Silicon photomultipliers for radiometry

To preserve the energy information, SiPMs consist of an array of microcells, each containing an individual avalanche photodiode. These microcells are typically very small, often on the order of tens of micrometers, allowing for high-density packing of APDs on a single silicon substrate. The small size also minimizes the probability of simultaneous events on one microcell. To ensure the SiPM operates within a controlled range, a quenching resistor is employed. This resistor helps limit the duration of the avalanche breakdown, preventing excessive charge buildup and ensuring a rapid reset of the microcell for subsequent photon detections. The microcell arrangement enables the SiPM to achieve high photon detection efficiency and excellent temporal resolution. The individual signals from each microcell are read out and processed. The output is a digital signal proportional to the number of photons detected. The high density of microcells allows SiPMs to provide excellent spatial resolution and sensitivity, making them particularly useful in applications demanding precise detection of low-intensity light signals. The signals from all the microcells are summed, providing a collective output that corresponds to the total photon flux incident on the SiPM. This summation process allows SiPMs to operate over a wide dynamic range, accommodating both low and high-intensity light conditions.