Here.

Over 10000 13KA connections alone!

I hadn’t read the four page report before writing, just the press release.

Pressure relief is via spring loaded disks in the short straight sections.

This sector was the only one which hadn’t been taken to 5.5 TeV equivalent currents prior to the incident.

Each of the eight 2K refrigerators at LHC is slightly larger than the previous record holder at Jefferson Lab. If there were more connections from 2K to room temperature the refrigeration costs would go up substantially. This is part of the risk-benefit tradeoff that was done during design. There are eight ~3km cryo loops.

Burst disks for pressure relief are graphite machined so they will burst at a precise pressure differential. When I was in the MRI magnet business two decades ago we specified the things to burst at 19-21 psi differential if memory serves. Bigger burst disks mean bigger stainless pipes and flanges; these cost a lot more than the graphite disk. Retrofitting bigger disks to existing magnets, if that is what’s planned, will be touchy because once can’t afford to get chips into the super-insulation. One will have to warm up the magnets to increase the size of the disks because one has to bring the insulation vacuum space to atmosphere.

Again, one models the anticipated failure modes, determines the gaseous helium flow rates needed to keep over-pressure down, and sizes the pipes and burst disks with appropriate engineering safety factor. Too big a disk and the cost is too high. CERN had to borrow from their employees pension fund to get the funds needed to build LHC – the member states wouldn’t increase their contributions enough to fund it otherwise. Cpst containment was VERY important.

The 5 TeV energy for the initial run was chosen because all of the sectors exceeded the field needed for this energy in sector by sector tests. All the magnets trained to fields above those needed for 7 TeV at acceptance, but some relaxed at room temperature or during installation.

I am sure CERN will work hard to determine what caused the interconnect to fail this time rather than during previous excursions to similar currents.

Using steel magnets one would need a ring ~150 km in circumference for this energy. The LHC tunnel was dug for LEP so only the enlarged detector caverns were needed WRT civil construction. Superconducting magnets are the only solution for hadron machines at these energies.

The next machine, if built, will be a linear collider. The larger international effort plans to use superconducting RF cavities to accelerate electrons and positrons. http://www.linearcollider.org/cms/?pid=0
The smaller effort, CLIC at CERN, works with room temperature RF. http://cdsweb.cern.ch/record/188858/

ObsessiveMathsFreak, sure there’s an alternative: using weaker conventional magnets, paying more for electricity, and tripling or quadrupling the circumference of the LHC!

Expensive I know, but if managing superconducting magnets at this scale proves to be beyond our feasible capability, perhaps these measures should ultimately be considered when building the next big particle accelerator. Lost time costs money as well.