A GEM readout with radial zigzag strips and linear charge-sharing response

TL;DR

This paper investigates the use of radial zigzag strips in GEM detectors to achieve high spatial resolution with fewer readout channels, improving cost-effectiveness for large-area tracking systems.

Contribution

It demonstrates improved linear charge-sharing response by optimizing zigzag strip interleaving, enabling precise position measurements in GEM detectors.

Findings

Achieved angular resolutions of 60-84 urad.

Corresponding spatial resolutions below 100 micrometers.

Validated the design on PCB and flexible foil prototypes.

Abstract

We study the position sensitivity of radial zigzag strips intended to read out large GEM detectors for tracking at future experiments. Zigzag strips can cover a readout area with fewer strips than regular straight strips while maintaining good spatial resolution. Consequently, they can reduce the number of required electronic channels and related cost for large-area GEM detector systems. A non-linear relation between incident particle position and hit position measured from charge sharing among zigzag strips was observed in a previous study. We significantly reduce this non-linearity by improving the interleaving of adjacent physical zigzag strips. Zigzag readout structures are implemented on PCBs and on a flexible foil and are tested using a 10 cm by 10 cm triple-GEM detector scanned with a strongly collimated X-ray gun on a 2D motorized stage. Angular resolutions of60-84 urad are achieved with a 1.37 mrad angular strip pitch at a radius of 784 mm. On a linear scale this corresponds to resolutions below 100 um.