Simulations of slow positron production using a low energy electron accelerator

TL;DR

This paper uses Monte Carlo simulations to estimate slow positron production from a low energy electron accelerator, predicting beam intensities and analyzing beam heating effects for different energies and currents.

Contribution

It introduces a simulation framework to predict slow positron yields from low energy accelerators, aiding design and optimization of positron sources.

Findings

At 5 MeV, 240 μA, predicted 5×10^6 s^-1 positron yield.

At 10 MeV, 30 μA, similar yield predicted.

Beam heating limits maximum positron production at low energies.

Abstract

Monte Carlo simulations of slow positron production via energetic electron interaction with a solid target have been performed. The aim of the simulations was to determine the expected slow positron beam intensity from a low energy, high current electron accelerator. By simulating (a) the fast positron production from a tantalum electron-positron converter and (b) the positron depth deposition profile in a tungsten moderator, the slow positron production probability per incident electron was estimated. Normalizing the calculated result to the measured slow positron yield at the present AIST LINAC the expected slow positron yield as a function of energy was determined. For an electron beam energy of 5 MeV (10 MeV) and current 240 $\mu$A (30 $\mu$A) production of a slow positron beam of intensity 5 $\times$ 10$^{6}$ s$^{-1}$ is predicted. The simulation also calculates the average energy deposited in the converter per electron, allowing an estimate of the beam heating at a given electron energy and current. For low energy, high-current operation the maximum obtainable positron beam intensity will be limited by this beam heating.