The stability and catastrophe of diffusion processes of plasma boundary layer
摘要
A new apparatus using the inductance method has been built to test the homogeneity of large area high-T-c superconducting thin films. The apparatus has an X-Y scanning probe that can be moved at liquid nitrogen temperature to test the different regions of the films. The sample chamber of the apparatus can provide large area with high temperature homogeneity. The maximum sample size that can be measured is 50x50 mm(2). A small size of high-T-c superconducting thin film is applied to test the temperature homogeneity of the testing system and the sameness of the gap distance between the surface of the film and probe. A method for testing the apparatus is illustrated, and some experiments for the test of the apparatus have been performed. Experimental results find that the maximum temperature difference is 0.05 K at the surface of the sample mounter, and the drive field remains constant within the error of 5% in the process of X-Y scanning. The apparatus can test the homogeneity of high-T-c superconducting films not only by the superconducting transition temperature T-c, but also by the critical sheet current density K-c. (C) 1996 American Institute of Physics.