An irradiation head adapted to be detachably attached to a massage gun, the irradiation head being configured to reciprocate in forward and backward motion, comprises one or more irradiation sources, and a converter configured to convert the forward and backward motion of the irradiation head into electrical energy. The one or more irradiation sources are configured to be activated by the converted electrical energy, wherein the converter includes a coil based linear alternator, the coil based linear alternator including, a coil wrapped around a hollow cylindrical body, and a magnet disposed within the hollow cylindrical body.