  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, particle detector arrays have
a much higher energy threshold and an inferior hadron rejection as compared to
Cherenkov telescopes. Low threshold particle detector arrays would have
potential advantages over Cherenkov telescopes in the search for episodic or
unexpected sources of gamma rays in the multi-TeV energy range. Ways to improve
the threshold and hadron 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 could be achieved is shown by examples for both methods. At mountain
altitude (about 4000 m or above) an energy threshold close to 1\,TeV could be
achieved. For any significant reduction of the hadronic background by selecting
muon-poor showers a muon detection area of at least 1000 m$^2$ is required,
even for a compact array.
