GEM Module Design for the ILD TPC

TL;DR

This paper presents a novel GEM module support structure for a TPC at the Linear Collider, improving flatness and field homogeneity, with successful tests demonstrating enhanced resolution and reduced distortions.

Contribution

Introduces a new support structure for GEM modules that minimizes material and enhances flatness, along with integrated field shaping for better charge collection.

Findings

Reduced dead material improves field homogeneity

Field shaping ring enhances charge collection in non-uniform fields

Successful test beam results show improved resolution

Abstract

A Time Projection Chamber (TPC) using micro-pattern gas detectors is planned as the main tracking device for a detector at the next Linear Collider. A novel support structure for Gas Electron Multipliers (GEMs), which minimizes the material and improves the flatness of the foils, has been developed and tested with multiple GEM modules in a large TPC prototype at DESY. Reducing dead material at the GEM module boundaries improves the field homogeneity. In addition, it was shown in simulation that a field shaping ring at the border of the module can improve the charge collection in regions with non-homogeneous fields. This shaping wire was integrated into the module design and a successful test beam campaign with three modules has been carried out. First results regarding resolution and field distortions will be discussed.