We are now 11 days into a period of 4 weeks during which the LHC beam team planed to run with a steady 25 bunch per beam filling scheme. The idea was that this point is a critical step in the commissioning at which the stored energy in the beams becomes critically dangerous at 1MJ which could do serious damage to the collider if it went out of control. They want to get used to running at this level before continuing to even higher beam intensities. Also, August is a traditional month of holiday for the French so many experts will be away.
This plot shows the progress so far with an 11 days plot of instantaneous luminosity on top and accumulated luminosity below. You can see 13 fills with peak luminosity reaching as high as 4.1/μb/s in CMS. The best individual run gathered 120/nb and the total from the 109 hours of running time is 730/nb which can be added to the 350/nb already accumulated previously. If they continue with this scheme they should be capable of adding another 1/pb during August approaching levels needed to have a small chance of seeing new physics.
The LHC beam team is notorious for changing their plans whenever things seem to be getting too easy so now they are considering further increases in luminosity during August. According to the new plan they will double the number of bunches to 48 next week and perhaps even to 80 the week after. They can do this while still using the current injection method that delivered four bunches at a time from the SPS, so it may not be considered too risky 😉
After August they will continue the increase in number of bunches by adding 32 bunches each week until November when they plan to switch to heavy ion collisions for a month. This would take them to 384 bunches per beam and a luminosity of 100/μb/s or about 3/fb/year
Taking into account downtime, luminosity falloff and recycle times this would probably not be sufficient to get them to their target of 1/fb collected during the 9 months of running time available in 2011. Realistically they need to double the number of bunches again to 768 as on Meyers’ plan shown at ICHEP, so there is still work to do. A few more plan tweaks should sort it out 🙂