.

The Field Quality Crisis Unit of the LHC main dipoles production

Calibration of magnetic length in 1st generation measuring systems

In the 1st generation measuring system, magnetic length is worked out through the main field measurement in first and last position, and assuming a nominal distance between the two positions (19 times 750 mm, i.e. 14250 mm). Indeed, the distance between the first and the last measuring position is given by the length of the extensions used to move the measuring coil. Three sets have been used, one per Firm. In April 2003, the 2nd generation measuring system is installed in Firm1 and there is a first indication of a systematic error in the magnetic length measured with the 1st generation. Therefore, it is decided to measure the length of the extensions in each firm. G. Peiro is in charge of the measurement that are carried out between April and June 2003. Results show that the length of extensions has a difference with respect to the nominal value of -27 mm for Firm1 (see report),of 25 mm for Firm2, and of -32 mm for Firm3 (see report).

The correction of the measurements is carried out on 2nd December 2003, when all the third generation measuring systems are installed in the manufacturers.

(... to be continued ...)