Alexander Pigarov - Academia.edu (original) (raw)

Papers by Alexander Pigarov

Review of Scientific Instruments, 2003

Visible light reflectivities are measured for graphite and molybdenum tokamak wall tiles as a fun... more Visible light reflectivities are measured for graphite and molybdenum tokamak wall tiles as a function of incident angle and wavelength. Using the measured reflectivities together with a ray-tracing routine, estimates of the effect of wall reflections on Dα light measurements in the DIII-D and Alcator C-Mod tokamaks are made. It is found that the contribution of reflections is small (typically <10%) for divertor view channels, but can be significant (>50%) for other view chords. Of the nondivertor channels, near-midplane view chords are found to be least susceptible to reflections from the divertor and are therefore best suited for main chamber recycling measurements.

Plasma Physics and Controlled Fusion, 2008

Journal of Nuclear Materials, 2011

Laser ablation is used to inject trace quantities (∼1%) of boron or aluminum impurities into stea... more Laser ablation is used to inject trace quantities (∼1%) of boron or aluminum impurities into steady-state, cylindrical He+ plasmas. The He+ plasmas have an axial flow velocity of about 2×103m/s, corresponding to Mach number M∼0.2. The parallel flow of the resulting B+ or Al2+ impurity ions is measured directly using photomultiplier tubes with line filters. Perpendicular loss of the impurity

Contributions to Plasma Physics, 2004

A comparison is made between solutions of the UEDGE multi‐fluid edge code and the full array of 2... more A comparison is made between solutions of the UEDGE multi‐fluid edge code and the full array of 24 poloidal and tangential Dα and CIII filterscope views available in DIII‐D for a lower single null L‐mode discharge. Wall reflections are included using measured graphite tile reflection data together with a 3D ray tracing code. It is found that divertor view chords are relatively unperturbed by reflections, while main chamber views can be dominated by reflected light. Main chamber view chords are shown to be important in distinguishing between different radial transport models: a hybrid model including both convection and diffusion is found to match measured main chamber Dα brightnesses well, while a pure diffusive model gives brightnesses which are of order 100× too small. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Anomalous plasma transport and plasma flows at tokamak edge, plasma-wall interactions, as well as... more Anomalous plasma transport and plasma flows at tokamak edge, plasma-wall interactions, as well as dust dynamics and transport in fusion plasmas are among the most important processes for reactor design and performance. Recent results of theoretical studies and simulations on some aspects of these processes (including formation of mesoscale convective structures, effects of blobby transport on plasma flow in scrape-off layer, impact of wall processes and plasma-wall interactions on plasma performance, and dust dynamics and dust diagnostics) are presented and discussed in this paper.

Aps Meeting Abstracts, Nov 1, 2002

Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role bot... more Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role both for protection of the chamber first wall from plasma impact damage and for favorable conditions of next pellet injection which will follow in a time scale 0.1s [1]. In this report we analyze main physics processes leading to residual gas/plasma cooling and plasma recombination. We

Submitted for the DPP07 Meeting of The American Physical Society Hydrogen dynamics under strong p... more Submitted for the DPP07 Meeting of The American Physical Society Hydrogen dynamics under strong plasma-wall coupling 1 A.YU. PI-GAROV, S.I. KRASHENINNIKOV, UCSD, A. PLETZER, Tech-X Corp.-The newly developed time-dependent one-dimensional code WALLPSI for wall temperature and erosion rates as well as for trapped, absorbed, and mobile hydrogen inside the wall is discussed. The code is a part of integrated model FACETS for core/edge/wall transport. To study the basic physic process, the code is coupled to the 1D edge plasma transport code. The results of self-consistent plasma/neutral/wall modelling which show strong plasma-wall coupling are presented. Variation of hydrogen inventory in the wall in response to changing plasma impact is discussed. Thermal instability of plasma in contact with hydrogen saturated wall is analyzed.

Submitted for the DPP06 Meeting of The American Physical Society Cross-field transport asymmetrie... more Submitted for the DPP06 Meeting of The American Physical Society Cross-field transport asymmetries in unbalanced double-null divertor configurations. A.YU. PIGAROV, UCSD, T.D. ROGNLIEN, LLNL, B. LABOMBARD, MIT, S.I. KRASHENINNIKOV, UCSD-A key feature of anomalous cross-field transport in the tokamak SOL is strong poloidal asymmetry where the plasma flux is much larger on low field side (LFS) than on high field side (HFS). As shown, this asymmetry can cause an enhanced main chamber recycling at LFS and the large, M∼1, parallel plasma flows. Recent experiments performed in Alcator C-Mod with an unbalanced double null (DN) configuration show (as measured by reciprocating probes at the LFS and HFS midplanes) that plasma density profiles have a much shorter cross-field decay length in the region outside the secondary separatrix on the HFS compared to the same region on the LFS. In well-balanced DN discharges, the density e-folding length measured at the HFS midplane is substantially smaller than that in single null (SN) configuration. These data independently indicate a strong ballooning-like asymmetry. We use UEDGE code to simulate plasma transport in unbalanced DN shots obtained in C-mod. From matching experimental profile data, we infer an asymmetry factors for the anomalous cross-field plasma transport (diffusive and convective) which are indicative of strong asymmetry. The effect of secondary separatrix on radial plasma profiles, parallel plasma flows, and impurity migration will be discussed. Simulated transport asymmetries in unbalanced DN, balanced DN, and SN shots will be compared. Work supported by DoE grant DEFG0204ER54739.

under the Department of Energy research grant No. DE-FG02-02ER54680 at UCSD during 2002-2005 fina... more under the Department of Energy research grant No. DE-FG02-02ER54680 at UCSD during 2002-2005 financial years was a more comprehensive understanding and characterization of non-diffusive transport occurring in the tokamak edge plasma.

The Framework Architecture for Core-Edge Transport Simulations (FACETS) is a SciDAC project for s... more The Framework Architecture for Core-Edge Transport Simulations (FACETS) is a SciDAC project for self-consistent simulations of core-edge-wall transport in tokamaks using leadership class computers [1]. For analysis of transient peak power load handling, PFC erosion/deposition and lifetime, plasma impurity contamination, and hydrogen retention issues in FACETS, we developed the 1D continuum code WALLPSI [2]. WALLPSI simulates highly non-linear transport, release

New Aspects of Plasma Physics - Proceedings of the 2007 ICTP Summer College on Plasma Physics, 2008

... gov CHARLES H. SKINNER Princeton Plasma Physics Laboratory, Princeton, NJ 08544, USAGIAN LUCA... more ... gov CHARLES H. SKINNER Princeton Plasma Physics Laboratory, Princeton, NJ 08544, USAGIAN LUCA DELZANNO Los Alamos National Laboratory, MS K717, Los Alamos, New Mexico, USA SERGEI I. KRASHENINNIKOV University of California, San Diego, San Diego ...

The goal of the FACETS project (Framework Application for Core-Edge Transport Simulations) was to... more The goal of the FACETS project (Framework Application for Core-Edge Transport Simulations) was to provide a multiphysics, parallel framework application (FACETS) that will enable whole-device modeling for the U.S. fusion program, to provide the modeling infrastructure needed for ITER, the next step fusion confinement device. Through use of modern computational methods, including component technology and object oriented design, FACETS is able to switch from one model to another for a given aspect of the physics in a flexible manner. This enables use of simplified models for rapid turnaround or high-fidelity models that can take advantage of the largest supercomputer hardware. FACETS does so in a heterogeneous parallel context, where different parts of the application execute in parallel by utilizing task farming, domain decomposition, and/or pipelining as needed and applicable. ParaTools, Inc. was tasked with supporting the performance analysis and tuning of the FACETS components and framework in order to achieve the parallel scaling goals of the project. The TAU Performance System ® was used for instrumentation, measurement, archiving, and profile / tracing analysis. ParaTools, Inc. also assisted in FACETS performance engineering efforts.

Physics of Plasmas, 2006

The cross-field power loss due to radiation, plasma, and neutrals are measured for hydrogen disch... more The cross-field power loss due to radiation, plasma, and neutrals are measured for hydrogen discharges in a linear divertor simulator experiment. Radiation appears to be the dominant power loss channel; however, power loss due to heating of H2 neutrals is found to be quite significant, being only 2× weaker than radiation in the higher neutral pressure experiments. The H2 vibrational temperature Tvib is found to be the most important channel for carrying neutral energy out of the plasma—more important than either kinetic temperature Tkin or rotational temperature Trot. Power carried radially to the wall by plasma cross-field transport is found to be negligible when compared to neutral and radiation losses. These results demonstrate the importance of including of H2 neutrals in understanding power balance in detached tokamak divertors.

Review of Scientific Instruments, 2003

Visible light reflectivities are measured for graphite and molybdenum tokamak wall tiles as a fun... more Visible light reflectivities are measured for graphite and molybdenum tokamak wall tiles as a function of incident angle and wavelength. Using the measured reflectivities together with a ray-tracing routine, estimates of the effect of wall reflections on Dα light measurements in the DIII-D and Alcator C-Mod tokamaks are made. It is found that the contribution of reflections is small (typically <10%) for divertor view channels, but can be significant (>50%) for other view chords. Of the nondivertor channels, near-midplane view chords are found to be least susceptible to reflections from the divertor and are therefore best suited for main chamber recycling measurements.

Plasma Physics and Controlled Fusion, 2008

Journal of Nuclear Materials, 2011

Laser ablation is used to inject trace quantities (∼1%) of boron or aluminum impurities into stea... more Laser ablation is used to inject trace quantities (∼1%) of boron or aluminum impurities into steady-state, cylindrical He+ plasmas. The He+ plasmas have an axial flow velocity of about 2×103m/s, corresponding to Mach number M∼0.2. The parallel flow of the resulting B+ or Al2+ impurity ions is measured directly using photomultiplier tubes with line filters. Perpendicular loss of the impurity

Contributions to Plasma Physics, 2004

A comparison is made between solutions of the UEDGE multi‐fluid edge code and the full array of 2... more A comparison is made between solutions of the UEDGE multi‐fluid edge code and the full array of 24 poloidal and tangential Dα and CIII filterscope views available in DIII‐D for a lower single null L‐mode discharge. Wall reflections are included using measured graphite tile reflection data together with a 3D ray tracing code. It is found that divertor view chords are relatively unperturbed by reflections, while main chamber views can be dominated by reflected light. Main chamber view chords are shown to be important in distinguishing between different radial transport models: a hybrid model including both convection and diffusion is found to match measured main chamber Dα brightnesses well, while a pure diffusive model gives brightnesses which are of order 100× too small. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Anomalous plasma transport and plasma flows at tokamak edge, plasma-wall interactions, as well as... more Anomalous plasma transport and plasma flows at tokamak edge, plasma-wall interactions, as well as dust dynamics and transport in fusion plasmas are among the most important processes for reactor design and performance. Recent results of theoretical studies and simulations on some aspects of these processes (including formation of mesoscale convective structures, effects of blobby transport on plasma flow in scrape-off layer, impact of wall processes and plasma-wall interactions on plasma performance, and dust dynamics and dust diagnostics) are presented and discussed in this paper.

Aps Meeting Abstracts, Nov 1, 2002

Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role bot... more Afterglow stage of plasma/gas temporal evolution in the ife chamber plays very important role both for protection of the chamber first wall from plasma impact damage and for favorable conditions of next pellet injection which will follow in a time scale 0.1s [1]. In this report we analyze main physics processes leading to residual gas/plasma cooling and plasma recombination. We

Submitted for the DPP07 Meeting of The American Physical Society Hydrogen dynamics under strong p... more Submitted for the DPP07 Meeting of The American Physical Society Hydrogen dynamics under strong plasma-wall coupling 1 A.YU. PI-GAROV, S.I. KRASHENINNIKOV, UCSD, A. PLETZER, Tech-X Corp.-The newly developed time-dependent one-dimensional code WALLPSI for wall temperature and erosion rates as well as for trapped, absorbed, and mobile hydrogen inside the wall is discussed. The code is a part of integrated model FACETS for core/edge/wall transport. To study the basic physic process, the code is coupled to the 1D edge plasma transport code. The results of self-consistent plasma/neutral/wall modelling which show strong plasma-wall coupling are presented. Variation of hydrogen inventory in the wall in response to changing plasma impact is discussed. Thermal instability of plasma in contact with hydrogen saturated wall is analyzed.

Submitted for the DPP06 Meeting of The American Physical Society Cross-field transport asymmetrie... more Submitted for the DPP06 Meeting of The American Physical Society Cross-field transport asymmetries in unbalanced double-null divertor configurations. A.YU. PIGAROV, UCSD, T.D. ROGNLIEN, LLNL, B. LABOMBARD, MIT, S.I. KRASHENINNIKOV, UCSD-A key feature of anomalous cross-field transport in the tokamak SOL is strong poloidal asymmetry where the plasma flux is much larger on low field side (LFS) than on high field side (HFS). As shown, this asymmetry can cause an enhanced main chamber recycling at LFS and the large, M∼1, parallel plasma flows. Recent experiments performed in Alcator C-Mod with an unbalanced double null (DN) configuration show (as measured by reciprocating probes at the LFS and HFS midplanes) that plasma density profiles have a much shorter cross-field decay length in the region outside the secondary separatrix on the HFS compared to the same region on the LFS. In well-balanced DN discharges, the density e-folding length measured at the HFS midplane is substantially smaller than that in single null (SN) configuration. These data independently indicate a strong ballooning-like asymmetry. We use UEDGE code to simulate plasma transport in unbalanced DN shots obtained in C-mod. From matching experimental profile data, we infer an asymmetry factors for the anomalous cross-field plasma transport (diffusive and convective) which are indicative of strong asymmetry. The effect of secondary separatrix on radial plasma profiles, parallel plasma flows, and impurity migration will be discussed. Simulated transport asymmetries in unbalanced DN, balanced DN, and SN shots will be compared. Work supported by DoE grant DEFG0204ER54739.

under the Department of Energy research grant No. DE-FG02-02ER54680 at UCSD during 2002-2005 fina... more under the Department of Energy research grant No. DE-FG02-02ER54680 at UCSD during 2002-2005 financial years was a more comprehensive understanding and characterization of non-diffusive transport occurring in the tokamak edge plasma.

The Framework Architecture for Core-Edge Transport Simulations (FACETS) is a SciDAC project for s... more The Framework Architecture for Core-Edge Transport Simulations (FACETS) is a SciDAC project for self-consistent simulations of core-edge-wall transport in tokamaks using leadership class computers [1]. For analysis of transient peak power load handling, PFC erosion/deposition and lifetime, plasma impurity contamination, and hydrogen retention issues in FACETS, we developed the 1D continuum code WALLPSI [2]. WALLPSI simulates highly non-linear transport, release

New Aspects of Plasma Physics - Proceedings of the 2007 ICTP Summer College on Plasma Physics, 2008

... gov CHARLES H. SKINNER Princeton Plasma Physics Laboratory, Princeton, NJ 08544, USAGIAN LUCA... more ... gov CHARLES H. SKINNER Princeton Plasma Physics Laboratory, Princeton, NJ 08544, USAGIAN LUCA DELZANNO Los Alamos National Laboratory, MS K717, Los Alamos, New Mexico, USA SERGEI I. KRASHENINNIKOV University of California, San Diego, San Diego ...

The goal of the FACETS project (Framework Application for Core-Edge Transport Simulations) was to... more The goal of the FACETS project (Framework Application for Core-Edge Transport Simulations) was to provide a multiphysics, parallel framework application (FACETS) that will enable whole-device modeling for the U.S. fusion program, to provide the modeling infrastructure needed for ITER, the next step fusion confinement device. Through use of modern computational methods, including component technology and object oriented design, FACETS is able to switch from one model to another for a given aspect of the physics in a flexible manner. This enables use of simplified models for rapid turnaround or high-fidelity models that can take advantage of the largest supercomputer hardware. FACETS does so in a heterogeneous parallel context, where different parts of the application execute in parallel by utilizing task farming, domain decomposition, and/or pipelining as needed and applicable. ParaTools, Inc. was tasked with supporting the performance analysis and tuning of the FACETS components and framework in order to achieve the parallel scaling goals of the project. The TAU Performance System ® was used for instrumentation, measurement, archiving, and profile / tracing analysis. ParaTools, Inc. also assisted in FACETS performance engineering efforts.

Physics of Plasmas, 2006

The cross-field power loss due to radiation, plasma, and neutrals are measured for hydrogen disch... more The cross-field power loss due to radiation, plasma, and neutrals are measured for hydrogen discharges in a linear divertor simulator experiment. Radiation appears to be the dominant power loss channel; however, power loss due to heating of H2 neutrals is found to be quite significant, being only 2× weaker than radiation in the higher neutral pressure experiments. The H2 vibrational temperature Tvib is found to be the most important channel for carrying neutral energy out of the plasma—more important than either kinetic temperature Tkin or rotational temperature Trot. Power carried radially to the wall by plasma cross-field transport is found to be negligible when compared to neutral and radiation losses. These results demonstrate the importance of including of H2 neutrals in understanding power balance in detached tokamak divertors.