Determination of neutron lifetime by ultraprecise helium isotope ratio measurement to contribute nuclear physics and space physics

2014 Fiscal Year Final Research Report

• Project/Area Number: 24654058
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: The University of Tokyo
• Principal Investigator: SUMINO Hirochika 東京大学, 理学(系)研究科(研究院), 助教 (90332593)
• Co-Investigator(Renkei-kenkyūsha): MISHIMA Kenji 大学共同利用機関法人高エネルギー加速器研究機構, 物質構造科学研究所, 特任助教 (20392136)
• Project Period (FY): 2012-04-01 – 2015-03-31
• Keywords: ヘリウム / 同位体比 / 中性子 / 質量分析 / J-PARCパルス中性子源

Outline of Final Research Achievements

In order to precisely and accurately determine isotope ratio of helium (3He/4He) filling a time projection chamber developed for neutron lifetime measurement using a pulsed cold neutron spallation source at J-PARC, we improved a noble gas mass spectrometer. Stabilizing magnetic field and optimizing ion optics resulted in 0.08% precision of 3He/4He determination, which satisfies the requirement for neutron lifetime determination better than previous reports. The tritium concentrations of standard water samples provided by IAEA were also determined using the 3He accumulation method to confirm accuracy of 3He/4He measurement with the mass spectrometer.

Free Research Field

同位体地球化学