Design and performances of a compact differential pumping unit for X-ray beamlines

In this contribution, we present a compact differential pumping unit with apertures ≥500 µm. It allows windowless operation for in-air sample environments as well as to connect low-quality in-vacuum sample environments to the beamline UHV (≤10^-8 mbar) section. The unit also protects the UHV section of the beamline from accidental venting due to operator errors. To simplify the design, an adjustment-free series of pinholes is used. The positioning of the apertures relies on tight machining tolerances. The assembly consists of just eight parts: one main aluminium body, four threaded cylinders with apertures and three covers with links to pumping units assembled with Viton seals. The overall footprint is restricted to 368 mm on the beam axis.