Modification of the calibration lines around 60 Hz and 355 Hz + addition of calibration lines with PCal
This is done in order to have frequencies multiple of 0.125 Hz to test Hrec with lower latency (test will be done with shorter FFTs of 8 s)
13h55 UTC, restart of CALnoise and update of the Hrec configuration
BS | WE | NE | PR | WE_PCAL | NE_PCAL |
35.0 | 36.5 | ||||
61.0 | 61.5 | 62.5 | 63.0 | 60.5 | 63.5 |
356.0 | 356.5 | 357.5 | 358.0 | 355.5 | 359.0 |
A small line at 1012.5 Hz has been added to NE and WE calibration signals. Its amplitude have been set to be seen in SC_MIR_Z_CORR channel, but not in DARM. The goal is to monitor the injection path from Acl the to DSPs (in particular the delay) without being seen in DARM. This line will be monitored by the process TFMoni.
Injections with the PCals
PCal at NE and WE switched on at 14h10 UTC, with their three calibration lines. Note that their frequencies will be updated in the coming months for h(t) monitoring purpose.
On the NE and WE cameras, the small PCal beam spot is visible close to the center of the mirror when the main beam is switched off. The bright spot seen on top-right is an image of the PCal injection bench due to diffuse PCal light (1047 nm).
- 14h25 start some injections of lines with PCal and then with end EM actuators (this will be analysed to calibrate the EM actuators with respect to the PCals) (10 Hz to 200 Hz)
- 14h35 start injections from 10 Hz to 500 Hz
- 14h40 start injection of a single line around 80 Hz to compare results with previous measurements where a series of lines were injected
Note: NE PCal photodiode was not switched on during the measurements. Only the WE injections can be analyzed.
More usual calibration injections
- 14h45 to 15h measurement for calibration transfer from mirrors to marionettes.
- 15h manual unlock.
- 15h02 measurement of CAL to Sc delays.
- 15h05 start to relock with NI, WI relays kept closed in HP mode. We had some issues with "SSFS synchro", which was probably resulted from the LNFS being free. It worked once Julia had relocked the LNFS on the timing system. ITF relocked around 16h25 UTC.
- 16h35 to 17h measurements for calibration transfer from input to end mirrors.
- Manual unlock
- 17h20 : Tune B1p phases at 6, 8 and 56 MHz and start free Michelson measurements.
Remarks
- Suspension DSPs: the delays from the CAL channels generated by Acl to the Sc channels sent back by the DSPs are the same for all the mirrors (714 µs) as expected. But they are all different for the NE, WE and BS marionettes (between 980 and 1200 µs) while there where all the same at 915 µs in the past. Something wrong is probably on-going on the injection path to the marionettes.
- There is still aliasing of the CAL channels into the Sc channels (see Sc_NI,WI,BS_MIR_CORR around 17h27 UTC)
- Around 15h30 UTC, we found that the Vbias of PCAL_NE_PD2 had the wrong sign and fixed it. This is related to the replacement of the photodiode made during last week (6_9 August) to investigate the presence of a lot of 50 Hz lines in this photodiode. It is the same with the new one, so we will have to continue investigation. The offset of this channel must be retuned.