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This paper studies the transport of hydrogen neutral particles towards the upstream region in the end cell of GAMMA 10/PDX by developing a neutral transport code. As a first step, a series of initial test calculations have been performed by injecting hydrogen molecules from the target plate with fixed plasma background. It has been shown that neutral particles concentrate near the target plate and reduce towards the upstream region. After these initial test calculations, the dependence of hydrogen gas puffing on the plasma parameters has also been investigated. Hydrogen gas puffing leads to a strong reduction in the ion temperature near the target plate. For the strong gas puffing case, Ti on the target plate is significantly reduced. Hydrogen gas puffing strongly enhances the momentum losses near the target plate via the charge–exchange reaction.

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The purpose of this study is to understand the Ar impurity transport process in the GAMMA 10/PDX. In the present study, the initial simulation using LINDA code and IMPGYRO code has been done to establish the basis of further understanding of the Ar impurity transport. The validity of the simulation model has been discussed by comparisons with those by the theoretical estimations of the friction force and the thermal force. The simulation results show that the Ar impurities with Z = 1 are transported towards the core region, since the thermal force dominates over the friction force under the present calculation conditions. The tendency does not contradict the experimental results and is reasonably explained by the theoretical prediction, i.e., the force balance between the thermal force and the friction force. The robust basis for further model validation and understanding of the Ar transport in the GAMMA 10/PDX has been established.

Metal plasma‐facing materials (PFMs) are expected to be candidates for future fusion power plants from the view point of tritium retention. The purpose of this study is to develop a model including a long timescale plasma interaction with metal PFMs. As a first step, we have developed a simple zero‐dimensional (0D) model, which consists of particle balance equations for the following three different particle species: (a) hydrogen plasma (elec., H+, H2+, H3+), (b) neutral hydrogen atoms (H) and molecules (H2) in the gas phase, and (c) the wall‐stored H atoms. The model has been applied to simulate long‐term operation in the limiter configuration of the QUEST tokamak. Modelling results of the long time evolution of the H atom wall inventory reasonably reproduce the experimental tendency. Although the present model is relatively simple, it is useful to understand the basic characteristics of overall plasma particle balance, the density control of the main plasma, and the H atom wall inventory for long‐term tokamak operation.