Abstract-More than 400 twin aperture lattice quadrupoles are needed for the Large Hadron Collider (LHC) which is under construction at CERN. The main quadrupole is assembled with correction magnets in a common cryostat called the Short Straight Section (SSS). We plan to measure all SSSs in cold conditions with an unprecedented accuracy: integrated gradient of the field within 150 ppm, harmonics in a range of 1 to 5 ppm, magnetic axis of all elements within 0.1 mm and their field direction within 0.2 mrad. In this paper we describe the automatic measurement system that we have designed, built, and calibrated. Based on the results obtained on the two first prototypes of the SSSs (SSS3 and SSS4) we show that this system meets all above requirements.Index Terms-LHC quadrupole, magnetic axis, magnetic measurements.

This power converter energize a deflection magnet (L= 10.8 mH , R=43 mΩ). It can ramp up and down in less than 10 ms, regulate a 450 A current flat top from 5 to 960 ms with a precision better than 10 -3 , works in both polarities and finally can also operate as a conventional DC current generator. With respect to others similar converters (i.e. Ref [4]), its versatility and internal power consumption has been optimized without increasing too much its complexity.