No significant changes in the distribution of the modes are to be noted for 2007 compared to the previous years (Figure 140). The multibunch modes remain dominant, making up 71% of the shifts. However, in the multibunch type filling patterns, the so-called “7/8 + 1” was a newcomer during run 2007-01. It represents a good compromise for most users. It satisfies many users who need a single bunch with no bunches filled in the vicinity as well as those who want the maximum current with the longest lifetime. The presence of an unfilled gap in the time structure (1/8 of the circumference) stabilises the electron beam against ion instabilities. The filling pattern is delivered with a vertical emittance of 25 pm. A single bunch of 2 mA, placed in the middle of the gap, is delivered with a filling ratio of 10-9 between filled and unfilled bunches. One week of uniform and 2 weeks of 7/8 filling pattern were converted to 2/3 filling pattern due to an RF cavity failure in June and July 2007. In addition, one week of uniform delivery was converted to 2/3 filling mode in August due to insufficient vacuum conditioning following numerous interventions during the summer shutdown. During run 4, the 16 bunch filling mode was delivered with a maximum of 70 mA instead of 90 mA due to outgassing induced by a defective RF liner immediately upstream of a radio frequency cavity.

Fig. 140: Distribution of filling modes scheduled for 2007.