Hefei Advanced Light Facility

01 Mission & Goals

The Hefei Advanced Light Facility (HALF)，a major national science and technology infrastructure, is a fourth-generation low-energy synchrotron radiation machine based on diffraction-limited storage ring technology. The brightness and coherence of the soft X-rays it generates are more than a hundred times higher than those of third-generation light sources. It will develop new experimental methods with higher precision and sensitivity in the dimensions of space, time, and energy, making it an important research platform to study the microscopic behavior of particles, the structure of lightweight elements, and the changes in the electronic, chemical, and spin states of materials.

Once completed, HALF will become one of most advanced synchrotron radiation facilities in the world. It will help the city of Hefei become a world-class center for photon science and applications. It also complete the China’s advanced light source system covering the entire energy range, promoting the development of cutting-edge science and technology, the construction of innovation capabilities, the transformation of strategic industries, and the enhancement of comprehensive national strength.

The construction period of HALF is about 64 months.

Science & Applications

Leverage the advantages of low-energy diffraction-limited storage light source in terms of brightness, coherence, energy and spatiotemporal resolution to develop new experimental methods with higher precision and sensitivity across spatial, temporal and energy dimensions. This will enable precise measurements of the electronic, chemical and spin states of non-uniform complex systems, achieving significant breakthroughs in the national strategic fields such as functional materials, lightweight materials, energy and environment, life and health. By acting as an innovative engine, HALF will promote industrial technological innovation and applications, and support the construction of innovative country in China.

Small spot size, high brightness, high coherence

Functional materials (high-temperature superconductors, optoelectronic/photovoltaic materials, novel magnetic materials, electronic ceramic materials)

Energy and environment (new-generation battery technologies, clean coal utilization, solar and hydrogen energy utilization, environmental protection and pollution control)

Lightweight materials (aerospace materials, advanced membrane materials, fine chemicals, photosensitive materials)

Life and health (aging and brain science, advanced biotechnology, new drug development, high-end medical devices)

02 Scheme & Plan

>The storage ring has a beam energy of 2.2 GeV with capability for future energy increase to 2.4~2.5 GeV. The natural beam emittance at 2.2 GeV is 86 pm•rad.

> In the photon optimization energy range, the peak brightness is higher than 10²¹ ph•s^-1• mm^-2•mrad^-2•(0.1%BW)^-1, and the proportion of coherent photons under the natural emittance reaches 30% at a photon energy of 1 keV.

>The capacity of high-performance beamlines is not less than 35, with the first batch consisting of 10 beamlines.

The circumference of the storage ring is 480 meters

The length of the linear accelerator is 192 meters

The length of the transfer line is 138.4 meters

Overall plan for construction of HALF beamlines

* the first batch of beamlines under construction

* the subsequent planned beamlines 

03 Design & Innovation

Storage Ring

Novel hybrid 6BA lattice design and technology

The HALF storage ring consisting of 20 identical lattice cells uses a novel hybrid 6BA lattice, which replaces the three combined-function bend unit cells of the typical hybrid 7BA lattice with two LGB-RB unit cells  (LGB: longitudinal field gradient bending magnet, RB: reverse bending magnet) and a mid-straight section. This novel lattice design has a superior ability to reduce both beam emittance and damping times while providing more straight sections for insertion devices. The length of the long straight section is 5.3 m, and the mid-straight section is 2.2 m long. The natural emittance is 86 pm·rad at 2.2 GeV. To further reduce the damping times and beam emittance, two damping wigglers are employed. The beam energy is considered to increase to 2.4~2.5 GeV in the future. The large dynamic aperture allows for off-axis injection.

Novel hybrid 6BA lattice of the HALF storage ring.

Main parameters of the HALF storage ring

On-mometum dynamic aperture and off-momentum horizontal dynamic apertures.

Momentum dependent tune shifts.

The maximum strengths of quadrupoles, sextupoles, and octupoles are ~50 T/m, ~2000 T/m2, and ~80000 T/m3, respectively. Electromagnetic variable-gap LGBs were developed to reduce beam emittance and enable beam energy increase to 2.4~2.5 GeV. The inner diameter of the round main vacuum chamber is 26 mm.  Both anti-septum and nonlinear kicker were developed to implement the conventional kicker-bump injection in the first stage and then the transparent nonlinear kicker injection in the second stage.

Element arrangement of a lattice cell without insertion devices

Electromagnetic variable-gap LGBs.

Anti-septum and nonlinear kicker.

quadrupole magnet, sextupole magnet

septum Magnet

Storage Ring Copper Vacuum Chamber

Pre-alignment Platform and Pre-alignment Measurement

The injector 

The injector will deliver electrons into the Hefei Advanced Light Facility (HALF) storage ring with full energy top-up injection operation mode. It is installed in a semi-underground tunnel and consists of two parts: a linear accelerator approximately 192 meters in length and a beam transport line about 138 meters long (The transport line length was strategically designed to accommodate the building layout.). The electron beam is generated and accelerated to 2.2 GeV in the linear accelerator, then directed into the transport line via horizontal bending magnets. Finally, two vertical bending magnets at the end of the transport line elevate the beam by 4.7 meters to bring it into alignment with the storage ring’s beam plane.

In the linear accelerator, the thermionic-cathode DC high-voltage electron gun generates electron bunches with an initial pulse width of ~1.0 ns. The beam first undergoes pulse compression in a 476 MHz sub-harmonic pre-buncher (PB) before entering the buncher (B), where the pulse width is further reduced to ~10 ps (FWHM) while simultaneously accelerating the beam to approximately 10 MeV. Subsequently, 20 accelerating units (labeled L01 to L20) operating at a frequency of 2856 MHz further boost the beam energy to the design value. Each accelerating unit can provide an energy gain of 120 MeV and consists of an RF unit and an accelerating segment. The accelerating segment comprises two traveling-wave accelerating tubes, each about 3.1 meters in length. The RF unit includes an 80 MW peak-power klystron and a solid-state modulator that supplies power to it. Among the 20 accelerating units, one is maintained as an online hot backup. The schematic layout of the linear accelerator is presented in Figure 1.

Fig.1: Schematic layout of the linear accelerator

The main parameters of linear accelerator are shown as below.

RF unit（80MW peak-power klystron and solid-state modulator ）

Accelerating tubes installed on the test platform

04 Construction Location

HALF is located in the future big science city of Hefei (Gangji Town, Changfeng County), about 17 kilometers away from Xinqiao Airport and 24 kilometers away from the National Synchrotron Radiation Laboratory (NSRL) of University of Science and Technology of China (USTC). It is also adjacent to superconducting EAST, Steady High Magnetic Field Facility (SHMFF）and CRAFT.

05 Organization & Committee

HALF Engineering Organization

HALF Project Leading Group

HALF Project headquarters

HALF Project Office

Injector system (electron source, injector physics, pulsed power source, magnet, magnet power supply, beam current measurement, control, vacuum, mechanical support, collimation, microwave, radiation protection)

Storage ring system (storage ring physics, magnet, magnet measurement, magnet power supply, injection, superconducting main HF, high harmonic cavity, ambient main HF, control, beam current measurement, vacuum, mechanical support, collimation, radiation protection, inserts, storage ring commissioning)

Beamline station system (Mass Spectrometry for Energy Transformation and Astrochemistry, Extreme Ultraviolet Electronic Structure Characterization and Lithography, Electronic Structure Characterization for Operando Micro/Nano Devices, High-sensitive, Space-Resolved and Time-Resolved Electron Spin Dynamics, In-situ/Operando Soft X-ray Spectroscopy and Scattering, Soft X-ray Spectromicroscopy and Ptychography, Resonant Coherent Scattering, High Throughput In-situ/Operando Tender X-ray Spectroscopy, Tender X-ray Spectromicroscopy and Ptychography, Test Beamline, Optics Systems, Optical Metrology and Fabrication, (Beamline) Mechanical Engineering, Thermal Management, Beamline Controls, Computing Resources, Databases and Software)

General utilities system (pre-civil engineering, power supply and distribution, water cooling, cryogenics, HVAC purification, integrated piping, foundation vibration, equipment installation, network, gas supply)

Construction and safety engineering system (building structural engineering, electrical engineering, HVAC/water supply and drainage)

Committee on Engineering Science and Technology

Director  ZHAN Wenlong, Academician, Chinese Academy of Sciences

Deputy Director  SUN Shigang, Academician, Xiamen University

Members

CHEN Hesheng, Academician, Institute of High Energy Physics, Chinese Academy of Sciences

CHEN Senyu, Academician, Institute of High Energy Physics, Chinese Academy of Sciences

HE Duohui, Academician, University of Science and Technology of China

LI Yongfang , Academician, Institute of Chemistry, Chinese Academy of Sciences

XIA Jiawen, Academician, Institute of Modern Physics, Chinese Academy of Sciences

XIE Yi, Academician, University of Science and Technology of China

XU Jian, Academician, China National Machinery Industry Corporation

ZHAO Hongwei, Academician, Institute of Modern Physics, Chinese Academy of Sciences

ZHAO Yuliang, Academician, National Center for Nanoscience and Technology

ZHAO Zhentang, Academician, Shanghai Advanced Research Institute, Chinese Academy of Sciences

ZHAO Zhengguo, Academician, University of Science and Technology of China

DING Hong, Professor, Shanghai Jiaotong University

DONG Yuhui, Research Fellow, Institute of High Energy Physics, Chinese Academy of Sciences

LI Hong, Research Fellow, Institute of Physics, Chinese Academy of Sciences

LI Zhen, Chairman, Gotion High-tech Co., Ltd.

LIU Kexin, Professor, Peking University

PAN Weimin, Research Fellow, Institute of High Energy Physics, Chinese Academy of Sciences

QI Fei, Professor, Shanghai Jiaotong University

TANG Chuanxiang, Professor, Tsinghua University

WANG Sheng, Research Fellow, Institute of High Energy Physics, Chinese Academy of Sciences

WANG Zhanshan, Professor, Tongji University

WU Yizheng, Professor, Fudan University

XU Ruiming, Professor, Institute of Biophysics, Chinese Academy of Sciences

YANG Guoqiang, Research Fellow, University of Chinese Academy of Sciences

YIN Lixin, Research Fellow, Shanghai Advanced Research Institute, Chinese Academy of Sciences