Keita Daniel

We took another look at the intensity noise at 50 W out of the IMC. The attached plot shows the relative intensity noise both in-loop and out-of-loop. The brown curve depicts the dark noise as measured by alog 30001. The in-loop curves ERR1 and RIN_INNER now agree fairly well. Between 20 Hz and 300 Hz the two curves are ADC noise limited. There is some additional noise in RIN_INNER below 20 Hz which is not understood. The amber line depicts the sum of the shot and the dark noise multiplied by √2. This is the expected noise level of the outer loop sensor, if we are gain limited. The outer loop sensor shows a fair amount of excess noise below 30 Hz. The red curve is the intensity noise measured by the first loop. It is identical to the control signal of the second loop.