A method for generating X-ray radiation, the method including providing a liquid target in a chamber, directing an electron beam towards the liquid target such that the electron beam interacts with the liquid target to generated X-ray radiation, estimating a number of particles produced from the interaction between the electron beam and the liquid target by measuring a number of positively charged particles in the chamber and eliminating a contribution from scattered electrons to the estimated number of particles, and controlling the electron beam, and/or a temperature in a region of the liquid target in which the electron beam interacts with the target, such that the estimated number of particles is below a predetermined limit. Also, a corresponding X-ray source.