KamLAND-Zen searches for neutrinoless double-beta decay with an ultra-pure liquid-scintillator (LS) filled with a custom-made clean nylon balloon. The primary backgrounds are radioactive impurities such as uranium and thorium series.
To reduce them, we developed a self-vetoing balloon vessel for a future upgrade program, "KamLAND2-Zen", instead of the current nylon-made balloon.
We selected a Polyethylene-Naphthalate (PEN) film that has a blue photon emission and performed the feasibility studies.
Due to its scintillation properties, we estimated that 99.7% of a 214Bi background could be identified in the KamLAND.
Moreover, thanks to the different waveforms between the LS and the PEN, we recently established the pulse-shape-discrimination for 212Bi background. We evaluated its background rejection efficiency as more than 90%.
Resulting from these studies, we proved to be able to use 100% of the fiducial volume.
|TIPP2020 abstract resubmission?||No, this is an entirely new submission.|