Future upgrades to machines like the Large Hadron Collider (LHC) at CERN will push accelerator magnets beyond 10 T forcing the replacement of NbTi superconductors with advanced superconductors such ...as Nb 3 Sn. In support of the LHC Phase-II upgrade, the US LHC Accelerator Research Program (LARP) is developing a large bore (120 mm) Nb 3 Sn Interaction Region (IR) quadrupole (HQ) capable of reaching 15 T at its conductor limit and gradients of 199 T/m at 4.4 K and 219 T/m at 1.9 K. The 1 m long, two-layer magnet, addresses coil alignment and accelerator quality features while exploring the magnet performance limits in terms of gradient, stress and structure. This paper summarizes and reports on the design, mechanical structure, coil windings, reaction and impregnation processes.
The upgrade of the LHC collimation system includes additional collimators in the LHC lattice. The longitudinal space for the collimators can be obtained by replacing some LHC main dipoles with ...shorter but stronger dipoles compatible with the LHC lattice and the existing powering circuits, cryogenics, and beam vacuum. A joint development programme aiming at building a 5.5 m long two-in-one aperture Nb 3 Sn dipole prototype suitable for installation in the LHC is being conducted by FNAL and CERN. As part of the first phase of the programme, 1 m and 2 m long single aperture models are being built and tested. Later on, the collared coils from these models will be assembled and tested in a two-in-one aperture configuration in both laboratories. A 2 m long practice model made of a single coil wound with Nb 3 Sn cable, MBHSM101, was developed and constructed at CERN. It has been completed, and tested at both 4.3 K and 1.9 K. This practice model features collared coils based on removable pole concept, S2-glass cable insulation braided over a mica layer, and coil end spacers made of sintered stainless steel with springy legs. The paper describes the main features of this practice model, the main manufacturing steps and the results of the cold tests.
BSCCO-2212 Wire and Cable Studies Barzi, E; Lombardo, V; Turrioni, D ...
IEEE transactions on applied superconductivity,
06/2011, Letnik:
21, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
BSCCO-2212 round wires and cables are being studied for possible use in very high field magnets (>; 25 T) within the multi-Lab Very High Field Superconducting Magnet Collaboration (VHFSMC). Billets ...produced by Oxford Superconducting Technology were used to make Rutherford-type cables of various geometries. The effect of the cable parameters was measured on the extracted strand performance and deformation. Transport properties were measured at 4.2 K in fields up to 14 T for the extracted strands across the edges, and compared with as-received round wire. The same wire used in the cables was also deformed by flat rolling to reproduce the deformation seen by the round strand when formed into a Rutherford cable. After heat treatment, rolled samples were characterized for transport properties and results compared to those obtained for strands extracted from the cables. Finally cables were tested at 4.2 K and self-field using a superconducting transformer and results compared to those of the extracted strands.
Recent advancements in the critical current density of conductors, coupled with a large effective filament size, have drawn attention to the problem of magneto-thermal instabilities. At low magnetic ...fields, the quench current of such high strands is significantly lower than their critical current because of the above-mentioned instabilities. An adiabatic model to calculate the minimum current at which a strand can quench due to magneto-thermal instabilities is developed. The model is based on an dasiaintegralpsila approach already used elsewhere . The main difference with respect to the previous model is the addition of the self-field effect that allows to describe premature quenches of non-magnetized strands and to better calculate the quench current of strongly magnetized strands. The model is in good agreement with experimental results at 4.2 K obtained at Fermilab using virgin Modified Jelly Roll (MJR) strands with a low residual resistivity ratio (RRR) of the stabilizing copper. The prediction of the model at 1.9 K and the results of the tests carried out at CERN, at 4.2 K and 1.9 K, on a 0.8 mm Rod Re-Stack Process (RRP) strand with a low RRR value are discussed. At 1.9 K the test revealed an unexpected strand performance at low fields that might be a sign of a new stability regime.
PDF