The design and performance of an effusive gas source of conical geometry for photoionization studies

The design, construction, and performance of an effusive gas source of conical geometry is reported. This gas jet enables experiments that require the gas and photon beams to be essentially collinear and has a focusing multicapillary array with the central portion left free for the photon beam. In total, the source comprises 90 “tubes” in three layers and has been designed by modeling free molecular gas flow and optimizing for highest gas density ∼2–3 mm from the jet’s exit plane. The nature of the gas flow through the source and its focusing properties are investigated theoretically and experimentally.