Control variables for performance optimization include heater
temperatures (powers), baseplate cooling, and reactor pressure.
A typical performance objective is to bring the wafers close to
a desired temperature,
while keeping wafer-to-wafer and across-wafer temperatures within
prescribed limits to avoid `cracking' of wafers and achieve
uniformity of wafers.
Compute heater powers to achieve uniform temperature
distribution on the wafers during steady-state operation.
Compute heater powers to track given temperature
for ramp, hold, and cool-down phase.