Cryogenic characteristic of SiPM detectors in a dilution refrigerator at temperatures down to 20mK.

Radiation impacts on superconducting qubits have been thought to be inneglectable in future quantum computing development. To detect radiation directly, scintillation detectors with silicon photomultiplier(SiPM) are commonly used in many high-energy physics experiments. However, their working characteristic at Milli Kelvin is not tested in detail. In our work, we characterise the SiPM detector in a dilution refrigerator. We show the working voltage, signal gain, dark count rate, and temperature-dependent changes down to 20mK. The detector works well and the dark count rate has a significant decrease. We believe the SiPM could be a suitable device to detect radiation impacts at Milli Kelvin, where superconducting qubits work.