DEVELOPMENT OF AN IMAGING TECHNIQUE OF MAGNETIC FLUX PENETRATING THROUGH SUPERCONDUCTING FILM

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The main theme of the present research is to observe the movement of magnetic flux that is penetrating through the type-II super-conducting film. We proposed to use the type-I magnetic contrast found in the scanning electron microscope (SEM) for observing the flux. It may be possible to find the causes of the pinning effect of the flux which influences the super-conductivity, such as the material, the structure, the imperfection in the specimen. Since the SEM has a spatial resolution of nm scale, this system may be used to probe the origin of the magnetic characteristics of the specimen.In the present research, first, we assume a simple magnetic structure of the material. Then, the magnetic flux and the electric field, which is produced by the electron detector are calculated. The electron trajectories are calculated in this electromagnetic field, and the electron detection position distribution is obtained in three-dimension. By converting the movement of the distribution, the magnetic structure can be predicted.The temperature of the specimen stage made in the present research in the SEM reaches down to 30K and the super-conductivity is confirmed. However, the magnetic contrast in the present system has not been observed yet. It may be because of the angular distribution and the energy distribution of electrons emitted from the surfacde. They cover the characteristic variation in the contrast. The simulation shows some preferable conditions to improve the signal to the noise ratio, and at the same time to improve the sensitivity. In the preliminary comparison between the experiment and the calculation, that is to observe the magnetic flux using ordinary magnetic films, the validity of the simulation is confirmed.