Emittance Growth during Bunch Compression in the CTF-II

Measurements of the beam emittance during bunch compression in the CLIC Test Facility (CTF-II) are described. The measurements were made with different beam charges and different energy correlations versus the bunch compressor settings which were varied from no compression through the point of full compression and to over-compression. Significant increases in the beam emittance were observed with the maximum emittance occuring near the point of full (maximal) compression. Finally, evaluation of possible emittance dilution mechanisms indicate that coherent synchrotron radiation was the most likely cause.