International Research Collaboration Program

NSJP (NIFS-SWJTU Joint Project)
Quasi-axisymmetric Stellarator Experiment Program

   National Institute for Fusion Science (NIFS) is contributing to the world stellarator program with remarkable experimental results from the Large Helical Device (LHD) covering various physical and engineering topics in fusion science. In addition to such contributions, NIFS has started a new stellarator program in 2017 for a small size experiment with the purpose of exploring a high degree of freedom of three-dimensional magnetic configuration design, which is a great advantage for stellarators compared to tokamaks. This program also has an important role in the strategy of the stellarator community in the world, that is, an initiation of a new stellarator program in China among many stellarator programs already started in Japan and western countries. The program NSJP (NIFS-SWJTU Joint Project) is an international collaboration between NIFS and Southwest Jiaotong University (SWJTU) , which is one of the largest Chinese universities located in Chengdu, Sichuan province and is famous for its special engineering department for the quality control of Chinese high-speed train system (Shinkansen). A new quasi-axisymmetric stellarator CFQS (Chinese First Quasi-axisymmetric Stellarator) will be built in this university. In research on physics and engineering design of CFQS, wide experiences in physics design studies of the CHS-qa device in NIFS are incorporated.
   A quasi-axisymmetric stellarator is a type of toroidal magnetic confinement devices with the plasma confinement properties similar to tokamak device. This concept does not require a plasma current and thus eliminates problems in tokamaks; disruptions, and technological difficulties of current drive. This research topic is very important recently for both stellarator and tokamak research communities.

1) Magnetic configuration
   The magnetic configuration of CFQS plasma was designed as a low aspect ratio stellarator with the quasi-axisymmetric property. Basic configuration parameters are: Toroidal period number N = 2, Plasma major radius R = 1 m, Plasma aspect ratio Ap = 4.0. Poloidal cross sections of the vacuum magnetic surfaces are shown for three toroidal positions of the torus.
   The rotational transform profile for vacuum field is almost flat with values below 0.4. The Boozer spectra of the magnetic field ripples consist of one dominant component of the toroidicity (m=1, n=0) and other small residual components.

   The magnetic surface calculation plots using the modular coils designed for the target boundary shapes are shown. The red lines show the target shape and the blue lines show the shape of vacuum chamber wall.


   When the toroidal field is reduced by activating auxiliary toroidal coils, an island bundle diverter configuration is formed.


2) CFQS Device
   A quasi-axisymmetric stellarator configuration is produced with 16 modular coils (312.5 kA current in each coil) for nominal toroidal field strength B = 1 Teslt(T). In addition, auxiliary toroidal coils for controlling toroidal field strength (and controlling rotational transform profile) and poloidal coils for controlling the plasma shape and position are equipped. Detailed information is described in the technical memo.
   The experiment will be operated in two phases. The first phase will be in a week magnetic filed of 0.1 T prepared in Jiuli campus and the second phase will be in a full mode operation of 1 T. For the first and second phases, all magnetic coils are manufactured for 1 T operation. However for the first phase, the power supply is designed and manufactured for 0.1 T operation. The power supply and the cooling system for 0.1 T experiment are shown below. (CFQS-T experiment)

   The second phase of the experiment will be prepared in the Tianfu new university site. The power supplies and heading devices will be strongly reinforced for larger magnetic field operation of CFQS device. (CFQS experiment)

   In October 2024, the experiments of CFQS-T started with 0.1 T magnetic field in Jiuli university campus. The measurements of magnetic surfaces were successful and the ECH experiments with 2.45 GHz magnetron started.

3) Manufacturing
   The components of the device are manufactured in the high-tech company, Hefei Keye Electro Physical Equipment Manufacturing Co., Ltd. All stuff in the company have highly challenging spirits attacking very difficult works of manufacturing modular coils. Photos for the manufacturing of modular coils and the design of vacuum chamber are shown. Finally the device construction was completed for the 0.1 T experiments of CFQS-T.

   
 
   
     

4) First phase experiment with 0.1 tesla magnetic field
   Plasmas with the quasi-axisymmetric magnetic configuration were produced. The CCD camera image shows a plasma produced with 2.45 GHz microwave. The probe measurement data show plasma edge profiles with different magnetic configurations.

 

5) Progress of the NSJP (NIFS and SWJTU Joint Project)
2015.5 SWJTU (Southwestern Jiaotong University) inquired NIFS for the transfer of CHS.
2015.12 Leaders of Chinese fusion community were invited to SWJTU and supported NSJP.
2016.7A plan of constructing a new quasi-axisymmetric stellarator was selected.
2017.7An MoU was concluded between NIFS and SWJTU for starting NSJP program.
2017.10NSJP team visited PPPL and HSX lab. for discussing technical issues for manufacturing a device.
2018.5Engineering design for CFQS was started.
2018.5 The 1st steering committee for NSJP was held in Chengdu.
2018.5CFQS techinical report V.1
2018.11NSJP team visited Greifswald for discussing technical issues for manufacturing a device.
2019.3 Manufacturing of a mockup coil started.
2019.11CFQS techinical report V.2 was published.
2020.1 Manufacturing of a mockup coil was completed.
2020.9 Manufacturing of the first modular coil (MC4) started.
2020.10Manufacturing of the vacuum chamber started.
2020.11CFQS techinical report V.3 was published.
2021.2 Metal block molds for shaping vacuum chamber wall
2021.3 Manufacturing of the first modular coil (MC4-1) was completed.
2021.3 Plasma discharge in SSHD at NIFS
2021.7 Conductor windings of modular coil MC4-3
2021.9Renovation of the CFQS experimental hall was completed.
2021.11 The 4th steering committee for NSJP was held in remote.
2021.11CFQS techinical report V.4
2021.12 Plasma discharge in SSHD at SWJTU
2022.3Second VPI is completed for MC4-1
2022.6A part of stainless steel vacuum chamber
2022.7Experimental hall is ready for setting the CFQS device
2022.714 coils are formed out of 16 total modular coils
2022.9Supporting design of 4 types of modular coils
2022.10Leak test of vacuum chamber with ribbon heater
2022.12 The 5th steering committee for NSJP was held in remote.
2023.3CFQS techinical report V.5.1
2023.6Manufacturing of 16 modular coils are completed
2023.7Face to face meeting after Corona pandemic
2023.7Assembling process for 0.1 Testa operation
2023.12 The 6th steering committee for NSJP was held in Hefei and Chengdu
2024.1Components of CFQS experiment are prepared in the test chamber
2024.3Baseplate for CFQS device
2024.4CFQS device is in assembling phase
2024.5A quarter of vacuum chamber
2024.5TFC (Toroidal Field Coil) coils
2024.5Assembling CFQS half period
2024.6Assembling CFQS full torus
2024.7Assembling CFQS complete device in Keye company
2024.7CFQS device in Jiuli experimental hall (CFQS-T experiment)
2024.7CFQS with NIFS team
2024.11CFQS-T experiment starting ceremony
2025.5Carry out CFQS for 1 Tesla modification
2025.5Starting construction for a new site in Tianfu

6) CFQS experimental sites
   The experimental site for the first phase (0.1 T) will be in SWJTU Jiuli campus at Chengdu city center. The second experimental site for the full operation (1 T) will be in Tianfu at the new academic site of the Chengdu city.

 
CFQS experimental site in Juili (CFQS-T)
First phase experiments for 0.1 Tesla was finished in 2025 May		 CFQS expeimental site in Tianfu

7) NSJP design team for CFQS
   An international design team for CFQS was organized with researchers from NIFS and SWJTU(Southwest Jiaotong University) and experienced engineers from Keye company in Hefei. A steering committee was also organized by NIFS and SWJTU in order to make important decisions in the NSJP program.

   NSJP Steering Committee for CFQS
National Institute for Fusion Science  Southwest Jiaotong Univertisy
Zensho Yoshida Director general Chuan He Vice president (SWJTU)
Mitsutaka Isobe Professor Yuhong Xu Professor (SWJTU)
Akihiro Shimizu Assistant professor Changjian Tang Professor (Sichuan univ.)
Shoichi Okamura Professor emeritus Dapeng Yin Chief engineer (Keye co.)

Members of steering committee and CFQS design team (2019.5)

Members of steering committee and CFQS design team (2023.12)


 NSJP team group photos

2017. 7 NSJP team with researchers and students in SWJTUNames
2019. 3 NSJP team in Keye company with general manager Ms. Xianlian Wu Names
2020. 1 NSJP team with engineers in Keye company Names
2021. 6 Members of Institute of Fusion Science (IFS) in SWJTU Names1
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2021. 7 (Part of) NSJP team in NIFS Names
2021.10 Vice president of SWJTU visited Keye company Names
2021.11 4th NSJP steering committee (in remote) Names1
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2022.12 5th NSJP steering committee (in remote) Names1
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2023.4 Vice president of SWJTU visited NIFS Names
2023.7 NIFS team visited CFQS experimental hall Names1
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2023.7 NIFS and SWJTU teams visited Keye company Names
2023.12 6th NSJP steering committee in Keye company Names
2023.12 6th NSJP steering committee in SWJTU Names1
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2024.3 NIFS and SWJTU teams visited Keye company Names
2024.9 SWJTU managers visited NIFS Names
2024.11 Program members in CFQS-T ceremony Names1
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8) Publication List