No, no, no – the world isn’t coming to an end – just summer and the Fermilab shutdown!
The daylight hours are noticeably shorter, my kids have been back to school for over 1 week, and I wore my long Sporthill pants on an early morning run this week (it got down to 42 degF in Batavia). Sigh…although it was a cool summer here, it was still summer. I wish I were still on the beach.
The shutdown work is wrapping up, too. The last 2 Tevatron houses that were warmed up for repairs are cooling back down to 80 degK. Hopefully the cooldown of the whole ring to 4 degK can begin soon afterward. Although the Main Injector may not be able to deliver us any beam until late next week, I would like to get the Tevatron cold as soon as practical so we can begin powering the superconducting magnets fully to look for any electrical problems. We have already begun “conditioning” the electrostatic separators used the kick the proton and antiproton beams onto different orbits such that they collide only in the centers of the experiments. Conditioning them means running them at higher voltages than usual (and maybe causing some electrical discharges, not unlike drawing a spark when dragging your feet on a carpet and then touching a metal object on a dry winter day) so that they will less likely to do that at the slightly lower voltages used for regular operation. There is plenty of preparation and check-out work to be done without beam.
We’ve also been making plans for the needed studies once we get beam. The machine won’t be quite the same as it was before the shutdown; although we haven’t made any significant changes, unrolling > 90 magnets will cause some minor changes that we’ll need to understand when tuning up. Once beam is available, Tevatron experts will be taking shifts in the MCR (Main Control Room) 24 hours a day taking data, implementing changes, and verifying all systems are functional for colliding-beam operation. We estimate it may take 5-7 days of shift work to recommission the Tevatron before returning to regular operation. Perhaps we will try a low-luminosity proton-antiproton store ~3 days after we first get beam to check our progress and to allow the CDF and D0 experiments to test their detectors after 3 months without collisions. They did plenty of work on their systems, too, during the shutdown, so they need time to make sure they are ready to handle efficiently all the collisions we give them. After that first colliding beam store, we will evaluate it, get feedback from the experiments, and continue tweaking the machine for a day or two before trying another proton-antiproton store. Once we’re satisfied, we’ll stop taking shifts and let the MCR crews get back to putting in the stores themselves. The start-up can be a gradual process because it takes all the machines some time the return to their peak performance and hopefully beyond!
I’m looking forward to having a smoothly running accelerator complex in a few weeks so the experiments can get back to collecting lots of data for their physics analyses!