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PIIC processing of run 74 beam maps (taken on 2025/07/13)

Three beam maps were taken on 2025/07/13, i.e. scans

On 2025/07/17 SB processed the three beam maps using PIIC. Below here I copy the usual FOV plots, that show the quality of the beam maps. They are self-explanatory (cfr also the previous re-commissioning runs for more information). It is worth to point out few features, though:

• also in this re-commissioning session, the Ar3 beam maps are bad. My feeling is that the main culprit is the focus offset of Ar3 with respect to Ar1 and Ar2.
• there is a focus difference of ~0.3 mm between Ar2 and Ar1, a difference of ~0.3 mm between Ar1 and Ar3, and therefore a difference of ~0.6 mm between Ar2 and Ar3. These values are preliminary and come from the quick focus analysis carried out during the observing session. Note that during the first re-commissioning (run 72), Ar1 and Ar3 seemd to have a similar focus offset, but things changed after re-opnening. The idea is that this is not a real hardware change, but rather due to the fact that in run 72 the Box C was missing. In my opinion this is not so obvious, though.
• the consequences of these focus offsets between the three arrays are that: focusing on Ar2, Ar3 is completely out of focus and not usable; fcusing on Ar1, Ar3 is still out of focus (but less dramatically) and only marginally usable.

• there have been issues with focusing at 1.2 mm during the observing session, because the Ar1 and Ar3 preliminary DAFs (run 72) are offset wrt the Ar2 DAFs (run 68). The solution would have been to use a combination of pointing offsets when focusing (see suggestions for the next re-commissioning run). The consequence of a sub-optimal Ar3 focus is that the Ar3 beam map is sub-optimal.

• All three beam maps are ok for Ar2, because the beam of Ar2 is much larger than for Ar1,3 and therefore the beams maps of Ar2 are usable even under sub-optimal focus conditions.

Quality of the beam maps: