Main point of research

• This research achieved spatial resolution of 22 μm.
• This device has a totally different principle from the conventional neutron detector.
• There is a possibility for applying a more precise nondestructive inspection.

Background of this study

The neutron has a unique feature of high penetration into most materials except for some neutron absorbing/recoiling atoms. In sharp contrast with the x-ray, it has sensitivity to light elements such as hydrogen atoms. Neutron imaging is one of the most powerful technique for a nondestructive inspection, but it has not been as precise as microscope image. Recent development of high power neutron source has made it possible to develop a neutron detector with high spatial resolution. Several kinds of high spatial resolution neutron imager using atoms with high neutron absorption capability, such as ³He, ⁶Li, or ¹⁰B, have been developed in the last decade around the world.

Abstract

We demonstrate the development of a high-speed neutron-imaging system via a solid-state superconducting detector. Our detector comprises superconducting detectors(X and Y superconducting Nb meander lines), and a ¹⁰B conversion layer, which converts a neutron into two charged particles (⁴He or ⁷Li ion). The high energy light ions are able to create two hot spots (a microscopic region in with the superconducting electron density is reduced temporally) simultaneously in the X and Y meander lines. A pair of electromagnetic-wave pulses are generated at the hot spot and signals propagate with a constant propagation velocity on the X and Y meander lines toward the ends. One can obtain the position of a local hot spot in terms of four different arrival time stamps at the ends of the meander lines. A time-to-digital converter based on KALLIOPE* was used to measure arrival time stamps, and successfully operated with temporal resolution of 1 nano-second. We performed neutron irradiation experiments at BL10 of J-PARC (Japan Proton Accelerator Research Complex), and successfully reconstructed the neutron image of a test pattern with a spatial resolution of 22 μm. Our detector has a detection rate tolerance of a few tens of MHz/cm². This neutron-imaging system is anticipated to be used to high spatial resolution neutron transmission imaging.

* KALLIOPE stands for KEK Advanced Linear and Logic board Integrated Optical detector for Positron and Electron.

This research was released in Physical Review Applied on October 17th, 2018.
Title of the paper: “High-speed neutron-imaging using a current-biased delay-line detector of kinetic inductance”

• “Physical Review Applied” American Physical Society Website
• Full text of press release (Japanese language)（990KB）

Authors and Affiliations

Dr. Hiroaki Shishido, Department of Physics and Electronics, Graduate School of Engineering, Yuya Miki, Yusuke Yamaguchi, Yuki Iizawa and Vu The Dang(present address: JAEA), Graduate students, Dr. Kenji Kojima(present address: TRIUMF) and Dr. Satoshi Suzuki, KEK, Dr. Masahide Harada, the  research executive of JAEA, Dr. Takayuki Oku, Section manager of JAEA, Dr. Shigeyuki Miyajima, a researcher of NICT, Dr. Mutsuo Hidaka, a researcher of AIST, guest researcher Tomio Koyama, and Visiting Professor Takekazu Ishida, Department of Quantum and Radiation Engineering, Graduate School of Engineering, Osaka Prefecture University, conducted the research supported by a Grant-in-Aid for Scientfic Research (A) (Grant No. 16H02450) from JSPS.

The research group of OPU proposed the detecting system, and was in charge of designing the detecting system, elucidating motion principle, constructing measuring system, and neutron-imaging.

Research Grants

This work is partially supported by a Grant-in-Aid for Scientfic Research (S) (Grant No. 23226019) and (A) (Grant No. 16H02450) from JSPS. The neutron-irradiation experiments at the Materials and Life Science Experimental Facility (MLF) of the J-PARC are conducted under the support of MLF programs (Proposals No. 2015A0129 and No. 2015P0301). This work is supported by the Cadence software of VDEC at the University of Tokyo. Development of Kalliope TDC and readout electronics/software is conducted under the collaboration of KEK Open Source Consortium of Instrumentation (Open-IT)*.

* Open-It （Open Source Consortium of Instrumentation）is an organization for sharing the technique to develop measuring system and the information of the systemizing technology for sustaining, improving and developing the advanced measuring technique.