Calibrating the PHENIX Muon Piston Calorimeter for Au+Au collisions at $\sqrt{S_{NN}}$=200, 62.4, 39, and 7.7 GeV

The PHENIX Muon Piston Calorimeter (MPC), a homogenous electromagnetic calorimeter, covers forward/backward pseudorapidities ($3.1<|\eta|<3.9$). MPC calibrations of data collected by PHENIX during the 2010 RHIC run are underway. These will be used for the measurement of transverse energy in the forward/backward direction. For the calibration, an iterative process is used in which photon clusters are paired to produce tower by tower mass plots containing neutral pion peaks. The gains of each tower are adjusted until the peaks in the mass histograms are shifted to the positions predicted by a full detector simulation. For towers in which a neutral pion peak is not immediately evident, other methods can be applied to adjust the gains until a neutral pion peak appears.