Recent experiments on the effect of coherent synchrotron radiation on the electron beam of CTF II

The drive beam of CTF II can provide single electron bunches with charges of more than 15 nC and rms lengths of less than 0. 13mm. If the bunches are bent in the dipoles of a magnetic bunch compressor, they emit coherent synchrotron radiation with strongly enhanced intensity with respect to incoherent synchrotron radiation. Here we report on the experimental and theoretical study of the effect of this coherent radiation emission on the distribution of the electrons in the six-dimensional phase space. Transverse emittances, bunch lengths, and energy spectra were measured for constant bunch compression ratios but different horizontal beam sizes in the bunch compressor. Further, the shielding effect of the finite vacuum chamber height on the mean beam energy loss was investigated by using two vacuum chambers of different heights in a four-magnet chicane. The results are compared with simulations using TraFiC/sup 4/ and ELEGANT.