Producing and measuring small electron bunches

Significant progress has been made in the last few years in ultra-short and high-brightness electron beam production and measurements. For many applications, such as laser and high-frequency RF (W-band) accelerators, and high-gain harmonic generation free electron laser, electron beams with bunch length and transverse emittance smaller than optical wavelength are required. The status of such small electron beam production around the world is briefly reviewed. The experimental results of small electron beam production using photocathode RF gun with magnetic bunch compression system, and emittance growth in the compressor are discussed. We also discuss various techniques for characterizing such small electron beam, specially RF kicker cavity for photocathode RF gun based linac, and using coherent radiation for bunch length measurement. The analysis of the kilo-Ampere 10 fs electron beam generation at the ATF is presented.