Results from a Beam Test Analysis of a Large-Area GEM detector with Low Mass and Zigzag-strip Readout

In this report, the assembly and analysis of a low cost, low mass GEM detector is presented. The detector we designed is optimized for use in the upcoming Electron Ion Collider (EIC) as a forward tracker due to its low material budget and reduced cost. Our design showcases a standard CMS Triple GEM (TGEM) detector with a few modifications which reduce the overall material budget by seven times and reduce the manufacturing cost. Internally, our design utilizes modified GEM foils to replace the PCB of the drift and readout board. With the PCB removed, the structure of the TGEM was reinstated by adding carbon fiber frames to the exterior. These frames include a central window made of aluminized polyimide foil to allow radiation to enter the inner volume as well as enclose the working gas. To reduce electrostatic forces between the drift foil and the outer window, the external polyimide window was connected to HV and held at a similar voltage. Another modification to the TGEM was to optimize the readout board strip geometry to test different possibilities. Our readout board compares the historical straight strips with two ZigZag designs as well as a method to combine strips across multiple sectors. These changes optimize the space read out by a single strip such that the manufactured board only needs one third of its original strips - thus reducing the overall cost. Once manufactured, this design was tested at the FermiLab test beam facility with a 120 GeV proton beam and has shown similar or improved characteristics to a mass produced CMS TGEM.