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Large Linear Plasma Testing Facility

9. Large linear plasma testing facility

Scientific objectives

Within the CRAFT project, a large linear plasma testing facility will be built to address some key R&D issues of plasma-facing materials and components for CFETR in appropriate physical regimes, size, and time scales of plasma-material interactions. This facility is expected to make significant scientific and technical contributions in thefollowing aspects:

  •  Lifetime qualification for the plasma-facing units (PFUs) of CFETR
  •  Selection of next generation plasma-facing materials (PFMs)
  •  Hydrogen isotope transport behavior in the PFMs
  •  Synthesized effects of hydrogen isotope, helium, heat flux as well as irradiation damages on the degradation of material properties
  • Other scientific problems relevant to intense plasma streams outside fusion research filed

After commissioning, this facility will be fully open to users in the whole plasma-materials interaction (PMI) research community. Proposals to advance scientific and technical frontier of intense plasma streams for variety of applications are also highly appropriate.

System description and machine parameters

The configuration of the facility is shown in the following figure. The main chamber, superconducting magnets, plasma source and relevant diagnostics compose a large linear plasma generator. Surface analysis tools are connected to the sample exchange chamber with a versatile target system. An operation control system will manage the plasma discharge and in-situ/in-vacuo materialanalysis processes.

 A powerful linear plasma generator

The linear plasma facility can deliver intense plasma streams of 1024 -1025 m-2s-1 particle flux with a beamdimension of 30-100 mm. A modified cascaded arc source has been selected to produce the high-density plasma. The magnetic field strength, which can be as high as 3 T at the source center, will be maintained by superconducting-magnets. That means the machine can beoperated in a steady-state manner with continuous plasma exposure time from~1000 s to several hours. The base line plasma diagnostics include emission spectrum and target probes. The machine parameters are summarized in Table 1.

Versatile materials and components testing capability

During plasma discharge, infrared/visible cameras and thermocouples will monitor the operation status of this machine. A manipulator will transport the samples or mockups with a maximum size of 250×250 mm between the irradiation chamber and the sample analysis station. Both translational motion and rotation of thesample holders are available to improve experimental efficiency. If the modified source design is fully successful, the plasma exposure width can be as large as 100 mm, enabling 3 ITER-like monoblock type PFUs to be tested simultaneously.

 Comprehensive tools for divertor materials testing

In-situ orin-vacuo material analysis tools like laser-induced breakdown spectroscopy(LIBS), laser-induced ablation spectroscopy (LIAS), ion beam analysis (IBA) and the rmal desorption spectroscopy (TDS) will be installed to examine hydrogen isotopes retention and surface composition of the materials after plasma exposures. Other surface analysis devices like X-ray photoelectron spectroscopy(XPS) and scanning electron microscope (SEM) will be available in the accessory laboratory as well.

Key technologies

  •  Powerful plasma source with long lifetime and large exposure area

  • Advanced vacuum system with high particle exhaust capacity

  • Compact superconducting magnets design and manufacturing

  • Advanced in-situ/in-vacuo materials analysis technologies