Effect of the proton irradiation on the thermally activated flux flow in superconducting SmBCO coated conductors

Abstract

We investigate changes in the vortex pinning mechanism caused by proton irradiation through the measurement of the in-plane electrical resistivity for H//c in a pristine and two proton-irradiated (total doses of 1 × 1015 and 1 × 1016 cm−2) SmBa2Cu3O7-δ (SmBCO) superconducting tapes. Even though proton irradiation has no effect on the critical temperature (Tc), the resulting artificial point defect causes an increase in normal state electrical resistivity. The electrical resistivity data around Tc shows no evidence of a phase transition to the vortex glass state but only broadens with increasing magnetic field due to the vortex depinning in the vortex liquid state. The vortex depinning is well interpreted by a thermally activated flux flow model in which the activation energy shows a nonlinear temperature change $${\boldsymbol{U}}{\boldsymbol{(}}{\boldsymbol{T}},{\boldsymbol{H}}{\boldsymbol{)}}{\boldsymbol{=}}{{\boldsymbol{U}}}_{{\boldsymbol{0}}}{\boldsymbol{(}}{\boldsymbol{H}}{\boldsymbol{)}}{{\boldsymbol{(}}{\bf{1}}-{\boldsymbol{T}}{\boldsymbol{/}}{{\boldsymbol{T}}}_{{\boldsymbol{c}}}{\boldsymbol{)}}}^{{\boldsymbol{q}}}$$U(T,H)=U0(H)(1−T/Tc)q (q = 2). The field dependence of activation energy shows a $${{\boldsymbol{U}}}_{{\bf{0}}}{\boldsymbol{ \sim }}{{\boldsymbol{H}}}^{-{\boldsymbol{\alpha }}}$$U0~H−α with larger exponents above 4 T. This field dependence is mainly due to correlated disorders in pristine sample and artificially created point defects in irradiated samples. Compared with the vortex pinning due to correlated disorders, the vortex pinning due to the appropriate amount of point defects reduces the magnitude of Uo(H) in the low magnetic field region and slowly reduces Uo(H) in high magnetic fields.

In-situ measurements of the effect of radiation damage on the superconducting properties of coated conductors

“…The fusion reaction between deuterium and tritium in a tokamak plasma emits neutrons with energies between 12-20 MeV [7,8], therefore fusion relevant neutron spectra need to contain a significant fraction of high energy neutrons. Since there are currently no sources of neutrons of an appropriate flux with these energies, previous experimental work has focussed on determining the effects of irradiation damage on the superconducting properties of CC using fission spectrum neutrons [9], heavy ions [10] or light ions/protons [11]. These experiments show, except in low magnetic fields, that there is an initial improvement in J c with increasing irradiation dose, followed by a decrease in both J c and T c and eventual complete loss of superconductivity.…”

“…These experiments show, except in low magnetic fields, that there is an initial improvement in J c with increasing irradiation dose, followed by a decrease in both J c and T c and eventual complete loss of superconductivity. Both the fluence at which the peak J c improvement is reached and the amount of any improvement are considered to be dependent on the sample temperature, type of projectile and the direction of the applied field [9][10][11][12]. For both ion and neutron irradiation, the degree of anisotropy in the superconducting properties of the textured REBCO in CC was also found to decrease with irradiation dose [10,[12][13][14][15].…”

Thermally activated flux flow and inter-granular coupling properties in (Bi, Pb)-2223 superconductor added with ZnO nanoparticles

“…where U = J c0 BVL is the thermal activation energy and ρ c = ν 0 LB /J c0 . The detailed de nitions of U and ρ c indicate that 2ρ c U/T is dependent on temperature and magnetic eld [31]. In cuprates and FeAsbased superconductors, ρ 0f = 2ρ c U/T is assumed as a temperature-independent constant [14, 31,…”

“…In this assumption, the natural logarithm of electrical resistivity is expressed as lnρ(T, B) = lnρ 0 − U 0 (B) /T where lnρ 0 = lnρ 0f + U 0 (B) /T C . This equation is known as the Arrhenius relation[31, 61, 62].According to the Arrhenius relation, the plot of lnρ vs. 1/T should show a linear behavior in the TAFF region. Consequently, the temperature dependence of the derivative D = − ∂(lnρ) /∂ T − 1 shows a the TAFF region.…”

“…As can be observed, however, the plateau is not seen but rather increases as temperature decreases. Such behavior has been observed in cuprates and iron-based superconductors[14,17,31, 61]. To solve this contradiction in the TAFF model,Zhang et al [63, 64] established a new model, called the modi ed TAFF model, by suggesting non-linear activated energy of the form U(T, B) = U 0 (B)(1 − T /T C ) q .…”