About State Key Laboratory of Nuclear Physics and Technology

State Key Laboratory of Nuclear Physics and Technology

Overview and identity

The State Key Laboratory of Nuclear Physics and Technology (Chinese: 核物理与核技术国家重点实验室) is a national State Key Laboratory hosted by Peking University in Beijing, attached to its School of Physics, with a published address at the School of Physics, Peking University, Beijing 100871, China. It covers experimental and theoretical nuclear physics and the technologies derived from it: nuclear structure and reactions, accelerator science and technology, ion beam applications, radiation detection and nuclear electronics, and applications of nuclear techniques in materials, energy and medicine. The university operates accelerator facilities on its Beijing campus that serve both fundamental research and applied programmes, and the laboratory trains a large share of China's nuclear physicists. As part of the Ministry of Science and Technology state key laboratory system, which counted 533 approved laboratories as of 2023, it is the university-based counterpart to the China Institute of Atomic Energy's laboratories and anchors Peking University's physics cluster alongside its turbulence laboratory.

The laboratory's institutional core is the university's Institute of Heavy Ion Physics, whose name appears jointly with the state key laboratory on the School of Physics' accelerator publications. That pairing expresses the laboratory's character: a university laboratory built around working accelerators, where students learn nuclear physics on machines the institution itself designs, builds and operates.

Research scope: structure, reactions and fundamental theory

The laboratory's theoretical work addresses the structure of nuclei and the nature of strongly interacting matter. Its theorists have published on the phase diagram and critical endpoint for strongly interacting quarks, on the commentary-level theory of excited and exotic hadrons, and on microscopic analyses of order parameters in nuclear quantum phase transitions in neodymium isotopes. A 2024 study from the laboratory examined the implications of neutron-skin measurements for Skyrme equations of state, optimising extended Skyrme forces against neutron-skin thicknesses from the PREX-II and CREX parity-violating electron-scattering experiments and following the consequences through to the equation of state of neutron stars and the gravitational-wave event GW170817. Work of that kind places a low-energy nuclear laboratory in direct conversation with astrophysics: the thickness of the neutron skin of lead, measured in a scattering experiment, constrains the matter inside merging neutron stars.

Photonuclear research shows the same theory-to-experiment span. A Peking University team used time-dependent Hartree-Fock plus BCS theory to calculate photonuclear absorption cross-sections — how atomic nuclei absorb light — validating the approach so that it can guide measurements at new facilities such as Shanghai's laser electron gamma source, SLEGS. Nuclear reactions with photons serve as unique probes of nuclear structure and dynamics, and reliable theory is what turns cross-section measurements into structure information.

Experimental nuclear physics and exotic nuclei

Experimentally, the laboratory is known for work on exotic, unstable nuclei. Reviews of its programme describe how, for more than 30 years, the Beijing Tandem-Accelerator Nuclear-Physics National Laboratory has provided a basic research platform for low-energy nuclear physics experiments, and how the experimental nuclear physics team at Peking University has continuously developed dedicated experimental apparatus, conducted a series of experiments at the Beijing HI-13 tandem accelerator, and achieved important results on exotic nuclear structures. Those results include investigation of the shape evolution of germanium isotopes around mass 70 using in-beam gamma spectroscopy, exploration of cluster structures in light neutron-rich nuclei through direct nuclear reactions, and the development and commissioning of collinear laser spectroscopy experiments at the Beijing Radioactive Ion-beam Facility.

Laser spectroscopy is a growth area in its own right. Xiaofei Yang of the School of Physics and the state key laboratory is an invited speaker internationally on laser spectroscopy for the study of exotic nuclei, a technique described in her seminar abstracts as a powerful tool to measure the basic properties of a nucleus — spins, magnetic dipole and electric quadrupole moments and charge radii — in a nuclear-model-independent manner. Charge radii and moments of short-lived isotopes are among the most sensitive tests of nuclear theory, and a university group able to measure them at radioactive-beam facilities occupies a distinctive place in Chinese nuclear science. Research directions named for Peking University nuclear physics in international colloquia — radioactive ion beam physics, hadron physics, accelerator physics and nuclear technique applications — summarise the experimental portfolio.

Accelerators at Peking University: Van de Graaff, RFQ and superconducting linacs

The laboratory's own campus accelerators document its technology programme across generations. Published work records quasimonoenergetic neutron fields generated by nuclear reactions via the 4.5 MV Van de Graaff accelerator at Peking University, used to build a compact neutron spectrometer, based on a liquid scintillator, that performed the first neutron spectrometry measurement at the HL-2A tokamak in Chengdu — an early demonstration of the laboratory's instruments travelling to national fusion facilities. The Peking University Neutron Imaging Facility, PKUNIFTY, is a compact accelerator-driven neutron source built around a radio-frequency quadrupole accelerator delivering a 2 MeV deuteron beam onto a beryllium target; its design comprises an electron cyclotron resonance ion source, low- and high-energy beam transport lines, the RFQ cavity, an RF transmitter and a control system, and the facility was designed for education and training, neutron radiography technology development and investigation of neutron radiography applications.

Superconducting radio-frequency technology is the laboratory's accelerator frontier. Its DC-SRF photoinjector, comprising a pair of DC Pierce electrodes and a 3.5-cell 1.3 GHz TESLA-type cavity, has been in operation since 2014 and can deliver 3 to 5 MeV electron bunches of 6 to 50 picocoulombs with bunch lengths of about 5 picoseconds and repetition rates tunable between 162.5 kHz and 81.25 MHz. A Peking University SRF linac consisting of two 1.3 GHz nine-cell TESLA-type cavities was brought into operation to accelerate the photoinjector's beam further, and laboratory researchers have used higher-order-mode signals excited by bunch trains in those cavities as an intra-cavity beam diagnostic — turning a known source of emittance dilution and beam-current limits into a measurement tool. Such work, supported by the National Natural Science Foundation of China, is accelerator science of direct relevance to future light sources and accelerators across China.

The Beijing tandem laboratory connection

The laboratory's experimentalists also work at China's national tandem facility. The Beijing Tandem Accelerator Nuclear Physics National Laboratory marked the 35th anniversary of its establishment in 2023; founded officially in 1988, it has served as a significant research hub for nuclear physics in China, achieving 140,000 hours of stable operation and undertaking research in nuclear physics, nuclear data measurement, nuclear physics applications and interdisciplinary studies. Accelerators and nuclear reactors are described in its 35-year review as the two main tools for studying nuclear science. Peking University's role at the HI-13 tandem — developing apparatus, leading experiments on exotic structures, and commissioning laser spectroscopy at the associated radioactive ion-beam facility — links the university laboratory to that national user facility, so that its students and staff work both on home-campus machines and on the country's principal low-energy nuclear physics platform.

Nuclear techniques: fusion, imaging, muons and medicine-facing work

The technology half of the laboratory's name is visible in its applications. Neutron spectrometry developed at Peking University was deployed at the HL-2A tokamak, serving fusion plasma diagnostics. Neutron imaging through PKUNIFTY applies accelerator neutrons as a non-destructive testing tool. Muon science is a newer direction: laboratory authors have proposed probing and knocking with muons, using GeV muon beams to explore rich physics, and have extended the Peking University Muon experiment — PKMuon, which uses resistive plate chambers manufactured by Peking University — from light dark-matter searches toward probing charged-lepton-flavour violation mediated by an extra massive neutral gauge boson. The laboratory is also jointly named with the Key Laboratory of High-Energy-Density Physics of the Ministry of Education and the university's Center for Applied Physics and Technology on work proposing observation of the two-photon Breit-Wheeler process with compact lasers, connecting nuclear and particle physics to high-field laser science.

These applications share a common base: accelerators, detectors and nuclear electronics built and understood in-house. Radiation detection and nuclear electronics are listed in the laboratory's scope precisely because instruments such as its scintillator spectrometers, resistive plate chambers and SRF diagnostics originate there rather than being bought in, and because ion-beam techniques developed for fundamental research transfer to materials analysis, energy research and medical applications.

People, training and academic life

As a university laboratory, training is central to its purpose, and the directory record notes that it trains a large share of China's nuclear physicists. Its researchers teach and supervise within the School of Physics, present the laboratory's programme at international colloquia — a 2010 Osaka colloquium, for example, introduced the history and current situation of nuclear physics and technology at Peking University, including its research directions, organisation and education — and publish with a steady flow of student and postdoctoral authors. Names recurring across its recent literature illustrate its breadth: Junchen Pei in nuclear theory and photonuclear reactions, Xiaofei Yang in laser spectroscopy of exotic nuclei, Jie Meng in relativistic nuclear theory, and the accelerator groups around Kexin Liu and Senlin Huang in superconducting RF science. Collaboration is built into the laboratory's style: its author lists join Peking University to the Institute of Modern Physics, the Institute of High Energy Physics, Argonne National Laboratory and universities in Croatia, South Africa and elsewhere.

Place in China's nuclear science landscape

China's nuclear research is distributed among academy institutes, national laboratories and universities. The China Institute of Atomic Energy operates the country's major nuclear facilities, the Institute of Modern Physics in Lanzhou leads heavy-ion research, and this laboratory is the university-based counterpart profiled separately in this directory: the place where nuclear physics is pursued inside a comprehensive university, alongside undergraduate and graduate teaching, and in the same physics school as the university's other national platforms. Its combination — theory of nuclei and quark matter, experiments on exotic nuclei at national facilities, home-built accelerators from a Van de Graaff to superconducting linacs, and techniques reaching fusion diagnostics, neutron imaging and muon experiments — makes it one of the most complete university nuclear laboratories in China, and the anchor of Peking University's physics cluster in the nuclear field.