Fermilab, Batavia, Illinois, USA
Main design challenges for 15 T accelerator magnets are large Lorentz forces at this field level. The large Lorentz forces generate high stresses in the coil and mechanical structure and, thus, need stress control to maintain them at the acceptable level for brittle Nb3Sn coils and other elements of magnet mechanical structure. To provide these conditions and achieve the design field in the FNAL 15 T dipole demonstrator, several mechanical structures have been developed and analysed. The possibilities and limitations of these designs are discussed in this paper.
Fermilab, Batavia, Illinois, USA
Nb3Sn accelerator magnet technology has made significant progress during the past decades. Thanks to that 11-12 T Nb3Sn dipoles and quadrupoles are planned to be used in accelerators such as LHC in near future for the luminosity upgrade and in longer term for the LHC energy upgrade or a future Very High Energy pp Collider. However, all the state of the art Nb3Sn accelerator magnets show quite long training. This specific feature significantly raises the required design margin or limit the nominal operation field of Nb3Sn accelerator magnets and, thus, increases their cost. To resolve this problem Fermilab has launched a study aiming to analyze the relatively large amount of Nb3Sn magnet training data accumulated at Fermilab magnet test facility. The ultimate goal is to correlate magnet design and manufacturing features and magnet material properties with training performance parameters which will eventually allow us to optimize both the magnet design, fabrication and the training processes. This paper describes the general strategy of the analysis and presents the first results based on partial data processing. Conclusions and further steps are also outlined and discussed.
Fermilab, Batavia, Illinois, USA
CERN, Geneva, Switzerland
FNAL and CERN magnet groups are developing a twin-aperture Nb3Sn 11 T dipole suitable for installation in the LHC to provide room for additional collimators in the dispersion suppressor (DS) areas. Two of these magnets with a collimator in between will replace one regular MB dipole. A single-aperture 2-m long dipole demonstrator and two 1-m long dipole models have been assembled and tested at FNAL in 2012-2014. The 1 m long collared coils were then assembled into the twin-aperture configuration and tested in 2015. The first magnet test was focused on the quench performance of twin-aperture magnet configuration including magnet training, ramp rate sensitivity and temperature dependence of magnet quench current. In the second test performed in July 2016 field quality in one of the two magnet apertures has been measured and compared with the data for the single-aperture models. These results are reported and discussed in this paper.
Fermilab, Batavia, Illinois, USA
Nb3Sn magnets with operating fields of 15-16 T are considered for the LHC Energy Doubler and a future Very High Energy pp Collider. Due to large coil volume, high critical current density and large superconducting (SC) filament size the persistent current effect is very large in Nb3Sn dipoles al low fields. This paper presents the results of analysis of the persistent current effect in the 15 T Nb3Sn dipole demonstrator being developed at FNAL, and describes different possibilities of its correction including passive SC wires, iron shims and coil geometry.
