Figure 4.

Scaling laws for the particle-beam focus with respect to entrance pressure. (a) Particle-beam widths (FWHM) for a range of pressures (see legend) are plotted against the distance from the injector tip. Particles were polystyrene spheres of 100 nm in diameter. The experimental data can be approximated with a Gaussian-beam model (solid lines). Scaling laws [solid lines in (b), (c) and (d)] were identified for the model parameters as functions of the entrance pressure p. (b) The particle-beam waist scales as p ^−(3/2). (c) The distance between particle focus and injector tip scales as p ^−(1/2). (d) The particle-beam divergence scales as p ⁻¹.