We have used MeV ion beams to fabricate nanopores in Poly(tetrafluorethylene-co-perfluoro-(propyl vinyl ether)) (PFA) fluoropolymer membranes. We have developed an in house system to produce nanopores. Using MeV ion beams we developed a method to produce pores from nanometers to one-micron diameter. A thin film of the PFA polymer was mounted to cover a window to a gas filled chamber and then exposed to a uniformly scanned MeV ion beam masked to define the exposed area. The gas leak rate through the fabricated pores was monitored by an in situ RGA system both during and after each bombardment to correlate the leakage with the total area of the pores produced. In this project we used MeV light and heavy ions to best define the pore diameter through each hole and the pore entrance and exit dimensions in the membranes.