A novel approach in the free-electron laser diagnosis based on a pixelated phosphor detector

Abstract

A new high-performance method for the free-electron laser (FEL) focused beam diagnosis has been successfully tested at the FERMI FEL in Trieste, Italy. The novel pixelated phosphor detector (PPD) consists of micrometric pixels produced by classical UV lithography and dry etching technique, fabricated on a silicon substrate, arranged in a hexagonal geometry and filled with suitable phosphors. It has been demonstrated that the overall resolution of the system has increased by reducing the diffusion of the light in the phosphors. Various types of PPD have been produced and tested, demonstrating a high resolution in the beam profile and the ability to measure the actual spot size shot-to-shot with an unprecedented resolution. For these reasons, the proposed detector could become a reference technique in the FEL diagnosis field.

Microfabricated wire scanner for photon beam characterization

“…The coupling of a scintillator screen with a photodetector, usually a CCD or a photomultiplier, allows the visualization of the profile of the incident radiation beam in two dimensions, with resolution in the micron range [2]. The recent years have seen the development of more sophisticated imaging screens, like phosphor detectors [3,4]: in a very recent implementation, for instance, micrometric holes in a honeycomb arrangement fabricated on a silicon substrate using microfabrication techniques, filled with phosphor powder and covered with Indium-Tin Oxide (ITO) are used to control pixel cross talk and achieve micron-sized spatial resolution. In general, however this approach blocks completely the beam and cannot evolve in an inline diagnostic tool.…”