Investigation of compatibility of low activation ferritic steel with high performance plasma by full covering of inside vacuum vessel wall on JFT-2M

Compatibility of reduced activation ferritic steel wall with high performance plasma on JFT-2M

“…It had been demonstrated by simple calculation that the systematic error on the plasma position is ∼2 cm for the typical experimental condition [7]. This effect is roughly inversely proportional to the toroidal field [7]. In the case of this experiment (low toroidal field), the normalized wall position (r wall /a) is affected by 5-10 %, which is not negligible.…”

“…It should be noted that the thickness of the ferritic steel in this experiment (∼10 mm) is much smaller than that of the blanket of DEMO, but the normalized effect is expected to be comparable. As discussed in [7] a perturbed field from the ferritic steel is roughly proportional to d/aB T , where d is the plate thickness. The difference in the thickness d will be cancelled by the larger minor radius (a) and the higher toroidal field (B T ) in DEMO.…”

“…The calculation might contain systematic errors due to the effect of the ferromagnetic wall. It had been demonstrated by simple calculation that the systematic error on the plasma position is ∼2 cm for the typical experimental condition [7]. This effect is roughly inversely proportional to the toroidal field [7].…”

“…The calculated results are compared with the experiments. As for the plasma position, it had been demonstrated that the calculated results agree well with the visible camera and soft x-ray array within an accuracy of the measurement, ∼3 cm [7]. To investigate the separatrix position more precisely, a new method was developed to measure the separatrix position using the 2-step electrostatic probes as follows [15,16].…”

“…Experimental clarification of the ripple reduction was also important. Thus, an advanced material tokamak experiment (AMTEX) has been performed in a medium size tokamak, JFT-2M (R = 1.31 m, a = 0.3 m, B T 2.2 T) in 3 steps in order to investigate the compatibility of ferritic steel with a high performance plasma and the effect of the ripple reduction [1,[6][7][8][9][10]. The reduced activation ferritic steel F82H (8%Cr-2%W-0.2%V-0.06%Ta-Fe) [11] is selected as the material for AMTEX.…”