Virgo Logbook

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Environmental Monitoring (Environmental Monitoring)

Paoletti - 9:17 Wednesday 21 August 2019 (46727)

ENV_CEB_ELECTRIC preamplifier has been moved closer to the WI tower

The title explains it all: for months we had a Stanford SR560 preamplifier (set on Gain = 10) located in EE_room, whose differential input was connected with two very long coaxial cables to the electrical ground of the WI electronic crate and to the electrical ground of the WI vacuum chamber.

Yesterday during maintenance we moved the preamplifier closer to the base of the WI tower, south side (see attached photo); now it's the preamplfier output that has a long coaxial cable connected to the ADC located in the EE_room.

The shape of the signal ENV_CEB_ELECTRIC has not changed (see attached plot).

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Paoletti - 11:40 Tuesday 10 September 2019 (46877)

Today I verified that this probe is working: disconnecting one arm (the negative one) of the differential input from the ground of the Sc_WI chassis and connecting it to the body of the tower (where the other positive arm is) has the effect of reducing the 50Hz power line and many other harmonics of about one order of magnitude.

The same happens to the 50Hz sidebands.

Note that in this test the two differential inputs were not physically close to each other: the positive was left connected to the base of the tower on a large flange, while the negative was connected at platform level to the flange from which the suspension's pink cables come out; this is a distance of a few meters.

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