This morning, we proceeded with the DAS differential tuning. In order to try to evaluate the effect of each DAS ring, the NI outer ring has been decreased by 15 %.
08.17 UTC: Locked at LN2
08.48 UTC: NI Outer ring power change (-15 % wrt the STEP_1S )
| STEP2_S 08.48 UTC | CH [W] | INNER DAS [W] | OUTER DAS [W] | |
| W | on the ITF | 0.068 | 0.078*(1+15/100)=0.090 | 1.615*(1+15/100)=1.857 |
| on the pickoff | 0.418 | 0.0127*(1+15/100)= 0.0146 | 0.263*(1+15/100)=0.302 | |
| N | on the ITF | 0.091 | 0.219*(1-15/100)+0.08= 0.266 | 1.172*(1-15/100)+1.8 =2.8 |
| on the pickoff | 0.561 | 0.036*(1-15/100)+0.013= 0.044 | 0.191*(1-15/100)+0.293= |
09.13 UTC- 9.18 UTC: Manuel tested a new filter
09.18 UTC: ITF unlocked
09.25- 09.46 : Diego P. went to the CB on the platform.
At the next relock, the ITF working point appeared degraded (see fig.1).
Thus, in order to investigate the ratio between NI inner and outer ring, the NI Inner ring power has also been decreased by the same amount (-15 %) .
10.40 UTC: NI Inner ring power change (-15 % wrt the STEP_2S ).
| STEP3_S 10.40 UTC | CH [W] | INNER DAS [W] | OUTER DAS [W] | |
| W | on the ITF | 0.068 | 0.078*(1+15/100)=0.090 | 1.615*(1+15/100)=1.857 |
| on the pickoff | 0.418 | 0.0127*(1+15/100)= 0.0146 | 0.263*(1+15/100)=0.302 | |
| N | on the ITF | 0.091 | 0.1861*(1-15/100)+0.08=0.238 | 1.172*(1-15/100)+1.8 =2.8 |
| on the pickoff | 0.561 | 0.026+0.013=0.039 | 0.191*(1-15/100)+0.293= |
Also this step had a negative impact on the ITF WP, B1p was very high and we were not able to lock in low noise 2 due to unbalance of B1P PC 56 MHz.
Thus, with the ITF in CARM NULL 1F, the NI DAS inner and outer ring powers have been increased again, at 12.08 UTC.
| STEP4_S (= STEP1_S) 12.08 UTC | CH [W] | INNER DAS [W] | OUTER DAS [W] | |
| W | on the ITF | 0.068 | 0.078*(1+15/100)=0.090 | 1.615*(1+15/100)=1.857 |
| on the pickoff | 0.418 | 0.0127*(1+15/100)= 0.0146 | 0.263*(1+15/100)=0.302 | |
| N | on the ITF | 0.091 | 0.219*(1-15/100)+0.08= 0.266 | 1.379*(1-15/100)+1.8 =2.972 |
| on the pickoff | 0.561 | 0.036*(1-15/100)+0.013= 0.044 | 0.225*(1-15/100)+0.293= 0.484 |
13.15 UTC: unlocked
13.24:WI DAS powers have been increased by 15%.
| STEP5_S 12.39 UTC | CH [W] | INNER DAS [W] | OUTER DAS [W] | |
| W | on the ITF | 0.068 | 0.090*(1+15/100)=0.104 | 1.615*(1+15/100)=2.13 |
| on the pickoff | 0.418 | 0.0146*(1+15/100)= 0.0169 | 0.302*(1+15/100)=0.347 | |
| N | on the ITF | 0.091 | 0.219*(1-15/100)+0.08= 0.266 | 1.379*(1-15/100)+1.8 =2.972 |
| on the pickoff | 0.561 | 0.036*(1-15/100)+0.013= 0.044 | 0.225*(1-15/100)+0.293= 0.484 |
At 14.05 UTC, the ITF locked in LN2.
It seems to be a good WP (see fig.2) but it is needed to dedicate some time to confirm it.
We left these DAS powers identified as STEP 5_S for the afternoon shift.
