A study of low background techniques using scintillation film

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K14727
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 15020:Experimental studies related to particle-, nuclear-, cosmic ray and astro-physics
• Research Institution: Tohoku University
• Principal Investigator: Ieki Sei 東北大学, ニュートリノ科学研究センター, 特任助教(研究) (70826940)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: シンチレーター / 波形弁別 / 散乱

Outline of Final Research Achievements

Xe permeability of PEN film was measured to confirm that it can be used as a container. The film would be weld in the process of making balloon, that effect on permeability was taken into account by measuring a sample with welding lines.
We plan to distinguish backgrounds on the film and signal events in liquid scintillator, and sequential decay of 212Bi and 212Po is one of the targets. Scintillation time spectra of PEN film and that of liquid scintillator were measured, and we found clear difference while it was a measurement with a 2-inch vial. Since the real detector is a 10-meter scale, physical processes in the pathway to light detectors make serious distortion in observed waveforms. In order to consider these effects, rough detector geometry and scintillation properties are reproduced in a Monte Carlo simulator. We developed a pulse shape discrimination method and the background rejection efficiency was estimated to be more than 80%.

Free Research Field

素粒子物理学実験

Academic Significance and Societal Importance of the Research Achievements

ニュートリノを伴わない二重ベータ崩壊の探索感度を改善するには低放射能化が重要である。発光フィルムを検出器として実用できれば、現状で3番目に多い背景事象である214Biを遅延同時計測によって同定可能になり、信号探索の有効体積を広げることが可能である。本研究はフィルムが高いキセノンバリア性を持つことを確認し、高確率で背景事象を除去する波形弁別手法を開発して、発光フィルムの実用化に一歩前進した。