Significant improvement of the lower critical field in Y doped Nb: potential replacement of basic material for the radio-frequency superconducting cavity

Abstract

The research of high energy and nuclear physics needs high power accelerators, and the superconducting radio-frequency (SRF) cavity is regarded as the engine of them. Up to now, the widely used practical and effective material for making the SRF cavity is pure Nb. The key parameter that governs the efficiency and the accelerating field (Eacc) of a SRF cavity is the lower critical field Hc1. Here we report a significant improvement of Hc1 of a new type of alloy, Nb1-xYx fabricated by arc melting technique. Experimental investigations with multiple tools including x-ray diffraction, scanning electron microscopy, resistivity and magnetization are carried out, showing that the samples have good quality and a 30-60% enhancement of Hc1. First principle calculations indicate that this improvement is induced by the delicate tuning of a Lifshitz transition of a Nb derivative band near the Fermi energy, which increases the Ginzburg-Landau parameter and Hc1. Our results may trigger a replacement of the basic material and thus a potential revolution for manufacturing the SRF cavity.

Accuracy of Ab Initio Technique in Predicting the Structural, Electronic, Mechanical and Elastic Properties of Rhodium and Ruthenium.

“…To describe completely the quantum mechanical conduct in transition metals it is strictly necessary to calculate the many-electron wavefunction for the system. In principle this may be obtained from the time-independent Schrodinger equation [1], but in practice the potential experienced by each electron is dictated by the behaviour of all electrons in the solid [2,3,4]. Accordingly, Pan and his team carried research on rhodium (Rh) and some alloys using quasi -harmonic Debye model [5].…”