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

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 [Formula: see text] (q = 2). The field dependence of activation energy shows a [Formula: see text] 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.

Applications of NMR imaging to the time-dependent swelling effect in polymers.

The swelling process is often observed in many polymers of interest and is an important phenomenon for the understanding of many biopolymers. This important process, however, is known as poorly understood in the area in polymer science. One of the reasons is that the conventional method of examining the swelling process is often inconsistent. Since it has many important properties including non-invasiveness, Nuclear Magnetic Resonance (NMR) Micro-imaging has become a significant method of analyzing biomaterials as well as biological specimens [1,2]. In the present study, a time-dependent swelling process was observed non-invasively to investigate the polymeric swelling effect using NMR micro-imaging. The present study provides a noble and non-invasive method of measuring the degree of swelling as well as volumetric changes occurring in polymers immersed in liquid. The information obtained relates to both a water ingress process and volumetric changes of polymer specimens. This proposed method also will provide more reliable techniques to ascertain the time-dependent swelling process than the other conventional methods. One of the important aspects of the present study is that the proposed method is a non-invasive technique and is also capable of ascertaining the time-dependent process of the swelling. This may be a new method of measuring the degree of swelling as well as the time-dependent water ingress process in a polymer.