The iterative Monte Carlo(MC)code EMC3-EIRENE is frequently used for plasma edge simulations in 3 D applications.So far,a quantitative evaluation of the numerical quality of the code results remains an open issue.In t...The iterative Monte Carlo(MC)code EMC3-EIRENE is frequently used for plasma edge simulations in 3 D applications.So far,a quantitative evaluation of the numerical quality of the code results remains an open issue.In this paper,we demonstrate a framework for the practical assessment of accuracy and convergence with EMC3-EIRENE.Moreover,we provide a first accuracy analysis with EMC3-EIRENE for a DIII-D divertor edge plasma case.First,we introduce post-processing averaging to efficiently reduce the variance of the statistical error.Then,we estimate the deterministic error contributions based on their theoretical reduction rates by comparing solutions with a different grid resolution,time step,or number of MC particles per iteration.Finally,using parameterized expressions for the error and the computational time,suitable numerical parameters are determined to achieve faster and/or more accurate results.We found that simulations can be more than twice as fast without losing accuracy by making use of post-processing averaging and choosing optimal parameters.In addition,we conclude that the discretization error is the dominant error contribution for the case selected in this paper,which demonstrates the importance of constructing an adequate mesh.展开更多
The recently modified EMC3-EIRENE code package has been widely applied as an edge-plasma analysis tool and resulted in successful validation against various measured trends seen in stellarator and tokamak plasma bound...The recently modified EMC3-EIRENE code package has been widely applied as an edge-plasma analysis tool and resulted in successful validation against various measured trends seen in stellarator and tokamak plasma boundaries.It has been shown that the code package applied for Wendelstein 7-X(W7-X)discharges in the interpretive mode can assess the impact of impurity effects on the electron density,measured by a set of Langmuir probes.In particular the spatial quantification of impurities and effects from the effective charge state Zeff and effective mass meff,which are non-trivial to record by diagnostics,were examined.The results showed that earlier assumptions of the effective charge-state distribution and effective mass for reported Langmuir probe measurements must be revised.Subsequently,reprocessing these measurements with code-interpreted spatial profiles of the effective charge state and effective mass led to an overall improved physical consistency.展开更多
High-density experiments in the high-field-side mid-plane single-null divertor configuration have been performed for the first time on J-TEXT.The experiments show an increase in the highest central channel line-averag...High-density experiments in the high-field-side mid-plane single-null divertor configuration have been performed for the first time on J-TEXT.The experiments show an increase in the highest central channel line-averaged density from 2.73×10^(19)m^(-3) to 6.49×10^(19)m^(-3),while the X-point moves away from the target by increasing the divertor coil current.The corresponding Greenwald fraction rises from 0.50 to 0.79.For the impurity transport,the density normalized radiation intensity(absolute extreme ultraviolet and soft x-ray)of the central channel density decreased significantly(>50%)with an increase in the plasma density.To better understand the underlying physics mechanisms,the 3 D edge Monte Carlo code coupled with EIRENE(EMC3-EIRENE)has been implemented for the first time on J-TEXT.The simulation results show good agreement with the experimental findings.As the X-point moves away from the target,the divertor power decay length drops and the scrape-off layer impurity screening effect is enhanced.展开更多
基金sponsored by Flanders Innovation and Entrepreneurship(IWT.141064)a travel grant(V4.128.18N)from Research Foundation—Flanders(FWO)+2 种基金supported by the Research Foundation Flanders(FWO)under project grant G078316Nfunded by the Research Foundation—Flanders(FWO)the Flemish Government—department EWI。
文摘The iterative Monte Carlo(MC)code EMC3-EIRENE is frequently used for plasma edge simulations in 3 D applications.So far,a quantitative evaluation of the numerical quality of the code results remains an open issue.In this paper,we demonstrate a framework for the practical assessment of accuracy and convergence with EMC3-EIRENE.Moreover,we provide a first accuracy analysis with EMC3-EIRENE for a DIII-D divertor edge plasma case.First,we introduce post-processing averaging to efficiently reduce the variance of the statistical error.Then,we estimate the deterministic error contributions based on their theoretical reduction rates by comparing solutions with a different grid resolution,time step,or number of MC particles per iteration.Finally,using parameterized expressions for the error and the computational time,suitable numerical parameters are determined to achieve faster and/or more accurate results.We found that simulations can be more than twice as fast without losing accuracy by making use of post-processing averaging and choosing optimal parameters.In addition,we conclude that the discretization error is the dominant error contribution for the case selected in this paper,which demonstrates the importance of constructing an adequate mesh.
基金This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under Grant Agreement No.633053.
文摘The recently modified EMC3-EIRENE code package has been widely applied as an edge-plasma analysis tool and resulted in successful validation against various measured trends seen in stellarator and tokamak plasma boundaries.It has been shown that the code package applied for Wendelstein 7-X(W7-X)discharges in the interpretive mode can assess the impact of impurity effects on the electron density,measured by a set of Langmuir probes.In particular the spatial quantification of impurities and effects from the effective charge state Zeff and effective mass meff,which are non-trivial to record by diagnostics,were examined.The results showed that earlier assumptions of the effective charge-state distribution and effective mass for reported Langmuir probe measurements must be revised.Subsequently,reprocessing these measurements with code-interpreted spatial profiles of the effective charge state and effective mass led to an overall improved physical consistency.
基金supported by the National Magnetic Confinement Fusion Energy R&D Program of China (Nos.2018YFE0301104 and 2018YFE0309100)National Natural Science Foundation of China (No. 51821005).
文摘High-density experiments in the high-field-side mid-plane single-null divertor configuration have been performed for the first time on J-TEXT.The experiments show an increase in the highest central channel line-averaged density from 2.73×10^(19)m^(-3) to 6.49×10^(19)m^(-3),while the X-point moves away from the target by increasing the divertor coil current.The corresponding Greenwald fraction rises from 0.50 to 0.79.For the impurity transport,the density normalized radiation intensity(absolute extreme ultraviolet and soft x-ray)of the central channel density decreased significantly(>50%)with an increase in the plasma density.To better understand the underlying physics mechanisms,the 3 D edge Monte Carlo code coupled with EIRENE(EMC3-EIRENE)has been implemented for the first time on J-TEXT.The simulation results show good agreement with the experimental findings.As the X-point moves away from the target,the divertor power decay length drops and the scrape-off layer impurity screening effect is enhanced.
