# Energy Deposition along The Helical Undulator at ILC-250GeV

## TL;DR

This paper analyzes the power deposition caused by synchrotron radiation in the superconducting helical undulator of the ILC-250GeV positron source, focusing on the design of photon masks to limit wall heating.

## Contribution

It provides a detailed study of power deposition in the undulator walls, informing the design of photon masks to ensure safe power limits at ILC-250GeV.

## Key findings

- Power deposition in the undulator walls is quantified.
- Photon masks are necessary to keep power below 1W/m.
- Guidelines for mask design are proposed.

## Abstract

The positron source of the International Linear Collider is based on a superconducting helical undulator passed by the high-energy electron beam to generate photons which hit a conversion target. Since the photons are circularly polarized the resulting positron beam is polarized. At ILC250, the full undulator is needed to produce the required number of positrons. To keep the power deposition in the undulator walls below the acceptable limit of 1W/m, photon masks must be inserted in the undulator line. The photon mask design requires a detailed study of the power deposition in the walls and masks. This paper describes the power deposition in the undulator wall due to synchrotron radiation.