aLIGO LHO Logbook

H1 ISC

daniel.sigg@LIGO.ORG - posted 11:45, Tuesday 20 June 2023 - last comment - 13:52, Thursday 22 June 2023(70610)

REFL_LF Whitening Improved

The DC routdout of the 2 LSC REFL RF detectors were ADC noise limited above ~200Hz. Today we improved the whitening filters to give us 10x higher gain above 30Hz.

In detail: D1102079, R20s were changed to 499Ohm from 1.58kOhm to extend the whitening filters from 1:10 to 1:30. Channel 4 was modified in ISC-R4 (LSC-REFL_A), and channel 2 in ISC-R1 (LSC-REFL_B).

Serial numbers:

	Old	New	Channel	Modified
ISC-R4	S1200460	S1200450	LSC-REFL_A	Channel 4
ISC-R1	S1200450	S1200452	LSC-REFL_B	Channel 2

The LSC model was modified to add the average of the 2 REFL RIN channels: LSC-REFL_RIN = (LSC-REFL_A_RIN + LSC-REFL_B_RIN) / 2.

Comments related to this report

jeffrey.kissel@LIGO.ORG - 13:52, Thursday 22 June 2023 (70732)CDS, FRS, ISC, SYS

Link

Quick links as an add-on to the documentation:
Chassis assembly drawing which Daniel cites: D1102079
Actually sub-assembly board drawing to which "R20" exists: D1102060 -- see page 3.

e-Traveler information on the serial numbers of these aLIGO LSC RFPD Interface chassis (not the of the board that's actually changed)
    S1200450
    S1200452

Work permits for the changes:
    WP 11272 -- electronics change
    WP 11273 -- front-end model changes

Measurement results that were possible as a result of these changes: LHO:70611.

My interpretation of verbal conversation with Daniel on 2023-06-22 about those measurement results: "Improving the electronics didn't seem to help making the measurement better, but I'm not going to revert it 'cause its doesn't matter whether it's in or not. #somewords #somewords L1 doesn't care about this. (a) This is a standard whitening chassis used for almost all ISC PDs, so we're not going to change the generic drawing, and (b) other than the OMC DCPDs [which have their own whitening design], most ISC PDs are not shot noise limited, so this change wouldn't help them."

Or something.

The above e-travelers on this particular whitening are therefore the sustained documentation about this deviation from design.