Upgrade of the KamLAND-Zen mini-balloon and future prospects

for the KamLAND-Zen Collaboration

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


KamLAND-Zen is neutrinoless double beta (0νββ) decay search experiment with Xe-loaded liquid scintillator (XeLS) containing about 91% enriched 136Xe. The mini-balloon is a container for holding XeLS at the center of the KamLAND detector without impairing the extremely low radiation environment. We have installed a new mini-balloon with a thickness of 25μm and a radius of 1.92 m, which was made in a class 1 clean room and is almost twice the volume of the KamLAND-Zen 400 mini-balloon. We installed about 745 kg of Xe gas in the XeLS and started the 0νββ decay search in January 2019. In this paper, novel hardware developments to collect data without loss just after a large light yield event, such as a cosmic ray muon spallation are also introduced in preparation for the KamLAND2-Zen which is a future upgrade of the KamLAND-Zen.


  • Low background detector
  • Neutrinoless double beta decay
  • Scintillator


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