Patent ID: 8459291

Claim:
A source gas concentration control system used for a source vaporization system comprising a tank that contains a source, an inlet line that introduces carrier gas for vaporizing the contained source into the tank, and an outlet line that leads out gas of source gas produced by the vaporization of the source and the carrier gas from the tank, the source gas concentration control system comprising: a first valve that is provided on the outlet line; a concentration measurement part that measures a concentration of the source gas in the mixed gas; a concentration control part that controls a stroke of the first valve so as to make the measured concentration of the source gas that is measured in the concentration measurement part become equal to a predetermined concentration setting; a temperature controller that controls a temperature inside the tank so as to make the temperature inside the tank become equal to a temperature setting; and a temperature setting part that sets the temperature setting of the temperature controller, wherein if at a time the stroke of the first valve exceeds a threshold stroke of an open side that is set on a basis of a limit stroke of the open side in a movable range, the temperature setting part changes the temperature setting to a higher temperature than the temperature setting that is set at the time.