An experimental 11.5 T Nb/sub 3/Sn LHC type of dipole magnet

Abstract

Ah9trud-This paper describes various design and production details of the magnet system as well as compoaent tests. I INTRODUCTIONThe various model magnets built for the LHC as well as SSC during the last years have demonstrated that a magnetic field in the bore in the main dipoles of about 10 T at 1.8 K can just be attained [1], [2]. With the critical current density of the NbTi conductors available today and the two shell cosine (e) design, this seems to be the ultimate limit.Exploration of higher fields can provide valuable information about the basic limitations and improvements of conductor design, mechanical support system and magnet production. Only with Nb,Sn conductors is the field range exceeding 10 T accessible. At present Nb3Sn conductors with non copper Jc of 2OO0-25OO "m2 at 10 T and 4.2 K have become available in industry with which fields of 13 to 15 T appear within reach during the coming years. The effective filament diameter of 20-40 pm in these conductors is still to large to be competitive with NbTi for application in accelerator magnets. Therefore the research is primarily focused on the m e c w c a l problems in the windings to improve the force handling to avoid premature quenching and training.In the framework of the LHC magnet development program, an experimental 1 m long, 11.5 T Nb3Sn dipole magnet has been designed and is under construction in the Netherlands. The principle design is based on the high pedorming ECN type of powder tube conductor which has a non copper Jc of 2000 Nmm2 at 10 T. At the start of the project this conductor was the Jc record holder, while other types of Nb3Sn conductors showed current densities of 800 to 1400 A/mm2. At this moment also some MJR W S n wires have current densities in the 2000-2500 "m2 range. These will be used to construct another experimental high field dipole magnet .Apart from the high target field which will be realised within the geometrical limitations of the LHC design, the aim of this project is to develop alternatives for cable design, mechanical support, conductor insulation and production techniques. The test results of a few twin aperture NbTi model magnets at CERN revealed no specific problems with respect to the common yoke configuration [ 11. Therefore the aim of this project has been altered into the realisation of a single aperture magnet. DESIGN CHARACTERISTICS A. Conductor designA general optimisation method for the design of the conductors in dipole magnets has been developed [3]. Apart from geometrical constraints or prefened solutions with respect to the position and tilt angle of the pole plane, the available space, the number of layers, the effective insulation thickness and the cable dimensions, the algorithm also includes the specific JC@) relation of the conductor and the required field homogeneity and strength. The starting points are: the ECN Nb3Sn conductor, a two layer cosine (9) design, 11.5 T central field, a net insulation thickness of 0.14 mm, a bore of 50 mm and all higher order multiples < The iteration pro...

State of the art powder-in-tube niobium–tin superconductors

“…In 1988, 200 kg 36 filament wire was manufactured for a 12 T insert for the Sultan facility in Villigen, Switzerland [15,61]. Rutherford-type cables were manufactured from 192 filament wire in 1990 and used in the world record setting 11 T MSUT dipole magnet [52][53][54], which was the first Nb^Sn dipole to surpass NbTi dipole limitations.…”

Niobium-tin magnet technology development at Fermilab

“…Included in the table also are the data reported by LBNL [5,7] and University of Twente [4]. The moduli of the composite tested here are much lower than that reported by LBNL and higher than that measured at [4]. These differences in the data quoted here and else where in the literature are not understood yet.…”

“…At room temperature, the behavior is nonlinear and hence two moduli are specified, one at low pressures and the other at higher pressures. Included in the table also are the data reported by LBNL [5,7] and University of Twente [4]. The moduli of the composite tested here are much lower than that reported by LBNL and higher than that measured at [4].…”

“…The most common insulation material used for Nb 3 Sn cables is S-2 fiber glass either in tape form or sleeve [4,5].…”

Post-LHC accelerator magnets

“…The group substantially exceeded the 10 tesla barrier with a Nb 3 Sn dipole in 1995 [14]. In collaboration with CERN, the group is now engaged in the development of a 10 tesla, 88 mm bore, Nb 3 Sn dipole for a possible upgrade for the low field LHC beam separator dipoles [15], Fig.…”