We have developed a surface alpha-particle imaging detector based on a time projection chamber (TPC) operating principle using μ-PIC, and are undertaking highly sensitive sample analysis using this detector.
　The TPC is a unique analytical technique that can reconstruct the alpha-particle tracks in three dimensions and identify where the alpha particles originated from on the sample surface, thus enabling high-sensitivity analysis with extremely low radioactivity noise.



One of the major advantages of imaging is the ability to measure multiple samples simultaneously. As shown in the photo above, this is an example of simultaneous measurement of seven crystals as small as 10 mm square on an effective area of 15 cm × 15 cm.
In the analysis and inspection of such new materials, it is not always possible to gain mass, and a method that allows simultaneous measurement with small sample measurement is effective in comparative inspections.

We started analytical operations in 2018 to analyze materials for a state-of-the-art detector for an underground space particle experiment.

In FY2021, the TPC field cage was upgraded to improve analytical sensitivity, and was ready for stable operation in September.

In FY2022, surface alpha-particle analysis was performed on PEN film sheets from the KamLAND experimental group, copper ribbons from the NEWAGE experimental group, and scintillator crystals being developed at the University of Tokyo and Tohoku University (see photo above and resulting contamination image).

In FY2020-FY2021, the project is supported by the New Academic Area "Unraveling the History of the Universe and Matter Evolution with Underground Physics" publicly solicited research.
In accordance with this policy, we aim to make wide use of our research not only in the field of subsurface particles but also in other field areas.
If you are interested in this project, please contact Dr. H. Ito at Tokyo University of Science.

News & information

26-27th, Sep., 2022 at the 4th Quantum Imaging Conference (QBI2022), titled "Development and application of a low-background alpha particle imaging based on a gaseous TPC detector. Development and application of a low-background alpha particle imaging based on a gaseous TPC detector" was presented at QBI2022.

15th, Jun, 2022 Alpha particle imaging chamber (AICHAM) for screening LowBG surface RI contamination was presented at UGAP2022.

22nd, Feb., 2022 The proceedings "A progress of upgrading alpha-ray imaging chamber in a low background radioactivity" (open access) of the international conference TAUP2021 was published in Journal of Physics: Conference Series. (Hiroshi Ito et al 2021 J. Phys.: Conf. Ser. 2156 012176).

14th, Sep., 2021 Research result was presented at the JPSJ Autumn Meeting 2021.

14th, Sep., 2021 The detector was upgraded and put into operation.

1st, Sep., 2021 A poster titled "Progress of upgrading alpha-ray imaging detector in low radioactivity background" was presented at TAUP2021. 2021.05.19 New Conference

19th, May, 2021 Research results were presented at the 2021 meeting of the new academic field "Underground Space".

2nd, Jun, 2020 Research results were presented at the joint workshop of the new academic field "underground space" + ultra-low radioactivity technology.

1st, Apr., 2020 The research funded by Grant-in-Aid for Scientific Research on Innovative Areas (Research Area Proposal Type) "Development of alpha-ray image analyzer using μ-TPC for ultra-low radioactivity measurement" was approved.

21st, Mar., 2020 Proceedings was published in TAUP2019.

25th, Oct., 2019 A paper titled "Development of an alpha-particle imaging detector based on a low radioactivity micro-time-projection chamber A. The paper entitled "Development of an alpha-particle imaging detector based on a low radioactivity micro-time-projection chamber" has been accepted for publication.

18th, Sep., 2019 Presented at the 2019 Annual Meeting of the Physical Society of Japan, 18aT12-6

13rd, Sep., 2019 Poster presentation at the international conference TAUP2019. #301

List of slides and papers presented at workshops and conferences

International Conference UGAP2022 Slides
"Alpha particle imaging chamber (AICHAM) for screening LowBG surface RI contamination"
(pdf)

Slides of the 2021 meeting of the "New Academic Field Underground Space"
"Group D: Development of a surface alpha-ray imaging analyzer using μ-TPC for measuring extremely low radioactivity"
(pdf) (in Japanese)

Joint workshop of the new academic field "Underground Space" + Extremely Low Radiation Technology (2020) slide
"Development of a surface alpha-ray image analyzer using μ-TPC for ultra-low radiation measurement"
(pdf) (in Japanese)

Paper: Academic journal Nucl. Instr. Meth.
"Development of an alpha-particle imaging detector based on a low radioactivity micro-time-projection chamber"
10.1016/j.nima.2019.163050
arxiv.1903.01090

International Conference Proceedings 2019
"Alpha-ray imaging chamber based on a micro-TPC in a low radioactivity structure"
10.1088/1742-6596/1468/1/012233

International Conference Proceedings 2021
"A progress of upgrading alpha-ray imaging chamber in a low background radioactivity"
10.1088/1742-6596/2156/1/012176