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[Koji, Manasa]
We looked at the MC modulation frequency on the spectrum analyzer and observed beat notes between MC modulation freq (29.5MHz) and modulation frequencies (11.06 MHz and 55.3MHz).
Beat notes were suppressed by changing the carrier frequency from 11.065910 MHz to 11.066147MHz.
Detailed discussion and data will be posted in the next elog.
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The goal was to tune the carrier modulation frequency, f1 ~ 11.06 MHz to match the FSR (c/2L) of the MC. (Reference to the technique: R.G.DeVoe et al., PRA 30, 5, Nov 1984)
We looked at the MC_REFL output on the spectrum analyzer. Since the MC FSR was not well matched with the carrier modulation frequency, we observed significant beat notes at the following frequencies (fMC-f1), (fMC+f1), (fMC-f2) and (fMC+f2); where fMC (the MC modulation frequency) = 29.5MHz, f1(carrier modulation frequency) ~ 11.06MHz and f2 ~ 55.3MHz. The carrier modulation frequency was changed at the frequency generator until these beat notes were suppressed i.e. until the cavity FSR matched the carrier modulation frequency.
The plot below shows the MC spectrum after the beat notes were suppressed.
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