Cosmic ray test of mini-drift thick gas electron multiplier chamber for transition radiation detector

Abstract A thick gas electron multiplier (THGEM) chamber with an effective readout area of 10×10 cm 2 and a 11.3 mm ionization gap has been tested along with two regular gas electron multiplier (GEM) chambers in a cosmic ray test system. The thick ionization gap makes the THGEM chamber a mini-drift chamber. This kind mini-drift THGEM chamber is proposed as part of a transition radiation detector (TRD) for identifying electrons at an Electron Ion Collider (EIC) experiment. Through this cosmic ray test, an efficiency larger than 94% and a spatial resolution ~ 220 μ m are achieved for the THGEM chamber at −3.65 kV. Thanks to its outstanding spatial resolution and thick ionization gap, the THGEM chamber shows excellent track reconstruction capability. The gain uniformity and stability of the THGEM chamber are also presented.