Virgo Logbook

AdV-SGD (FDS commissioning)

delauren, vardaro - 2:17 Wednesday 13 October 2021 (53468)

LO/BAB from FC MM: FC recovery

RECOVERY FC alignment after SQB1 recovery

GREEN recovery
1) SQB1_M1 to center FCEB_GR_cam (FC_IM off)
2) FC alignment with FC_IM and EM;
3) TEM00 max ~ 6.3 V on FCEB_GR_PD_DC when cavity locked.

IR alignment

1) reset ESQB1_M3 and M5 in the positions of Monday evening (11/10)
2) Beam spot search on the SQB1_cams and HD_cams by scanning in both directions SQB1_M21 and M22;
3) Clipping check by comparing power with and with out DL on PD_MONI and HD_PD1, supposing that PD1 was well aligned on DL.
    FIrst of all we deduced that PD_MONI is not well aligned, since when the reflection is maximum on HD_PD1 it is is minimum on PD_MONI and viceversa.
    So we look only to HD_PD1 to remove the clipping and with multliple iterations we scanned the SQB1_M21 and M22 to maximize the BAB TEM00 transmission
and then on EQB1_M3 and M5 to recovery the maximun in reflection on HD_PD1 and viceversa.
    In this way the power ratio measured on HD_PD1 (V) changed
    from 0.848 V (from DL) and 0.754 V (from FC) => 1.12 ratio [h 22.39 CEST 12/10]

    to 0.772/0.84=0.92 [h 00.24 CEST 13/10]

N.B: We set the SQB1_HWPs to have the maximum trasmission toward FC and toward EQB1 of the FC reflected beam.
-> MAX TEM00 measured on FCEB_IR_PD: SC~13 V; BAB~2.25 V.

At the end to measure the clipping after the we maximized the alignment on HD_PD1 with the HD AA*

Balancingof theLO-BAB power on HD (looking the power on HD_PD1 and PD_MONI)

FC out of RESENONANCE: AA on to align BAB from FC on HD_PDs

MAX VIS 23.41 23 UTC

VIS=visibility(4.34, 0.15,0.0033)

VIS = 0.9346

power on PD_MONI

BAB: 1.07 V mean
LO: 1.14 V mean

losses from FC path:

BAB_DL: 1.12 V => 5% losses from FC, in agreement with the observation that the BA seems clipped on SQB1_cams and on HD_cams and with the fact that we measure a difference of in power between the beam coming from DL and from FC ~5%

NEXT STEP for tomorrow: completely remove the clipping and PD_MONI alignment.

* (in mean time just to check we measure the VIS: h 22.44.42 UTC we check eben the visibility LO/BAB from DL (56%) [h 00.46 CEST HD_PD1_dark: 0.025 ; HD_PD2_dark= 0.0056 V])

We left the system in the following statu:

BAB power not maximum: ~1/3 max;
SC shutter closed
BAB out of resonance
DL off
LO on
VISIBILITY MEASUREMENT ON GOING

Images attached to this report

53468_1634083561_VIS_Schermata del 2021-10-13 02-03-02.png

Comments to this report:

vardaro - 13:33 Wednesday 13 October 2021 (53473)

The cavity remained locked until 3:05 UTC after this thime it was unlocked by the SQZ_FLT automation node. It was in down but it decided to exit by itself and go in the state for the discharge of the actuators. After this event the cavity was unlocked becasue the node come back in DOWN disabling the lock and the auto alignment loops. See fig 1.

In fig 2 a plot of the visibility before the unlock (~3 hours) and it remained constant.

Images attached to this comment

53473_1634124657_2021-11-13 - Unlock_by_automation.png

53473_1634124657_2021-11-13 - Visibility_night.png

delauren, vardaro - 16:15 Wednesday 13 October 2021 (53474)

Some more details of the yesterday shifts:

Waveplates

EQB1 HWP position to equalize LO and BAB: 109470
SQB1 HWP1 position to maximize the incoming beam toward FLT: 36297
SQB1 HWP2 position to send all the reflection back to EQB1: 82525
Final position of SQB1 HWP2 in order to have a weak transmission after SQB1 FI 83025

N.B in order to minimize the homodyne detection losses we had to change the polarization axis from poth the waveplates. To change polarization we have to do about 27000 steps whereas to change axis about 54000. The waveplates have a lot of hysteresys thus these number are not an absolute reference.

BAB and SC Mode contents:

Afrer the alignment of the cavity we checked the power of TEM 00, TEM 10 and TEM 20 of BAB and SC. During the measurement we realized that we had the cavity well aligned on SC and the SC and BAB not well superposed. Afrer the measurement we aligned the BAB into the cavity with IR_M3 and M5 then we aligned the SC into the cavity using SC_M1 and SC_M3.

We found the following results:

	BAB [V]	SC [V]	AOM SET BAB [V]	AOM SET SC [V]
TEM00	1.99	12.62	-0.0081	0.0676
TEM10/01	0.157	0.11	-3.63133	-3.555
TEM20/02	0.011	0.06	3.4652	3.541

Attached a plot of the AOM scan between -4V and +4V with SC and BAB shutter open.

We found the sidebands at the following AOM set:

SC Lower: -1.38 V (about 0.6V of transmission)
SC Upper: 1.51 V (about 0.6V of transmission)
BAB Lower: -1.952 V (about 0.12 V of transmission)
BAB Upper: 2.09 V (about 0.12V of transmission)

To be sure we need to check id the -1.952V and 2.09V sidebamds are due to the modulation of the BAB inside the AEI Box. We will check it soon by switching off before SC sidebands and after by switching off the SC itself.

Images attached to this comment

53474_1634133769_2021-11-13 - MM big.png

53474_1634133770_2021-11-13 - MM zoomed.png

bawaj - 0:50 Thursday 14 October 2021 (53482)

The automation was in the DOWN state where it checks for the suspension condition [FCEM_locked() function]. At 3:05 it detected a problem with the SBE actuator.

"2021-10-13-03h05m36-UTC>WARNING-SBE FCEM act2 out of range"

After that, the automation left the DOWN state and proceeded accordingly with the growing order of state numbers. Immediately next state after DOWN is the recently introduced UNLOCK state. This caused that the node re-entered DOWN automatically and unlocked the cavity. A side effect of this bug is that is leaves the automation node in a loop until the warning condition persists.

I corrected the "return None" to "return 'DOWN'" in the DOWN run() function to force metatron to behave in the desired way. Vpm automation process needs to be restarted to apply and test the solution.

bawaj - 0:44 Saturday 16 October 2021 (53515)

This evening I've tested the solutions proposed in the previous comment. Thanks to the unstable conditions of the cavity today, there were many opportunities to test abnormal behaviour of the cavity.
A the beginning I solved the issue spotted in the original post. The real problem was a decorator pointing to the unlock state but used to decorate DOWN.

I wrote several new functions to operate on the setf and inif:
repair_setf() - repairs the .set file in case the automation finds it empty (and stuck for this reason), finding .set is probable as it is automatically written by the automation;
read_setf() - reads the .set file truly by overwriting setf structure entirely;
read_inif() - reads the .ini file truly by overwriting inif structure entirely.
inif does not need repair.

I introduced a new section [Options] to the .ini file. It contains "automatic_discharge" parameter. If it is set to true (case sensitive) it performs integrators discharge in the unlock state.
This parameter can be modified on-the-fly when the automation is running. Unlock state will take the updated value in consideration while deciding if to discharge the integrators.

In the future any parameter included in .ini can be updated on-the-fly if the automation uses read_inif() correctly. If you introduce a new parameter please indicate in the comment if you wish it to be considered in this way.

Discharge is based on values stored in .set file. There are two new function to check the condition of this file:
setf_empty() - check if the file is filled with values (being repaired is not enough);
setf_old() - check if the file was updated more than one hour ago (interval to be decided).

At the end of the shift the AFC and BPC drift much probably due to the SQB1 in air and thus saturate their actuators. I leave the automation in down for the stability test.

vardaro - 23:50 Sunday 17 October 2021 (53527)

I left the automation in DOWN but I realigned and relocked the cavity. I also realigned the IR (vertical of SQB1 M21) the SC Transmission is about 10V whereas the BAB transmission is about 2V.

This operation is ended at 21:50 UTC