LHC Chief Steve Myers gave a very interesting talk on the LHC Status today to a packed auditorium here at CERN. The slides and video can be found here: http://indico.cern.ch/conferenceDisplay.py?confId=62277
Here is a brief summary of what I took to be the most important lessons from the talk (although of course you’ll learn more from going back to the original):
- The LHC schedule has been delayed by about three weeks from what was forseen in February. That’s routine schedule slippage and no big deal as far as I’m concerned; if there are no other major issues than we will certainly be running this Fall.
- The limiting factor in when and how the LHC starts are the measurements of the resistances of the welding between copper busbars at the connection between magnets, which only carry current when the superconducting wire isn’t superconducting. Some of them have resistances that are too high, and if one of these is affected during a quench, then both the copper and the superconducting wire can melt and cause a current arc. This is what happened last September, and was part of the chain of events that caused significant damage to the LHC. There are other busbars with resistances that are too high, and the highest one in the LHC will limit the total current in the magnets and therefore the accelerator energy.
- So far about half the resistances in the accelerator have been fully checked. The rest are planned to be checked by early August, and if there are no significantly higher resistances are found than those seen so far, the LHC will probably be able to do an initial run with energy of about 4 TeV.
- Once all these resistances have been measured, and in particular if higher values are found, the LHC experts will have to decide what the highest safe machine energy is. Then CERN, the LHC, and the experiments can decide together if it is better to run at that energy or wait longer in order to repair the worst resistances.
- There have been significant upgrades to a variety of systems for preventing and reducing large-scale problems caused by future current arcs or other damage to the helium cryostats in the LHC magnets, although of course the goal is to avoid these in the future.
