Closed-cycle noble gas recycling system for high-repetition rate high-harmonic generation.

We present a compact closed-loop recycling system for noble and inert gases. It has been developed for an extreme-ultraviolet (XUV) frequency comb based on high-harmonic generation at 100 MHz repetition rate. The system collects gas injected at several bars of backing pressure through a micrometer-sized nozzle into the laser-interaction region with a differential pumping system comprising turbomolecular pumps, and subsequently compresses the gas to a pressure of up to 200 bar.