LOW-THRESHOLD PARTICLE ARRAYS

While atmospheric Cherenkov telescopes have a small field of view and a small duty fraction, arrays of particle detectors on ground have a 1 sr field of view and a 100% duty fraction. On the other hand, particl e detector arrays have a much higher energy threshold and an inferior hadron rejection as compared to Cherenkov telescopes. Low threshold pa rticle detector arrays would have potential advantages over Cherenkov telescopes in the search for episodic or unexpected sources of gamma r ays in the multi-TeV energy range. Ways to improve the threshold and h adron rejection of arrays are shown, based on existing technology for the timing method (with scintillator or water Cherenkov counters) and the tracking method (with tracking detectors). The performance that co uld be achieved is shown by examples for both methods. At mountain alt itude (about 4000 m or above) lan energy threshold close to 1 TeV coul d be achieved. For any significant reduction of the hadronic backgroun d by selecting muon-poor showers a muon detection area of at least 100 0 m(2) is required, even for a compact array.