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I was going to lock MICH, but I don't see anything on dataviewer for either AS55Q or ASDC. I went out onto the table, and there is beam on the diode, but no mV out on a voltmeter connected to the DC monitor point. I shine a flashlight, and still I see 0.0mV. So, something is up with AS55, but since the michelson is aligned right now, I'm not going to mess with the PD. I won't lock MICH, I'll just move on. Koji is taking a look at the diode, but if he doesn't get it figured out tonight, we can take a closer look after we pump down.
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Never mind. I was using an LED flashlight, which doesn't emit light that the PD is sensitive to. A regular flashlight gives plenty of signal on the DC out.
Using an SR560 with 30Hz low pass and gain of 100, it was pretty easy to align the light on the PD.
Koji calculates in his head that there is about 6 microwatts of light incident on the PD, which is not a lot of light. Our SNR may be kind of lame for locking right now. |