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AdV-DET (Commissioning)
bonnand - 12:11 Wednesday 29 June 2022 (56301) Print this report
OMC scan in CITF

This morning I made some scans of the OMC in CITF as requested by the commissioning crew.

The slow shutter was opened at 08:49:25 UTC.

Figure 1 shows a time plot of all the scans, as one can see I first did "fast" scans (by mistake) between 08:52 UTC and 09:03 UTC (fig 2) and then I did a "slow" scan (temp going up then down) between  09:21:30 UTC and 09:42:30 UTC (fig 3).

Finally, the slow shutter was closed at 09:45:45 UTC.

The photodiodes B1 PD1 and PD2 remained closed during the scans.

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Comments to this report:
bonnand - 15:25 Wednesday 29 June 2022 (56305) Print this report

Here a plot of the slow scan (with OMC temperature going up) over a whole FSR with images of the main peak.

Not sure how to interpret this.

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mwas - 12:05 Thursday 30 June 2022 (56312) Print this report

I have looked at the downgoing scan (so it is further away from the steps of the fast scan which will make the relation between the temperature of the OMC, and the temperature of the copper plate measured by the thermistance more linear). Starting from 09:32 UTC.

Also roughly calibrated time into MHz by using the OMC FSR spacing of 864MHz. And then indentified a few modes using the camera image (but I did not check all of them). The power shown in the following figures is B1 PD3 multiplied by 1000, which should be the power transmitted by the OMC, as B1 PD3 looks at a 0.1% pick-off.

Figure 1 shows the FSR scan around the order 0, 1 and 2 modes. WIth the carrier TEM00 highlighted in red. The tick markes show the 6MHz and 56MHz, LSB and USB.

Figure 2 shows the same with tick marks for the 56MHz LSB order 0, 1 and 2 modes.

Figure 3 shows the same with tick marks for the 6MHz USB order 0, 1 and 2 modes.

Figure 4 shows the same with tick marks for the 6MHz LSB order 0, 1 and 2 modes.

Figure 5 shows the same with tick marks for the 56MHz USB order 0, 1 and 2 modes.

Power (mW) TEM00 Order 1 Order 2 Order 1 / TEM00 Order 2 / TEM00
Carrier

2

       
6MHz LSB 2.4 1.1 1.2 0.46 0.50
6MHz USB 0.69 0.29 0.80 0.42 1.16
56MHz LSB 13.5 3.7 8.3 0.27 0.61
56MHz USB 2.9 3.4 3.2 1.17 1.10

Figure 6 confirms that on the phase camera the LSB (both for 6MHz and 56MHz) has much higher power  ( by a factor few) than the USB.

The mode mismatch mode (order 2) is much higher in relative power for the USB (both 6MHz and 56MHz) at ~110% of the TEM00, than for the LSB (both 6MHz and 56MHz) that are at about 50% of the TEM00 opwer.

/users/mwas/OMC/OMC_scan_20220630

 

 

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mwas - 14:02 Thursday 30 June 2022 (56313) Print this report

Actually, the OMC FSR should 834MHz not 864MHz. This makes the spacing of the modes in MHz in the figures is 3.5% wider than it should, due to the wrong conversion of time into MHz.

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