A power conversion system converts the horizontal momentum and downward forces of wheeled vehicles into a circular motion capable of driving a shaft, which can be used for generating electricity. When a space region longer than the radius of the beam spot and shorter than the diameter of the beam spot is formed, an assist pulse is applied to the end of the space region to be formed. The collapse is caused by attempting to detect the first photon at the transmitter. This system and method of pressure control is particularly advantageous for chemical vapor deposition application yielding improved process repeatability over an extended period of runtime.