# Optimization of Undulator Parameters for 125 GeV Drive Beam

## TL;DR

This paper theoretically investigates how to optimize undulator parameters for the ILC positron source at 125 GeV drive beam energy, focusing on radiation spectra, power deposition, and positron yield to meet physics requirements.

## Contribution

It provides a detailed theoretical analysis of undulator radiation properties to optimize parameters for lower energy operation in the ILC.

## Key findings

- Optimal undulator parameters identified for 125 GeV drive beam.
- Analysis of power deposition and shielding effectiveness.
- Predicted positron production rates for various configurations.

## Abstract

In the baseline design of the International Linear Collider (ILC) an undulator-based source is foreseen for the positron source in order to match the physics requirements. The baseline parameters are optimized for the ILC at sqrt(s)=500 GeV, that means an electron drive beam of 250 GeV. Precision measurements in the Higgs sector, however, require measurements at sqrt(s)=250 GeV, i.e. running with the electron drive beam only at 125 GeV, which imposes a challenge for achieving a high yield. Therefore the baseline undulator parameters have to be optimized as much as possible within their technical performances. In this bachelor thesis we therefore present a theoretical study on the radiation spectra of a helical undulator, based on the equation for the radiated synchrotron energy spectral density per solid angle per electron in the relativistic, far-field and point-like charge approximation. From this starting point the following undulator properties are examined: the deposited power in the undulator vessel, which can disrupt the functionality of the undulator magnets, the protective property of a mask on this disturbances and the number of positrons produced by the synchrotron radiation in a Ti6Al4V target. Those quantities were evaluated for various values for parameters as undulator period, undulator length and magnetic flux in order to find optimal baseline parameter sets for sqrt(s)=250 GeV.