Status of the Production of the LHC Superconducting Corrector Magnets

Abstract

Abstract-The Large Hadron Collider (LHC) will be equipped with a large number (6400) of superconducting corrector magnets. These magnets are powerful, with typical peak fields of 3-4 T on the coils, but at the same time compact and of low cost. There are many types: sextupoles, octupoles and decapoles to correct the main dipole field, dipoles, quadrupoles, sextupoles and octupoles to condition the proton beams and several nested correctors from dipole to dodecapole in the inner triplets. The sizes vary from 6 kg, 110 mm long, nested decapole-octupole spool pieces to 1800 kg, 1.4 m long, trim quadrupoles. THE fabrication of the 11 different types of magnets is assured by 10 contracts placed at 6 firms, two of which are in India. A number of magnets are now in series production, others in their pre-series production. The paper describes the present state of the fabrication and the testing of these magnets.Index Terms-Correctors, LHC, magnets, superconducting. I. LHC CORRECTOR MAGNET OVERVIEWT HE Large Hadron Collider (LHC) will be equipped with more than 6400 corrector magnets ( Fig. 1 shows two examples). About 3800 single aperture and 1000 twin aperture corrector magnets will be used. The 194 mm beam separation gives sufficient lateral space to build all correctors as single bore modules, with a nominal working point between 40-60% along the load line. Twin aperture units are assembled by keying corresponding modules into laminated support structures. The assembly by keying insures mechanical precision and allows flexibility during mounting, since the same type of module is used for a normal or for a skew magnet. To optimize the cost of the corrector magnets, common design and fabrication principles II. CORRECTOR TYPES AND CIRCUITSWe distinguish several types of correctors for LHC.

Qualification of the LHC Corrector Magnet Production With the CERN-Built Measurement Benches

“…offsets between magnetic and mechanical axis, roll angle errors, and main field. Tolerance values were typically 0.1 mm for dX, dY , 3.5 mrad for , and 1% for the spread of the main field [5]. These limits gave an indication of whether a magnet should be accepted or rejected.…”

“…The excitation current used was between 0.1 A and 1 A depending on the magnet type [8], whereas cold measurements were performed on a small sample of magnets at different current values from zero to nominal current. In order to effectively use the magnets in the LHC, it is necessary to know the correlation between warm and cold measurements.…”

The LHC Main Quadrupoles During Series Fabrication

“…It must be pointed out that a certain number of components for the quadrupole magnets themselves, but also for the cold masses, were CERN supplies, originating from other factories under contract with CERN and from are the integral transfer function (i.e. the gradient times magnetic length over the current) and the dodecapole component, b 6 , the evolutions of which are shown in Fig. 1 and 2.…”

“…40 variants of these cold masses exist due to the different combinations of corrector magnets [6] with the focusing and defocusing function of the main quadrupoles and the polarity of the protection diodes, combined with the four types of interfaces to the helium supply line and cryostat. In fact, together with different types of the cryostats, 61 variants of cryostated arc quadrupole units will be installed in the LHC tunnel.…”

Status of the Large Hadron Collider (LHC)

“…Half of the MCS and MCDO magnets are being manufactured in India in the framework of a collaboration agreement. Detailed reports on the LHC supercon- TABLE I ducting magnet status can be found in specialized contributions to this conference [4]- [6].…”