May 24 – 28, 2021
America/Vancouver timezone

A study of self-vetoing balloon vessel for liquid-scintillator detectors

May 26, 2021, 5:30 AM
Parallel session talk Sensors: Light-based detectors Sensors: Light-based detectors


Shuhei Obara (Tohoku University)


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.

Primary author

Shuhei Obara (Tohoku University)


Koji Ishidoshiro (Tohoku University) Mr Rikuo Nakamura (Tohoku Univ.) Sei Ieki (Tohoku Univ.) Yoshihito Gando (Tohoku Univ.) Haruo Ikeda (Tohoku Univ.)

Presentation materials