I am on shift today, here in building 5 (the SLAC accelerator main control center, or MCC). I am filling the shift position referred to as “liaison”, and my job is to make sure that the experiment (Babar) know’s what the accelerator (LINAC and PEP) is doing, and vice versa. The Babar experiment is housed in a submerged building about 1/2 mile from MCC, where the accelerator is operated. Traditionally, one avoids miscommunications between the two bodies by having a liaison sit in a common place and pass information.
The liaison shift was “done away with” a while ago by Babar, since operations of the accelerator and detector had become so routine as to make the role obsolete. But at times like this one, when we are restoring the experiment to running condition after 8 months of down-time, the laision serves a vital role as people on both sides tackle independent sets of non-standard problems. So, here I am!
Being in MCC at startup time is really the best damn shift. There’s tangible emotion hanging in the air as the accelerator physicists and the machine “operators” work as a single living organism to restore the collider. It always starts a little slow – a magnet problem here, a water leak there, a feedback problem – but as the dominos start to fall faster and faster the excitement reaches a frenzied pace. This always ends with PEP breaking a luminosity record. That means they exceed the maximum number of particle collisions per second, per square-centimeter, that they had previously achieved. Sometimes this is only by a little, but the great days are when they not only shelve the old record, they tear down the down the house around it.
It’s pretty quiet right now. There are techs all over the site (on a Sunday!) addressing the nagging issues for the accelerator. Babar, too, has its fair-share of startup issues. We typically shakedown the detector by running our cosmic ray trigger, but this is only possible when beam isn’t in the machine. Right now, however, we have electrons coursing through the machine, with positrons to soon follow. This is a great time for a high-energy physicist, when the two hands of the acccelerator are getting ready to clap.
Which brings me to my final thought. As a child, there were always logical nonsense problems that were brought to my attention. For instance, “What is the sound of one hand clapping?”.
It’s the muted cheer from the operators and the physicists, when the electrons alone make their first hundred turns around the collider ring, that is the sound of one hand clapping.
