Free-diaphragm pump

A pump for ultra-pure fluids comprises a flexible diaphragm separating a fluid chamber from an air chamber. The diaphragm creates an airtight seal between the fluid chamber and the air chamber when a self-centering and trapezoidal shaped wedge compressively forces the diaphragm into a trapezoidal shaped perimeter cavity surrounding the chambers. Any leak from the fluid chamber into the air chamber is detected by a fiber optic system comprising two optical fibers that are disposed at an angle that is calculated to enable light to pass between the fibers only in the presence of a liquid having a predetermined index of refraction. The fiber optic system can also be used to determine the stroke of the pump by disposing the fiber optic lines at an angle calculated to reflect light off of the oscillating diaphragm when the diaphragm arrives at a predetermined location.