Plasma generator and cooling jacket

A plasma generator comprising:

• a microwave-generating source that generates a microwave;
• a plasma generation tube that has a cylindrical shape and through which a gas to be plasmatized by the microwave flows;
• a waveguide that transmits the microwave generated by the microwave-generating source to the plasma generation tube;
• a matching device provided to the waveguide between the microwave-generating source and the plasma generation tube;
• a cooling jacket that is provided on an outer peripheral surface of the plasma generation tube and cools the plasma generation tube;
• and
• a casing that has a cylindrical shape, and that houses the plasma generation tube and the cooling jacket,
• wherein the cooling jacket includes:
• three slits that extends along a traveling direction of the gas flowing through the plasma generation tube, or along a direction inclined with respect to the travelling direction, and through which the microwave passes toward the plasma generation tube;
• and
• a cooling channel that is provided between the slits adjacent to each other, and through which a cooling fluid for cooling the plasma generation tube flows.