All of the activities in the two categories—workshops and personal exchanges—that had been scheduled for the 2009- 2010 JIFT program were carried out during the past year. Four workshops were successfully held, in addition to the JIFT Steering Committee meeting. In the category of personal exchanges, two Visiting Professors and six Visiting Scientists made exchange visits. Summary reports about JIFT activities for 2009-2010 are given below.

2009-2010 Workshops

JAPAN to US

• Integraged Modeling and Simulation in Toroidal Plasmas
  Organizers: Paul Bonoli (MIT) and Atsushi Fukuyama (Kyoto)
  Location: MIT PSFC, Cambridge, Masachusetts
  Dates: February 23-25, 2010

  Summary:
  This workshop was the first in a new series of JIFT workshops on integrated modeling and simulation of fusion plasmas, following the previous series that had been held from 2003 to 2006. The scope of the present workshop included progress in integrated modeling, framework development for integrated modeling, and associated physics issues (core transport, edge transport, extended MHD and wave-particle interactions). During the workshop, 12 scientists from the US, seven from Japan, and one from EU presented a total of 23 talks. The US reported about the Fusion Simulation Program (FSP), which is under planning study, and three proto-FSP projects in the SciDAC program; Europe reported about Integrated Tokamak Modeling Task Force (ITM-TF) and EUFORIA; and Japan reported about three integrated codes—TASK, TOPICS-IB, and TASK3D—being developed under the Burning Plasma Simulation Initiative (BPSI). Two talks described the framework for earth system modeling. There were presentations and discussions about integrated modeling for both tokamaks and helical systems.

  Related publications:

  • All of the presentation materials were posted on the web site at
    http://www.psfc.mit.edu/JIFT09/JIFT09.html.

• Hierarchical Self-Organization of Flows and Turbulence in Plasmas, Oceans, and Atmospheres
  Organizers: P. Diamond (UCSD) and Y. Kishimoto (Kyoto)
  Location: UCSD, La Jolla, California
  Dates: March 23-25, 2010

Summary:
This workshop was aimed at sharing interdisciplinary aspects related to turbulence and flows among different research fields. The participants were 11 scientists from the US and 5 scientists from Japan. A total of 14 talks (6 from Japan and 8 from the US) were presented. The talks covered a wide range of theory and simulation topics in turbulent transport and related structure formation in magnetically confined fusion plasmas, space and astrophysical plasmas, fluids, oceans and atmospheres, etc. The latest experimental results identifying detailed turbulent structures in the linear magnetic confinement machine at UCSD were also presented. In the workshop, the physical origin of large-scale structures such as zonal flows and vortices generated from micro-scale turbulence and their impacts on self-organization and structure formation were intensively discussed. The universality and generality of the phenomena across different fields were stressed. This workshop was arranged as a discussion-oriented meeting with a new style, in which each speaker was assigned one hour, with additional time for discussion, and was requested to emphasize the background and status of his respective research field. This new style was successful in leading to intensive discussions and deep understanding across the fields and also in encouraging further collaborations. A follow-up workshop will be held next year at Kyoto University.

US to JAPAN

• Theory and Simulation on Ultra-Intense Laser Plasmas
  Organizers: H. Nagatomo (Osaka) and V. Khudik (IFS)
  Location: Osaka University, Osaka
  Dates: March 14-15, 2010

  Summary:
  Dr. Khudik replaced Dr. Shvets (IFS) as the US organizer when Dr. Shvets was unable to travel to Japan for family reasons. Dr. Khudik presented a talk on “Hybrid simulations and analytical study of strong filamentation of relativistic electron beam propagating through plasma.” In this talk he described a hybrid code for studying the interaction of an electron beam with plasma, which takes into account a violation of charge quasi-neutrality near electron plasma-void regions. Prof. Mima (Osaka University) gave a talk on “Electron Energy Spectrum in Laser Produced Plasmas,” in which he presented an analytical explanation of the shape of the electron energy spectrum. Dr. Wei Yu (Shanghai Institute of Optics and Fine Mechanics) presented a talk about “The Collapse of Solid-Density Plasma Shell Induced by Two Ultra-Intense Laser Pulses”. He described interesting results concerning the interaction of short lasers pulses with a target whose radius is only several times less than the pulse width.

• Advanced Simulation Methods in Plasmas
  Organizers: H. Ohtani (NIFS) and A. Arefiev (IFS)
  Location: NIFS, Toki
  Dates: December 14-16, 2009

  Summary:
  Participants at the workshops included 11 Japanese scientists and six US scientists. The 17 presentations at the workshop covered a range of subjects related to advanced simulation methods and issues about fusion plasmas, laser-plasma interaction, and solar and space plasmas. These research problems were investigated by means of reduced MHD model, hybrid simulation of MHD fluid with energetic particles, gyrokinetic PIC simulation, gyrokinetic Vlasov simulation, PIC simulation with a collision effect, gyro-Landau fluid model, multi-scale simulation model, MHD simulation with collision and radiation effects, and adaptive mesh refinement methods. One of the reports described how virtual-reality technology is a useful method for analyzing simulation data. This workshop was a follow-up to the JIFT workshop “Progress of Multi-Scale Simulation Models” that had been held November 21-22,22 2008, in Dallas, TX.
  

  Related publications:

  • Abstracts and presentation files by all of the speakers were posted on the web site
    http://www.dss.nifs.ac.jp/ohtani/JIFT2009/.

Participants at the JIFT Workshop on Advanced Simulation Methods in Plasmas
(December 2009, National Institute for Fusion Sciences, Japan)

• JIFT Steering Committee Meeting
  Organizers: Ritoku Horiuchi (NIFS) and James W. Van Dam (IFS)
  Location: NIFS, Toki
  Dates: December 10, 2009

  Summary:
  Participants at the Steering Committee meeting reviewed the status of JIFT activities for 2009-2010 and discussed recommendations for exchange activities during 2010-2011.

2009-2010 Exchange Visits

JAPAN to US

• Theoretical and Numerical Studies of the Parallel Electric Field in Shock Waves
  Visiting Professor: Yukiharu Ohsawa (Nagoya University)
  Location: IFS, University of Texas at Austin
  Dates: August 6-23, 2009 (18 days); paid by US

  Summary:
  Recently, Dr. Ohsawa’s group at Nagoya University has shown that the electric field parallel to the magnetic field can be strong in large-amplitude magnetosonic waves. Then, in collaboration with Wendell Horton and Charles Chiu at the IFS, they began to investigate the effect of the parallel electric field on particle acceleration in shock waves. They examined three different acceleration mechanisms: incessant acceleration of relativistic ions, acceleration of trapped electrons, and positron acceleration along the magnetic field. The main purpose of Dr. Ohsawa’s visit to the IFS was to complete the paper of the above study, and they did it during his stay. Their paper, which was submitted right after his returning to Japan, appeared in Physics of Plasmas in November 2009. During his stay, Dr. Ohsawa gave a seminar related to this subject entitled “Parallel electric field and particle acceleration in shock waves.”
  

  Related publications:

  • S. Takahashi, H. Kawai, Y. Ohsawa, S. Usami, C. Chiu, and W. Horton, “The effect of parallel electric field in shock waves on the acceleration of relativistic ions, electrons, and positrons,” accepted for publication in Physics of Plasmas (November 2009).

JIFT visiting Professor Y. Ohsawa (middle) with Dr. W. Horton and Dr. J. Van Dam
at the Institute for Fusion Studies in Austin, Texas.

• Structure Formations in Electric and Velocity Fields by Dust in Swirling Vortices
  Visiting Scientist: H. Miura (NIFS),
  Location: IFS, University of Texas at Austin
  Dates: March 8-17, 2010 (10 days); paid by Japan

  Summary:
  This collaborative research started in 2008, when Prof. Horton of IFS stayed at NIFS for three month. In this research, the intention is to study numerically the particle influences in local velocity and electric field structures. This study provides important and basic information to construct advanced numerical codes for numerical experiments of toroidal systems, since the contributions of particles such as dust and energetic particles acquire more importance than the current, fluid-based simulations In this study, Prof. Horton provides the theoretical framework of swirling vortices by applying the theoretical framework of the stability theory, while Dr. Miura develops a numerical codes for high performance computing purposes. So far the basic functions required for the dust simulations are completed, and some test simulations will be carried out. During his visit, Dr. Miura presented a seminar on “"MHD simulations of the Large Helical Device and Hall MHD simulations of Whistlers.”

• Simulation Study on Core Heating Process in Fast Ignition Laser Fusion
  Visiting Scientist: Tomoyuki Johzaki (Osaka U)
  Location: University of Nevada, Reno, Nevada
  Dates: January 31-February 7, 2010 (8 days); paid by Japan

  Summary:
  During an earlier JIFT visit to the University of Nevada, Reno, in 2007, Dr. Johzaki had initiated a collaborative research project with Prof. Sentoku. During that first visit, they had discussed the simulation method for fast electron generation and transport and found the importance of collision and target ionization in fast electron generation and its transport using 1D collisional PIC and Fokker-Planck codes. During the present visit, they discussed and modified the model for collisions between fast electrons and bulk particles. In the collisional PIC and Fokker-Planck code, they added the effects of collisions between fast electron and bounded electrons in partially ionized plasmas. In addition, they modified the model of scattering by ions so as to include the interaction with the un-shielded nucleus potential by bounded electrons, since the impact parameter becomes smaller than the ion sphere size. As a result of these modifications, they found that the collisional effect becomes large.
  

  Related publications:

  • T. Johzaki, Y. Sentoku, et al., "Core heating properties in FIREX-I - influence of cone tip", Plasma Phys. Control. Fusion 51, 014002 (2009).

• Systematic Statistical Analysis of Numerical Turbulence in Magnetized Plasmas
  Visiting Scientist: O. Yamagishi (NIFS)
  Location: IFS, University of Texas at Austin
  Dates: January 15-February 28, 2010 (45 days); paid by Japan

Summary:
Dr. Yamagishi visited to the Institute for Fusion Studies (IFS), University of Texas at Austin. His host was Dr. W. Horton. He collaborated with Dr. F. L. Waelbroeck, Dr. P. J. Morrison, and graduate student C. Correa. He carried out 2D simulations based on the classic drift wave model, which includes drift wave (DW), zonal flow (ZF), and geodesic acoustic mode (GAM). They discussed the relationship of the steady state and the excited modes in the system. The simulation results were compared with existing predictive linear theories such as those involving quasi-linear flux, the Green-Kubo formula, and shearing rate prediction.


Related publications:

• W. Horton, O. Yamagishi, and A. Sen, “Electron temperature gradient drift mode in the Columbia Linear Mirror,” to be presented at the International Sherwood Fusion Theory Conference (April 19-21, 2010, Seattle, Washington).
• O. Yamagishi, W. Horton, F. L. Waelbroeck, P. J. Morrison, and C. Correa, “Numerical study of zonal flow generation with the Hasegawa-Wakatani model and comparison with linear predictions,” to be presented at U.S. Transport Task Force Workshop (April 13-16, 2010, Annapolis, Maryland).

US to JAPAN

• Heat Transport and Pressure Gradient in Chaotic Field of LHD
  Visiting Professor: Stuart R. Hudson (PPPL)
  Location: National Institute for Fusion Science (Japan)
  Dates: July 17-September 17, 2009 (three months); paid by Japan

  Summary:
  Since 2005, Dr. Hudson has been collaborating with Dr. N. Nakajima on MHD stabilities, and they have written several joint papers. During his visit to Japan, the target of their joint research was the MHD equilibrium with a chaotic field. They have argued that ∇p = J x B, with a continuous pressure, only has solutions with an uncountable infinity of singularities in both the pressure gradient and the current when the field is chaotic. Such solutions are not suited to numerical approximation. By including non-ideal terms, they have eliminated the pathological singularities. By including an anisotropic diffusion equation for the pressure, it is no longer necessary to specify the pressure a priori as a boundary condition. Their work demonstrated that the addition of these terms is required for computational tractability. They have a complete mathematical model that can consistently treat pressure gradients in chaotic fields. In future work they hope to investigate the so-called soft-beta limit, where transport is linked to the breaking of magnetic surfaces.

  Related publications:

  • S. R. Hudson and N. Nakajima, “Pressure, chaotic magnetic fields and MHD equilibria,” submitted to Physics of Plasmas (January 2010).

• Investigation of Multi-Scale Simulation Models in Plasma Physics
  Visiting Scientist: Alex Arefiev (IFS)
  Location: Osaka University and National Institute for Fusion Studies
  Dates: November 21-December 17, 2009 (27 days); paid by US

  Summary:
  During his visit to Japan, Dr. Arefiev presented his recent research on two relevant topics: determining microcluster size distribution, and stochastic collisionless electron heating in laser-irradiated microclusters. He discussed these topics with a number of researchers in Japan and wrote a paper covering these topics that will be published in the journal Plasma and Fusion Research. He spent his first week at the Institute of Laser Engineering at the University of Osaka (Suita), where his host was Dr. Hideo Nagatomo. He gave a talk about a recently developed diagnostic technique for determining the size distribution of microclusters. This is a collaborative project that involves experiment and simulations. The knowledge of the size distribution is crucial for calculating the neutron yield produced by laser-irradiated microclusters. He discussed this work, as well as his other microcluster related research, with Dr. Masakatsu Murakami. He also discussed a possible collaboration with Dr. Toshihiro Taguchi of Setsunan University, who has done extensive modeling of lasercluster interactions. The goal would be to identify the proposed collisionless mechanism in three-dimensional simulation, using the existing code of Dr. Taguchi. The second part of his trip was spent at NIFS, where his host was Dr. Ohtani. He had discussions with Dr. Ohtani and Dr. Usami about his recent research on collisionless electron heating in microclusters, with the main emphasis on reducing the problem to a one-dimensional model and the corresponding PIC simulation of electron dynamics. He and Dr. Ohtani discussed collaborating on a full three-dimensional model for electron heating. He also gave a talk at NIFS about a technique for recovering the cluster size distribution. Several ideas were proposed for improving the model by the inclusion of several effects that are currently neglected.

  Related publications:

  • A. Arefiev, “Generation of fast ions by microclusters,” submitted for publication to Plasma and Fusion Research.

• Simulation Study of Toroidal Flow Generation by ICRF Heating
  Visiting Scientist: Linjin Zheng (IFS)
  Location: Kyoto University
  Dates: December 17-26, 2009 (10 days), paid by US

Summary:
Dr. Zheng first participated in the JIFT workshop on Advanced Simulation Methods in Plasmas (December 13-16), where he gave a talk about his research on current-interchange tearing modes. Then he visited Kyoto University (December 17-23), where his host was Dr. Murakami. They discussed theoretical and computational studies of direct rotation drive due to ICRF heating. In order to prove this conjecture, they will try to extend the GNET code of Murakami to simulate numerically the momentum input from the ICRF heating. For this purpose, they worked on extending the gyrokinetic theory to construct the Monte Carlo collisional operator that can account for the momentum input and implement it in the GNET code. In the long term they are also considering to couple the GNET and TASK/VM codes to the energetic particle physics studies conducted at the Institute for Fusion Studies. The last part of his visit was spent at the University of Tokyo, Kashiwa campus (December 24-26), where his host was Dr. Furukawa. They discussed the conversion from interchange modes to tearing modes due to a gradient in the plasma of the current (or resistivity).

Related publications:

• S. Murakami, K. Itoh, L. Zheng, J. W. Van Dam, and A. Fukuyama, “Simulation Study of Toroidal Flow Generation by the ICRF Minority Heating,” abstract and synopsis submitted to IAEA Fusion Energy Conference (Daejeon, Korea, October 11-16, 2010).
• L. Zheng and M. Furukawa, “Current-interchange Tearing Modes: Conversion from Interchange-type Modes to Tearing Modes,” abstract and synopsis submitted to IAEA Fusion Energy Conference (Daejeon, Korea, October 11-16, 2010).
  

• Theory on Ultra-Intense Laser Plasmas
  Visiting Scientist: Vladimir Khudik (IFS)
  Location: Osaka University
  Dates: March 16-20, 2010 (5 days); paid by US

Summary:
Dr. Khudik replaced Dr. Shvets (IFS) as visiting scientist when Dr. Shvets was unable to travel to Japan for family reasons. His host was Dr. Nagatomo and Dr. Azechi of Osaka University. He discussed with them his research work on ultra-intense laser plasma and beam-plasma interactions and potential application. They also discussed hybrid simulations and analytical studies of strong filamentation of a relativistic electron beam propagating through plasma. Dr. Khudik also had discussions with Dr. Johzaki about modeling of Coulomb collisions by using the Monte-Carlo technique (i.e., solving the Langevin equation) and by directly solving Fokker-Planck equation. Dr. Johzaki uses thelatter approach in his work on core heating simulations for cone-guiding fast ignition. Dr. Khudik also had talks with Dr. Taguchi in which they compared the description of cold electron plasma in their respective simulations of beam filamentation and discussed possible extension of the models from two dimensions to three. He briefly visited the Kansai Photon Science Institute in Kyoto,where he gave a seminar and had discussions with Dr. Bulanov about the applicability of different models for beam-plasma systems.