End-cell Of GAMMA Research Articles

Effects of the gas puffing neutral on the plasma parameters in the end-cell of GAMMA 10/PDX by using the multi-fluid code “LINDA”

This research numerically investigates the behavior of plasma flow in GAMMA 10/PDX. The impact of impurity gases seeding into the divertor region on the plasma parameters and the energy loss processes has been investigated numerically by using the multi-fluid code “LINDA”. The neutral particles are injected into the bulk hydrogen plasma and the upstream plasma parameters on the z-axis are ni=1.0×1019m−3, Ti=100eV,Te=30eV. A reduction in the plasma temperature has been observed with the increasing H neutral injection. The ionization and Charge-exchange (CX) power loss increase almost linearly with the increasing H neutral density, which induce a reduction in the plasma temperature. During H seeding, Ar and Ne are seeded simultaneously to observe the influence of Ar and Ne on the electron and ion energy loss mechanism. In this study, the fraction of impurity density to upstream plasma density (nz/ni) is used to be 10%. A comparison between Ar and Ne shows that Ar is effective on the electron cooling. The radiation power loss of Ar is found to be higher than that of Ne. The radiation cooling effect and CX loss significantly reduces the electron and ion temperature, respectively. A slight influence of Ar and Ne seeding on the ion energy loss terms has been observed. The electron energy loss terms increase significantly during impurity gas Ar and Ne seeding. These outcomes represent the impact of gas seeding for reducing the plasma energy on the divertor target plates.

Numerical simulation study towards plasma detachment in the end cell of GAMMA 10/PDX by a coupled fluid‐neutral code

AbstractThis 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.

Investigation of plasma behavior during noble gas injection in the end-cell of GAMMA 10/PDX by using the multi-fluid code ‘LINDA’

The linear divertor analysis with fluid model (LINDA) code has been developed in order to simulate plasma behavior in the end-cell of linear fusion device GAMMA 10/PDX. This paper presents the basic structure and simulated results of the LINDA code. The atomic processes of hydrogen and impurities have been included in the present model in order to investigate energy loss processes and mechanism of plasma detachment. A comparison among Ar, Kr and Xe shows that Xe is the most effective gas on the reduction of electron and ion temperature. Xe injection leads to strong reduction in the temperature of electron and ion. The energy loss terms for both the electron and the ion are enhanced significantly during Xe injection. It is shown that the major energy loss channels for ion and electron are charge-exchange loss and radiative power loss of the radiator gas, respectively. These outcomes indicate that Xe injection in the plasma edge region is effective for reducing plasma energy and generating detached plasma in linear device GAMMA 10/PDX.

Numerical simulation of detached plasma in the end-cell of GAMMA 10/PDX for divertor simulation study

This research investigates the effect of Argon (Ar) and Neon (Ne) injection on the plasma parameters in the end-cell of GAMMA 10/PDX numerically by using a multi-fluid code. Reduction in the temperature of the electrons and ions is observed according to the increment of impurity injection. The electron density and the particle flux show tendency of roll-over phenomena for Ar injection. Temperature reduction in the electrons and ions during Ar injection is higher than those of the Ne injection. It is also observed that the charge-exchange (CX) loss and radiative power loss for Ar injection is higher than that of the Ne injection. These outcomes indicate that Ar is more effective radiative gas for generating detached plasma.

Development of microwave interferometer system for divertor simulation experiments in GAMMA 10/PDX

Microwave interferometer has newly been installed on GAMMA 10/PDX for divertor simulation study. A divertor simulation experimental module (D-module) is used to investigate the physics of divertor in the end-cell of GAMMA 10/PDX where an open magnetic field configuration is formed. D-module has a rectangular chamber with an inlet aperture. Two tungsten target plates are mounted in V-shape inside the chamber. In order to develop understandings of divertor simulation experiments the microwave interferometer using heterodyne scheme and a 1D horn-antenna mixer array (HMA) is applied to obtain electron density and density distribution inside the V-shaped target plates. Line-averaged electron density distributions inside D-module are first observed in H2 gas injection experiments.

Numerical Simulation Study for Background Plasma in the GAMMA 10 End-Mirror Cell

We have started a simulation study of background plasma in the GAMMA 10 west end-cell using a fluid-code in order to understand divertor simulation experiments. In this fluid-code, the configuration of magnetic field lines in the west end-cell of GAMMA 10 is adopted with a mesh structure and basic physical processes such as reflection coefficient and recombination are considered. An initial computation result reveals that in the case of the plasma density range: ne ~ 1019 m-3, ion and electron temperature could not be reduced significantly to the suitable temperature for achieving the detachment. The effect of heat transfer coefficient on the target plasma is also discussed.

Measurement of Divertor Heat Flux at the End-Cell of GAMMA 10

In GAMMA 10, divertor simulation study has been started as a new research plan. Finding of the reduction method of high heat-load to the divertor plates is an important key of an operation scenario of fusion reactors. So precise estimation of divertor heat flux is an important task to do it. The paper describes advanced concept of heat flux estimation and proposes the improvement of the sensor used in GAMMA 10. First experimental result of a new sensor is also shown.