HALIMA: Anovel Hybrid Array for nuclear structure research

Researchers from the Institute of Modern Physics and collaborating institutions have developed a novel hybrid detection system, named HALIMA, for lifetime measurement. Published in Nuclear Science and Techniques, their work introduces the characteristics of all kinds of instruments in HALIMA, enabling precise sub-nanosecond lifetime measurements of neutron-rich nuclear excited states using the four-fold FF/β-Ge-LaBr₃(Ce)-LaBr₃(Ce) coincidence technique.

CsI(Tl)-shielded LaBr₃(Ce) detection system
To reduce Compton continuums, a more cost-effective, compact and novel CsI(Tl)-based anti-Compton shield was developed. Each LaBr₃(Ce) detector is enclosed by a CsI(Tl) anti-Compton shield composed of four separated CsI(Tl) crystals. The signals of these crystals are read out using silicon photomultipliers(SiPMs). The employment of CsI(Tl) anti-Compton shields enhances the peak-to-total ratio by a factor of 1.5.

Enhanced selectivity via fission fragments(FFs) implantation
In the present work, a solar cell array was used as FFs detectors. Following fission, the recoiling FF traversed 8 cm and was detected by solar cells. In this configuration, the solar cells act as implantation detectors, enabling event-by-event correlation between FFs and associated γ rays. With this great selectivity, isomer-specific events were effectively selected, and the overwhelming background was significantly suppressed.

Precise lifetime measurement of neutron-rich nuclear excited states
The lifetimes of three excited nuclear states in ¹³⁴Te, ¹³⁸Ba and ¹³²Te were measured by applying FF/β-Ge-LaBr₃(Ce)-LaBr₃(Ce) coincidence methods, covering a range from a few picoseconds to several hundred nanoseconds. The results were in good agreement with the literature values, demonstrating the capability and precision of this setup.

The research was supported by the National Natural Science Foundation of China, the Natural Science Foundation of Guangdong Province, China, the International Atomic Energy Agency Coordinated Research Project F41034, the computational resources from Sun Yat-sen University the National Supercomputer Center in Guangzhou, the Open Project of Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology, the Central Government Guidance Funds for Local Scientiffc and Technological Development, China, the Guangdong Major Project of Basic and Applied Basic Research, Young Scientists Fund of the National Natural Science Foundation of China and the National Key Research and Development Program. Data and methodology are openly accessible to foster global collaboration in nuclear science.

the complete study is via by DOI: 10.1007/s41365-025-01830-0