Jennie Wright, Khanh Vu

Below is a summary of the work we did on the JAC IOT1 table today, July 17th.

For JAC commissioning, we had planned to install a higher-attenuation ND filter on the JAC Trigger PD and turn down the power on the JAC REFL A PD. Our concern was that the power in the Trigger PD path might be too high and cross its trigger threshold. We came in to measure the beam power with and without the ND filter.

With ND filter: 12.51 mW between the ND filter and beam splitter; 2.1 mW in front of the REFL PD.
Without ND filter: 0.39 V on TrPD; 6 mW on REFL PD.

The power on REFL PD is not too high even without the ND filter and with JAC unlocked, so we decided to check our calculations.

Using existing data from when the JAC was locked vs. unlocked (attached below), we found a visibility of 65.9/922.2 = 0.07. This is higher than my previous calculation of 0.056, but since the numbers are so small, the fluctuation is acceptable. A higher visibility also allows a larger error margin, which is preferable for ensuring the power does not get too high during a run.

The calculated power on REFL PD at 65 W locked is 13 mW, and the calculated voltage on TrPD is 0.89 V. These numbers look good even without ND filters, so we don't need to change or install them.