A new gamma-ray detector with gold-plated gas electron multiplier

For biomolecular analysis and nuclear medicine, we are developing a novel gamma camera based on a gaseous detector that uses gas electron multipliers (GEMs). To increase the gamma-ray-detection efficiency, we have constructed a novel GEM foil. The gamma-ray-conversion layers of the GEM foils are plated with 3 μm of gold on both surfaces. To evaluate the detection efficiency of the gamma-ray energy that corresponds to 99mTc, which is the target isotope for our gamma camera, the measurements were performed using 241Am and 57Co as gamma-ray sources. Our measured detection efficiency was 0.81% (241Am) and 0.75% (57Co) for the sources, which agreed well with a Monte Carlo simulation based on Geant4. In addition, we were able to increase the efficiency using multiple gold-plated GEM foils.