Future Developments in Electron Linac Diagnostics

The next generation of electron linacs will fill two different roles: (1) ultra-low emittance, very high power accelerators for linear colliders and (2) ultra-short bunch, high stability accelerators for SASE X-ray production. In either case, precision control based on non-invasive, reliable, beam instrumentation will be required. For the linear collider, low emittance transport is an important concern for both warm and superconducting linacs. Instrumentation will be used for control and diagnostics will be used to validate emittance preserving strategies, such as beam based alignment and dispersion--free steering. Tests at the KEK ATF and the SLAC FFTB have demonstrated the required performance of beam position and beam size monitors. Linacs intended for FEL's will require precision bunch length diagnostics because of expected non-linear micro-bunching processes. A wide variety of devices are now in development at FEL prototypes, including TTF2 at DESY and SPPS at SLAC. We present a review of the new diagnostic systems