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One Week Down October 11, 2006

Posted by gordonwatts in physics.
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The Fermilab accelerator is down for a week. A power glitch caused one of the superconducting magnets (D3) to fail. The D3 magnet is very close to DZERO (we call DZERO “D0”). In order to replace the magnet they have to do something like the following:

  1. Warm up that section of the Tevatron to room temperature. It is currently at -269 C!
  2. Remove the dead magnet. These magnets must be about 30 feet in length, and then are in a large circular tunnel. And cart the magnet out of there.
  3. Truck the new one in, and connect it up.
  4. CAREFULLY align in. If the magnet is rotated as much as a degree about its axis the Tevatron wouldn’t even turn on. They talk about micro-radian tolerances. Lasers are used to survey the magnet’s new position and alignment (see this article in FermiNews, look for “Going for precision”)
  5. Cool down that section of the tevatron to 269 C. It takes about 2 days for this to happen.
  6. Re-tune the magnet lattice. This is physics-geek-speak for re-tuning the beam focusing elements to account for small differences between the old and new magnets and their positions.

It is sort of like having a telescope, and one of the many lenses breaks. So you replace it. But your focusing isn’t exactly as it was before because the new lens is slightly different, so you have to compensate. Only on the telescope they have one knob, and on the Tevatron they have 1000’s, and they are all inter-related. Cool!

It is a good thing this happens rarely. I’m not sure when the last magnet failed; I bet it was close to a year ago.

I couldn’t locate a schematic of the magnets for the Tevatron on the web. Anyone know where to look?

What caused this? The rumor mill has it a rat ate through a power cable. The price one pays having an accelerator in the prairie, I guess!

Comments»

1. More Downtime « chi c’e’ in ascolto - October 21, 2006

[…] I’m on shift this week. I started yesterday and I’ll go on until next Thursday. Seven days, 8 hours from 8.00AM to 4.00PM in the noisy CDF control room. The Tevatron is still down but the hope is for Tuesday to start seeing collisions again. In the meanwhile a whole bunch if things get fixed, accesses are performed on the detector and cosmic runs are taken (we use naturally occuring cosmic rays to test the our instruments anyway). There are three shifts a day, and this is the first time I’m on “day shift”. I usually pick the “owl shifts” the ones from midnight to 8.00AM, which are the quieter and give me the possibility to enjoy the best part of the day (morning!) with no work-related activities. By the end of the week of course my social life is reduced to zero (since I go to sleep at 2.00PM) but, especially in Summer, it is a nice break from the usual routine. Not this time, though, when I ended up on day shift and I didn’t find a suitable swap for an owl shift. Oh well! […]


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