H8 Electron beam quality improvement during 2001

Since 1999 the ATLAS calorimeter groups who are the main users of the H8 beam line were observing a deterioration of the electron beam quality of the beam. Several studies, within the limited time available due to the tight SPS schedule, were performed before 2001 but without success. Following a systematic study of the problem in 2001, and in collaboration with the ATLAS colleagues, the origin of the problem was found and the beam quality was restored to the level before 1999. Details of the studies performed and the final results on the electron beam quality are summarized here.