1. General Seminars

The Effect of Tritium Upload on Superconductivity

by Prof. Viorel Sandu (National Institute of Materials Physics, Dept. Magnetism and Superconductivity)

Aula Seminari (LNF INFN)

Aula Seminari


Via Enrico Fermi, 40 00044 Frascati
We present the effect of tritium upload on superconductivity of different class of materials: a) Ta, a type I superconductor; b) Nb, a type II low temperature superconductor and c) MgB2 an intermediate temperature superconductor. Superconductivity is rather robust in all materials after tritium upload. However, some differences are notable. The critical temperature,Tc, a basic property does not change in the case of Nb at low field, decreases slightly in case of Ta, but has a very interesting behavior in the case of the MgB2. It slowly changes in time but is independent on the duration of tritium uptake. Immediately after tritiation, Tc shows a slight increase to 39.1 K but decreases to the critical temperature of the untritiated (pristine) sample, Tc = 38.8 K, after 370 days. The magnetic properties are also different: the tritium loaded Nb shows a higher remanent magnetization which we attribute to the subsurface accumulation of defects, but the high field irreversible magnetization, hence, the critical current density, is smaller than for the bare sample. In the case of Ta, both the remanent magnetization and the irreversible magnetization are slightly reduced after tritiation. In the case of MgB2, the critical current density is strongly dependent on the tritium upload time, mainly at high magnetic fields. The underlying physics is discussed.