System and Method for Extending Gas Life in a Two Chamber Gas Discharge Laser System

A method of replenishing gas in a dual chamber gas discharge laser light source having a master oscillator and an amplifier, each of the master oscillator and amplifier having a laser chamber containing a lasing medium gas comprising a halogen, the method comprising the steps of:

• selecting a plurality of inject opportunities occurring at regular intervals;
• injecting into the selected laser chamber at each inject opportunity a quantity of a non-halogen containing gas and a quantity of the halogen containing gas estimated to result in a desired amount of halogen gas in the chamber after the inject opportunity;
• and
• after each M injects, where M is a predetermined number, adjusting the pressure in the chamber to compensate for any change in the efficiency of the laser due to the length of operation of the laser.

A non-transitory computer-readable medium having embodied thereon a program, the program being executable by a processor to perform a method of replenishing gas in a dual chamber gas discharge laser light source having a master oscillator and an amplifier, each of the master oscillator and amplifier having a laser chamber containing a lasing medium gas comprising a halogen, the method comprising the steps of:

• selecting a plurality of inject opportunities occurring at regular intervals;
• injecting into the selected laser chamber at each inject opportunity a quantity of a non-halogen containing gas and a quantity of the halogen containing gas estimated to result in a desired amount of halogen gas in the chamber after the inject opportunity;
• measuring an operating parameter of the selected laser chamber that is indicative of the efficiency of the laser during each injection of gas into the chamber;
• estimating the ratio of the change of the measured operating parameter to the number of shots fired by the laser;
• measuring the change in pressure during each inject opportunity;
• determining the ratio of the change of the measured operating parameter to the change in pressure in the chamber;
• and
• after each M injects:
• estimating the change in the operating parameter over the M injects;
• estimating the pressure in the chamber that is appropriate to reverse the change in the operating parameter over the M injects;
• and
• adjusting the pressure in the chamber to the estimated pressure.