Hadron therapy is a cancer treatment that employs hadrons: a crucial component of a treatment facility is the gantry, a rotating machine that irradiates the patient from multiple angles, significantly improving treatment effectiveness. Currently, several initiatives are developing the first European ion gantry using superconducting magnets to reduce both weight and cost compared to existing ones. Among these initiatives, the EuroSIG project is working on new technologies for this gantry, including the development of bending superconducting magnets that guide the particles toward the patient, facing the challenge of combining strong curvature, moderate ramp rate and conduction cooling. The project is manufacturing a demonstrator magnet for this application, which will first be tested in a helium bath. The design, however, is also compatible with a subsequent test in conduction, marking the first step toward developing the prototype. This paper presents the preliminary design of the conduction cooling system of the EuroSIG dipole magnet, including both the demonstrator and prototype, and its integration into the mechanical structure designed by INFN-Genoa. This work constitutes the first step in assessing the feasibility of conduction cooling for this novel magnet layout. Experimental validation of the proposed cooling concept, assembly and manufacturing approach will be the subject of future activities.
Extended mean-field theory of the dilute two-dimensional Hubbard model treats superconducting, charge-density-wave (CDW), and spin-density-wave orders on an equal footing. With the phase of the gap retained in the Bogoliubov self-consistency, the on-site repulsion U> 0 admits no s-wave pairing solution at any pair center-of-mass momentum - a sign-resolved null result consistent with quantum Monte Carlo - so on-site electron-electron repulsion cannot by itself produce the superconductivity of SrTiO3. For an attractive on-site interaction U = -|U| with |U| = 5-100 meV, of the effective phonon-mediated kind established for SrTiO3, a nodeless (s-wave) gap exists below a critical pair momentum qc that contracts with filling; gap and transition temperature decrease monotonically with & micro; across the computed window, and in the deepest dilute sets the gap exceeds the Fermi energy, placing those solutions on the BCS-BEC-crossover side. At equal coupling the charge channel competes: a like-for-like grand-canonical condensation-energy comparison - both channels evaluated as Omega(order)-Omega(0) per k-state on the same window - makes pairing the ground state of the deep-dilute window, with charge order a close competitor (2%-15% margins) that prevails only where |U| <= 3 & micro; and whose material order melts by 5-7 K at |U| = 5 meV. The diagonalized charge channel renormalizes the band-edge mass: the heavy principal mass locks to the bounded-branch cap approximate to 2.0 m(e) across the ordered landscape, matching the doping-independent bulk enhancement of SrTiO3. Pairing in dilute SrTiO3 therefore requires the electron-phonon channel; the on-site repulsion acts through the charge sector, shaping order and carrier mass rather than pairing.
The performance degradation of niobium-based (Nb-based) Josephson junctions (Nb/Al-AlOx/Nb) at elevated temperatures restricts their fabrication processing temperature, hindering the large-scale integration of superconducting devices. Oxygen diffusion within the AlOx-barrier is the dominant cause of this degradation, representing an intrinsic material issue. In this work, Two types of Nb-based Josephson junctions with different barrier materials were fabricated: Nb/Al-AlN/Nb and Nb/Al-AlOx/Nb junctions. At 4.2 K, the electrical characteristics of junctions with initial critical current density (Jc0) of 2-20 kA/cm2 were characterized before and after annealing. The results show that, after annealing at 250 degrees C for 30 minutes, the critical current (Ic) of aluminum nitride (AlN)-barrier junctions retain about 100% of their initial critical current(Ic0). In contrast, AlOx-barrier junctions retain only approximately 40% of their initial critical current, representing an absolute improvement of 60 percentage points. Furthermore, the AlN-barrier junctions maintain excellent on-chip Jc uniformity after annealing. These results indicate that AlN-barrier junctions may offer improved annealing stability and could extend the process temperature window by more than 50 degrees C, potentially enhancing their compatibility with advanced semiconductor fabrication processes.
The interface structure of the Bi2Sr2CaCu2O8+x/YBa2Cu3O7-x (Bi-2212/YBCO) superconducting heteroepitaxial multilayer films epitaxially grown via an all-chemical-solution approach on (00l) oriented LaAlO3 (LAO) substrates was investigated using high-resolution transmission electron microscopy (HRTEM). This study reveals the formation of an atomic-scale disordered layer at the Bi-2212/YBCO interface, resulting from lattice mismatch between the two superconducting phases. The formation mechanism of this disordered layer is analyzed. More importantly, we find that a step-terrace structure at the interface can effectively alleviate lattice distortions induced by mismatch stress. Preliminary electrical transport measurements indicate that this optimized microstructure correlates with enhanced superconducting transition properties and critical current. These findings provide fundamental insights for the interface engineering of high-temperature superconducting heterostructures fabricated by chemical methods.
Magnets stacked with gourd-shape high temperature superconducting (HTS) sheets can operate in persistent current mode (PCM) and have the capability of magnetic flux density amplification, which hold promising application prospects in high-field research, magnetic energy storage, and maglev transportation. In this paper, the cooling structure and cryo-stability of the HTS magnet stacked with gourd-shape sheets under gaseous helium cooling are numerically studied. Two types of gas-cooling structures with copper sheets, the alternating stack and back-to-back configurations, are proposed. Cooling holes are fabricated on the copper sheets to enhance cooling efficiency. Three-dimensional simulation models of the magnet cooled by gaseous helium with the interference of a linear heat source are established. The effects of the outer edge extension length and thickness of copper sheets, as well as the number of cooling holes on the cryo-stability are studied. Results indicate that the two proposed gas-cooling structures possess superior cryo-stability compared with the direct stack structures, and the heat transfer efficiency can be effectively optimized by tuning the parameters of copper sheets and cooling holes. This work provides a new reference for the gas-cooling structure design of HTS stacked magnets.
