Here I explain usage of my scripts for loss map measurement. There are 7 script files in a same directory /opt/rtcds/caltech/c1/scripts/lossmap_scripts. With these scripts, round trip loss of an arm cavity with the beam spot on one mirror shifted to 5x5 (option: 3x3) points is measured. You can choose on which cavity you measure, the beam spot on which mirror you shift, and maximum shift of the beam spot in vertical and horizontal direction.
To start measurement from the beginning
Run the following command in an arbitrary directory and you will get several text files including the result of loss map measurement:
> python /opt/rtcds/caltech/c1/scripts/lossmap_scripts/lossmap.py [maximum shift in mm (PIT)] [maximum shift in mm (YAW)] [arm name (XorY)] [mirror name (E or I)]
Optionally, you can add "AUTO" at the end of the above command. Without "AUTO", you will be asked if the dithering has already settled down or not after each shift of the beam spot and you can let the scripts wait until the dithering settles down sufficiently. If you add "AUTO", it will be judged if the dithering has settled down or not according to some criteria, and the measurement will continue without your response to the terminal.
The files to be created in the current directory by the scripts are:
- lossmapETMX1-1.txt # [POX power (locked)] / [POX power (misaligned)]
- lossmapETMX1-2.txt # standard deviation of [POX power (locked)] / [POX power (misaligned)]
- lossmapETMX1-3.txt # TRX
- lossmapETMX1-1_converted.txt # round trip loss (ppm) calculated from lossmapETMX1-1.txt
- lossmapETMX1-1_converted_sigma.txt # standard deviation of round trip loss calculated from 1-1.txt and 1-2.txt
- lossmapETMX_result.txt # round trip loss and its error in a clear form.
The name of the files would be "lossmapITMY1-1.txt" etc. depending on which mirror you have chosen.
To restart measurement from a certain point
Run the following command in a directory containing "lossmap(mirror name)1-1.txt", "lossmap(mirror name)1-2.txt" and "lossmap(mirrorname)1-3.txt" which are created by previous not-completed measurement:
> python /opt/rtcds/caltech/c1/scripts/lossmap_scripts/lossmap.py [maximum shift in mm (PIT)] [maximum shift in mm (YAW)] [arm name (XorY)] [mirror name (E or I)] [restart point (PIT)] [restart point (YAW)]
You can also add "AUTO".
How to designate the restart point:
Matrix elements of output of this measurement procedure are characterized by a pair of two numbers as the following shows.
(-1,-1) -> (-1,-0.5) -> (-1,0) -> (-1,0.5) -> (-1,1)
(-0.5,1) <- (-0.5,0.5) <- (-0.5,0) <- (-0.5,-0.5) <- (0.5,-1)
(0,-1) -> (0,-0.5) -> (0,0) -> (0,0.5) -> (0,1)
(0.5,1) <- (0.5,0.5) <- (0.5,0) <- (0.5,-0.5) <- (0.5,-1)
(1,-1) -> (1,-0.5) -> (1,0) -> (1,0.5) -> (1,1)
Please write the numbers that correspond to the matrix element you want to restart at. Arrows show the order of sequence of measurement. About the correspondence between the matrix elements and real position on the ETMY and ETMX, see elog 11818 and 11857, respectively.
This script will overwrite the files (~1-1.txt etc.) so it is safer to make backup of the files before you run this script.
Some notes on the scripts and measurement
- Calibration has been done only for ETMs, i.e. for ITMs unit of [maximum shift] is not mm, but the values written in [maximum shift] equal to the maximum offsets added just after demodulation of ASS loop (ex. C1:ASS-YARM_ITM_PIT_L_DEMOD_I_OFFSET).
- It should be checked before doing measurement if the following parameters are correct or not.
POXzero (L47 in lossmapx.py and L52 in lossmapx_resume.py: the value of C1:LSC-POXDC_OUTPUT when no light injects into POXPD.)
POYzero (L45 in lossmapy.py and L50 in lossmapy_resume.py: the value of C1:LSC-POYDC_OUTPUT when no light injects into POYPD.)
mmr (L11 in lossmap_convert.py: (mode matching carrier power)/(total power))
Tf (L12 in lossmap_convert.py; transmittivity of ITM)
Tetm (L13 in lossmap_convert.py: transmittivity of ETM in ppm)
- Changing n (L50 in lossmap.py) from 5 to 3, the grid points will be 3x3 changed from the default value of 5x5. If 3x3, the matrix elements are characterized by
(-1,-1) -> (-1,0) -> (-1,1)
(0,1) <- (0,0) <- (0,-1)
(1,-1) -> (1,0) -> (1,1)
similarly to the case of 5x5.
- You can copy the directory lossmap_scripts anywhere in controls and use it. These scripts will work as long as all the 7 scripts exist in a same directory.