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Hi Stephen,
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<div>This is brilliant…</div>
<div>Thank you again.</div>
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<div>Cheers,</div>
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<div>Alex<br>
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<div dir="ltr">Sent from my iPhone</div>
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<blockquote type="cite">On Oct 27, 2022, at 11:08 PM, Brooks, Stephen via FFA_CEBAF_Collab <ffa_cebaf_collab@jlab.org> wrote:<br>
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<div dir="ltr"><span>As an example of how it reduces the field, here are graphs of the field magnitude on all six orbits (through 2 magnets each), with a single rectangular magnet and with the 6 displaced segments.</span><br>
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<span>The displacements flatten out the peak field within a magnet (due to orbit curvature) while keeping the average field the same.</span><br>
<span></span><br>
<span> -Stephen</span><br>
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<span>________________________________________</span><br>
<span>From: FFA_CEBAF_Collab <ffa_cebaf_collab-bounces@jlab.org> on behalf of Brooks, Stephen via FFA_CEBAF_Collab <ffa_cebaf_collab@jlab.org></span><br>
<span>Sent: 27 October 2022 14:56</span><br>
<span>To: ffa_cebaf_collab@jlab.org</span><br>
<span>Subject: [FFA_CEBAF_Collab] [EXTERNAL] Magnets for recent single-FFA lattice (Sep'22)</span><br>
<span></span><br>
<span>Attached are pictures of somewhat feasible magnets that go with our one-turn FFA lattice. I had to do some tweaking:</span><br>
<span></span><br>
<span>1. Energies used to define the aperture range are after synchrotron radiation emission, which reduces the apertures a bit (helps).</span><br>
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<span>2. Rectangular magnets are broken into 6 longitudinal segments and displaced by</span><br>
<span>dx, -0.2*dx, -0.8*dx, -0.8*dx, -0.2*dx, dx</span><br>
<span>respectively, with dx being a value for each magnet around -1.5mm. This allows the peak magnetic field to follow the particle trajectory better and gives improved magnetic efficiency, for example reducing |B|_max from 1.706 to 1.573T in the hardest magnet.</span><br>
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<span>3. Overall gradient has been scaled to 0.6 of its original value. This means orbit excursions are larger by 1/0.6 and cell length is longer by sqrt(1/0.6). But tunes stay constant in this scaling, as does packing factor (bonus: drifts also go up from
8cm to 10.3cm).</span><br>
<span></span><br>
<span>Design rules are +/-8mm (16mm total) vertical aperture in the beam region, +/-3mm (6mm total) vertical minimum vertical gap for synchrotron radiation escape. (This is small but +/-4mm doesn't work well at the moment, I may need to mess with the magnet
geometry some more). And +/-12 degrees opening angle for the external vacuum chamber for synchrotron radiation (makes it mechanically a lot stronger).</span><br>
<span></span><br>
<span>B_r in the model is 1.248T not 1.3T. This is to compensate magnetic interactions, which in the case of my prototype magnet, reduced the magnetisation to 96% of the simple mu_r=1 prediction. (That's why I have a 1.536T magnet not a 1.6T magnet). It
is also consistent with mu_r being slightly above 1 in the B-H curve.</span><br>
<span></span><br>
<span> -Stephen</span><br>
<img id="40172625-FBFF-4F4A-901E-BDB51ACD80E8" src="cid:40172625-FBFF-4F4A-901E-BDB51ACD80E8"><span>_______________________________________________</span><br>
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