A control circuit includes a controller that provides a master PWM signal indicative of a difference between a predetermined setpoint and a process signal. The print head includes an input that receives data or commands associated with printing from the printer. When the fasteners are fastened toward the heat sink, the shafts move upwardly relative to the bottom cover, whereby a distance between the top cover and the heat sink is decreased, so the heat sink makes tight contact with the top cover. Therefore, by properly determining the implant energy of helium, it is possible to exactly determine the junction depth.