LightMon monitors the light in the interferometer arms by way of the normalized light leaking through the end test masses to quadrant photodiodes (QPDX, QPDY). The raw sum of the currents from the four quadrants is called QPDX_DC, e.g., H1:ASC-QPDX_DC. Separate channels, LA_PTRX_NORM and LA_PTRY_NORM, e.g., H1:LSC-LA_PTRX_NORM are rescaled versions of these channels, where a value of 1 indicates the light leakage measured during lock acquisition, when neither the arm nor the recycling cavity is resonant. When the interferometer fully resonates at high power the normalized value is O(1000-2000).
LightMon's main purpose is to create the following data quality flags based on the arm light:
OUT_OF_LOCKThis is set when either of the transmitted light values falls below 100.
PRE_LOCKLOSS_10_SEC PRE_LOCKLOSS_30_SECThese are set for the period of N (=10,30,60,120) seconds preceding a lock loss.
PRE_LOCKLOSS_60_SEC PRE_LOCKLOSS_120_SEC
LIGHTDIP_01_PERCENT LIGHTDIP_02_PERCENTThese are set for any 1-second interval for which the minimum of the average measured arm powers is XX (=1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20) percent below the average minimum powers over the last 10 seconds (excluding seconds containing already identified dips).
LIGHTDIP_03_PERCENT LIGHTDIP_04_PERCENT
LIGHTDIP_05_PERCENT LIGHTDIP_06_PERCENT
LIGHTDIP_07_PERCENT LIGHTDIP_08_PERCENT
LIGHTDIP_09_PERCENT LIGHTDIP_10_PERCENT
LIGHTDIP_12_PERCENT LIGHTDIP_15_PERCENT
LIGHTDIP_20_PERCENT
Author: Keith Riles - U. Michigan
This monitor is based strongly on the LockLoss monitor
written by David Chin.