Today activity has been devoted to the tuning of the DAS powers with the ITF locked in Low Noise 1.
In the first part of the afternoon Alessio and Viviana performed a new calibration of the DAS powers, because the ADC offset changed after the timing upgrade.
After that, Julia relocked the ITF in Low Noise 1 with the TCS on (P in/out=456/912 mW on NI and P in/out=233/466 mW on WI). After the ITF reached the thermal steady state, we started to change the DAS power applied in order to maximize the 56 MHz sideband gain.
The different annuli powers applied are summarized in the following table.
Step | P NI (IN/OUT) | P WI (IN/OUT) | Time (LT) |
1 | 450/900 | 450/900 | 20:43 |
2 | 900/1800 | 450/900 | 20:55 |
3 | 600/1200 | 450/900 | 21:20 |
4 | 600/1200 | 200/400 | 21:45 |
5 | 450/900 | 200/400 | 22:25 |
6 | 350/700 | 200/400 | 22:54 |
The behaviour of the 56 MHz gain, B7, B8 and B1p are shown in Figure 1 and 2.
At 23 LT Julia checked the alignment and improved the position of the BS and of the PR, but few minutes after the intervention the ITF unlocked due to the earthquake in Molise.
We left TCS on with the DAS powers of step 5, that seems to maximize the 56 MHz gain.
The fine tuning will be finalized in the next shifts.