J.P. Ozelis

Investigation of cable insulation and thermo-mechanical properties of epoxy impregnated Nb/sub 3/Sn composite

Within the framework of the Fermilab high field magnet program, cable insulation and thermo-mechanical properties of epoxy impregnated Nb/sub 3/Sn composite were studied. As a part of cable insulation development, a new wrappable ceramic insulation was investigated to understand its mechanical properties and its influence on magnet fabrication technology. Measurements of modulus of elasticity and Poissons ratio of Nb/sub 3/Sn composite made out of ten-stack samples were performed under compression at room temperature and at 4.2 K. The results from both monotonic and cyclic loading tests are presented. Finally, measurements of the coefficient of thermal contraction for the composite using strain gauges is discussed.

Field quality in Fermilab-built models of quadrupole magnets for the LHC interaction region

Superconducting quadrupole magnets for the interaction regions of the Large Hadron Collider are being developed by the US-LHC Accelerator Project. These 70 mm bore quadrupole magnets are intended to operate in superfluid helium at 1.9 K with a nominal field gradient of 215 T/m. A series of 2 m model magnets has been built and cold tested at Fermilab to optimize their design and construction and to study the performance of the magnets. Field measurements of the 8 model magnets and comparisons with the required field quality are reported in this paper.

Development of the 11 T Nb/sub 3/Sn dipole model at Fermilab

A one meter long Nb/sub 3/Sn dipole model with 11 T nominal magnetic field in a 43.5 mm bore is being developed at Fermilab in collaboration with LBNL and KEK as part of the R&D efforts for a future Very Large Hadron Collider. This paper describes the magnet design and fabrication procedure as well as summarizes the results of magnetic, mechanical and quench protection analyses. The main parameters of superconducting strand and cable are also reported.

Conceptual design of a common coil dipole for VLHC

Superconducting magnet technology and cost reduction are key issues in the R&D effort towards a post-LHC, 100 TeV hadron collider. A dipole field of 10-12 T at 4.5 K operating temperature results in acceptable machine length and refrigeration power requirements, and allows taking advantage of synchrotron radiation damping to achieve low beam emittance. In this paper, the conceptual design of a react-and-wind common coil dipole is presented, which aims at these operating parameters with minimum cost and complexity.

Development of react and wind common coil dipoles for VLHC

Common coil magnets are a promising option for post LAC hadron colliders. Fermilab, in collaboration with LBNL, is involved in an R&D program to develop 11 T, 30-40 mm aperture, common coil dipoles. The use of Nb/sub 3/Sn wound after reaction is chosen in order to address cost reduction that is a key issue for future hadron colliders. The common coil design concept allows a large bending radius at the coil ends and is well suited to the react-and-wind technique with brittle superconductors. The horizontal component of the magnetic forces in a common coil is larger than the radial component in a shell type layout, imposing demanding requirements on the mechanical structure. Both a 2-layer and a single layer design have been studied. The development of the program is presented focusing on the mechanical designs and assembly techniques. R&D activities and plans are also presented.

Design, development and test of 2 m quadrupole model magnets for the LHC inner triplet

Fermilab and LBNL are in the midst of a model magnet program to develop and prove the design of quadrupoles for use in the LHC Interaction Region inner triplets. These magnets have a nominal gradient of 205 T/m in a 70 mm bore, and operate in superfluid helium at 1.9 K. The R&D program addresses magnetic, mechanical, thermal design and quench protection issues. This paper describes design, fabrication experience and test results from the first 2 m models.

Field quality in Fermilab-built models of high gradient quadrupole magnets for the LHC interaction regions

Superconducting quadrupole magnets for the interaction regions of the Large Hadron Collider are being developed by the US-LHC Accelerator Project. These 70 mm bore quadrupole magnets are intended to operate in superfluid helium at 1.9 K with a nominal field gradient of 215 T/m. A series of 2 m model magnets are being built and tested at Fermilab to optimize design and construction parameters. Measurements of the field quality of the model magnets tested to date and comparisons with the required field quality are reported in this paper.

Thermal studies of a high gradient quadrupole magnet cooled with pressurized, stagnant superfluid

A 2-m long superconducting model of an LHC Interaction Region quadrupole magnet was wound with stabrite coated cable. The resulting low interstrand resistance and high AC losses presented the opportunity to measure magnet quench performance in superfluid as a function of helium temperature and heat deposition in the coil. Our motivation was to duplicate the high radiation heat loads predicted for the inner triplet quadrupoles at LHC and study the coil cooling conditions in the magnet. At the Magnet Test Facility in Fermilabs Technical Division, the magnet quench performance was tested as a function of bulk helium temperature and current ramp rate near the planned high luminosity interaction region field gradient of 205 T/m. AC loss measurements provided a correlation between current ramp rate and heat deposition in the coil. Analysis indicates that the results are consistent with there being little participation of superfluid helium in the small channels inside the inner layer in the heat removal from the coil. However magnet performance will be limited by the outer coil pole turn in LHC at a current level well above the operating current.

Mechanical design and analysis of LHC inner triplet quadrupole magnets at Fermilab

A series of model magnets is being constructed and tested at Fermilab in order to verify the design of high gradient quadrupole magnets for the LHC interaction region inner triplets. The 2 m models are being built in order to refine the mechanical and magnetic design, optimize fabrication and assembly tooling, and ensure adequate quench performance. This has been carried out using a complementary combination of analytical and FEA modeling, empirical tests on 0.4 m mechanical assemblies and testing of model magnets during fabrication and under cryogenic conditions. The results of these tests and studies have led to improvements in the design of the magnet end restraints, to a preferred choice in coil end part material, and to a better understanding of factors affecting coil stress throughout the fabrication and operational stages.

Recent results from the LHC inner triplet quadrupole development program at Fermilab

Fermilab, in collaboration With LBNL and BNL, is in the process of developing a focusing quadrupole for installation in the interaction region inner triplets of the LHC. This magnet is required to have an operating gradient of 215 T/m across a 70 mm coil bore, and operates in superfluid helium at 1.9 K. The design is based on a two layer cos (20) coil, mechanically supported by standalone steel collars. The collared coil assembly is surrounded by a iron yoke for flux return, and the assembly enclosed by a stainless steel shell. The development program has addressed mechanical, magnetic, quench protection, and thermal issues, through a series of model magnets constructed at Fermilab. This paper summarizes results from the recent model tests, and the status of the program.