Beam diagnostics challenges for future FELs

Designs are being developed to produce diffraction-limited sources based on storage-ring free-electron lasers (FELs) for the VUV and soft x-ray regime and linac-given FELs in the few Angstrom regime. The requirements an the beam quality in transverse emittance (rms, normalized) of 1-2 pi mm mrad, bunch length (1 ps to 100 fs), and peak current (1 to 5 kA) result in new demands on the diagnostics. The diagnostics challenges include spatial resolution (1-10 mu m), temporal resolution (<100 fs), and single-pulse position measurements (similar to 1 mu M). Examples of recent submicropulse (slice) work are cited as well as concepts based on spontaneous emission radiation (SER). The nonintercepting aspects of some of these diagnostics should also tie applicable to high-power FELs.