Trends in Field Quality Along the Production of the LHC Dipoles andDifferences Among Manufacturers

Abstract

More than two thirds of the dipoles of the Large Hadron Collider have been manufactured and their magnetic field has been measured at room temperature. In this paper we make a review of the trends that have been observed during the production. In some cases, the trends were traced back to displacements of conductors with respect to the nominal lay-out. The analysis allows detecting the most critical zones in the superconducting coil as far as field quality is concerned. The second part of the paper makes the point of the observed differences in field quality between the three manufacturers. The analysis allows evaluating which multipoles are more affected, what magnitudes of displacements are necessary to explain these differences (the manufacturers all producing the same baseline), and what could be the origin of such differences. Abstract-More than two thirds of the dipoles of the Large Hadron Collider have been manufactured and their magnetic field has been measured at room temperature. In this paper we make a review of the trends that have been observed during the production. In some cases, the trends were traced back to displacements of conductors with respect to the nominal lay-out. The analysis allows detecting the most critical zones in the superconducting coil as far as field quality is concerned. The second part of the paper makes the point of the observed differences in field quality between the three manufacturers. The analysis allows evaluating which multipoles are more affected, what magnitudes of displacements are necessary to explain these differences (the manufacturers all producing the same baseline), and what could be the origin of such differences.

The Development of Superconducting Magnets for Use in Particle Accelerators: From the Tevatron to the LHC

“…For this reason, the spread inside magnets assembled by the same firm is similar to the global spread for even multipoles, and is ∼30% lower for the odd ones (see Table 6). A few trends [62] were observed in the production; some trends in b 3 and a 4 have been traced back to the position of the upper block in the inner coil, close to the pole, as also shown in Fig. 22.…”

Magnetic Performance of the Main Superconducting Magnets for the LHC

“…The normal 14th pole is marginally above the beam dynamic targets by 0.2 units. For no differences between assemblers are found [11]. The multipoles , and show assembler signatures justified by coil movements of less than 100 m. At injection persistent currents affect the first allowed multipoles with a contribution of respectively units and unit for and .…”

“…The MQM and MQY magnets fulfilled all requirements during qualification tests and no further design adjustments in the design were needed. The dipole production was shared between three manufacturers (firm 1, firm 2 and firm 3) that followed different procedures for collared coils and collars assemblies, using also two different collars suppliers and different tooling for the coil curing [11]. The MQ, MQM and MQY magnets were produced, for each magnet type, by a single manufacturer.…”

Superconductivity: its role, its success and its setbacks in the Large Hadron Collider of CERN

“…Though small, these changes (at two different times) will be essential for good performance of the accelerator. In Figure 12 the harmonic b3 (sextupole) of the LHC dipole measured at room temperature in the factories [31] is shown with the time of intervention indicated. The construction of the LHC magnets has been described in previous papers [32][33][34][35], here it is worth to recall that the three manufacturers: Alstom MSA-Jeumont Framatome (Fr) consortium, Ansaldo ASG (It), Babcock Noell (De), have produced magnets according to CERN's detailed design, which allowed small differences in the manufacturing technology.…”