Kiwamu, Stefan

The story of the evening is short:
 - H1:ALS-C_DIFF_PLL_GAIN was accidental increased to 26dB. Up there the PLL oscillates - the gain has to be 6dB.
 - The power on the ETMX UIM coil driver was off - it should be on.
 - The ESD was in a dead state - we had to recycle the power to get it back.
 - Fixing these things took a very short time - its finding them that took all evening...

 - Before starting to chase these 3 needles in the haystack we also updated the L3 inverse plant filters to match the 0.5Hz resonance of the upper stages exactly. This should guarantee a stable behaviour of the blend filters at 0.5ish Hz.

 - Finally we measured the gain ratio between the TOP/UIM combined actuator and the TST actuator at two frequencies:
           TST/(TOP&UIM) ratio
    2.5Hz      2.9
    4.0Hz      1.9 
i.e. the TST drive was  2 to 3 times stronger than the TOP/UIM actuator. We set the TST gain to 0.5.

 - When we finally tried this at the end of the evening, and got the UGF to 1.2Hz. This was done with two additional p5z50 roll-offs.
 - The resulting coil output spectra are attached.

 - Next Kiwamu put in a boost at low frequency to suppress some noise - we got an RMS of ~100Hz in infrared.
 - In this configuration we are limited by the ESD around 3Hz and the UIM drive around 10Hz in about equal amounts.
    Ideas:
      - Get a factor of two in ESD range by using additional drive offset and linearisation
      - Get a factor of two in total range by using ETMY too.
      - Fine-tune the the UIM/TST blend filters with the measured coil noise in mind.
      - Resurrect PUM drive around 10Hz?
      - What is the diff noise from 3hz to 10Hz?