I sit here at the SLAC Surface Control Center for EXO. I was originally supposed to be at WIPP right now, but I recovered slower than anticipated from a minor wrist surgery. This week is my first shift – I had avoided taking the owl shift up to now since I didn’t have daytime experience. With no WIPP trips on the horizon, it became time to bite the bullet. During the day there is a group of people at WIPP and a supervisor at SLAC. During the night there is just one shifter at SLAC. And right now, that is me.
The SLAC surface control center.
I was a bit nervous the first night – with 8 screens of data (and hundreds of channels to plot) it was quite overwhelming. I’ve worked very little with the cryogenic systems and xenon systems, so everything was unfamiliar to me. While I would be by myself, it was supposed to be fairly easy (even boring). The evening shift would put the system into a stable state and then I would just have to monitor to make sure nothing goes wrong.
As you can imagine, things went wrong. Around 1:30 AM our pump stopped. I didn’t know at the time what went wrong – I just saw a bunch of the numbers I was watching suddenly change. I called one of our co-coordinators and she had me shut down the pump. Luckily, this is not a problem on the scale of the magnets at CERN quenching. This pump circulates xenon in the system between the condenser and heater. The condenser and heater do the work of keeping our pressure constant by balancing the amount of liquid and gaseous xenon in the system.
This actually ended up being a great experience. I made many plots trying to understand if anything had happened before the pump failed. I looked for evidence that the system was warming up or becoming unstable. I learned a lot about our system! I’ve now had a few quiet nights, and then there really isn’t anything interesting to plot and learn about. The next shift that went into WIPP checked the pump and it had simply been a screw failure – something easy to fix. So in the end, I learned a huge amount about our experiment, the collaboration learned about a mechanical weakness, and we learned that the system could sustain itself without the pump. The xenon levels didn’t drop after the initial failure and later the system started filling itself. Few night shifts are that exciting!
The desk of power
