# Status of the undulator-based ILC positron source

## TL;DR

This paper reviews the current status of the undulator-based positron source design for the ILC, focusing on target design, cooling, optical matching, and potential optimizations for the 250 GeV configuration.

## Contribution

It provides an update on the design studies of the ILC positron source, highlighting key technical challenges and possible improvements.

## Key findings

- Target design and cooling are critical for positron yield.
- Optical matching device issues impact system performance.
- Potential optimizations could enhance positron production efficiency.

## Abstract

The design of the positron source for the International Linear Collider (ILC) is still under consideration. The baseline design plans to use the electron beam for the positron production before it goes to the IP. The high-energy electrons pass a long helical undulator and generate an intense circularly polarized photon beam which hits a thin conversion target to produce $e^+e^-$ pairs. The resulting positron beam is longitudinally polarized which provides an important benefit for precision physics analyses. In this paper the status of the design studies is presented with focus on ILC250. In particular, the target design and cooling as well as issues of the optical matching device are important for the positron yield. Some possibilities to optimize the system are discussed.