Jennie W, Ryan S, Sheila D

We changed the calibrated JAC trans power readout to be the front-end channel H1:JAC-TRANS_A_LF_OUTPUT. This is now the channel displayed on the OPS_OVERVIEW_CUSTOM screen labelled as 'IMC INPUT POWER'.

The calibration filter for 'H1:JAC-TRANS_A_LF' is in FM10 labelled W_in_HAM2.

This was previously set as the Beckhoff channel H1:JAC-TRANS_A_DC_POWERMON but this is too noisy and was also not calibrated correctly as it displays in mW and was on the ops screen as W.

I have changed the calibration for this channel so it is actual mW leaking out of the JAC towards JACT_BS1 beamsplitter, which reflects approximately 1% (alog #89251) of light that hits it towards the JAC-TRANS PD (see image).

After checking the calibration measurements we took in chamber, I have realised that the amount of power we get out of the JAC curved mirror (the beam of which goes to the JAC TRANS after reflecting off a laser window) is too high to match the input power we inferred. Looking at the power budget Masayuki and I took at CIT (see elog #863). This predicts a transmission through the curved mirror of 7.5e-5 and from our calibration measurements (alog #89251) we saw (2.7e-3W/1W) = 2.7e-3. The other measurements we took in that entry (BS1 reflectivity ~ 1%, JAC throughput ~ 96mW/115mW = 83 %) don't seem unrealistic.

I can use instead the 7.5e-5 transmission of the curved mirror to calculate that the HAM 2 input power for a certain value of W on the JAC-TRANS_A_LD PD is ~ 1.11e6.

As JAC-TRANS_A_LF has some high frequency noise multiplying by this large number causes it to show high values when there is no light on it. Therefore I propose adding another filter bank to the model where I can low-pass this noise so the display of the HAM2 input power makes sense.

Jenne has turned off FM10 in the JAC TRANS A LF filter bank (see image of the filter banmk with the filter still on here) so the value on the screen looks close to zero for the moment. See Jenne's alog #89823.