The Resonaances blog has a report from Planck 2009 on a talk about the status of the LHC. The slides of the talk explain the problems with training quenches that have necessitated initially running the machine at 5 TeV per beam instead of the 7 TeV design energy. They also explain the analysis of what caused the accident last September: bad soldering of the interconnections between copper bus-bars connecting the magnets.
There has been an ongoing campaign to check the quality of the interconnections by careful measurements of the resistance, with slide 44 noting:
Ongoing race to identify and repair faulty joints. Unfortunately poor quality joints are localized in many places – likely to slow down progress with the machine re-commissioning.
It remains unclear exactly how many joints will have to be opened up and repaired, and what impact that will have on the re-commissioning schedule. While this remains to be decided, the latest draft schedule I’ve seen has about 1-2 weeks of slippage from the current official schedule, with powering tests on all sectors not finished until the first week of October, whereas the official schedule now envisages first circulating beam the week of September 21. The Planck 2009 talk just says “Beam commissioning scheduled to resume in September or October 2009”.
For some misinformation about the LHC schedule, see here.
“It remains unclear exactly how my joints will have to be opened up and repaired”
Get well soon!
Thanks roland, my joints are now fine and the posting is fixed…
So what is the difference between “beam commisioning” and “circulating beam.?
My understanding of the terminology is that beam commissioning starts when they first try and circulate a low energy (450 GeV?) beam around the ring. They got this far last year. From there, one has to get stable circulating beams in both directions at high energy (4-5 TeV), get them to collide, and get the luminosity in each beam up to a usable level. This is scheduled to take a month or so.