Background: We previously took scavity scans with Ring Heater on to determine level of astigmatism in the cavity. For those results, see https://logbook.virgo-gw.eu/virgo/?r=66742
This measurement
In this measurment, I report on data taken with the ring heater off. First, I took a standard stretch of data with the cavity aligned. Then, I misaligned the cavity with a set of predetermined alignments (from Jerome Dellagaix). Using the method of Clément Jacquet, one is able to determine the angle of the astigmatism.
The system was in the NARM metatron node in "down" and the ALS_NARM metatron node in LOCKED_REALLOCATION. The relevent channels were:
- LSC_ALS_NARM_SET This is the setpoint that I was actuating on to measure the cavity scan
- SC_NI_MAR_Z_CORR, this is the longitudinal correction signals. This should follow cavity motion
- LSC_B7_DC, this is the PD in transmission that we use to take data
- SC_NE_MAR_TX_50Hz this is the readback of the angular actuator in pitch. The low passed 1 Hz value I refer to as MAR_TX
- SC_NE_MAR_TY_50Hz this is the readback of the angular actuator in yaw. The low passed 1 Hz value I refer to as MAR_TY
All times are local. The procedure was:
- After each measurement, unlock green, lock IR
- Wait for MAR to stablize
- Lock green, unlock IR, move to locked_reallocation
- Apply offset
- Start scan
The scan was always run with 10 iterations, vFSR=2, offset=0.7 and timescan = 120.
| Time | Action | MAR_TX | MAR_TY | ||
| 19th May | |||||
| 07:39 | Lock achieved on IR | Not recorded | Not recorded | ||
| 08:27 | Lock on green, run 10 scans "aligned" | N/R | N/R | ||
| Lock cavity on IR, wait for B7 power to stablize | |||||
| 09:23 | Lock on green, run 10 scans "aligned" | ||||
| 10:05 | Lock on IR, wait for alignment to stablize | ||||
| Lock on IR, alignment stablizes to | -107.92 | 46.54 | |||
| 10:49 | Add 0.5urad TX | -107.45 | 46.57 | ||
| 10:50 | Scan finishes | -107.45 | 46.45 | ||
| 11:33 | Lock on IR | -107.95 | 46.61 | ||
| 11:38 | Add 0.5 urad, TY | -107.92 | 47.11 | ||
| 11:38 | Run 10 scans | -107.92 | 47.11 | ||
| 12:20 | Scan ends | " | " | ||
| Lock on IR | -107.81 | 46.67 | |||
| Lock on green, MAR moves slightly during acq. | -107.92 | 46.65 | |||
| ty=+0.35urad, tx=+0.35urad | -107.57 | 46.98 | |||
| 12:24 | Run 10 scans | ||||
| 13:09 | Scan ends | -107.57 | 46.99 | ||
| Relocked on IR, MAR stabilized | -107.88 | 46.42 | |||
| 13:23 | ty=-0.35urad, tx=+0.35urad; begin scan | -107.58 | 46.14 | ||
| end | -107.57 | 46.15 | |||
| Lock IR, MAR stabilizes | -107.91 | 46.75 | |||
| ty=+0.25urad, tx=+0.43urad & begin scan | -107.46 | 46.82 | |||
| 20/05 | |||||
| ~14:00 | Lock on IR | ||||
| 14:12 | Green lock achieved, | -110.00 | 47.38 | ||
| ty=+0.43urad, tx=-0.25urad | -110.26 | 47.79 | |||
| 14:15 | Scan starts | ||||
| 14:50 | Scan finishes | -110.26 | 47.82 | ||
| 14:56 | IR Lock | -109.96 | 47.49 | ||
| 15.02 | Green lock, ty=+0.13urad, tx=+0.48urad, start scan | -109.45 | 47.64 | ||
| 15.43 | measurement finished | -109.46 | 47.62 | ||
| 15.44 | IR lock | -110.10 | 47.55 | ||
| Green lock, MAR moves slightly | -110.03 | 47.54 | |||
| ty=0.48urad, tx=-0.13urad | -110.16 | 48.01 | |||
| 15:50 | Start last scan | -110.16 | 48.01 | ||
| 16:46 | End final scan | -110.16 | 48.01 |
Next steps: Clément Jacquet will analyze the data, using his method in https://git.ligo.org/virgo/osd/optchar/-/tree/master/Code_FSR_scan_CJacquet?ref_type=heads