Reports 1-1 of 1 Clear search Modify search
MIF (General)
takafumi.ushiba - 19:25 Thursday 16 January 2025 (32362) Print this report
Test of BPC on ITMX for critical coupling of PRMI

[Tanaka, Ushiba]

Abstract:

We added offsets on ITMX PIT BPC so that the laser power on REFL PD is as small as possible.
Though PRFPMI became unstale when largely moved beam spot on ITMX, we could reduced REFL beam power by a factor of 2.

Detail:

As proposed in klog31908, the beam jitter noise might be able to reduce by achieving critical coupling of PRMI, so we tested if such situation can be achieved by adding offsets on BPC.
This time, we changed the value of  K1:BPC-PIT_ITMX_INF_OFFSET from 0 to 50 to move the beam spot on ITMX up.
Figure 1 shows the POP90, TRX/Y, REFL DC, and BPC signals.

Initially, REFL DC power was about 2.4 mW, which could be reduced by a factor of 2 while keeping PRFPMI RF lock.
Thuogh we haven't checked if this beam spot change works with DC readout, it might be possible to reduce the REFL power by moving the beam spot on ITMX.

Note:

As reduced the REFL power, TRX/Y and POP90 fluctuation became large, so the stability seems to be degradated by moving the beam spot on ITMX from the current nominal position.
Soon after reaching REFL DC power around 1.2 mW, PRFPMI lost lock but we are not so sure the reason of the lckloss at this moment.

Images attached to this report
Search Help
×

Warning

×