Fig. 1. Experimental setup.

A solution containing GroEL particles, each roughly a cylinder 14 nm in diameter and height, is aerosolized, using electrospray ionisation followed by neutralisation, and focused into a thin stream using an aerodynamic lens. The stream is then intersected with the path of the XFEL beam and the diffracted signal is collected on a pair of pnCCD detectors downstream of the interaction region. To minimise the amount of background, the beam is cleaned up by apertures both before and after the interaction region⁵³