X-Ray simulation of the sawtooth phenomena on TFTR

The m= 1 island size or m=1 deformation of magnetic surfaces during sawtooth crashes is estimated on TFTR by comparing experimental observations of X-rays and ECE electron temperature with a simple simulation which calculates signals of line-integrated X-ray and local electron temperature assuming rigid rotation of the plasma. Sawteeth oscillations with a slow crash (r_crash ~ several ms) can be simulated by a Kadomtsev-type reconnection model in which an/w=l island grows to the size of the q=1 surface during the sawtooth crash. In the sawteeth which have a fast crash (50 ßs ~ T_crash ~ 500 μs), the m = 1 island size sometimes (not always) becomes ~ 1 /2 of the sawtooth inversion radius during the crash phase. The final structure, however, is hard to identify, because of the slow plasma rotation frequency. The ⁴'Hot Core appears to move away from the plasma center in a Kadomtsev-type reconnection without causing very large transport or diffusion.