J. Kissel, K. Venkateswara

Because we continue to find the reference mirror signal -- a proxy for the autocollimator noise -- to be a useful signal to judge where the Beam Rotation Sensor's noise floor lies, we've output this channel out of the laptop's DAC, and piped it into the H1 ISI EX ADC on Channel ADC_0_29, and stored it in the science frames at 256 [Hz]. We expect the reference mirror to be stable, so we've not applied the very-low-frequency 1 [mHz] high-pass, but otherwise the calibration of the signal is identical to that of the beam balance mirror (see 13448):
3.5e-6 [rad/pixel] * 1 [pixels/V_sing] * 1/2 [V_sing / V_diff] * 40/2^16 [V_diff/ct] * 1e9 [nrad/rad] =  1.0681 [nrad/ct]
This gain, called "cts2nrad" has been installed into FM1 of the H1:ISI-GND_BRS_ETMX_REF filter bank, as with the beam balance mirror.


This required a recompile, reinstall, restart, and restore of the H1ISIETMX. We have not yet reboot the frame builder, so it remains with a 0x2000 status until the next DAQ restart at a more convenient time. I've committed the changes both the top-level h1isietmx.mdl model, and the H1ISIETMX.txt filter file to the userapps repo. We haven't yet added the filter bank to the BRS screen, but we'll get there.