Akutsu, Yano, Tanaka, Simon

Alignment (continue)

(see also the report from klog: 6680)

• we firstly continued with the yesterday mentioned issue about a strangly pitching hook-point and tried to understand it further
  • We confirmed that the +X/+Y suspension point on the baffle is 1mm lower than the other three and ruled-out any strange bending from the wire-lock bracket (also the wire-clamps show the same 1mm lower level than the other points)
  • However, we confirmed that the baffle itself is not pitching! → We set the laser-level to the upper edge of the baffle and could compare both ends with each other. The found difference of 0.5mm within a distance of ~500mm is totally within the error margin
  • So, we still don't know why decreasing of only one point actually happened. But, it seems (as the baffle is not pitching) that the lowered point caused also the respective wire to elongate a little bit. Otherwise, a non-pitching baffle would not be understandable
• In a next step, we checked the horizontal (transversal) and yaw-alignment by setting the laser-level on a prepared plastic-box to focus a vertical line along the cryostat's center
• In the pictures (to be found: here), one can see that there is no yawing measurable. It seems, however, that the transversal position is shifted by ~0.5mm toward +X, which is, anyway, within an acceptable margin. So, we did not do any further alignment.
• As a last step, we checked the roll by comparing the center-position of the wire-lock brackets on +X and -X side (on +X, we did this only with the bracket at +X/-Y because of the above mentioned reasons). In both cases, we found a center-line height of 269.5mm → no roll misalignment measurable! (pictures: here)

Put baffle in "saving mode"

• at first, we set the feet-blocks to the four destinated positions on the T-beams at the ground-level of the cryostat
  • We measured the approximate distance of the T-beams at +X and -X to the base-plate. The result was 60.1mm for +X and 61mm for -X. These numbers were to set an initial number for the feet-block heights
  • We set the two inner blocks first and confirmed they are ending up edge to edge with the base-plate. We aligned them to each other with the aid of a bubble-level (see pictures here)
  • Then, we put the two outer blocks and aligned them first with the two firstly set blocks. After that, we aligned them with each other (all with the aid of a bubble-level) → we also confirmed that each block has a stable, non-obliqued surface
• After that, we set-up the traverser. This time, they showed a slight obliqueness toward -Y, which was, however, not a big problem as toward this side, we were not to set the WAB.
• We hooked the WAB as usual and released the fixing-screws a liitle to further lift the WAB in still kind of fixed state. After lifting, we removed all the screws completely
• Although the hook-point was set as before for all the other baffles, we recognized a slight obliqueness of the whole suspended structure... maybe it is, because we rotated the whole upper-part for a better accessibility of the thermometer screw-holes?
• Anyway, because it is not a big issue, we proceeded to insert the baffle into the duct without any further problems (a small transversal adjustment was anyway necessary for the inserting)
• lowering and placing the WAB on the feet-blocks went without any issues! The WAB sits stable and the traverser-structure has been removed again.
• As a last step, we placed the baffle protectors on the -Y side and placed an AL-foil onto the baffle opening