Test beam results of a Cylindrical GEM detector for the BESIII experiment

TL;DR

This paper presents the development, construction, and initial testing of a novel Cylindrical Gas Electron Multiplier (CGEM) detector for the BESIII experiment, demonstrating its feasibility and performance in high-energy physics applications.

Contribution

It introduces a new cylindrical GEM detector design with innovative construction techniques and improved readout, validated through beam tests for the first time.

Findings

Successful construction of a CGEM prototype

First beam test results demonstrating detector performance

Validation of innovative assembly and readout techniques

Abstract

Gas detector are very light instrument used in high energy physics to measure the particle properties: position and momentum. Through high electric field is possible to use the Gas Electron Multiplier (GEM) technology to detect the charged particles and to exploit their properties to construct a large area detector, such as the new IT for BESIII. The state of the art in the GEM production allows to create very large area GEM foils (up to 50x100 $\mathrm{cm}^2$) and thanks to the small thickness of these foils is it possible to shape it to the desired form: a Cylindrical Gas Electron Multiplier (CGEM) is then proposed. The innovative construction technique based on Rohacell, a PMI foam, will give solidity to cathode and anode with a very low impact on material budget. The entire detector is sustained by Permaglass rings glued at the edges. These rings are used to assembly the CGEM, together with a dedicated Vertical Insertion System and moreover they host the On-Detector electronic. The anode has been improved w.r.t. the state of the art through a jagged readout that minimize the inter-strip capacitance. The mechanical challenge of this detector requires a precision of the entire geometry within few hundreds of microns in the whole area. In this contribution an overview of the construction technique, the validation of this technique through the realization of a CGEM, and its first tests will be presented. These activities are performed within the framework of the BESIIICGEM Project (645664), funded by the European Commission in the action H2020-RISE-MSCA-2014.