Measurement of the impacts of the J-TEXT TBM mock-up on the toroidal and vertical magnetic field

A 1/3 scaled mock-up of the China Helium-Cooled Ceramic Breeder Test Blanket Module (CN HCCB-TBM) was integrated into the J-TEXT tokamak to study the eddy current distribution, electromagnetic load and thermal load modes on the TBM during plasma disruption. The J-TEXT TBM mock-up is made of reduced activation ferritic/martensitic (RAFM) steel and supported by a cantilever structure, with the ability to move along the radial direction. To investigate the effects on the equilibrium magnetic field in the presence of the mock-up containing ferromagnetic material, two poloidal arrays of printed circuit board (PCB) coil-type magnetic probes are developed and installed inside the J-TEXT vacuum vessel. The toroidal field (TF) ripple along the toroidal direction and the difference of vertical field (VF) over the plasma region are measured. Corresponding simulations are also performed, and the results fit well with the measured ones. It is shown that the TBM mock-up in J-TEXT will change the shape of equilibrium magnetic field in the vacuum vessel significantly, introduce large TF and VF ripple, especially in low field side in front of the mock-up. On the other hand, the effects will produce only a few potentially troublesome problems on the normal discharge when the recession of the mock-up is up to 15 cm away from the port.