In the "Compact carbon AMS" system it counts ¹⁴C ions of 975 keV energy. For samples of modern material, the detector counts ca. 12,000 ¹⁴C ions per minute. For samples of old material, it gives less than 10 counts per minute


¹⁴C detector is a semiconductor silicon detector with surface barrier. It has sensitive area of 1 cm² and energy resolution of 25 keV. Semiconductor detector is built like a large semiconductor diod. It is polarised with a constant voltage so that it does not conduct electric current. Passing-through high-energetic charged particle (like ¹⁴C ion in the AMS spectrometer), releases some number of free carriers of electric current (electrons and "holes") and produces small scale discharge in the semiconductor volume. This can be detected as a single short-lasting voltage drop (pulse).