A Novel Type of Absorber Presenting a Constant Detection Efficiency for up to 25 keV X-Ray Photons

A novel type of absorber, dedicated to cryogenic detectors, was conceived to reach a high and constant intrinsic detection efficiency (>98%) for up to 25 keV X-ray photons. The absorber consists of two layers having a different atomic number Z. The role of the first layer (large Z) is to make negligible the transmission through the absorber; while the second layer (medium Z) has to reabsorb the escape photons from the first layer. A metallic magnetic calorimeter was realized with an Au-Ag absorber. The required thicknesses of both layers were determined using Monte Carlo simulation of the efficiency. To show the advantages of such a detector, its efficiency and its energy resolution are compared to the efficiency and energy resolution of a gold absorber using a 241Am source.