Sawtooth oscillation in the IR-T1 Tokamak with tomographic reconstructions

Summary form only given. The IR-T1 tokamak is an air-core transformer type with major and minor radii of 45.00 cm and 12.50 cm respectively. The major heating system is ohmic. In order to investigate and study the instability we used tomography in conjunction with Cormack´s method. Fourier expansion of Cos(m/spl phi/) and Sin(m/spl phi/) were applied to soft X-ray profiles. The rigid rotation assumption of the plasma column and the least-square fit method for derivation of coefficients of Zernicke polynomials were used to find the final dispersion equation. As a result large m=1 oscillations in soft X-ray signals have been observed in the IR-T1 tokamak and it has been found that this phenomenon is caused by rotation of the plasma column containing perturbations, the reconstructed images revealed that in the phase before a sawtooth crash, the hot plasma core has moved gradually toward the wall. This is considered as the increasing m=1 kink mode.