Alexa, Evan, Dan, Kiwamu,

We measured the power recycling gain for the 45 MHz sidebands in the PRMI sideband lock condition. It was estimated to be about 21 according to our OMC scan measurements.

(Method)

We measured the power of a 45 MHz RF sideband at the dark port using the OMC. We measured it in two different configurations -- (1) when PRMI was locked and (2) single bounce from ITMX. We did not measure that of the 9 MHz sidebands because we had a difficulty indentifying it from the carrier light.

Based on the measurement, we estimated the power recycling gain for the 45 MHz sideband. Assumptions we made are:

• Schnupp asymmetry is 9.5 cm (see alog 10879)
• PRM transmissivity Tp = 3 %
• ITM transmissivity Ti = 1.4 %
• Tbs = Rbs = 50 %

The measurement were made with 10 W of the light incident on IMC. Note that POP_RF18 was approximately 160 uW during the measurement.

(Result)

Pprmi_at_45MHz = 6.6 (in DCPD_SUM) -- this is the highest we could get by utilizing the dither ASC loops. Without a dither loop, DCSUM would have fluctuated between 3 and 5 presumably due to some alignment fluctuation.

Psinglebounce_at_45MHz = 0.288 (in DCPD_SUM)

(Recycling gain) = Pprmi / Psinglebounce * Tp *Tbs * Rbs / Ri / sin( 2 * pi * lsch * fm / c)^2

where fm is the modulation frequency and it was set to 5 * 9100230 Hz. This gave us a power recycling gain of 21.3.