[PEPPo] Start-To-End Simulations of a Compact, Linac-Based Positron Source

[Jay Benesch]

interesting



https://arxiv.org/abs/2508.07549

Start-To-End Simulations of a Compact, Linac-Based Positron Source

Sophie Crisp, Ryland Goldman, Arif Ismail, Spencer Gessner

Slow positrons are increasingly important to the study of material 
surfaces. For these kinds of studies, the positrons must have low 
emittance and relatively high brightness. Unfortunately, fast positron 
sources like radioactive capsules or linac driven sources have broad 
energy and angular spread, which make them difficult to capture and use. 
Moderators are materials that produce slow, mono-energetic positrons 
from a fast positron beam. Since their efficiencies are typically less 
than  slow  per fast , research into how to maximize efficiency 
is of great interest. Previous work has shown that using a linac, one 
can decelerate the fast positron beam in order to greatly increase 
moderation efficiency. We present here start-to-end simulations using 
G4beamline to model a 100 MeV electron beam incident upon a Tungsten 
target, focused by an adiabatic matching device, and decelerated by a 
1.3 GHz, 5-cell pillbox cavity. We show that by decelerating the 
positrons after their creation we can increase the number of positrons 
under 500 keV by 15 times, translating to a 16.3 times improvement in 
moderation efficiency, and therefore leading to a brighter positron source.

Subjects:	Accelerator Physics (physics.acc-ph)