The TRAPS Apparatus: Enhancing Target Density of Nanoparticle Beams in Vacuum for X-ray and Optical Spectroscopy

Abstract

We present an experimental setup that allows the injection of charged nanoparticles in a diameter range of 3–15 nm into a vacuum chamber and their storage there in an electrodynamic cage. The nanoparticle density in the trap is limited by space charge and can be several orders of magnitude higher than in a free nanoparticle beam. The setup provides for the first time a tool for the application of advanced techniques of spectroscopy to free nanoparticles in this size range. It consists of a combination of (1) a plasma discharge nanoparticle source that generates a high density of nanoparticles of various composition suspended in helium carrier gas at a pressure of about 10–150 mbar, (2) an aerodynamic lens optimized for small particles (diameter 3–15 nm) that forms a well-collimated beam of charged nanoparticles and focuses it into (3) an octopole ion trap operated at low frequencies and filled with helium buffer gas at 10⁻² mbar in order to moderate and store the nanoparticles at densities of more than 10⁷ cm⁻³.

We wish to thank V. Szabo for support with the design and buildup of the microwave plasma particle source. We also give thanks to ANSYS and CADFEM for their support and fruitful help with the CFD code design and Johan Söderström for working with us on the simulation of aerodynamic lenses. This work was supported through the framework of FSP 301—FLASH (Förderkennzeichen 05 KS7VHA) of the German Federal Ministry for Education and Research, Bonn, Germany.