The primary function of a booster in ultrasonic welding is to amplify the low amplitude, high-frequency vibrations produced by the transducer and focus them on the workpiece. The booster is designed to resonate at the same frequency as the transducer, but with a larger amplitude, which increases the amount of energy that is transferred to the workpiece. Boosters can also be used to match the impedance of the transducer to that of the horn, which maximizes energy transfer and improves the efficiency of the ultrasonic welding process. Overall, the booster plays a crucial role in the ultrasonic welding system by helping to produce strong, reliable welds.