Positron Source Simulations for ILC 1 TeV Upgrade

TL;DR

This paper simulates polarized positron generation for the ILC 1 TeV upgrade, analyzing undulator parameters, polarization levels, and target stress to optimize source performance.

Contribution

It provides detailed simulations of positron polarization and target stress for various undulator configurations and collimation setups, advancing positron source design.

Findings

Maximal positron polarization of 25% without collimation at K=0.7

Polarization increases to 54% with collimation at K=2.5

Target thermal stress reaches 224 MPa with collimation

Abstract

The generation and capture of polarized positrons at a source with a superconducting helical undulator having 4.3 cm period and 500 GeV electron drive beam have been simulated. The positron polarization has been calculated for the different undulator K values (up to K = 2.5). Without applying a photon collimator, the maximal polarization of positrons is about 25% for 231 meters active magnet length of undulator with K = 0.7. Using an undulator with K = 2.5 and a collimator with an aperture radius of 0.9 mm results in increase of positron polarization to 54%. The energy deposition, temperature rise and stress induced by high intense photon beam in the rotated titanium-alloy target have been estimated. The maximal thermal stress in the target is about 224 MPa for the source with photon collimation to achieve a positron polarization of 54%.