Potential diagnostics for the next-generation light sources

Abstract

There is continued interest in developing a diffraction-limited soft or hard X-ray source. Candidate paths include the storage-ring-based free-electron laser (FEL) and the linac-based self-amplified spontaneous emission (SASE) FEL for the two regimes, respectively. As previously discussed, target beam parameters are σ x,y∼10 μm, σ x′,y′=1 μrad , and σ t ∼1 ps (0.1 ps for the linac case). We report the use of few- to sub-angstrom radiation emitted by a 7-GeV beam transitting a 198-period diagnostics undulator and a bending magnet to characterize the particle beam. A particle beam divergence as low as σ y′=3.3 μrad was measured using an X-ray monochromator. Additionally, a particle beam size of σ y<45 μm and a bunch length of σ t=28 ps with 4-ps resolution were measured using an X-ray pinhole camera with a unique synchroscan and dual-sweep X-ray streak camera as the detector. The adjustable pinhole aperture was varied by more than a factor of 100 to assess spatial resolution and dynamic range issues in the system. These diagnostics demonstrations should scale to next-generation applications.