Static and dynamic properties of wall recycling in TRIAM-1M

A large difference between properties of wall recycling in the continuous gas feed case (i.e. static condition) and the additional gas puff case (i.e. dynamic condition) has been observed. In the static condition, the effective particle confinement time, τp*, increases almost linearly to about 10 s during the 1 min discharge. In the dynamic condition, τp* is 0.2–0.3 s during the 1 min discharge. This difference of τp* is also confirmed in the ultra-long discharge. τp* in the static condition becomes ∼100 s before the global balance between particle absorption and release of the wall is achieved at t∼30 min. τp* in the dynamic condition is, however, still on the order of ∼0.3 s. The large difference between τp* in the static and dynamic conditions is attributed to a reduction in the recycling coefficient due to enhanced wall pumping resulting from the gas puff.