Status of the production of the LHC superconducting corrector magnets

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.     

Principles developed for the construction of the high performance, low-cost superconducting LHC corrector magnets

The Large Hadron Collider (LHC) needs more than 6000 superconducting corrector magnets. These must be sufficiently powerful, have enough margin, be compact and of low cost. The development of the 11 types of magnets was spread over several years and included the magnetic and mechanical design as well as prototype building and testing. It gradually led to the systematic application of a number of interesting construction principles that allow to realize the above mentioned goals. The paper describes the techniques developed and presently used in practically all the LHC corrector magnets ranging from dipoles to dodecapoles.     

BYBROOK BARN GARDEN CENTRE v KENT COUNTY COUNCIL: CULVERTS AND LIABILITY FOR FLOODING

On 12 August 1996, a storm occurred which resulted in the flooding of Bybrook Barn Garden Centre at Ashford (Kent), a doctor's surgery, and part of the M20 motorway. This was the latest in a long history of flooding incidents and prompted a case being brought against the highway authority (Kent County Council). The flood was caused by the inadequate capacity of a culvert under a highway. The culvert had been adequate when constructed in the 1930s, but had become inadequate over a period of time as a result of increased upstream development. The claim succeeded before the Court of Appeal in 2000. It was stated that Kent County Council had failed in its duty, in that it had failed to take reasonable steps to enlarge the culvert once it was aware of the flood risk. The decision represents an extension of the law of nuisance. Liability had not been imposed in these circumstances before.     

Development of superconducting tuning quadrupole corrector (MQT) prototypes for the LHC

The main quadrupoles of the Large Hadron Collider (LHC) are connected in families of focusing and defocusing magnets. In order to make tuning corrections in the machine a number of quadrupole corrector magnets (designated MQT) are necessary. These 56 mm diameter aperture magnets have to be compact, with a maximum length of 395 mm and a coil radial thickness of 5 to 7.5 mm, while generating a minimum field gradient of 110 T/m. Two design options have been explored, both using the "counter-winding" system developed at CERN for the fabrication of low cost corrector coils. The first design, with the poles composed of two double-pancake coils, each counter-wound using a single wire, superposed to create 4-layer coils, was developed and built by ACCEL Instruments GmbH. A second design where single coils were counter-wound using a 3-wire ribbon to obtain 6-layer coils was developed at CERN. This paper describes the two designs and reports on the performance of the prototypes during testing.     

A study of the thermal conductivity of alumina/glass dispersed composites

The thermal diffusivity of five groups of alumina/glass composite systems has been measured at room temperature using a laser flash system. These data have been used, in conjunction with specific heat and density measurements, to calculate the effective thermal conductivity of these composites. In each of the five groups a systematic variation in glass concentration was made, and each group represents systematic variations in glass and alumina particle sizes. The thermal conductivities calculated are compared with those predicted by four models. It is apparent from these comparisons that the geometry and orientation of porosity within the sample measured are a key factor in determining which of these models (if any) is appropriate for describing the thermal conductivity of these composites.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.