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 t he q(r) profile on the alpha particle ripple loss using a radially mov able scintillator detector 20 degrees below the outer midplane. The ex perimental results were compared with toroidal field (TF) ripple loss calculations done using a Monte Carlo guiding centre orbit following c ode (ORBIT). Although some of the experimental results are consistent with the ORBIT code modelling, the measured variation of the alpha par ticle loss with q(r) could not be explained by this code. This inconsi stency is most likely due to the effect of limiter shadowing on alpha particle diffusion into this detector, which cannot be modelled with O RBIT.