Reports until 14:56, Monday 14 April 2014
H1 ISC
alexan.staley@LIGO.ORG - posted 14:56, Monday 14 April 2014 - last comment - 13:50, Thursday 17 April 2014(11329)
IMC VCO changes

(Alexa, Daniel)

 

We added an FDD in the IMC VCO path (currently borrowed the ALS DIFF FDD). In doing so,  we have reduced the signal by a factor of 10. We adjusted the MC common mode board fast gain to 14dB from the original -6dB. The MCL-MCF Crossover is still the same (UGF: 14.7Hz w/ 39 deg phase margin). I have attached a DTT plot with the current crossover and a reference taken on 03-17-2014. We have also adjusted the gain in the IMC_F filter to be 0.1 to account for the reduced VCO DC gain. We remeasured the IMC_F noise as done in alog 5311; the results are suffeciently consistent (see second DTT image; DTT is saved uner my public directory). Finally, we measured the IMC OLTF; the UGF is 31kHz with a phase margin of 38deg (close enough to the nominal UGF: 53kHz, 45 deg phase margin). The data and plot are attached. 

 

I have placed an IFR below the 79Mhz RF source on the ISC C4 Rack. The IFR is set to 78.95MHz with an RF level of 10dBm and is now used instead of the RF source.

 

We are waiting for the x-arm to test if the 1/f noise has actually decreased with these changes...TBD.

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alexan.staley@LIGO.ORG - 13:50, Thursday 17 April 2014 (11412)

(Alexa, Sheila)

This alog is refering to work done yesterday...

We have reverted to the nominal configuration, i.e. no FDD for the IMC VCO and we are using the RF source at 79.2MHz again.