Supercurrent Density Correlation Function of Y BaaCus 07-6 Grain Boundary Josephson Junctions

We have measured the thermal noise in- duced slope Rp(B) of the current-voltage character- istics of YBa~Cu307-~ Grain Boundary Josephson Junctions (GBJs) for I + 0 in magnetic fields up to B = 12 T. From the measured Rp(B) dependences the magnetic field dependence of the critical current Ic(B) was derived in the large magnetic field range between 0 and 12 T. Finally, the supercurrent density correla- tion function was obtained from the Ic(B) dependence using the Wiener-Khinchine relation. By introducing the concept of the bright (BGCF) and dark ground correlation function (DGCF) a spatial Altering of the information on the supercurrent density distribution