  Silicon Photomultipliers (SiPMs) are single photon detectors that gained
increasing interest in many applications as an alternative to photomultiplier
tubes. In particular in the field of space experiments, where volume, weight
and power consumption are a major constraint, their advantages like
compactness, ruggedness, and their potential to achieve high quantum efficiency
from UV to NIR, makes them ideal candidates for spaceborne, low photon flux
detectors. During space missions however, SiPMs are usually exposed to high
levels of radiation, both ionizing and non-ionizing, which can deteriorate the
performance of these detectors over time. The goal of this work is to compare
process and layout variation of SiPMs in terms of their radiation damage
effects to identify the features that helps reducing the deterioration of the
performance and develop the next generation of more radiation tolerant
detectors. To do this we irradiated with protons and X-rays several NUV-HD
SiPMs with small area (single microcell, 0.2x0.2 mm2 and 1x1 mm2) produced in
FBK. We performed online current-voltage measurements right after each
irradiation step and a complete functional characterization before and after
irradiation. We compare the results and show the most promising variations for
future production of SiPMs for space applications.
