time reversal

the stories of four physicists separated by the whims of fate

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The Black Dewar

June 17th, 2009 by liz

Almost exactly 3 months ago today I posted that I started taking apart my cryostat to refurbish it and make it bad-ass. It’s finally done, and it works really well. I can optically test 160 detectors at a time at 250mK. I presented the preliminary tests from our first optical cold run at our collaboration meeting today, and people seemed pretty excited about my new test setup. This is the first time that I’ve really built something like this from the ground up–I had to do everything from modifying electronics to wirebonding to machining to messing with control software. Making the setup really nice has paid off too. As I’m sitting here in this meeting in Chicago, I’m running experiments back in Berkeley from my laptop.

Below is a picture of the setup, and a plot of the differential detector response to my cold load (3.6 K vs. 11 K cold load temperature). The lower 1/3 of the array is dark, so we can calibrate out any changes in cold stage temperature (which is where the wedge sits). You can see that the load isn’t as big as the array, so the response is higher in the middle where the bolometer sees more of the load, and falls off as you get towards the edges. Soon, I’ll put in a filter stack and we will be able to look at things in the room, like a Fourier transform spectrometer.

The black dewar with readout electronics and fridge controller.

Response of a wedge of detectors to a cold load.

This wedge was tested at pole, so we’re going to compare it to 4 new wedges that Erik made before he left to winterover to decide which of them (if any) will be good enough to put in the receiver next season on the South Pole Telescope. Wooo! My experiment works!

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