Yesterday and this morning, some measurements with the INJ and DET HWS have been performed during the transition to CARM null, in order to check the tuning of the CH beams.
Some of the measurements were done using the TCS automation and, as reported in 55262, due to a bug, only 41 wavefronts have been generated, despite the lock being actually longer in some cases. The other measurements have been performed manually, starting the HWS acquisition when 480 mW are stored in the arm cavities. The complete list of available data is reported in the table below.
| HWS | Folder | # wavefronts | Duration [min] |
| INJ | 20220322T1609 | 41 | 20 |
| INJ | 20220322T2144 | 41 | 20 |
| INJ | 20220322T2240 | 41 | 20 |
| INJ | 20220322T2346 | 100 | 50 |
| INJ | 20220323T1117 | 111 | 55 |
| DET | 20220322T2031 | 41 | 20 |
| DET | 20220323T1524 | 65 | 32 |
As can be seen from figure 1, the wavefronts are dominated by tilt. So, before performing the curvature computation, the piston and tilt contributions have been removed from the maps. Figure 2 shows the same wavefront as in figure 1 after cleaning.
The curvature trends for HWS-DET and HWS-INJ are shown in figures 3 and 4 respectively.
Some preliminary conclusions can be drawn from these data:
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In both cases, the signal is very small, with HWS-DET being larger and less noisy than HWS-INJ;
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The curvature measured by HWS-DET decreases when the North CH is switched off, which means the CH is overcompensating;
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The various HWS-INJ data sets are all in good agreement for the first 20-30 minutes;
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The curvature measured by HWS-INJ increases when the West CH is switched off, which means the CH has to be increased, by a tiny amount;
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To have quantitative results, longer (60-90 minutes) data stretches are needed;
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In both cases, the data can be used to look for point absorbers.
