time reversal

I’ve written about my numerous adventures here, but I haven’t really explained what it is that I’m actually doing here in Berkeley, and how it is that I have so much time to explore California. First of all, I’m working in the Experimental Cosmology Group at UC Berkeley under Professor Holzapfel. Right now, one of the grad students is making new bolometer arrays (detectors), and I’m testing them to see if they meet our performance standards for the South Pole Telescope. We then send what we think will be good detector wedges (based on these initial tests) to some of our collaborators for full characterization. In three weeks, we’ll take all the wedges that we think will work well based on all of our testing, and bring them to the South Pole. There, we will install them on the focal plane of SPT, where they will replace some of this season’s detectors. Sounds simple enough, right?

It turns out that the detectors, and more importantly the SQUIDs that we use to read them out, can be finicky little beasts. This results in some extremely late nights in lab trying to make the system behave and give me my data. However, there is an upside: all of our testing is done at ~250 mK, which is very cold. We use a closed cycle cryostat and a 10He fridge to get everything this cold, and from the time I hit the “on” switch until the time it is cold enough to start the first fridge cycle is about 52 hours. From the time I start the first fridge cycle until I can start setting up for experiments is about 6 hours. If I can find someone to kindly start the first fridge cycle for me *coughundergradminion* that leaves me almost 3 whole uninterrupted days during every test cycle of about 1.5 weeks to enjoy sunny warm California.

Ahhh science.

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