. . "Reference number 1401 represents a heater; 1402, an inert gas supply source; 1403, an air outlet for releasing excessive heat; 1404, a power source for controlling heat sources for heating the inert gas (examples of the heat sources: resistance heating elements composed of a compound such as silicon carbide or lanthanum chromate, or a metal wire such as a platinum, Nichrome or tungsten wire; metal" . .