Proton (1), helium (2), carbon (3), nitrogen (4), and oxygen (5) response functions of the first PDH sensor (D1). Each colour corresponds to a different deposited energy threshold. The larger the threshold, the less efficient the detector is for high-energy proton, helium, and carbon nuclei. Efficiency to lower-energy particles decreases for proton and helium nuclei if the threshold is larger than 0.5 MeV and 2–5 MeV, respectively. Efficiency of low-energy heavy ions (Z>2) only decreases at very high thresholds.