Reports 1-1 of 1 Clear search Modify search
VIS (SRM)
terrence.tsang - 18:00 Tuesday 19 March 2019 (8451) Print this report
SRM OPLEV

I finalized the position of the LEN QPD and it should be minimally sensitive to tilt.

Tilt QPD calibration data is available at 7985, and other useful parameters are available at 7952. See attacted srmlenoplevcal20190319.png for LEN QPD calibration data.

I worked on diagonalization matrix. For the tilt sensing QPD, a rotational transformation of ~-0.4° is needed while ~1.3° is needed for that of the length sensing QPD.  It is estimated that the beam spot is 2.1 mm off-centered horizontally towards the +T direction.

The coupling between all degrees of freedom is less than 1%. I also observed some L2Y coupling and it is possiblly due to some non-zero transverse component of the beam. It can be cancelled later with the diagonalization matrix but I didn't bother for now because the coupling ratio is very low.

Please see srmtml.png, srmtmp.png and srmtmy.png for the transfer function measurements.

OL2EUL with L2P correction and off-centered correction
  TILT_PIT TILT_YAW LEN_PIT LEN_YAW
L

-0.0000414742151

0.0064504166 -3.22191337 0.07563197
P 2.26222884 0.014484793 1.33690529 -0.0313828382
Y -0.0197496262 3.07430555 0 0

I have also implemented damping control for the TM, and IM to TM DC control.

I also measured IM to TM transfer functions which will be used to generate L2P cancellation filters later. See srmiml.png and srmimp.png for the transfer functions.

Images attached to this report
Comments to this report:
terrence.tsang - 10:49 Friday 22 March 2019 (8485) Print this report

Updated OL2EUL matrix

rotational angle: -0.6 ° (TILT), 1.3°(LEN)

off-center: 0.7 cm (-V), 0.2 cm (+T)

OL2EUL
  TILT_PIT TILT_YAW LEN_PIT LEN_YAW
L 0.01577279 0.00663606 -3.21255503 0.07541229
P 2.26214272 0.02574525 1.33690529 -0.03138284
Y -0.02962414 3.0742119 0 0
terrence.tsang - 10:08 Tuesday 26 March 2019 (8510) Print this report

Updated OL2EUL matrix for removing L2Y coupling due to a non-zero horizontal angle of incidence.

Estimated horizontal angle of incidence: 1.7 degrees (beam bends towards -T side)

Update in the afternoon: Found yet some residual 0.5% P2L coupling. Drastically reduced by saying that beam is 5 mm above the center of the optic.

OL2EUL
  TILT_PIT TILT_YAW LEN_PIT LEN_YAW
L -0.0113729243 0.00632711877 -3.22842443 0.0757848163
P 2.26214272 0.02574525 1.33690529 -0.03138284
Y -0.02962414 3.0742119 0.0826017272 -0.00193901293
fabian.arellano - 10:57 Tuesday 09 April 2019 (8585) Print this report

I corrected a term in the diagonalization matrix. The picture shows the wrong value in the element Y, LEN_YAW.

I took a Safe Snapshot.

Images attached to this comment
Search Help
×

Warning

×