Abstract:
Gas Electron Multipliers (GEMs) play a crucial role as amplification stages in modern gaseous detectors. GEM foils consist of a polyimide substrate coated with copper on both sides. Microscopic holes are etched into the structure using a photolithographic process.
The precision of the etching process is sensitive to various factors such as chemical concentration/temperature or treatment duration, leading to potential irregularities in the resulting GEM which can have undesirable effects during detector operation. Since we are about to establish a GEM production in Bonn for small-sized GEMs, a rigorous and reliable quality assurance of the produced foils is indispensible.
To ensure the quality of the 10 × 10 cm2 GEMs commonly used for testing purposes, a small-scale versatile Spark Detection System (SDS) was developed. It allows one to apply high voltage to the GEM foil while a built-in camera monitors electric discharges within the holes. Simultaneously, the leakage current flowing through the polyimide is measured, providing valuable insights into the GEM’s overall quality.
In this talk, I will explain the SDS design and address challenges encountered with leakage currents inside the system. Sample measurements will be presented to illustrate the system’s effectiveness, and the efficiency as well as possible optimization options are discussed.