Laser scattering signals that indicate the presence of small dust particles (diameter ⩽ 2 μm) have been occasionally observed in the JIPPT-IIU tokamak chamber. This phenomenon was reproduced deliberately by spreading carbon dust from the top of the vacuum chamber. No noticeable effect on the plasma was observed for dust falls of up to at least 106 particles (10 μg) in 20 ms during discharges. Dust falling just before plasma startup seemed to be confined but it was soon ejected (in less than 30 ms)

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