Reports 1-1 of 1 Clear search Modify search
AdV-TCS (Point Absorbers Mitigation)
melo, spinicelli, nardecchia, gherardini - 19:33 Friday 05 December 2025 (68316) Print this report
IPATSiA shift continuation

Today we continued to investigate the IPATSiA effects on the ITF through the PA injected on the WI HR surface mirror. The last IPATSiA shift was reported here #68304.

In the morning, at 9 UTC we switched on the chiller, the laser and started shining the mirror with 32 mW of CO2 power at 10:35 UTC when the ITF was stabilized at LN2. 

In Fig.1 we can see the new position of the PA (POS 1). To be noted that this position is different from all positions from the other shifts. We moved in the horizontal direction to the left and the idea is to scan some points in the vertical direction. Also to be noted that the thermocamera used is a different one w.r.t the other shifts. Since the thermocamera used before had an issue and we had to restart it every few seconds, we installed a new one, but this time facing the HR mirror with the same height and therefore there is no vertical angle of view. Moreover, this camera is not flipped upside down as the other one (this was necessary to install it in the setup), so to understand the relative position of the PA it is necessary to keep this in mind (see Fig. 2: here we have the old thermocamera image of the POS1, i.e., the same position of the new thermocamera shown in Fig. 1). 

When we started shining the mirror a big oscillation in all signals of the ITF (PR, BS, arms signals, ect) unlocked the ITF. After locking again in LN2, we tried again (started shining the mirror at 11:27 UTC) but we had the same effect as before so we decided to stop shining the mirror (11:32:37 UTC) and change position (+10k steps of the picomotor, corresponding roughly to 8 mm dwon w.r.t the previous position). 

So, here below a list of the positions and corresponding UTC time. Each position is 8 mm down w.r.t the previous one:

- At 11.45 UTC we started shining the mirror in POS2 (Fig. 3);

- At 12:52 UTC we moved to POS3 (Fig. 4);

- At 13:53 UTC we moved to POS4 (Fig. 5);

Then, at 14.55 UTC we moved the PA horizontally in the mirror towards the right direction - POS5 (Fig. 6). However the ITF unlocked and we stopped shinning the mirror at 15 UTC. After some atempts to shine the mirror with the PA, the ITF did not manage to remain locked in LN2 in this position. At 17.36 UTC we moved again the PA upwards (8mm up) to try in this new position. The ITF relocked in LN2 and we tried to shine the mirror at 17.59 UTC but the ITF unlocked again at 18.09.15 and we stopped the shift here.

Around 18.15 we switched off the CO2 laser and the chiller.

On Fig. 7 we show a summary of the main signals during the whole shift. 

 

Images attached to this report
Comments to this report:
corubolo, gherardini, melo, nardecchia, spinicelli - 13:52 Saturday 06 December 2025 (68321) Print this report

Yesterday, similarly to the shift on Dec 3rd, we synchronized the HWS-INJ acquisitions with the CO2 PA switched on, aiming to identify the PA position on the WI HR surface.
An example of the wavefront recorded with the PA projected on the WI HR surface for each tested CO2 PA position, is reported in Fig. 1.

Figure 2 shows a summary map of the CO2 PA positions for both the December 3 and December 5 shifts. The origin (0,0) corresponds to the maximum YAG-induced Delta OPL, which is assumed to represent the mirror center.

The X and Y coordinates of the CO2 PA were evaluated from the HWS maps by identifying the minima of the Delta OPL.
Only the Y coordinates of the CO2 PA positions, evaluated from the HWS maps, were flipped to be consistent with the thermal camera installed in front of the viewport which observes the HR surface at a horizontal angle of 33° but at the same height as the mirror center (i.e., the ZnSe viewport installed to monitor inside the tower, not the one used to inject the heating profile generated by the PA mitigation system). By flipping the Y coordinates of the HWS maps, when the CO2 PA moves from top to bottom on the thermal camera (and consequently on the mirror), the same movement is observed in the HWS maps. Regarding horizontal displacements, when the CO2 PA moves from left to right on the thermal camera, the same movement is observed on the HWS maps without the need to flip the X coordinates.

 

Images attached to this comment
Search Help
×

Warning

Error

The present report has been modified outside this window. Please check for its integrity in the main page.

Refreshing this page will move this report into drafts.

×