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Sophie and Spencer will be presenting at the November LEEPP workshop here at JLab!</div>
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-Joe</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> PEPPo <peppo-bounces@jlab.org> on behalf of Jay Benesch via PEPPo <peppo@jlab.org><br>
<b>Sent:</b> Tuesday, August 12, 2025 9:31 AM<br>
<b>To:</b> peppo@jlab.org <peppo@jlab.org><br>
<b>Subject:</b> [PEPPo] Start-To-End Simulations of a Compact, Linac-Based Positron Source</font>
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<div class="PlainText">interesting<br>
<br>
<br>
<br>
<a href="https://arxiv.org/abs/2508.07549">https://arxiv.org/abs/2508.07549</a><br>
<br>
Start-To-End Simulations of a Compact, Linac-Based Positron Source<br>
<br>
Sophie Crisp, Ryland Goldman, Arif Ismail, Spencer Gessner<br>
<br>
Slow positrons are increasingly important to the study of material <br>
surfaces. For these kinds of studies, the positrons must have low <br>
emittance and relatively high brightness. Unfortunately, fast positron <br>
sources like radioactive capsules or linac driven sources have broad <br>
energy and angular spread, which make them difficult to capture and use. <br>
Moderators are materials that produce slow, mono-energetic positrons <br>
from a fast positron beam. Since their efficiencies are typically less <br>
than  slow  per fast , research into how to maximize efficiency <br>
is of great interest. Previous work has shown that using a linac, one <br>
can decelerate the fast positron beam in order to greatly increase <br>
moderation efficiency. We present here start-to-end simulations using <br>
G4beamline to model a 100 MeV electron beam incident upon a Tungsten <br>
target, focused by an adiabatic matching device, and decelerated by a <br>
1.3 GHz, 5-cell pillbox cavity. We show that by decelerating the <br>
positrons after their creation we can increase the number of positrons <br>
under 500 keV by 15 times, translating to a 16.3 times improvement in <br>
moderation efficiency, and therefore leading to a brighter positron source.<br>
<br>
Subjects: Accelerator Physics (physics.acc-ph)<br>
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