The characteristics of the internal transport barrier (ITB) have been investigated under reactor relevant conditions with edge fuelling and electron heating in JT-60U weak shear plasmas. In order to investigate the effects of edge fuelling and electron heating separately, two independent classes of experiments were performed, i.e. one with edge fuelling and ion dominant heating and the other with central beam fuelling and additional electron heating. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection. The ion temperature (T i) in the central region inside the ITB decreased due to cold pulse propagation even with edge fuelling. By optimizing the injection frequency and the penetration depth, the decreased central T i recovered and a good ITB was sustained with enhanced pedestal pressure. The T i-ITB also degraded significantly with electron cyclotron heating (ECH), when the stiffness feature was strong in the electron temperature (T e) profile. The ion thermal diffusivity in the ITB region increased with the electron thermal diffusivity, indicating the existence of a clear relation between ion and electron thermal transport. On the other hand, the T i-ITB remained unchanged or even grew, when the stiffness feature was weak in the T e profile. The density fluctuation level at the ITB seemed unchanged during ECH; however, the correlation length became longer in the T i-ITB degradation case and shorter in the T i-ITB unchanging case.

Supersonic molecular beam injection (SMBI) was successfully operated in JT-60U after improving the performance of the vacuum seal used inside the injector head. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with filling gas pressures (P FG) of 0.2–0.6 MPa. The fuelling efficiency exhibited a weak dependence on P FG and the injection direction (high- and low-field-side injections). The amount of fuelling necessary for achieving the same density level is much smaller for SMBI than for gas puffing. It is comparable for SMBI and pellet injection even with shallower penetration of SMBI as discussed. The SMBI ionization area was estimated based on emission measured using a fast TV camera with a time resolution of 0.167 ms. The estimations indicated a similar penetration position for P FG = 0.6 and 0.2 MPa, although the ionization area was larger for 0.6 MPa. This result supports the weak P FG dependence of the fuelling efficiency. The front of the ionization area moved between the first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded even in the first frame from the expected SMB size and the expansion was enhanced in the second frame. These relatively slow changes between the two frames suggest that the interaction between the SMB and the plasma significantly influences the fuelling characteristics.

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In the collision of a liquid droplet onto a flat surface, a splashing parameter (K=We0.5Re0.25) has been used to evaluate the flattening behavior, and a critical value of K (KC) was introduced as a criterion for splashing. In order to evaluate K of thermal sprayed particle, in-flight measurement for the velocity and temperature of the particle was conducted in this study. As a flattening pattern of the thermal sprayed particle changed significantly with a substrate temperature, the transition temperature (Tt) was also measured by changing the substrate temperature. Both K and Tt showed a tendency of monotonous decreasing with increasing the spray distance and a strong linearity was recognized in a K-Tt relationship. This straight line corresponds to a critical value for the splashing. However, as the influence of substrate temperature on the flattening is essentially independent of K, a new criterion for the splashing in the flattening of the particle was proposed in the study. That is, a splashing parameter on flattening was proposed, which considers the ratio of the flattening velocity to the impact velocity of the particle.

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