Dan, Travis
During the earthquake tonight we finally closed the loop on the HAM6 power budget measurements. This is something Koji had asked for many, many months ago. orz
With IMC-PWR_IN at 2.2388 +/- 0.0004 watts (not sure about the calibration for this channel) and a single bounce off ITMY, we collected the following data (30 seconds of slow channels, uncertainties are stdevs) with the OMC locked & unlocked:
| OMC Unlocked | OMC Locked | |
| AS_A_DC_SUM_OUT [cnts] | 436.3 +/- 0.6 | 436.3 +/- 0.7 |
| AS_B_DC_SUM_OUT [cnts] | 427.3 +/- 0.07 | 427.5 +/- 0.7 |
| AS_C_SUM_OUT [cnts] | 289.8 +/- 0.2 | 289.8 +/- 0.3 |
| OMCR_A_SUM_OUT [cnts] | 142.1 +/- 0.2 | 23.3 +/- 0.1 |
| OMCR_B_SUM_OUT [cnts] | 150.7 +/- 0.1 | 22.9 +/- 0.1 |
| DCPD_A_OUT [mA] | -- | 1.775 +/- 0.0023 |
| DCPD_B_OUT [mA] | -- | 1.761 +/- 0.0023 |
| DCPD_SUM_OUT [mA] | 3.537 +/- 0.0046 |
AS_C has 36dB of whitening gain. The OMCRs and DCPDs have no DC whitening. I'm not sure about AS_A and AS_B (I think they have zero whitening, but I haven't looked at the electronics chain for the WFS DC signals so I'm not sure of the transimpedance, etc). Since AS_C gets 400ppm of the light entering HAM6, the total light into the chamber is:
289 counts / (1638.4 counts/V * 0.8 A/W * 1000 V/A * 2 * 36dB * 400ppm) = 4.38 mW
(PD responsivity = 0.8, QPD transimpedance = 1000 ohms, differential output = 2x, whitening gain = 36dB)
The alignment into the OMC is probably not perfect in this state, but the mode-matching for the carrier should be better than 90% -- same as here, since we apply central heating to ITMX. The modulation depths are also the same; the power in the carrier should be 94.3% of the total.