Design Studies for a TPC Readout Plane Using Zigzag Patterns with Multistage GEM Detectors

TL;DR

This paper presents the design and simulation of zigzag-shaped GEM detector readout pads for a TPC, demonstrating improved spatial resolution and discussing fabrication challenges and prototype performance.

Contribution

It introduces a novel zigzag pad design for GEM detectors in TPCs, optimizing shape and size through simulations and validating with prototype measurements.

Findings

Enhanced charge sharing with zigzag pads improves spatial resolution.

Simulation results guide optimal pad shape and size.

Prototype tests confirm improved resolution and fabrication feasibility.

Abstract

A new Time Projection Chamber (TPC) is currently under development for the sPHENIX experiment at RHIC. The TPC will be read out using multistage GEM detectors on each end and will be divided into approximately 40 pad layers in radius. Each pad layer is required to provide a spatial resolution of ~250 microns, which must be achieved with a minimal channel count in order to minimize the overall cost of the detector. The current proposal is to make the pads into a zigzag shape in order to enhance charge sharing among neighboring pads. This will allow for the possibility to interpolate the hit position to high precision, resulting in a position resolution many times better than the 2mm pitch of the readout pads. This paper discusses various simulation studies that were carried out to optimize the size and shape of the zigzag pads for the readout board for the TPC, along with the technical challenges in fabricating it. It also describes the performance of the first prototype readout board obtained from measurements carried out in the laboratory using a highly collimated X-ray source.