Also,
radial temperature was measured at the mark L0 in Fig. 1(a).
Generally, the plasma column length in the microwave plasma
torch depends on the amount of swirl gas. In previous literature
[5], the plasma column length was about 20–30 cm for 1-kW
microwave power, for a quartz discharge tube with 27-mm inner
diameter and for 20 L/min of air swirl gas. The plasma column
length reduced to 10 cm when the swirl gas increased from
20 to 80 (L/min).