Nature of magnetic fluctuations in CASTOR tokamak

The magnetic fluctuations are monitored in radial and poloidal directions deep into the tokamak. First time the magnetic fluctuations are studied near the core of the tokamak with the magnetic probes. For carrying out these experiments different sets of movable probes, which could move from r/a = 1 to r/a = 0.4, were used. A set of two movable poloidal probes, which are poloidally spaced from each other, were taken up to r/a = 0.4 for observing the poloidal field fluctuations near the core of the CASTOR. The radial profile of the poloidal magnetic fluctuations level is obtained from r/a = 1 to r/a = 0.4. The correlation values and poloidal wavenumbers are also obtained at different radial positions. Two movable sets, each of two probes, were installed for registering the radial magnetic field fluctuations. In one set the probes were toroidally spaced and each was facing radial magnetic field of the tokamak. The data from these toroidally spaced radial probes tell the behavior of radial magnetic field fluctuations in the toroidal space. The correlation and wavenumber values are computed. In the other set the radial magnetic probes were poloidally spaced from each other. This time poloidal wavenumber and correlation values are obtained at different radial positions and compared particularly for two cases, r/a = 1 and r/a = 0.4. The initial results indicate that the level of magnetic fluctuations in both, radial and poloidal, directions is in the range of 10-5--10-4T between the radial positions r/a = 1 and r/a = 0.4 and is continuously increasing as probes are taken towards the core of the CASTOR. The correlation values are constantly increasing near the core which tells about the broadening and synchronization of the fluctuations in the toroidal and poloidal frame. It is observed that radial magnetic fluctuations are moving in the poloidal frame also and formation of two dimensional structures is taking place