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Posts Tagged ‘installation’

The dice have been cast

Tuesday, September 23rd, 2008

This just came in from the CERN directorate:

LHC re-start scheduled for 2009

Geneva, 23 September 2008. Investigations at CERN following a large helium leak into sector 3-4 of the Large Hadron Collider (LHC) tunnel have indicated that the most likely cause of the incident was a faulty electrical connection between two of the accelerator’s magnets. Before a full understanding of the incident can be established, however, the sector has to be brought to room temperature and the magnets involved opened up for inspection. This will take three to four weeks. Full details of this investigation will be made available once it is complete.

“Coming immediately after the very successful start of LHC operation on 10 September, this is undoubtedly a psychological blow,” said CERN Director General Robert Aymar. “Nevertheless, the success of the LHC’s first operation with beam is testimony to years of painstaking preparation and the skill of the teams involved in building and running CERN’s accelerator complex. I have no doubt that we will overcome this setback with same degree of rigour and application.”

The time necessary for the investigation and repairs precludes a restart before CERN’s obligatory winter maintenance period, bringing the date for restart of the accelerator complex to early spring 2009. LHC beams will then follow.

Particle accelerators such as the LHC are unique machines, built at the cutting edge of technology. Each is its own prototype, and teething troubles at the start-up phase are therefore always possible.

“The LHC is a very complex instrument, huge in scale and pushing technological limits in many areas,” said Peter Limon, who was responsible for commissioning the world’s first large-scale superconducting accelerator, the Tevatron at Fermilab in the USA. “Events occur from time to time that temporarily stop operations, for shorter or longer periods, especially during the early phases.”

CERN has received similar words of support from several laboratories, including Germany’s DESY, home of the HERA superconducting particle accelerator, which ran from 1992 to 2007.

“We at DESY have been following the commissioning of the LHC with great excitement and have been very impressed with the success of the first day,” said Albrecht Wagner, DESY Director. “I am confident that our colleagues at CERN will solve the problem speedily and we will continue to support them as much as we can.”


Pixeling along, 24-7

Tuesday, August 12th, 2008

The LHC startup is getting closer and closer. A few previous blog entries already informed you that there was a successful insertion of beam into the LHC. This is of course great news, but means that the testing and final preparations of the detectors has now become serious business. As the CMS pixel detector was planned to be installed as one of the final components before the first beam was delivered, we are very much under pressure to be ready in time. The initial performance of the CMS forward pixel detector You can read that as ‘continuously on shift until things are stable enough to be run by non-experts’. This also explains the lack of blog entries by me and some of the other people working closely on the detector, at the moment the pressure is really on and the detector comes first!


Small Wheels Descend

Tuesday, February 19th, 2008

I fully and completely admit that I am a total sucker for heavy machinery. It is something I have in common with most four-year-olds. Take us to a construction site, feed us peanut butter and jelly sandwiches and we will be happy all day.

On that note, I couldn’t resist showing some pictures of the ‘small wheels’ being lowered. The small wheels are part of the Muon system. They are located between the end of the calorimeter and the toroid magnet end-caps. And they are the last big piece of the detector to be installed.

As the small wheels were assembled on surface, the first order of business is transporting the wheels to the ATLAS surface building. Fortunately CERN has many custom trucks for this kind of transport. Seen here one of the wheels is moved (very slowly) into the surface building on this massive, two-lane wide flat-bed truck. And this truck is just one of many in CERN’s armada of very cool transportation vehicles. These vehicles do contribute to frustrating local drivers, though. It is one of the interesting ‘features’ of the area. It is not uncommon, for example, to get stuck behind either some slow-moving tractor carrying hay or some slow-moving truck carrying a huge super-conducting dipole magnet.

Moving the Small Wheel

From the surface building, the wheel is lowered by the crane down one of the access shafts to the ATLAS cavern. In the picture, one small wheel is attached to the crane and suspended over the access shaft, while the second (in the foreground) waits its turn.

Small wheels at surface

So why do we call them small wheels? In this picture as the small wheel is lowered into the cavern, you can see one of its siblings, the ‘Big Wheel’ on the right. Small really is just relative.

small and big wheels


Down and Up Again

Tuesday, February 5th, 2008

The looming nature of ‘the closing’ has injected an increased sense of urgency into all those still working on detector installation. Since TileCal has been installed in the pit for several years now, you would think we would be exempt from such urgency. But no. In the past year or so, TileCal has undergone a campaign to repair some less-than-optimal components in our electronics. The front-end electronics for the TileCal are organized in long ‘drawers’ which can be pulled out from the ends of the calorimeter. We are replacing things like the power connectors which have been causing some problems over time. In the past year, we had the time and detector access to make these repairs so we decided not to wait for the problems to worsen.

There are 256 electronics drawers in TileCal so upgrading every single one is more than a day’s work. The drawer itself is almost nine feet long. It has to be removed from the calorimeter, lowered down to the floor of the detector cavern. On the floor, three electronics tables are set up where technicians can make the modifications. Once done, the drawer is tested, raised back to the calorimeter, re-inserted and re-tested.

One of the most difficult parts of this procedure is just getting the drawer from the calorimeter to the technician’s tables. There is no space to make the modifications right at the calorimeter so moving the drawer is the only solution. Furthermore, the scaffolding surrounding the calorimeter is accessible by ladders so we have to invent some creative ways to get the electronics drawers up and down the scaffolding.

One technique is to lower and raise the drawers through the access areas in the scaffolding. As seen here. The blue boxes at the top of the picture is the part of the calorimeter, where the electronic drawers are inserted. In the center of the picture, part of one of the drawers is being raised between two access ladders. This is delicate work. You don’t want to go banging your newly repaired electronic drawer against the sides of the scaffolding. And these are all custom-built electronics. It is not like you can go get a replacement at Radio Shack. On my former experiment, SNO, the electronics racks had signs reading, ‘Careful! These electronics cost more than your house!’.

raising a drawer

It is times like these where I really admire a technician’s patience. The pressure of ‘the closing’ is increasing, everyone knows that soon the scaffolding will come down, the collective heart rate has gone up several beats. But the technicians are never fazed and continue to raise the drawers with the same patience and precision as ever. They know better than anyone: you raise the drawer too fast, you will break it. We are in good hands with those guys.