The CANDLES Trigger System for the Study of Double Beta Decay of

The CANDLES experiment is a study of the double beta decay of nuclei. The detector consists of two scintillators. One is the crystal that acts as a source of double beta decay and a scintillator. The other is a liquid scintillator, which is used for gamma-veto. The total light collected from the liquid scintillator is on the same order of magnitude as that of the scintillator, but the decay constant of the liquid scintillator is one or more orders of magnitude shorter than that of the scintillator. Therefore, if we trigger the signal by pulse height, the energy threshold of the liquid scintillator light will be one or more orders of magnitude lower than that of the scintillator. A high counting rate in the liquid scintillator causes deadtime; in order to avoid this problem, we have developed a new trigger system. In this paper, we describe the use of this trigger system in the CANDLES experiment and its performance after installation in 2013.