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The Field Quality Crisis Unit of the LHC main dipoles production

Inspection of CC 2092 during the de-collaring procedure (due to QH problems)

5th July 2004, Manufacturer 2. Warm magnetic measurements of collared coil 2092 (see file) show various red and yellow alarms in different positions in both apertures. Since this collared coil has to be opened due to a quench heater problem, it could be profited from the opportunity to inspect the poles of both apertures directly instead of having a short mole measurement. The worst alarms in aperture 1 could be seen in position 18: b3 (4.9 sigma), b5 (6.5 sigma), b6 (6.1 sigma), b7 (5.7 sigma), b8 (11.8 sigma), b11 (6.3 sigma), b12 (10.5 sigma), b13 (5.9 sigma), b14 (5.9 sigma), a6 (8.8 sigma), a8 (4.3 sigma), a9 (5.0 sigma), a12 (6.8 sigma).  In aperture 2, the worst spots are at position 2: b3 (4.3 sigma), b5 (4.7 sigma), b8 (5.4 sigma), b12 (5.4 sigma), b13 (5.6 sigma), b15 (4.3 sigma), at position 3: b8 (6.3 sigma), b12 (5.4 sigma), a7 (4.1 sigma), a11 (5.9 sigma), in position 8: a6 (6.1 sigma), a12 (4.8 sigma), at position 9: b8 (6.7 sigma), b12 (5.3 sigma), at position 16: a6 (6.8 sigma), a12 (5.8 sigma), at position 17: a6 (9.2 sigma), a12 (7.5 sigma), a14 (5.9 sigma), and at position 18: b5 (5.7 sigma), b7 (4 sigma), b8 (5.3 sigma), b13 (5.8 sigma), a6 (9.9 sigma), a8 (4 sigma), a12 (7.9 sigma), a14 (5.6 sigma).

The analysis of the inverse problem shows that the field anomaly of aperture 1, pos. 18 is compatible for all multipoles with an inward radial movement of 0.45 mm (best fit) of block 6 in quadrant 1 (see Figure below). The calculated frame for this movement is 0.35 to 0.7 mm. In aperture 2, we calculate for the positions 17 and 18 conductor movements of block 6 radially inwards in the 2nd quadrant of about 0.3 and 0.35 mm, respectively (best fit), with a calculated frame of about 0.25 to 0.35 mm and 0.25 to 0.45 mm, respectively.

   Fig.: Expected defect in CC 2092 is a conductor movement of block no. 6.

7th July 04, Firm 2:  The collared coil 2092 undergoes the procedure of disassembling in presence of A. Musso from CERN. The collared coil was entirely disassembled and the poles were separated. The entire length of the coils have been inspected, but no defect or damage was visible. It is also remarkable that the cable was well glued along the entire length in both apertures.