(Alexa, Daniel, Sheila)
We just returned from EX and did a few things:
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Adjusted delay line for remote control
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toggled switches: 8, 4, 1, 1/8 --> 210 steps
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Adjusted phase on delay line to 115.3deg. We tried minimizing Q as best we could by adjusting the phase; however, we were not very sucessful since the arm was not staying well aligned
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Returned the modulation frequency to 24.407079MHz
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Took an open loop TF of the PDH. The UGF is about 5kHz with a phase margin of 70deg
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We measured shot and dark noise (data to come...). With ITM misaligned green REFL A PD read 6.2mW with 3V at 30dB gain.
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Measured an RF AM offset of 25mV at IMON with ITM misaligned. With ITM aligned, the error signal peak-to-peak was 1.9V out of IMON.
I have attached the matlab files for the PDH open loop TF, the shot noise, and dark noise. We need to remeasure the dark noise with more refined ranges.
Did you get an idea of how stable (or variable) the RF AM is? The pk-pk demod signal of 1.9 V corresponds to the cavity linewidth (for green), of about 3 kHz (at least to within a factor of 2). The RF AM of 25 mV thus corresponds to a frequency offset of about 35 Hz. If this is a static offset, it doesn't matter. If it varies at the level of 25 mV, it does matter, as we need stability of a few Hertz or less.