The objective of this work is to investigate the dosimetric properties of a newly developed phosphor, which is potassium sulfate doped with copper. K2SO4:Cu exhibits high sensitivity as a radiation detector in the infrared stimulated luminescence (IRSL) method. The phosphor allows for dose measurements of the order of μGy using an appropriately sensitive luminescence reader. Basic dosimetric properties were examined, including: detection limit, dose-response over a wide dose range (eight orders of magnitude), reproducibility, reusability, signal bleaching and signal stability (fading) during a long time after irradiation (up to six months). The results showed dose linearity in the range of at least 1 mGy - 10 Gy, minimum detectable dose in the order of μGy and no signal loss several days after irradiation. At longer intervals after exposure, the signal begins to fade. Due to the high sensitivity of the material, despite fading, the IRSL signal still remains at a sufficient level after several months. In addition to fading, signal regeneration was noticed in the material and preliminarily studied.