Speaker
Description
The challenging magnetic problem of producing internal fields in compact spaces can be solved by high temperature superconducting bulk materials, such as MgB$_2$, which are promising tools for trapping fields around polarized substances, while shielding out external fields, as required for fundamental physics studies in scattering experiments.
They are also of great interests, as they allow to easily generate holding fields for accumulation and transport of polarized fuel in nuclear fusion tests.
A facility has been commissioned, which allows to control the bulk superconductor temperature down to 8 K, thanks to a cold head, driven by a helium compressor, thus satisfying also the requirement of eco-sustainability.
The facility has been tested on various superconducting hollow MgB$_2$ cylinders, each sintered starting from boron powders having different grain sizes, and it allows to measure the holding and shielding capabilities, together with the corresponding long-term stability.
The facility allows to map the trapped field along the symmetry axis and radially, as a function of both the temperature and the magnetic field. The measurements have been performed in transverse magnetic fields up to 1.2 T, due to the available magnet in our lab. And it can be moved for tests with higher transverse magnetic fields and also, after its preparation for transverse field generation, can be moved in longitudinal magnetic fields for shielding them.
In the context of an electron scattering experiment, such a solution minimizes beam deflection and the energy loss of reaction products, while also eliminating the heat load to the target cryostat from current leads that would be used with conventional electromagnets.
In the context of polarized fuel for fusion its use is straightforward, because the system can trap the magnetic field required during fuel production, and then it can provide the holding field for its transfer in fusion test facilities.
