Development Of 3d Tracking Detectors In The Dcba Experiment For Studies Of Double Beta Decays

DCBA(Drift Chamber Beta-ray Analyzer) experiment is aiming to search for neutrinoless double beta decay (0 nu beta beta). The DCBA detector is a momentum analyzer to measure individual electron energy from double beta decays. Since 0 nu beta beta is extremely rare, the detector must be low background and accommodate a lot of decays source. And also the excellent energy resolution is required at the Q-value to distinguish 0 nu beta beta from two-neutrino double beta decay (2 nu beta beta). The DCBA detector consists of drift chambers, a magnet and cosmic-ray veto counters. A test prototype DCBA-T2 has been constructed and operated with natural Mo source containing 9.6% Mo-100 in order to solve operation problems. Another new prototype called DCBA-T3 is under construction at KEK. DCBA-T3 will have better performance than DCBA-T2 in view points of the energy resolution and the source accommodation volume. The results of the DCBA-T2 test operation and the DCBA-T3 status are described together with the future plan temporarily called Magnetic Tracking Detector (MTD), which is designed based on the experiences of DCBA-T2 and T3.