The Calibration System of the new g-2 experiment at Fermilab

The muon anomaly (g-2)/2 has been measured to 0.54 parts per million by E821 experiment at Brookhaven Lab, and at present there is a 3 to 4-standard deviation difference between the SM and experimental values. A new muon (g - 2) experiment, E989, is being prepared at Fermilab that will improve the experimental error by a factor of four to clarify this difference. A central component to reach this fourfold improvement in accuracy is the high-precision laser calibration system which should monitor the gain fluctuations of the Calorimeter Photodetectors at 0.04% accuracy. I will review this system, focusing on the technical challenges, solutions, and achievements obtained so far.