aLIGO LHO Logbook

H1 CAL (CAL)

travis.sadecki@LIGO.ORG - posted 17:43, Tuesday 18 October 2016 - last comment - 12:58, Monday 24 October 2016(30642)

PCal X and Y OFS Optimization

Rick, Evan G., Travis

As part of the bi-annual PCal maintenance, today we optimized the drive range of the PCal OFS for both end stations. The procedure for this was:

1) Turn off PCal lines and inject 10 Hz sine wave.

2) Break the OFS lock.

3) Note that the AOM drive is large (~1.5V) with loop open.

4) Adjust the offset in 1V steps to find the maximum OFS PD output.

5) Record max OFS PD output.

6) Close shutter and record minimum OFS PD output.

7) Set offset to half of 95% of max OFS PD output.

8) Find amplitude of injected sine wave that give us the maximum p-p OFS PD voltage.

9) Record magnitudes of carrier and sideband frequencies of the OFS and TX PDs.

Results:

PCal X:

Max OFS PD out = 10.5 V

95% of Max OFS PD out = 10 V p-p

OFS PD output with shutter closed = -0.01 V

Offset set to 5.00 V

64000 cts. peak is maximum - > ~10V p-p

Harmonics:

OFS PD

carrier 14 dB

1st SB -42.7 dB

2nd SB -43.5 dB

TX PD

carrier -234 dB

1st SB -294 dB

2nd SB -291.1 dB

Max modulation at 90% of this value - > 57,000 cts. PEAK (out of 64000 cts.)

PCal Y:

Max OFS PD out = 7.9 V

95% of Max OFS PD out -> 7.5 Vp-p

OFS PD output with shutter closed = -0.01

Offset set to 3.75 V

49000 its peak is maximum -> ~7.5V p-p

Harmonics:

OFS PD

carrier 11.75 dB

1st SB -67.4 dB

2nd SB -56 dB

TX PD

carrier -230.2 dB

1st SB -294.5 dB

2nd SB -295.1 dB

Max modulation at 90% of this value - > 44,000 cts. PEAK (out of 49000 cts.)

Comments related to this report

travis.sadecki@LIGO.ORG - 10:28, Wednesday 19 October 2016 (30655)

Link

As the final part of the maintenance for PCal Y, we took a transfer function of the OFS. See attached traces.

Images attached to this comment

evan.goetz@LIGO.ORG - 12:58, Monday 24 October 2016 (30802)CAL, INJ

Link

The limit on the excitation amplitude is total number of counts that should be allowed to be sent to the Pcal. This is a frequency independent value. So for Pcal Y, the the maximum in H1:CAL-PCALY_EXE_SUM should be no larger than 44,000 counts. For Pcal X, the total of H1:CAL-PCALX_EXE_SUM and H1:CAL-PINJX_HARDWARE_OUT should be less than 57,000 counts.

Right now, Pcal Y has the following injections set:

Freq. (Hz)     Amp. (cts)
-------------------------
   7.9         20000.0
  36.7           750.0
 331.9          9000.0
1083.7         15000.0
-------------------------
Total = 44750.0

This is just above the threshold. It might be worth returning the 331.9 Hz line to O1 level (see LHO aLOG 30476 for the increased amplitude lines) since the detector noise in this region is recently improved.

Pcal X has the following injections set:

Freq. (Hz)     Amp. (cts)
-------------------------
1501.3         39322.0

And CW injections on the Pcal X are totaling ~1585 counts giving Total = 40907.