The summer is flying by too quickly! The “12-week” shutdown of the Fermilab accelerator complex is about 2/3 complete – here’s an update on the Tevatron maintenance.
In an earlier post, I wrote we needed to warm up 6 “houses” to room temperature to fix leaking components. Well, after technicians did some more leak-checking in the first week of the shutdown, it looked like we needed to warm up 2 more houses! Fortunately, we discovered one of those extra houses had an “outside air leak” that was readily repaired by applying some epoxy on a thin pipe to prevent air from getting in – no need to warm up that house! Unfortunately, during the repair of an outside air leak on another (still cold) house, too much air got sucked into the beampipe and froze on the 80 degK surface. That house had to be warmed up to melt the iceball. You win some, you lose some.
Overall, I think the work is going rather well. Six houses have been warmed up, another is on its way to 300 degK, and one last (I hope) house is still on the schedule. Of the six warmed-up houses, one has been repaired and already cooled back down to liquid nitrogen temperature 80 degK. Three more are ready for cool-down – hopefully they will be cold next week. So far, only 1 of the leaks was internal to a magnet that required replacing the entire component. The others have been fixed by replacing valves or seals accessible from the outside of the magnets. In addition, no new electrical problems developed during the warm-ups. It’s good news that the techs have only needed to fix the problems we expected and not any new ones that cropped up along the way.
The survey and alignment group has unrolled over 60 Tevatron magnets to bring them back within our desired tolerance of < 1mrad. Eight magnets need new stands since they can no longer be adjusted properly for alignment.
All in all – the shutdown work has been proceeding smoothly. Five weeks from now, I hope we are recommissioning a leak-free, well-aligned Tevatron. We will be pulling our own long shifts tuning up the machine with beam to return to normal operation providing high-luminosity proton-antiproton collisions to the CDF and D0 experiments!