Abstract:The interaction among plasma, neutrals and surfaces in fusion reactors is of immense importance for heat and particle control, specially for the next generation of devices. Heat loads of 10 MW m-2 are expected for steady state operation at ITER and up to 20 MW m-2 in slow transient situations. To study the complex physics appearing between the plasma and the divertor material, as well as techniques for heat flux mitigation, plasma linear devices are employed. Magnum-PSI, located at DIFFER, can reproduce heat a… Show more
“…The plasma and neutral solutions for B2.5-Eunomia are the same as in [11]. In the high density scenario the cases have been re-run to account for the issue in double counting p + H collisions [16]. For each of these plasma scenarios, two neutral pressures in the target chamber are analysed in deep.…”
Section: Resultsmentioning
confidence: 99%
“…Although these differences are barely noticeable, they should be noted as they have a small impact in the final solution. However, the big difference between the two suites is still the different implementation of plasma-neutral processes explained in [16].…”
Section: Main Differences Between Solps-iter and B25-eunomiamentioning
confidence: 99%
“…As stated in [16], Eirene and Eunomia use a different wall reflection model. Eunomia always assumes a thermal reflection of atoms and molecules.…”
Section: Main Differences Between Solps-iter and B25-eunomiamentioning
confidence: 99%
“…out in the future to determine the impact of the distribution of vibrational levels in the simulation of Magnum-PSI. As stated in [16], Eirene and Eunomia implement some relevant plasma-neutral collision processes in a distinct way. This leads to significant differences in the sink and sources of particles, momentum and energy passed to B2.5 to generate a new plasma scenario.…”
Section: Collisionmentioning
confidence: 99%
“…The trend of peak electron density and temperature as a function of the target chamber's neutral pressure is studied for a wide range of values. The disparate neutral distributions and sources of particles and energy obtained in the standalone comparison of [16] result in completely different plasma states. Due to the free parameters present in the simulation of Magnum-PSI [11], both codes are able to reach plasma profiles close to the TS experimental data a few centimetres in front of the target.…”
Heat loads of 10MW m-2 are expected for steady state operation at ITER and up to 20MW m-2 in slow transient situations. Plasma linear devices like Magnum-PSI can recreate situations close as those expected to be achieved at ITER divertor, providing easier access for diagnostics than in a tokamak. Numerical models are still necessary to complement experiments and to extrapolate relevant information to fusion devices, as the relevant Atomic and Molecular (A\&M) processes. SOLPS-ITER (formerly known as B2.5-Eirene) is typically employed to solve the plasma and neutral distribution in a coupled way for tokamak devices. For Magnum-PSI, B2.5 has been coupled with a different neutral module, named Eunomia, developed mostly for linear devices. Nevertheless, there is an interest in using SOLPS-ITER for simulating Magnum-PSI, as it would ease the process of relating linear device results with tokamaks. A previous work found significant differences in the implementation of relevant plasma-neutral processes in Eirene and Eunomia. A wide range of plasma scenarios are compared between B2.5-Eunomia and SOLPS-ITER. Although both codes produce results close to experimental Thomson Scattering (TS) density and temperature near the target once the electric potential at the source is adjusted, these are achieved with completely different plasma and neutral distributions. Anomalous transport coefficients, which are other of the free-parameters in Magnum-PSI simulation, are set equal between the two codes. When studied in a wide range of neutral pressures, SOLPS-ITER shows a trend closer to experiments, as well as providing a converged solution at neutral pressures higher than $\unit[4]{Pa}$ for which B2.5-Eunomia was unable to provide a converged solution. Additional measurements of the neutral distribution in the target chamber as well as the electric potential at the source are required to determine which code is producing results closer to the experiment.
“…The plasma and neutral solutions for B2.5-Eunomia are the same as in [11]. In the high density scenario the cases have been re-run to account for the issue in double counting p + H collisions [16]. For each of these plasma scenarios, two neutral pressures in the target chamber are analysed in deep.…”
Section: Resultsmentioning
confidence: 99%
“…Although these differences are barely noticeable, they should be noted as they have a small impact in the final solution. However, the big difference between the two suites is still the different implementation of plasma-neutral processes explained in [16].…”
Section: Main Differences Between Solps-iter and B25-eunomiamentioning
confidence: 99%
“…As stated in [16], Eirene and Eunomia use a different wall reflection model. Eunomia always assumes a thermal reflection of atoms and molecules.…”
Section: Main Differences Between Solps-iter and B25-eunomiamentioning
confidence: 99%
“…out in the future to determine the impact of the distribution of vibrational levels in the simulation of Magnum-PSI. As stated in [16], Eirene and Eunomia implement some relevant plasma-neutral collision processes in a distinct way. This leads to significant differences in the sink and sources of particles, momentum and energy passed to B2.5 to generate a new plasma scenario.…”
Section: Collisionmentioning
confidence: 99%
“…The trend of peak electron density and temperature as a function of the target chamber's neutral pressure is studied for a wide range of values. The disparate neutral distributions and sources of particles and energy obtained in the standalone comparison of [16] result in completely different plasma states. Due to the free parameters present in the simulation of Magnum-PSI [11], both codes are able to reach plasma profiles close to the TS experimental data a few centimetres in front of the target.…”
Heat loads of 10MW m-2 are expected for steady state operation at ITER and up to 20MW m-2 in slow transient situations. Plasma linear devices like Magnum-PSI can recreate situations close as those expected to be achieved at ITER divertor, providing easier access for diagnostics than in a tokamak. Numerical models are still necessary to complement experiments and to extrapolate relevant information to fusion devices, as the relevant Atomic and Molecular (A\&M) processes. SOLPS-ITER (formerly known as B2.5-Eirene) is typically employed to solve the plasma and neutral distribution in a coupled way for tokamak devices. For Magnum-PSI, B2.5 has been coupled with a different neutral module, named Eunomia, developed mostly for linear devices. Nevertheless, there is an interest in using SOLPS-ITER for simulating Magnum-PSI, as it would ease the process of relating linear device results with tokamaks. A previous work found significant differences in the implementation of relevant plasma-neutral processes in Eirene and Eunomia. A wide range of plasma scenarios are compared between B2.5-Eunomia and SOLPS-ITER. Although both codes produce results close to experimental Thomson Scattering (TS) density and temperature near the target once the electric potential at the source is adjusted, these are achieved with completely different plasma and neutral distributions. Anomalous transport coefficients, which are other of the free-parameters in Magnum-PSI simulation, are set equal between the two codes. When studied in a wide range of neutral pressures, SOLPS-ITER shows a trend closer to experiments, as well as providing a converged solution at neutral pressures higher than $\unit[4]{Pa}$ for which B2.5-Eunomia was unable to provide a converged solution. Additional measurements of the neutral distribution in the target chamber as well as the electric potential at the source are required to determine which code is producing results closer to the experiment.
The collisions between neutral particles and plasma in the divertor region determine divertor detachment and heat flux to the target. However, the diagnostic of neutral particle information in the tokamak experiment is very lacking. To study the behavior of neutral particles in the boundary region flexibly and comprehensively, a two‐dimensional kinetic neutral transport code based on Monte Carlo method is developed in this work. The code is applied to simulate the neutral particles in the boundary of EAST device. Firstly, the simulation results are compared with EIRENE using an identical plasma background, and good agreement is obtained. Secondly, the transport of methane and the corresponding hydrocarbon compounds is simulated using the developed code. The methane injection case is compared with the injection of carbon and deuterium molecule mixture gas (ratio 1:2) to investigate their impact on detachment and fueling. The simulation reveals that, compared to the direct carbon atom injection case, charge‐exchange collision is the dominant collision of neutral methane (hydrocarbons), which suppresses divertor power radiation and plasma detachment while promoting the improvement of fueling efficiency.
A vapour box is a physical device currently being considered to reduce the high heat and particle fluxes typically impacting the divertor in tokamaks. This system usually consists of a series of boxes that retains neutral particles to increase the amount of collision events with the impacting plasma. The neutral particles come from recycling and recombination of the plasma, gas puffing inside the box or by the evaporation of a liquid metal, typically Li or Sn. Currently, a vapour box is being constructed for testing in the linear plasma generator Magnum-PSI, operated at DIFFER. Its modular design will allow for open (not enclosing the target) and closed (enclosing the target) configurations, as well as evaporating a liquid metal to create a vapour cloud inside the box. The experiments carried out with this device will investigate its capabilities to reduce the plasma flux towards the target. This work presents a numerical study performed with SOLPS-ITER about the effectiveness of the current vapour box design in its open configuration to retain neutrals and its effect on the plasma beam properties. This is a first step before validation against experiments and studying closed configurations to ensure that the VB can successfully operate in a wide range of plasma parameters. Simulations show that the VB is capable of retaining neutrals and reducing fluxes to the target without requiring additional gas puffing in High and Low plasma flux scenarios. When lithium is evaporated from inside the box, the hydrogen plasma is completely extinguished and replaced by a low temperature \ce{Li} plasma with lower flux. The fraction of Li and Li+ transported upstream the vapour box is three orders of magnitude below the amount evaporated form the central box, as most of the lithium is condensed in the side boxes and another small portion (two orders of magnitude below the amount evaporated) is deposited on the target. The VB design in its open configuration can mitigate incoming plasma peak heat flux by 0.6MW m^-2, which represents a fraction of 75 and 81% for the High and Low flux scenarios. This effect is expected to be higher when a closed configuration is employed, which could result in a significant reduction of heat fluxes on the divertor of tokamaks once that this design is extrapolated to the toroidal geometry, with just a minimal amount of \ce{Li} and \ce{Li+} reaching the core.
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