Radiation efficiency of Ar torch short plasma as function of length near 100 A

When reduction of waste and dissolution of iron are carried out by using arc plasma, we need to reduce the arc radiation power, because there are some cases of damaging the furnace wall due to the radiation. On the other hand, we can use it as a clean source for heating materials. In this case, it´s expected that radiation becomes greater. In both cases the radiation power from plasmas has to be precisely controlled. So, we measured the radiation power from torches with a plasma length from 1 to 3 cm. The radiation power decreased in proportion to the 1.8~1.9th power of the current. The radiation power in a unit length decreases with the appearance plasma length. The radiation efficiency was 41% for the appearance plasma, 32% for the wall-stabilized arc model, and 20% for the plasma torch at 100 A and length of 3 cm