Effects of q(r) on the alpha particle ripple loss in TFTR

An experiment was done with TFTR DT plasmas to measure the effect of the q(r) profile on the alpha particle ripple loss using a radially movable scintillator detector 20° below the outer midplane. The experimental results were compared with toroidal field (TF) ripple loss calculations done using a Monte Carlo guiding centre orbit following code (ORBIT). Although some of the experimental results are consistent with the ORBIT code modelling, the measured variation of the alpha particle loss with q(r) could not be explained by this code. This inconsistency is most likely due to the effect of limiter shadowing on alpha particle diffusion into this detector, which cannot be modelled with ORBIT.