In 2007, 682 shifts (5455 hours) of beam were initially scheduled. Of these 5455 hours, 5343 were effectively delivered (including 56 hours of refill). This represents a beam availability of 97.94%, which is slightly less compared to the previous year, mainly due to a single major failure of a stripline chamber (see below). Dead time due to failures accounts for the remaining 2.06% (Table 4). The number of failures is however comparable to the previous year, thus leading to a Mean Time Between Failures of 56.8 hours. In July 2007, a major vacuum leak developed in the feedthrough of a stripline vacuum chamber used for beam diagnostics. Consequently, two cells (~ 50 m) of the ring circumference reached atmospheric pressure requiring full vacuum processing with baking. Seventy-six hours of user time (user service mode, USM) were lost following this incident. The autumn operation schedule was subsequently revised and it was possible to gain two days within the user program to compensate for the lost beamtime. Thirteen long delivery periods (i.e. more than 100 hours) without a single interruption took place in 2007, two of those weeks even lasted 168 hours! Figure 139 highlights the fifth week of run in 2007-02, when the beam was delivered in the new hybrid mode “7/8 + 1” for 144 hours without a single hitch.

Table 4: Overview of storage ring operation in 2007.


Fig. 139: An example of a full week of delivery without a single failure, in the new hybrid mode.