Minutes of the MAS/MA geometry meeting
22/04 2005
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Present:
Jerome Beauquis, Gijs de Rijk (part time), Zhengwei Gao, Jean-Pierre Koutchouk, Patrick Winkes, Elena Wildner
Pen: ElenaWildner
Non conformities from SSS measurements:
For the Dipole service line and flange geometry values are stored as coming from the last fiducialization. If the results out of tolerance at the fiducialization this is seen in the results from the measurement and SU opens a non-conformity. After consultation with SSS coordination the lines are repaired and put to nominal and the non conformity is closed. This can be traced in the data-base. However what cannot be traced is “use as is” cases. We will make the necessary effort to make this available in the database.
For the SSS we cannot trace if the non conformities are closed or not so we do not know if the lines are in tolerance or not. This is due to the fact that no clear work-flow is defined for the SSS in the MTF. We will arrange a meeting with E.Manola, P.Winkes and M.Modena to change this.
Patrick needs an official document for the tolerance to be applied in his procedure (WGA).
For the backlog of recalculations needed for the calibration of the AC-mole, new NCs may appear. Those should be created and we must make sure that the MTF can support the creation of non-conformities a second time.
There may also be inconsistencies between the MTF-file and the data base since adjustments by specialists may be done on the files before upload. As long as this is traceable it is ok. For the AC-mole magnetic axis measurement this is not guaranteed yet.
A complete cartography of the service lines at WP09 is asked by B.Jeanneret. This is not cost less and we can maybe remedy this by adding information in the DB.
The tolerance tables in the DB should be filled, for the line we have the tolerances; for the magnetis axes Jean-Pierre will give us the values.
The Alstom magnets with special treatment in industry:
The magnet 1203 had a shape exceeding the bound ±1.5 mm at itp15 (2.1 mm sagitta error). To avoid having too large cat’s ears and to “save” this magnet it was decided to constrain this magnet at the mounting of the corrector magnets and ends by 0.5 mm on the mid cold foot pad so as to decrease this magnet’s sagitta (resulting sagitta error 1.1 mm). The decrease of the sagitta is theoretically 1.8 times the value on the mid cold feet pad relative to the other two. Statistics from Marco La China shows that this value is 1.5 mm. This magnet should have been adjusted at CERN with the statistical value for Alstom magnets + 0.5*1.8 (this value was communicated to TS/SU). However this was not done and this magnet was out of tolerance after statistical adjustment. If the extra correction asked for had been applied, the magnet ends would have been within tolerance. The magnet is now adjusted to itp20.
With this idea to reestablish a good shape at WP08, it was decided by the project engineer to assemble the following magnets by constraining the magnet 0.5 mm on the central cold foot pad: 1209, 1165, 1210, 1211, 1214, 1212, 1213, 1218, 1127, 1105. The aim was to decrease the sagitta to compensate for the high natural increase of the sagitta between industry and CERN. The result of this adjustment was that the change of the sagitta between itp15 and itp20 is not correlated to the adjustment. For some magnets the change in a positive direction gave an effect on the sagitta with opposite sign. These magnets were not in tolerance when adjusted statistically at WP08. They were, after discussion, all adjusted to itp20. The conclusion of this experiment is that the effect of the adjustment on the cold feet pad is still a mystery and we need to further investigate.
We will report to the WGA about these magnets.
Possibility to use a simple fiducialization to improve the spool piece position:
The statistical adjustment works well within the limits for the spool piece positioning. However, recent doubts on the spool piece position in industry have revived wishes to be able to improve the spool piece position at WP08 where possible (adjustment to itp20). A very simple extra fiducialization of one tube takes some 40 minutes. For the moment this amount of time would be available because transport problems and problems with missing fiducials slow down the rate of available magnets on the benches. The fiducialization rate today is around 3.5 magnets per day (Statistics by Zhengwei). The rate aimed at is ???. We would like to profit of the possibility to make this simple measurement, without any impact on the fiducialization rate. To make this measurement, Patrick needs to implement some modifications in the measurement program. He believes that this can be finished by the end of next week, after which we will discuss all together with Davide.