Chamonix For You

The 2009 Chamonix workshop on the commissioning of the LHC has just finished, ending with a message from the Director General, and the opening to the public of the web-site with slides from the meeting (bearing the warning “The Chamonix workshop was an open exchange of views and opinions. All the presentations made at the workshop are available here. The views expressed in individual presentations do not necessarily represent those of the CERN management.”)

Here’s the press release and message from Rolf Heuer:

Many issues were tackled in Chamonix this week, and important recommendations made. Under a proposal submitted to CERN management, we will have physics data in late 2009, and there is a strong recommendation to run the LHC through the winter and on to autumn 2010 until we have substantial quantities of data for the experiments. With this change to the schedule, our goal for the LHC’s first running period is an integrated luminosity of more than 200 pb-1 operating at 5 TeV per beam, sufficient for the first new physics measurements to be made. This, I believe, is the best possible scenario for the LHC and for particle physics.

There were discussions in Chamonix between accelerator and detector physicists on several important issues. Agreements were reached whereby teams drawing from both communities will work together on important subjects, such as the detailed analysis of measurements made during testing of magnets on the surface.

Since the incident, enormous progress has been made in developing techniques to detect any small anomaly. These will be used in order to get a complete picture of the resistance in the splices of all magnets installed in the machine. This will allow improved early warning of any additional suspicious splices during operation. The early warning systems will be in place and fully tested before restarting the LHC.

Another important topic for the future was the radiation hardness of electronics installed in the service areas and the tunnel. For many years, particle detector electronics have been designed to cope with events such as loss of beam into the detectors. Until now, this has not been necessary for the accelerators, but will become so when the LHC moves to higher beam intensity and luminosity. Again, with detector and accelerator physicists working closely together, the experience gained from the detectors can be applied to the LHC itself.

As the Bulletin reported on 30 January, opening up a magnet in which an anomalously high electrical resistance was measured made the reason for the anomaly immediately obvious – a splice had not been correctly made. This is one of two such splices that were identified in the five sectors tested, and as a result the magnet containing the second will also be removed from the tunnel for repair. Since resistance tests can only be conducted in cold magnets, three sectors remain to be tested: sector 3-4 where the original incident occurred and the sectors on either side. Within sector 3-4, the 53 magnets that are being replaced in the tunnel will all be tested before cool down, and the sectors either side will be cooled down early enough to intervene if necessary with no impact on the schedule. This leaves around 100 dipole magnets that we’ll not be able to test until September and a correspondingly small chance that we may find further bad splices that will need to be repaired before operation.

The Chamonix workshop involved a lot of work by many people. Much progress has been made, and the management now has all it needs to make an informed decision next Monday on LHC restart. I’d like to thank all those involved, and I will be writing to you again early next week to let you know our decision.

Looking at a few of the slides, it seems that the schedule for work this year has slipped, with the current plan that the machine will be cold in August, checkout in September, with powering tests in Sector 34 taking place in parallel with the checkout, which will end the third week of September. Beam commissioning will not be able to start until then, and the assumption has been that it would take two months to commission the beam and begin collisions for physics. If first collisions are not until late November, it’s clear why they want to run over the winter. The main consideration evidently is cost, they will have to come up with 8 Million Euros more for more expensive power.

This assumes not all sectors are warmed up. Warming them all up to install the quench protection they would like would add another 5 weeks to the schedule.

Update: CERN has a press release today confirming the new schedule:

The new schedule foresees first beams in the LHC at the end of September this year, with collisions following in late October. A short technical stop has also been foreseen over the Christmas period. The LHC will then run through to autumn next year, ensuring that the experiments have adequate data to carry out their first new physics analyses and have results to announce in 2010. The new schedule also permits the possible collisions of lead ions in 2010.

The decision was made to go ahead while installing additional relief valves in the four sectors that have been warmed up, leaving installation in the four remaining sectors for next year.

Update: There was a talk today at CERN by Lyn Evans on LHC status and future plans. The current plan for upgrading the LHC luminosity involves a “Phase I” in 2013 that would double the luminosity, and an upgrade of the accelerator complex that would be completed in 2017 and allow further luminosity increases.