Inner balloon production for KamLAND-Zen 800

KamLAND-Zen Collaboration

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KamLAND-Zen searches for neutrinoless double-beta decay with 136Xe loaded liquid scintillator (LS). The LS container, a 25-µm-thick clean nylon inner balloon is a key of the experiment since one of the main backgrounds in the ROI is 214Bi from the inner balloon. In KamLAND-Zen 400 (operated from 2011 to 2015), dust contamination of the inner balloon from the environment limited the sensitivity, although the inner balloon was fabricated at a class-1 super clean room. We improved the production method of the inner balloon for KamLAND-Zen 800 (started DAQ in January, 2019) and successfully reduced the 214Bi background level to one fifteenth as compared to the 2nd phase of KamLAND-Zen 400. The inner balloon film material and requirements, improved fabrication scheme, including establishment of clean environment and dust control, will be described.

Original languageEnglish
Article number012145
JournalJournal of Physics: Conference Series
Issue number1
Publication statusPublished - 2020 Mar 20
Event16th International Conference on Topics in Astroparticle and Underground Physics, TAUP 2019 - Toyama, Japan
Duration: 2019 Sept 92019 Sept 13


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