Virgo Roma Tor Vergata

(Viviana, Alessio)

This entry is to report on the activities performed on wednesday afternoon and thursday morning.
On wednesday 27, we worked on the polarizer issue (see NI TCS bench works):
we performed a test with the IR cameras. The set-up or the
measurement is shown in figure 1. On the North bench, with the new
laser, the effect is still there. We than mad...

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(Viviana, Alessio)

This morning we worked on the NI intensity stabilization. We have
set the laser temperature to about 20.9 deg, that gives a
good stability of the output power.
Figure 1 shows a comparison between the open loop noise spectrum
(pink) and closed loop spectrum (black). The reduction factor is the
same as the WI bench (our reference).
...

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(Chiummo, Day, Di Paolo Emilio, Fafone, Morgia, Rocchi, Sperandio)

This is a summary of the works on the NI TCS bench of the last week.
First we tested the new CO2 lasers from Access Laser Co. We measured the output power: 22W for laser #1 and 28W for laser #2.
We placed the IR camera after the Brewster attenuator and measured the beam profiles (figure 1 for laser #1 and...

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Today we tested the new CO2 lasers: we measured the maximum delivered power, the open loop noise and the beam profile at the laser output. For reference, we first measured the intensity profile of the WI laser, since we know this laser is working properly. Then, we measured the profile of the laser installed on the NI bench by Julien and Richard. Finally, we tes...

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Work perfomed by D. Le Galliot and R. Cavalieri.

This morning we implemented a laser overtemperature protection based on PLC for the TCS system.
In case the temperature of one of the two laser goes above 29 degrees, the laser is switched off and a red lamp is on.
The rearm of the laser is possible only by human action on a push button installed in the TCS room (labelled...

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After the work done yesterday (NI ring adjustment) that did not seem to be enough, this morning we (Laura and I) tried again to improve the NI ring.
First we tried Eric suggestion: to put the iris where the beam is focused (between L1 and L2). Unfortunately, this did not help, since the beam is so small that the residual hole in the iris is far too large. A real pin-hole would be needed....

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This morning (with Laura, Maurizio and G. Vajente) we tried to improve the NI ring. According to NI laser changed, the beam out of the laser is not a good TEM00. Indeed, after the AOM, it is possible to notice an halo around the main beam. Moreover, the beam is astigmatic before the AXICON.
At first, we tried to improve the contrast of the ring, by putting an iris after the AOM to get rid of...

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I checked the performances of the ISS on the two benches.

NI bench: the loop is doing fine with respect to the open loop noise, but it is still far from the PD dark noise. We should understand the reasons. There is still margin for improvement of about a factor of 2. Blue is the dark noise, black is the closed loop noise spectrum and purple is open loop.



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