Short Bunch Beam Diagnostics

. With the emergence ,of 4th generation FEL based ,light sources there is now considerable interest in both producing and characterizing ultra-short (<100 fs) electron bunches. Knowledge of the extremely high peak current in a short bunch is required to diagnose the SASE (self amplified stimulated emission) process. Measuring the femtosecond,duration of the pulse is inherently interesting, particularly for experimenters using the beam to measure fast phenomena (e.g. femto-chemistry). Diagnostic techniques that have the necessary femtosecond ,resolution will be reviewed: These include high-power RF transverse deflecting structures that “streak” the beam,in the accelerator allowing the bunch length to be recorded on a,profile monitor. Electro optic crystal diagnostics use the electric field of the electron bunch to modulate ,light thereby