's my comment in slide 2). If one is using field maps, showing the problem is easy: just a matter of flipping the field map, in an equivalent way to y-rotating the dipole magnet by pi. The
<i>strong</i> change in the optics this causes comes from the fact that the end chamfers in the dipole have been designed (for some reason) not symmetric with respect to the vertical plane (s,y). At the time, I asked to take a look at the dipole in cause in
the recombiner, but I was told it was not possible to see the chamfers from outside, too much packed, no room left to sneak an eye.</div>
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Beyond that issue in that "conventional" style of beam line, in a general manner, we do know since KEK FFAG developments started in the 1990s that it is indispensable to model FFAG lattices using magnet field maps. Well... if we don't, then it is still time
to learn 🙂 Our MURA colleagues 70 years ago were already using field maps and Runge-Kutta integration of Lorentz force to design their machines, and they succeeded making those three electron rings work - ~10,000 passes acceleration, and they might as
well have subsequently decelerated to injection energy as succesfully ... may be they did! Same at KEK and KURRI with the proton rings, design and operation based on OPERA field maps. Same with RACCAM prototype spiral FFAG dipole and the fine lattice optics
which its OPERA as well as its <i>measured</i> field maps resulted in. This was just deemed useless for CBETA operation ...</div>
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In passing, we also know that a radial dependence of dipole gap height causes a radial dependence of the flutter (a substantial dependence, as Thomas used just that property to make the cyclotron isochronous - 85 years ago). An additional reason to work with
field maps when dealing with FFAG lattices based on offset quadrupoles, just what we did in EMMA 20 years ago. </div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">Anyway, back to the
</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);">JLAAC</span><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">'s point above, the question is still pending
and might contribute answering Oliver: is (any) CBETA recombiner dipole y-rotated by pi? and, an ancillary question, was for that reason its (their) actual optics missed in CBETA on-line model? </span></div>
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<div><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0);">François</span></div>
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</span><span style="font-family: Calibri, Helvetica, sans-serif; color: rgb(0, 0, 0);">François Méot</span><span style="color: rgb(0, 0, 0);"><br>
</span><span style="font-family: Calibri, Helvetica, sans-serif; color: rgb(0, 0, 0);">Brookhaven National Laboratory</span><span style="color: rgb(0, 0, 0);"><br>
</span><span style="font-family: Calibri, Helvetica, sans-serif; color: rgb(0, 0, 0);">Collider-Accelerator Department</span><span style="color: rgb(0, 0, 0);"><br>
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<span style="font-family: Calibri, Helvetica, sans-serif; font-size: 13px; color: rgb(0, 0, 0);">Adjunct Professor
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<div style="font-size: 13.3333px;"><span style="font-family: Calibri, Helvetica, sans-serif; font-size: 13px; color: rgb(0, 0, 0);">Dpt of Physics & Astronomy</span><span style="font-family: Tahoma; font-size: 13px; color: rgb(0, 0, 0);"><br>
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<span style="font-family: Calibri, Helvetica, sans-serif; font-size: 13px; color: rgb(0, 0, 0);">Stony Brook University - SUNY</span><span style="font-family: Tahoma; font-size: 13px; color: rgb(0, 0, 0);">
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> FFA_CEBAF_Collab <ffa_cebaf_collab-bounces@jlab.org> on behalf of Ryan Bodenstein via FFA_CEBAF_Collab <ffa_cebaf_collab@jlab.org><br>
<b>Sent:</b> Friday, January 26, 2024 12:11 PM<br>
<b>To:</b> Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab@jlab.org><br>
<b>Cc:</b> Planche Thomas <tplanche@triumf.ca><br>
<b>Subject:</b> Re: [FFA_CEBAF_Collab] FFA@CEBAF WG mtg. this Friday, Jan. 26</font>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">Dear Colleagues,</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"> </span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">That was quite an active meeting! Attached (and uploaded) you’ll find our minutes.</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">Everyone have a great weekend.</span></p>
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Cheers!</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">Ryan</span></p>
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<p class="x_MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt; color:black">From:
</span></b><span style="font-size:12.0pt; color:black">FFA_CEBAF_Collab <ffa_cebaf_collab-bounces@jlab.org> on behalf of Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab@jlab.org><br>
<b>Date: </b>Monday, January 22, 2024 at 7:25 PM<br>
<b>To: </b>Alex Bogacz via FFA_CEBAF_Collab <ffa_cebaf_collab@jlab.org><br>
<b>Cc: </b>Planche Thomas <tplanche@triumf.ca><br>
<b>Subject: </b>[FFA_CEBAF_Collab] FFA@CEBAF WG mtg. this Friday, Jan. 26</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt"><span style="color:black; background:white">Dear Colleagues,</span>
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<p class="x_MsoNormal" style=""><span style="font-size:11.0pt">We will continue our design efforts this Friday, Jan. 26, at 11:00 am.</span></p>
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<p class="x_MsoNormal" style=""><span style="font-size:11.0pt">* Recent JLAAC recommendations and upcoming FOA opportunities
<span style="color:black; background:white">- Alex Bogacz</span></span></p>
<p class="x_MsoNormal" style=""><span style="font-size:11.0pt">* Extending FFA energy acceptance with sextuple component
<span style="color:black; background:white">- Stephen, Dejan</span></span></p>
<p class="x_MsoNormal" style=""><span style="font-size:11.0pt">* AOB <span style="color:black; background:white">- ALL</span></span></p>
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<p class="x_MsoNormal" style=""><span style="font-size:11.0pt; color:black; background:white">Please, follow a ZOOM invitation below.</span><span style="font-size:11.0pt"></span></p>
<p class="x_MsoNormal" style=""><span style="font-size:11.0pt; color:black; background:white">Cheers,</span><span style="font-size:11.0pt"></span></p>
<p class="x_MsoNormal" style=""><span style="font-size:11.0pt; color:black; background:white">Alex</span><span style="font-size:11.0pt"></span></p>
<p class="x_MsoNormal" style=""><span style="font-size:11.0pt"> ___________________________________</span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">S. Alex Bogacz,</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">Accelerator Physics Group Leader</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">Center for Advanced Studies of Accelerators</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt">Jefferson Lab</span></p>
<p class="x_MsoNormal"><span style="font-size:11.0pt"><span class="x_MsoHyperlink">12000 Jefferson Avenue,</span></span></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">ZOOM connection:<br>
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The link is here: </span><a href="https://urldefense.com/v3/__https://jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09__;!!P4SdNyxKAPE!CRRrPkMxAZEEUkRVyQcc8dIt0sqnCHVPdrMIgnV2UXprPjplBPjAI3FycgJvfVgMfVwKgdB2ggm7uZFZUzgub5uboA$" title="https://jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09">https://jlab-org.zoomgov.com/j/1614898082?pwd=TnUzMS81M2sxbDZIbERJU01tYkJCQT09</a><br>
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In case of problems, the zoom room is below:</p>
<p class="x_MsoNormal">Meeting ID: <u><span style="color:blue">161 489 8082</span></u></p>
<p class="x_MsoNormal"><u><span style="color:blue">Passcode: 123456</span></u></p>
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<p class="x_MsoNormal"><span style="font-size:11.0pt">________________________</span></p>
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