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Entry  Mon Mar 26 21:25:55 2018, rana, Summary, IOO, MC2 Trans table has issues 20180326_201929.jpg
    Reply  Mon Mar 26 21:40:26 2018, gautam, Summary, IOO, MC2 classical radiation pressure noise IMC_RIN.pdfIMC_RadPress.pdfMC2_radPress.tgz
Message ID: 13705     Entry time: Mon Mar 26 21:25:55 2018     Reply to this: 13706
Author: rana 
Type: Summary 
Category: IOO 
Subject: MC2 Trans table has issues 

Gautam, Rana

While at the MC2 table, we noticed that it has some optical problems:

  1. There is an ND filter mounted to the beam reducing lens. ND filters are illegal, Steve. It causes too much scattering noise. We should instead have a beamsplitter and a dump.
  2. One of those bad U100-AC28 mounts is in use. This is one of those ones with plastic clips that Osamu liked, but the plastic gets in the way of the beam. Needs to be removed.
  3. Reflections from the QPD and the PDA255 are not dumped. This causes noise. Bad.
  4. The QPD transimpedance should be reduced so that it can handle more light. I don't know what it has now, but its probably 10-100 kOhm.

We estimated that the power in the IMC is (1 W)*Finesse/pi = 500 W. The MC2 Transmission spec is < 10 ppm, so the power on the table is probably ~5 mW. Since the PDA255 has a transimpedance of 10 kOhm and a max output power of 10V, it can handle up to ~1 mW. Probably we can get the QPD to handle 4 mW.

Gautam, Steve  3-27

We measured MC2 transmitted power right at the uncoated window ~2.5 mW  The beam was just a little bigger than the meter.

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