Optical injector of particles for X-ray diffractive imaging

Motivated by the need for new single particle sample delivery methods to be used with our coherent diffractive imaging program [1-4] we have developed an optical pipeline [5] to produce a highly collimated stream of particles in either gaseous or vacuum environments. We present first results of our efforts to guide particles with micron-size precision in gaseous and vacuum environments using a first order quasi-Bessel beam operating either independently or collinear with a particle laden gas stream produced by an aerodynamic lens. The centimeter long, low divergence, optical pipeline is formed by a first order Laguerre-Gaussian beam imaged trough an axicon. When used in conjunction with an aerodynamic lens the optical forces assist the migration of particles to the centerline of the gas flow. This produces a higher particle number density and therefore an easier target to hit when probing with a Free Electron Laser (FEL) or other pulsed source. We present estimated optical forces exerted on the particles and the stiffness of trapping in the transverse plane, both depending on the particle size, optical reflectance, laser power, and background-gas pressure.