Pyrolytic carbon membranes enabling novel low-energy photon sources

A compact non-radioactive ionization source is required for various detectors. A photoionization source utilizing a pure pyrolytic carbon membrane grown via chemical vapor deposition is developed and characterized. The efficient transmission of the carbon fluorescence line results in a high source efficiency at an acceleration voltage of 500 V. Comparative studies demonstrate that this source generates significantly higher ion currents at voltages below 2 kV compared to traditional configurations, including a carbon membrane coated with a 50 nm gold target and a 125 μm beryllium membrane coated with a 750 nm silver target. As a preliminary proof of principle, the photoionization source is evaluated using a field-switching ion mobility spectrometer. At an acceleration voltage of 500 V and an emission current of 5 μA, the pure carbon membrane configuration exhibits a twofold increase in the intensity of the ion peak compared to a tritium ionization source.