Micro-pattern gaseous detectors (MPGDs) are essential in high energy physics experiments due to their high gain factors, low material budget and resilience in harsh radiation environments. However, in high rate environments, time projection chambers based on MPGDs suffer performance degradation due to ion backflow. This phenomenon, characterized by the drift and accumulation of positive ions throughout the detector, distorts the drift and transfer fields, thereby reducing effective gain.

To address this problem, our study explores the integration of graphene membranes onto gaseous electron multiplier (GEM) detectors. Graphene properties make it an ideal candidate to prevent ion backflow while maintaining electron signal integrity, thus potentially enhancing the overall performance of MPGDs.

We focus on optimizing the transfer of polycrystalline graphene, grown by chemical vapor deposition, to develop a suitable method for integrating graphene membranes onto custom-made 1x1 cm² GEM foils and Au meshes. Our approach explores the transfer of monolayer, bilayer, and trilayer graphene membranes. Bilayer and trilayer membranes have been integrated in order to improve the number of covered holes, reaching coverages of 95% in GEM foils.
In an ultra-high vacuum (UHV) chamber, we investigated the transparency of bilayer graphene for electrons covering an energy range from 0 to 1800 eV.

This presentation will detail the graphene transfer procedure on GEM foils and metallic meshes, addressing challenges such as high coverage and polymeric residuals.
Results on the electron transparency of bilayer graphene in UHV over the investigated energy range will be discussed, with a particular focus on the low energy range (<100 eV) typically obtained in the MPGD operating conditions and the high energy range (>200 eV) where the transmission coefficient is strongly influenced by the emission of secondary electrons due to the interaction between the primary electrons of the beam and the electrons in the target.
 

GEM,Graphene,E