Thermal Stretching of Large-Area GEM Foils Using an Infrared Heating Method

As GEM foils continue to increase in size, traditional methods of stretching and framing become more cumbersome and costly. We have developed a low-cost method of foil stretching based on a modified thermal technique using Plexiglas frames and infrared heat lamps. An overall temperature variation of not more than 5 o C across a 1.2 m x 0.7 m stretching frame is observed. We have applied this scalable technique to stretch and mount several 30 x 30 cm GEM foils for use in a muon tomography station and to stretch a 1 m x 0.5 m drift foil for the prototype of the CMS high-η muon detector upgrade. Two 30 cm x 30 cm triple-GEM detectors were successfully constructed from foils stretched by this method. Potential future improvements to this method and one other potential low-cost method of thermal stretching of large-area GEM foils are also discussed.