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.
LBNL, Berkeley, California, USA
BNL, Upton, Long Island, New York, USA
The Relativistic Heavy Ion Collider (RHIC) arc dipoles at Brookhaven National Laboratory are operated at low field for low energy Au-Au studies. Indications of strong nonlinear magnetic fields have been observed at these low currents due to the persistent current effects of superconducting NbTi filaments. We report the details of the measurement and calculation of the field errors due to persistent current effect. The persistent current induced field errors calculated with a model based on the strand magnetization data agree well with the measurements of a spare arc dipole magnet. The dependence of the persistent current effects on the park current is calculated based on the validated model.
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.
