High-pressure xenon gas time projection chamber with scalable design and its performance at around the Q value of 136Xe double-beta decay
Masashi Yoshida, Kazuhiro Nakamura, Shinichi Akiyama, Sei Ban, Junya Hikida, Masanori Hirose, Atsuko K Ichikawa, Yoshihisa Iwashita, Yukimasa Kashino, Tatsuya Kikawa, Akihiro Minamino, Kentaro Miuchi, Yasuhiro Nakajima, Kiseki D Nakamura, Tsuyoshi Nakaya, Shuhei Obara, Ken Sakashita, Hiroyuki Sekiya, Hibiki Shinagawa, Bungo Sugashima, Soki Urano- General Physics and Astronomy
Abstract
We have been developing a high-pressure xenon gas time projection chamber (TPC) to search for neutrinoless double beta (0νββ) decay of 136Xe. The unique feature of this TPC is in the detection part of ionization electrons, called ELCC. ELCC is composed of multiple units, and one unit covers 48.5cm2. A 180L size prototype detector with 12 units, 672 channels, of ELCC was constructed and operated with 7.6bar natural xenon gas to evaluate the performance of the detector at around the Q value of 136Xe 0νββ. The obtained FWHM energy resolution is 0.73+-0.11% at 1836keV. This corresponds to 0.60+-0.03% to 0.70+-0.21% of energy resolution at the Q value of 136Xe 0νββ. This result shows the scalability of the AXEL detector with ELCC while maintaining high energy resolution. Factors determining the energy resolution were quantitatively evaluated and the result indicates further improvement is feasible. Reconstructed track images show distinctive structures at the endpoint of electron tracks, which will be an important feature to distinguish 0νββ signals from gamma-ray backgrounds.