THz based shape analysis of sub-ps electron bunches at BESSY

Short electron bunches in storage rings emit strong THz and sub-THz radiation if the length of the bunches is lower than the wavelength of the radiation. Two strong broad band THz sources have been established at the BESSY storage ring: 1. Coherent THz generation by compressed bunches at 500 MHz repetition rate gained by up to 10⁷ in average power compared to incoherent sources. 2. Recently, ultrashort THz radiation emitted by the interaction of a femtosecond laser at a repetition rate of 1 kHz and the electron bunch in an undulator was detected. Experimental results on bunch length measurement using THz radiation are presented.