Status of the Alignment

17/12/04Dario Autiero

Measurements taken so far:

13/9 TT8 On the mounting arch

12/11 TT7 Standalone in the target19/11 TT7 Standalone with some improvements

7/12 Tuning for wall 1 (light conditions)8/12 Tuning for wall 1 (targets)

9/12 Wall 1 + TT710/12 TT 8 after wall115/12 Wall 1 Standalone16/12 TT 8 Standalone

Coordinates System in measurements with photogrammetry:

The Y axis is along the beam direction (The zero is on the magnet, Borexino is negative)The X axis is horizontal going from the rock to the galleryThe Z axis is vertical, going from bottom to top

All the results are give in an absolute frame of the magnet, which is measured inEach set of picturesSo we can compare absolute positions in X,Y,Z among different measurements and verticality or horizontality

•Units are mm, be careful since the scale of the histograms is self normalizing on the range of the points

•The position in XZ of the magnetic targets is not the same in the two measurements, they had to be moved on the end-caps during the cabling, the pin targets by construction cannot move

•Each type of Target (magnetic, adhesive, pins) has its own offset perpendicularly to the TT plane due to the tickness of the Target holder. These ticknesses are not subracted from the measured values (unless explicitely indicated in some plots).

•The long scale calibration with the 4 reference point on the magnet is not included (wating for the fine direct measurement with a laser tracker) it is anyway an effect of the order of 1.5/10000 which will be negligible for the considerations shown in all the next pages. All measurements have been checked to be consistent with the 4 points on the magnet at the mm level.

Definition of an absolute « magnet » coordinate system for the measurements Set 1 and Set2

200 201

202203

1) We take the points 200-203 measured in both Set1 and Set2 with the photogrammetry at the same time as all the other targets on the TT

2) These 4 points are sligthly off the surface of the magnet, with an equal offset for the 4

3) We define a plane with the 3 points 200,201,203

4) We define the origin of the new coordinate system in 200

5) We take as Z axis (203-200) and as X axis (201-200)

6) These two axes are orthogonal, a very small deviation from 90 degrees is corrected by rotating (201-200) staying on the plane 200,201,203

7) The Y axis perpendicular to the magnet is defined by the vector product of the Z and X

X

ZY

After computing the 3 versors we have an orthonormal system centered on 200 with the XZ plane passing for the points 200,201,203 (parallel to the surface of the magnet), and with the Z axis defined by (203-200) and the X axis (201-200)

Long scale calibration sources: installation of Target holders on the XPC supports, 4 point will appear systematically in all the measurements. These 4 points have to be measured once forever with the laser tracker in order to provide 6 long distances for the calibration of all the measurements (replacing the 4 holes made on the mounting arch)

We should also measure with the laser tracker the 4 holes on the mounting arch in order to perform a reanalysis of the pictures taken on plane 8

The long distance calibrations are not available yet, so the results should be considered preliminary since are based only on the extrapolation of the local scales, the analysis will be redone with the long range scales:

200 201

202203

mm

No significative syst. effects (up/down, left/rigth) visible on the external control frame

Some latest news from Friday afternoon discussion with Mario about the position of the bolts on the magnet that we want to use in order to provide the long range calibration for the photogrammetry. …

See next page

TT

The bolts were positioned with the laser-tracker already with 0.1 mm precision and these positions are known. In principle they should not have changed during the assembly of the magnet and also the M16 hole and the support for the photogrammetric targets should not have introduced a significative bias (they should be both more precise than 0.1 mm). So while waiting for the occasion to remeasure directly these positions with the laser-tracker we can already use this information from Mario. These 6 distance informations will be introduced in the analysis in order to calibrate exactely the scales.

Meanwhile, it is quite interesting to compare Mario's distances with the ones measured with the photogrammetry by extrapolating the short scale bars.This use of the short scale gauges is something that we do temporary in the analysis just to have a fast result but the final result in XZ will have to rely on the long distance calibration.

Targets Mario Photogrammetry with local gauges

203-202 Horizontal top 8125.0+-0.1 8123.7200-201 Horizontal bottom 8125.0+-0.1 8123.8

200-203 Vertical left 5750.0+-0.1 5749.9 201-202 Vertical rigth 5750.0+-0.1 5751.5

It is good to see that the photogrammetry with the last improvements, even with a scale defined as the extrapolation of the short scale bars, is already able to find over long distances the correct values at the level of about 1 mm.