Annual Report(MS-Word)

Executive Summary

1. Mission of Large Tokamak Implementing Agreement and relevance to the international fusion program

The objective of this Implementing Agreement (IA) is to enhance the scientific and technological achievements of the Large Tokamaks (LT) by means of co-operative actions for the advancement of the tokamak concept. This IA is one of the largest co-operations among the fusion IA's under the IEA. The achievements of the large tokamaks under this IA provided essential data and operating experience for ITER and the advancement of the tokamak concept.

2. Current foci and objectives of LT IA

Current foci of large tokamak experiments are energy confinement (dependence on plasma pressure, collisionality and aspect ratio); dependence of density peaking on collisionality; control of plasma instabilities (resistive wall modes, neoclassical tearing modes at high beta, edge localised modes, disruptions); identity and similarity studies of the edge plasma; material erosion, migration re-deposition and fuel retention; long-duration sustainment of steady-state high plasma pressure plasma discharges with reduced TF ripple and high bootstrap currents; hybrid and other advanced modes; effect of q profile on triggering high confinement and fast particle induced MHD instabilities; real time control of plasma profiles. On JET, R&D is being completed and procurement packages being placed for the longer-term programme (2007-2010) which includes major enhancements of high scientific value and strategic importance, focusing on ITER scenarios with increased heating power and an ITER-like combination of first wall and divertor materials. ITER scenario development is also a major element of DIII-D in the U.S. and JT-60U in Japan.
Through this IA, experiments, theory and modelling in these topical areas, especially joint experiments requested by ITPA were performed using JET (EU) and JT-60 (Japan) with contributions from the U.S. national devices such as DIII-D, CMOD and NSTX. A workshop on "Implementation of the ITPA coordinated research recommendations" was held at General Atomics, San Diego, USA on 1-2 November 2005. This activity is maturing and making substantial contributions to the advancement of tokamak research for ITER. In this fourth in the series of such workshops, leaders representing 17 major world tokamak programmes from the six ITER partners at the time (European Union, Japan, Korea, the People's Republic of China, the Russia Federation and the United States), members of the Executive Committees of the IEA LT, Pumped Divertor (PD) and TEXTOR IA's, the ITPA and the ITER IT were among the participants. It was noted that remote participation in experiments can be effective. Current foci of large tokamak technology are the development of negative-ion-source-based neutral beam injector (N-NBI) in JT-60U, tritium and remote handling in JET (including cleaning of plasma facing components using a flash lamp and a small plasma torch), as well as diagnostics improvements. In general, it was considered that the interactions between IEA/ITPA/ITER were working well, with the primary path for the proposal of experiments being the ITPA Topic Groups. The need for improved coordination in joint modelling activities was also recognized.

3. Highlights and accomplishments during the reporting period June 2005-May 2006

In the EU, the EFDA covering JET was extended to 31 December 2007. JET was in Shutdown or Restart for much of the reporting period for modifications and improvements, including the installation of a new divertor target for high power, high triangularity operation, about 15 new/upgraded diagnostics/systems (including four with significant U.S. involvement), and improvements to both the neutral beam and Ion Cyclotron Resonance heating systems. Four weeks of experiments were conducted at the end of the operating period, involving scientists from 19 EU countries, together with participants from Japan and the U.S.. In Japan, JAERI and the National Fuel Corporation (JNC) were joined in a new organisation, called the Japan Atomic Energy Agency (JAEA). T. Tsunematsu replaced M. Seki as Director General of the Fusion Research Development Directorate in JAEA. JT-60U operations resumed in November 2005 with 8 weeks of conditioning operations followed by 12 weeks of experiments during the remainder of the reporting period. Operations followed the repair and commissioning of the motor-generator system, improvements to the neutral beam system, installation of ferritic steel plates to reduce TF ripple losses, modification of the centrifugal pellet injector and installation of a supersonic molecular beam injector. A major modification to JT-60 (JT-60 Super Advanced) was discussed extensively as a Broader Approach project. In the U.S., major management changes occurred with the retirement of A. Davies and M. Roberts. A U.S. ITER Project Office (USIPO) was formed to manage the U.S. hardware and fund contributions to the ITER Project, and a U.S. Burning Plasma Organization (USBPO) was established to involve the U.S. scientific community with the ITER Physics issues. The BPO will coordinate U.S. fusion research on ongoing experimental facilities, theory and modeling, and plan for burning plasma experiments on ITER. Thus, ITER is an integral part of the U.S. fusion programme with the five-year budget including full funding for ITER and sufficient funding for the base programme. DIII-D was in shutdown for most of the reporting period to re-orient a neutral beam line, upgrade the Electron Cyclotron Resonance Heating system and modify the lower divertor. CMOD focused on Lower Hybrid heating and current drive and high Z issues, while NSTX tested MHD mode modification systems. A summary of the Status and Plans of Three Parties is included in Attachment A1.
The physics-related work in the collaboration is conducted under eight topical areas, six of which correspond to those used in the ITPA. These are Transport and ITB Physics, Confinement database and modelling, MHD, Edge and pedestal physics, SOL and divertor physics, and Steady State Operation. In addition, Tritium and Remote Handling Technologies, and Other issues, such as Diagnostics and Power Supplies issues, are conducted in two separate Task Areas. Accomplishments in these Task Areas are described in Attachment A2.
Two Workshops were held during the reporting period. These were:

W60: Burning Plasma Physics and Simulation; Tarragona, Spain on 4-5 July 2005;
W62: Fourth Joint Workshop on LT, PD and TEXTOR IA's on "Implementation of the ITPA Coordinated Research Recommendations"; General Atomics, San Diego, USA on 1-2 November 2005.

4. Future strategy

The implementation of the ITPA coordinated research recommendations was successfully started in 2002 under the IEA LT IA. This joint experiment arrangement among JT-60U-JET-USDOE will be strengthened to prepare for the successful start-up of ITER operation with wider participation from the other IEA/IA�fs and Bilateral Agreements. Thus, and in response to FPCC requests on cooperation among IEA IA�fs, Workshop W62 was held jointly by the IEA LT, PD and TEXTOR IA�fs with participation from the six ITER partners at the time (European Union, Japan, Korea, the People�fs Republic of China, the Russia Federation and the United States), together with the Chair and some members of the ITPA Coordinating Committee, the Chair or co-chair of the ITPA Topical Groups and members of the ITER IT. Some of the personal exchanges for the ITPA joint experiments were made under Bilateral Agreements. Also technological cooperation under the LT IA will be strengthened in the areas of tritium and remote handling, heating system development such as N-NBI, and diagnostics and power supplies development.

5. Collaborations inside/outside IEA

In recognition of the significance of the activities conducted under the LT IA by a broad representation of the fusion community, the Executive Committee of the IA assented to an extension from 16 January 2006 to 15 January 2011, subject to the amendment of the Preamble and Articles 3, 4, 9 and 10. Issues related to steady-state operation, being addressed by an FPCC Study Group, were the subject of a Joint Session of the IEA LT and PD IA�fs. Key to the discussion on steady-state physics and technology, including tokamak and helical devices and in particular superconducting devices, is the avoidance of overlap among the IA�fs. Indeed, a new IA may not be necessary, since all existing IA�fs can contribute to steady-state research. On-the-other-hand, all issues related to superconducting devices are not covered by the existing IA�fs. Thus, a superconducting device IA may be preferable to a topic-based IA. In addition, the inclusion of KSTAR, EAST, SST and, on the longer term, JT-60SA in the tokamak IA�fs needs consideration. Thus, the Executive Committee of the LT IA recommended the start of discussions in early 2007 on a new framework/re-structuring of the IEA fusion IA�fs in view of these changes in the world fusion programme.
The IEA LT homepage (http://www-jt60.naka.jaea.go.jp/lt/) is open to all IEA IA�fs and the public.

6. Message to policy makers

The IEA Large Tokamak Implementing Agreement is one of strongest fusion IA�fs and has been effective in developing tokamak research to reach break-even conditions and in developing the necessary databases for the next step device ITER and a steady-state tokamak reactor. This Agreement provides leadership in coordinating ITPA joint experiments with other tokamak related IEA IA�fs. Please visit the homepage of the LT IA to understand the activities carried out and to send comments for improvement.

7. List of attachments

These reports can be found on the IEA LT IA web-site, http://www-jt60.naka.jaea.go.jp/lt/index.html, in the �eInternal Use�f sub-area. Please contact Kouji Shinohara or Francesco Romanelli for password to access this part of the website.
A1 : Status and Plans of Three Parties
A2 : Accomplishments in Task Areas
A3 : Summary Reports on Workshops
A4 : List of Personnel Exchanges
A5 : Minutes of Executive Committee meeting at Cadarache, France

The Status and Plans of Three Parties

<EFDA-JET>

The last year on JET has been difficult, with the start of the Campaigns being delayed on several occasions due to system faults. Nevertheless, the period has been productive with many new enhancements being commissioned (a new divertor target for high power, high triangularity operation, 15 new/upgraded diagnostics/systems (including 4 with significant US involvement), and some power upgrades), new experiments being started (participation from 19 European Countries; Japanese and US collaborations concentrating on ITPA ITER high priority coordinated experiments conducted through IEA Implementing Agreements; Russian Federation collaborations mainly on diagnostics and codes), R&D being completed and procurement packages being placed for the longer-term JET programme (2007-2010) which includes major enhancements of high scientific value and strategic importance, focusing on ITER scenarios at high power with acceptable plasma/wall interactions.
The 2004/5 shutdown was completed, as expected, with the closure of the vacuum vessel on 7 July 2005. The 2005/6 Campaigns, with a strong ITER focus (bringing new systems to full performance, critical issues for ITER, preparation of ITER operating scenarios, and specific physics issues for ITER), were scheduled between 28 November 2005 and 12 April 2006, but a turbo-molecular pump failure (10 November 2005), a NB duct obstruction (mid-January 2006) and a NB water leak (25 May 2006) introduced considerable delays and allowed the execution of only Campaign. The Campaigns are expected to resume on 3 July 2006 and continue to 20 October 2006 to recover lost time and to include new experiments in which the magnitude of the Toroidal Magnetic Field Ripple will be varied to study its effect on ELMs, H-mode pedestal, plasma and fast ion confinement.
Despite these difficulties, new results have been achieved, including a JET record coupled power in H-mode peaking at 29MW, pulse-by-pulse measurements of erosion/deposition using QMB�fs, power loss observations during ELMs and disruptions using wide angle IR camera, localized radiation features between and during ELMs using improved divertor bolometry, measurement of reduced heat diffusivity in a narrow layer ITB either side of which modulated RF power was deposited, observation of localized Alfvn cascades with X-mode reflectometry to determine the location of q_min, and scintillator probe measurements of velocity distribution of MHD-induced fast particle losses.
Following the successful operation on the JET Test Bed in Summer/Autumn 2006, the ITER-like ICRH antenna (7MW power; ELM-resilient coupling; High Power Prototype support tests completed at ORNL) will be installed on JET. Progress towards the longer-term strategic goals has been good. Major R&D has been conducted and many procurement packages placed for the installation on JET from late 2008 of an ITER-like combination of first wall and divertor materials (tungsten divertor and beryllium wall). The subsequent experiments will address critical issues in preparation of ITER operation, including the minimization of T-retention, material erosion and migration, mixed materials effects, melt layer behavior, impurity control, and the development of operational scenarios fully compatible with a Be/W material mix. Procurements related to increasing the NB power to 35MW for 20s (to allow scenario development at high current, beta and density) and to an high frequency pellet injector for ELM-pacing are proceeding to plan. In addition, a power supply upgrade for plasma control, a package of upgraded and new diagnostics and a programme of machine refurbishments is being finalized. The use of ergodisation coils for ELM suppression is also being studied, with a view to its possible implementation.

<JT-60>

1) Facility status: The installation of ferritic steel was carried out in order reduce of energetic ion loss due to the TF ripple reduction. Ferritic steel plates were installed in place of graphite armors by about 10 % surface area in about 8 months in 2005. The plasma operation was successfully resumed from November 2005. As other change in hardware, the modification of centrifugal pellet injection to long pulse operation, and the installation of Supersonic molecular beam injector were performed. This is a JT-60 - CEA collaboration. There is a progress in a long pulse operation of NNB. A long pulse beam injection of 20 s (18 s) has been performed with 3.2 MW (3.6 MW) at 320 keV (340 keV) by using two ion sources.
There are also progress in diagnostics; BES measurement by using MSE system successfully has started the operation, the resolution of the infrared imaging bolometer system has been improved by the modification of neutron shield and data acquisition system, high-repetition and high-energy transversely excited atmospheric (TEA) CO₂ laser has been developed for the collective Thomson scattering for -particle diagnostics, fabrication of the Li beam probe system for measurement of edge current density has started.
JT-60 operation is suspended for one month due to the machine trouble because an outer dome tile (CFC) was out of place on 16th June 2006.

2) Experiments: Since 20^th Ex-Co meeting, JT-60 operates 8 weeks of conditioning operation and 12 weeks of experiments from November 2005 to June 2006. Major missions of the experimental campaign are 1) the sustainment of plasma with =2-2.5, HH~1 for 25s, 2) the achievement of high > 3.5 (above no-wall), 3) the extension of long sustainment of high bootstrap current fraction (70-80%) discharges, 4) the long high fusion triple product, 5) the sustainment of performance under wall saturation. The investigation of some of these missions has been achieved and some are ongoing.
The benefits of the ferritic steel installation were brought. Not only the reduction of energetic ion loss was observed, but also the improvement of the thermal confinement was observed.
Other major results are; the change of the rotation profile due to the ripple reduction, the sustainment of plasma for ~2.5s by the bootstrap current, Control of m/n=3/2 NTM stabilization by EC injection, the observation of the wall pumping in detached divertor, the investigation of impurity and hydrogen transport in different divertor conditions.
Most of these experimental results will be reported in 21^st IAEA Fusion Energy Conference at Chengdu.

3) International Collaboration: The following activities were carried out; JET (Focus on ripple effect on tokamak performance, ITPA SS, PEP, TP, DSOL, H retention), DIII-D (RWM, NTM, small ELM, QH mode etc.), AUG (PEP joint experiments, NTM, Tile analysis, W experiments. New IPP-JAEA agreement now under signing), Tore Supra (Supersonic gas injection), KSTAR (NBI development, Thomson scattering, etc.) Lausanne (gyro-kinetics code).
As for the ITPA/IEA joint experiments, we had 2 visitor2 from JET for PEP1+3, sent 2 scientists to AUG for PEP-13 in JFY 2005.

4) National Research Collaboration: The number of national collaborators was 176, coming from 24 research institutions, in JFY 2005. The number will reach 165 in JFY2006. Five IAEA papers from Tokyo U., Tohoku U., Tsukuba U. and 2NIFS (2 oral) and seven PSI papers from Hokkaido U., Keio U., Tokushima U., Osaka U., Kyushu U., 2NIFS) will be written. And, "Remote operation" has been tested June 2006 between Kyoto U. and Naka (JAEA).

5) JT-60SA Program: The tokamak as one of Broader Approach projects in Naka was named as JT-60SA (JT-60 super advanced). Basic design of JT-60SA was discussed at JA-EU Satellite tokamak working group. Conceptual design activity (CDA) is in progress. The CDA report will be prepared till the end of 2006, and the design will be approved around the March 2007 after the design review. The arrangement of TF coil procurement will start early in 2007.

6) Theory and Simulation: By executing the benchmarking tests between the linear ideal MHD stability codes MARG2D, developed in JAEA, and DCON, used in GA, the validity of the MARG2D code was confirmed for low-n (n=1,2,3) ideal MHD modes stability analysis. The benchmarking tests is being executed between MARG2D and ELITE, developed and used in GA, in order to the validity of MARG2D for medium-n (n=5-50) ideal MHD modes stability analysis.

7) Management Items: Dr. M. Seki had been replaced by Dr. T. Tsunematsu as a director general of the fusion research development directorate in JAEA.

<U.S>

Major management changes have occurred in the Office of Fusion Energy Sciences. Anne. Davies and Mike Roberts have retired. Jim Decker is acting as the Associate Director, OFES.

We are entering a new era with ITER, which is the centrepiece of the US MFE Program. The mission of the U.S. program was articulated about ten years ago. It is to advance plasma science, fusion science and fusion technology, the knowledge base needed to develop economically and environmentally attractive energy source. This mission is still valid in this new era. The five year budget plan for Fusion Energy Sciences includes full funding of ITER with sufficient funding for the base program.

Major facilities (DIII-D, C-MOD, and NSTX), theory and computations, diagnostics development, and enabling technologies are major contributors to ITER. ITER is thus an integral part of the U.S. fusion program. We have established the US Burning Plasma Organization to coordinate the scientific work in support of burning plasmas and ITER. The US ITER Project Office manages the U.S. hardware, cash, and manpower contributions to the ITER Project.

The three facilities (DIII-D, CMOD and NSTX) provide research in complementary areas. DIII-D has finished a long shutdown period to reorient the beam line, upgrade ECH and modify the lower divertor. CMOD is focused on Lower Hybrid heating and current drive and high Z issues. NSTX is testing mode modification system.

The USBPO Director is Ray Fonck, and the Deputy Director is Tony Taylor. About ten topical areas are identified in USBPO; the topical groups establish special task forces to deal with specific issues that require expertise from several different topical areas.. Integrated scenarios and integrated simulation & modelling groups are included. 200 community members are participating. Workshop summaries are available at www.burningplasma.org. USBPO will act as US arm of ITPA.

IEA Cooperation Among Large Tokamak Facilities
Reports and Plan on Task Assignment Programmes (June 2005 - May 2006)

Task 1: Transport and ITB Physics

Collaborative work on ITPA-IEA joint experiments was performed. JT-60U experiments started on December 2005, while JET operations were only restarting at the end of the period under review and no new experiments were performed on DIII-D during this period.

In the experiments on hybrid scenario (TP-2), transport analysis on existing hybrid scenario shots in JET, JT-60U, DIII-D and ASDEX Upgrade were carried out and reported by F. Imbeaux in an invited talk and paper at the EPS conference on plasma physics and controlled fusion in 2005. The shots on JET and JT-60U were newly put into the ITPA profile database. In the new experiment after June 2005, the duration of high beta sustainment with high confinement has been extended in JT-60U with reduction of toroidal field ripple; = 2.5 with H_H98y2 ~1.1 was maintained for 17.6 s and = 2.1 with H_H98y2 ~0.9 for 28.6 s. In the experiments on steady-state scenario (TP-1), the duration of a high fraction of bootstrap current (70%) was extended to 8 s in JT-60U, while =4 was sustained for 2 s, with ITBs, in non-stationary DIII-D discharges.

In the experiments on ITB degradation with ECRF electron heating (TP-3) in weak positive shear plasmas, it was found that the degradation effect depended on the plasma current, less effective at a higher current, in JT-60U.

Significant progress was made in analysis and understanding of results from the experiment on rational q effects on ITB formation and expansion (TP-8.2). On JET, the Alfvn cascade eigenmodes were detected with high time resolution by interferometry and it was found that the ITB triggering events occurred in most cases just before grand Alfvn cascades, namely rational q appearance. On DIII-D, the initial increase/jump in electron and ion temperatures were seen to be simultaneous and occur before the rational-q surface entered the plasma (time difference is of order of 10-12 ms). Nonlinear "full physics" gyrokinetic simulations using the GYRO code suggest that the transport improvement is due to modifications in zonal flow structures associated with the low density of rational-q surfaces in the vicinity of low-order rational-q values ("gaps").

There was one US to EU and one JA to EU personnel exchange in this task. W. Houlberg of ORNL visited JET three times for the transport modeling of JET plasmas with recent focus on rotation. He worked to upgrade the installation of the NCLASS module in the JETTO analysis code and to analyze the poloidal rotation in JET. Work with K. Crombe showed good agreement between the multiple ion species NCLASS model and two analytic two-ion species models. H. Takenaga of JAEA visited JET for analysis of trace tritium experiments on JET. In these experiments, the tritium density profile evaluated from the neutron emission profile had a larger gradient than the deuterium density profile. He found that it was not attributed to the difference in source profiles of deuterium and tritium, but to the difference in transport of deuterium and tritium.

Task 2: Confinement, database and modeling

There has been considerable activity in the LTA execution of ITPA joint experiments and analysis this year. The key areas of focus are (i) confinement scaling with beta CDB-2, (ii) confinement scaling with collisionality in ELMy H-mode plasmas CDB-4, (iii) extension of global database studies to low aspect ratio CDB-6, (iv) ^* scaling of confinement at ITER relevant dimensionless parameters at low and high beta CDB-8 and (v) particle transport at low and high collisionality CDB-9.

A key topic is the study of the beta degradation of confinement in ELMy H-mode plasmas CDB-2. New results were obtained in dimensionless parameter scaling experiments on JT-60U indicating a rather strong degradation of confinement, ^-0.6, which is in contrast with previous individual and joint DIII-D and JET dimensionless parameter scaling experiments. An even stronger confinement degradation was observed based on a database of ELMy H-mode discharges in JT-60U. Analysis of AUG data in the H-mode confinement database show that the upper triangularity is possibly a key factor governing degradation of confinement. JET data in the H-mode confinement database shows very weak degradation but reveals that strong gas puffing can degrade confinement. Preliminary results from dedicated scaling experiments on AUG in early 2006 also show a strong degradation. Additional H-mode experiments in 2006 are planned for AUG, MAST, and NSTX. Also in 2006, JET plans an experiment to test the scaling of confinement in a Hybrid-like scenario.

JET and C-Mod experiments were performed to determine whether collisionality or the Greenwald fraction, n/n_GW , is a key confinement scaling parameter (CDB-4). A JET scan of n/n_GW and collisionality, matched in other dimensionless parameters to a C-Mod case, showed that B scales better with collisionality than with n/n_GW. A result was obtained from previous experiments on DIII-D and JET. Additional C-Mod experiments are planned for 2006.

Progress was made on CDB-6. A large number of NSTX data points was added to the international H-mode confinement database, increasing significantly the amount of low aspect ratio data. Synthesis of this and other low aspect ratio data with data at higher aspect ratio led to confinement scalings with a stronger (=a/R) dependence than those with a limited range of aspect ratios. These exhibit an unfavorable dependence on , although the low aspect ratio data introduce a strong correlation between and in the H-mode dataset. Similarity experiments at fixed poloidal dimensionless parameters were performed among DIII-D, NSTX and MAST. Analysis of a MAST/DIII-D pair is consistent with a negative exponent if B~^{*-3 0}.

Initial experiments for CDB-8 are planned between JET and C-Mod at low beta. JET and C-Mod, which lie at the extremes of ^*, have experiments planned for early summer 2006. After analysis of these initial experiments, the plan is for DIII-D and ASDEX-Upgrade to add the intermediate ^* results if needed. The JET/C-Mod experiments will choose a shape each can match. DIII-D has plans for an experiment in June 2006 that will match the ITER shape and other dimensionless parameters, except , at low rotation velocity.

The CDB-9 activity is new this year and came out of a joint decision to initiate a particle transport working group. Many new experimental results now indicate the possibility of stronger density peaking in ITER than previously assumed which can have both strong positive and negative influences on ITER performance. Thus the TP and CDBM TGs decided to assemble experimental, theoretical and modeling expertise on particle transport to improve collaborations in this area, identify appropriate joint experiments and assemble appropriate databases with the goal of improving the projections for ITER. The main target for first experiments was to study density profiles at low collisionality. The primary collaboration for 2006 is between JET and AUG. Plans include experiments on density peaking at low density scheduled for late June on AUG and experiments in June and July on JET focused on the shear dependence at low collisionality and the effect of electron heating in H-mode. Discussions are underway for experiments in 2006 on C-Mod.

Task 3: MHD, Disruptions and Control

MHD physics tasks proposed by the ITPA and implemented under the IEA LTA have been conducted in a range of areas.

Resistive Wall Modes: There has been significant progress in this area, as reported in an invited presentation at the 2005 APS-DPP meeting by H Reimerdes and most recently by the NSTX in a paper to be published in Physical Review Letter. Detailed similarity experiments have been performed between JET and DIII-D, and NSTX and DIII-D. These consist of comparisons of resonant field amplification (RFA) and of the critical rotation for RWM stabilisation. The critical rotation agrees well between JET and DIII-D when evaluated at q=2 and normalised to the Alfvn or sound speed - suggesting damping in the vicinity of q=2 plays a key role. The comparison between the critical rotation in NSTX and in DIII-D breaks the degeneracy between scaling with the Alfven or sound speed. It is found that the results agree better when a scaling with sound speed is assumed. Alternatively, the critical rotation, which is a higher fraction of the Alfvn velocity at low aspect ratio, is consistent with a model, where trapped particles do not contribute to the stabilisation. Preliminary results of effects of nearly zero rotation on RWM stability have been obtained by tailoring the NB momentum source in JT-60U and in NSTX by operating below the critical rotation frequency by braking the rotation with the n=3 coils, and can be compared in the future with new results from DIII-D.

Low error fields: The one outstanding issue from the 2004 C-Mod, DIII-D and JET identity experiments was the apparent difference in the B_t scaling on C-Mod. Two sets of C-Mod experiments have been completed on this issue and seem to give inconsistent results. A scaling at constant Greenwald fraction showed the error field threshold (b_r/B_t) scales as B_t^-1.06, while a scaling performed using the error field identity configuration shows a scaling as B_t^-2.05. Further experiments at 8T are planned on C-Mod to address this issue. Studies are also on-going to resolve the influence of aspect ratio on the error field threshold using MAST and NSTX data.

NTM physics and error fields at high : Preliminary experiments have been conducted on ASDEX Upgrade in the ITER relevant regime where the ECCD deposition width exceeds the island width, and the results indicate modulated ECCD is much more efficient at stabilising the 3/2 NTM than DC ECCD. More experiments in this area are planned on ASDEX Upgrade and DIII-D. On JT-60U a combination of experiment and modelling shows the stabilization effect is sensitive to ECCD location and destabilisation occurs for misalignments of the ECCD of about the island width.

Disruption Mitigation : In ASDEX Upgrade disruption mitigation by massive gas injection (MGI) has been used as a routine tool and is found to be very successful in reducing vessel forces, along with a reduced excursion and lower halo currents during the vertical disruption. In C-Mod the higher plasma pressure gives a good test of gas jet penetration under ITER-like conditions. Best mitigation in C-Mod was obtained with Ar or Kr MGI. However, analysis clearly shows that the gas jet is not penetrating very far in radially (as on DIII-D) and that it appears MHD plays a significant role in the quench process. Studies in JT-60U have concentrated on runaway electrons (REs). Mitigation of post-disruption REs by impurity pellet injection was demonstrated and avoidance of the current quench by conversion to a controlled RE column using combined injection of impurity pellets and ECRF was shown. Finally, from JT-60U initial studies on the recovery of the plasma current by additional heating, even after the beginning of current quench, have been made.

With regard to future plans from June 2006 to May 2007, it is expected that joint experiments on Disruption Mitigation, Neoclassical Tearing Modes, Resistive Wall Modes and Error Fields will continue, together with the related personnel exchanges.

Task 4: Edge and Pedestal Physics

Coordinated experimental activities/exchange of personnel took place for the following ITPA pedestal and edge topics.

PEP 1 & 3: JET/JT-60U pedestal identity experiments and modelling.
New experiments in JT-60U (June 2006) with the JET identity shape will be carried out in the third week of June 2006. The scope is to study ELMy H-modes with JET-similar shape at reduced toroidal magnetic field ripple (compared to the ~1% at the separatrix of the previous experiments). To take maximum advantage of the ripple reduction of the ferritic insets, the toroidal field will be 2.2T (instead of 3.1T), the plasma current 1.08MA (same as old similarity experiments), for a q₉₅~3.6. Variations of the injected torque/fast ion losses are planned, as well as a mini-density scan. V. Parail (EJ44) will participate in the experiments and, as for the previous joint experiments, numerical modelling analysis is planned (using ASCOT, with 3D JT-60U equilibria provided by JAEA). The aim is then to conduct similarity experiments in JET with the new plasma parameters, together with H-modes with the new Ip/Bt being tested at normal and increased ripple (note that the ripple in JET and JT-60U can be matched exactly (at the midplane)). In preparation for JET experiments with enhanced toroidal magnetic field ripple, the JAEA Orbit Following Monte Carlo (OFMC) was used to begin the analysis of JET heat loads and machine safety during the visit of J. Lonnroth to JAEA in Autumn 2005 (EJ45).

PEP 6: AUG/MAST/NSTX pedestal structure and ELM comparison in double null.
The aim is to compare pedestal structure and ELM stability in LSN, DN, and USN on ASDEX Upgrade, MAST and NSTX in similar shaped plasmas with similar global parameters. Experiments in ASDEX Upgrade and MAST were carried out in 2005. A change in ELM frequency was observed between USN, DN, and LSN. In DN the ELM frequency was lowest, and the confinement was the best. More development was needed because of a 2/1 NTM degrading confinement in LSN, as well as a fine scan in near Double Null (uncertainty in the magnetic reconstruction). The planned experiment on ASDEX Upgrade in May 2006 did not take place because operations were interrupted due to a flywheel generator incident. NSTX is preparing to participate in the comparison. In fact, results obtained from on-going experiments (not part of this PEP) indicate ELM size to be very sensitive to changes in the magnetic balance in high discharges. NSTX is preparing a shape adequate for comparison with ASDEX Upgrade and MAST.

PEP 9: Dependence of the H-mode Pedestal Structure on Aspect Ratio (DIII-D/MAST/NSTX)
The aim was to assess the effect of aspect ratio (DIII-D vs. MAST and NSTX) and wall proximity (MAST vs. NSTX) on pedestal height, widths and gradients in ELMy H-mode, at constant pedestal ^* and _e^*. Good data has been obtained from all machines (new experiments in NSTX in April 2006). Common shape selected for the experiments is a double null, with ~ 2, ~ 0.55-0.6. _e^* ~ 1, ^* ~ 0.01 matched at the top of the outboard pedestal. The actual pedestal values of n_e, T_e and P_e are also quite close. Under these conditions the three machines observed ELMy H-modes. The preliminary conclusion is that the pedestal width increases with R/a. Data analysis is in progress. NSTX will carry out further experiments in the near future to obtain H-modes at reduced pedestal collisionality of ~0.5 (to match data from DIII-D and MAST).

PEP 10: Collaborative experiments between MAST and ASDEX Upgrade on the effect of pedestal parameters on ELM radial extent.
These experiments, carried out in March and April 2006, were designed to investigate the effect of pedestal parameters on the radial extent of Type I ELMs. The ASDEX Upgrade part of these experiments was completed partially, with A. Kirk (UKAEA) being an external participant. The MAST part is planned for the near future

PEP 13: Comparison of small ELM regimes in JT-60U, ASDEX Upgrade and JET.
Experiments on JT-60 and ASDEX Upgrade were carried out in March 2006. Previous attempts had been made (2003 and 2004) to establish the JT-60U grassy ELM regime in ASDEX Upgrade. While no direct identity is possible (details of shape and aspect ratio cannot be matched), basic ingredients from JT-60U were reproduced in ASDEX Upgrade, namely high triangularity (~ 0.45), high _poloidal (< 1.6) and high safety factor q₉₅ (~ 6.5). A change in ELM type was observed, in both campaigns but only in one pulse each. These 'grassy' ELMs are so far only observed in near DN R_sep ~ -6, -10 mm (in addition to the above ingredients). The aim of the 2006 experiments was to connect the ASDEX Upgrade Type II regime to the "grassy" ELM regime of JT-60U, specifically by exploring access density/ _e^* and taking high quality edge profiles for MHD stability analysis. In the experiments, the nominal discharge parameters were reproduced, but only Type I ELMs obtained. In the 2006 experiments, the edge collisionality was higher than in 2004. JT-60U plans to test the idea of a possible upper limit in collisionality for access to grassy ELMs in July 2006. External participants in the experiments were N. Oyama (JAERI), and A. Loarte and G. Saibene (EFDA). Experiments were also carried out in JET (May 2006) to reproduce the grassy ELMs high _poloidal H-modes obtained in 2004. As in ASDEX Upgrade, the main plasma characteristics (, _pololidal and q₉₅) are similar to JT-60U, but no direct identity is possible. In these new experiments, grassy ELMs were not obtained, probably due to a lack of input power available on the day, limiting _poloidal ~1.65. Details of the shape (different from that of 2004) are also being investigated. New experiments are planned for the near future. G Saibene (EFDA) participated in the experiments.

PEP 16: C-MOD/MAST/NSTX small ELM regime comparison.
The aim of these experiments is to establish dimensionless comparison of the edge pedestal with small ELMs. Since only three of the four parameters q₉₅, _ped^*, _ped, and _ped^* can be held constant, it was decided to perform a two-point scan in ped and _ped, to identify similarities and differences between the regimes. First experiments were carried out at C-MOD and NSTX in April 2006. On C-MOD, the shape development was successful, although obtaining the required high beta pedestal at high pedestal density proved to be difficult. Only a few pulses with high ICRF heating power (up to 4.7MW) were obtained, and no sustained small ELMs observed. In particular, at the highest RF power, no small ELMs were observed, and the target T_e(95%) = 0.6keV at a density of n_e(95%) = 4e²⁰m^-3 proved to be impossible to obtain. The effort to maximize the ICRF heating power in the C-MOD runs took up most of the experimental time, and only a limited scan of I_p and B_t was obtained, but spanning a small ^* range. On NSTX, the shape development was not as smooth as expected and the first run in April 2006 was unsuccessful. New experiments are scheduled for the 2007 campaign. So far, MAST has undertaken only the shape development, but experiments are planned for later this year, when high power will be available.

Task 5: SOL and Divertor Physics

Flows: Flows are central to determining impurity transport (determining core impurity levels) and play a role in material migration and co-deposition of D/T (DSOL-9). SOL flows may also be linked to the L-H transition power threshold. Better understanding of what drives the flows will improve prediction of core impurity levels, T retention, and the L-H threshold. In both circular limited plasmas and shaped, diverted configurations the SOL poloidal flow is observed to be from the low field side (LFS) to the high field side (HFS). Modeling of these flows has only been partly successful. On JET, the difference between the average flows for normal and reversed toroidal magnetic field directions could be driven by ballooning-like transport. However, at the moment, the only mechanism found to increase the magnitude of model flows to the levels measured is to force the radial transport across the separatrix to be poloidally non-uniform, much higher at the plasma LFS (factors of 10 variation poloidally). The capability to predict the relative importance of the various terms, which drive the SOL flows, must be developed. This will require more flow measurement capability (multiple poloidal locations) as well as more experiments aimed at delineating the importance of various terms (toroidal field direction, magnetic topology, attachment/detachment). Data are needed for a variety of conditions: Ohmic, L-mode, ELMing H-mode and Advanced Tokamak regimes, to establish dependence on collisionality etc.

Cross-field transport (DSOL-3): One of the issues facing the ITER team is whether to modify the design requirement to limit the ITER divertor re-circulating flux to 10% of the fuelling/pumping rate. The divertor design and projected pumping rate could be considerably improved if the requirement could be relaxed. Since estimates of main chamber recycling particle flux are larger than this 10% flux, this restrictive requirement might be relaxed. Further experimental measurements on a variety of tokamaks, including comparisons of pedestal gradients across machines are needed. This would also facilitate further testing (DSOL-1) of the model that describes ELM filament structures on JET in terms of parallel losses and polarization drifts. A result of this model is that a high ion temperature in the filaments is expected to strike the main chamber wall in ITER: T_i = 350 eV having implications for sputtering on outer limiters and the upper divertor. Roughly 8% of the initial energy is expected to reach the second separatrix and thus, vessel structures. A lower level of ELM energy, ~2%, would reach the limiter radius, r - r_sep = 15 cm.

Task 6: Steady State Operation

International collaborative experiments coordinated through IEA IAs have made significant progress and expanded multi-machine data sets for further analysis in view of steady state operation development. Concerning new data during the period of this review; on JT-60U experiments had resumed since December 2005 and are under way, on JET operations had just restarted and no new experiments had performed in DIII-D.

Preparation of ITER steady-state scenario (SSO-1.2~1.3); On JT-60U, very high bootstrap current fraction (f_BS) plasmas had been studied for qualification of other q-profiles than that foreseen for ITER steady-state operation and to investigate controllability of such a very high f_BS plasmas. Duration of f_BS ~70% was extended to ~8 s. Quite a flat q profile was fond to be maintained in the plasma, and it was found that ECRF could lower shear reversal in a similar plasma. Moreover, sustainment of I_p~0.58MA with almost 100% of f_BS for 1.5 s was demonstrated. On DIII-D, detailed analysis of existing steady-state candidate discharges confirmed a ~100% non-inductively driven discharges with ITER relevant performance (fusion gain factor, G=0.3, =3.6, q₉₅=5.0).

Preparation of ITER hybrid scenario (SSO-2.1~2.3); For the development of hybrid scenario demonstration discharges, which have a flat q profile with q_min>~1, the duration of high beta sustainment with high confinement and such a q profile has been extended in JT-60U with reduction of toroidal field ripple; b_N = 2.5 with H_H98y2 ~1.1 was maintained for 17.6 s and = 2.3 with H_H98y2~0.9 for 28.6 s.

Real-time q-profile control in hybrid and steady state scenarios (SSO-3); In order to prepare future joint experiments on real-time control, real-time control scheme and experiments had been developed in each device. In JT-60U, real-time q-profile control by LHCD demonstrated suppression of an MHD activity and retrieval of the stored energy in a high b_N plasma. In JET, a new dynamic-model approach for simultaneous control of distributed magnetic and kinetic parameters had been developed.

Concerning personnel exchange, there was one exchange carried out. That is EU76, Dr. T. Jonsson visited GA for about four weeks. The objectives were; porting of the Orbit-RF code to the Linux cluster at JET, and getting training in using the Orbit-RF code. The objectives were successfully completed. Dr. S. Ide had been prepared to visit JET under JE139, but that has been postponed due to cancellation of the JET experiments during his expected stay.

As for the future plan from June 2006 to May 2007, the research on steady state operation will be continued. During that period, new data will be available from DIII-D, JET and JT-60U. The ITPA "SSO" TG is proposing researches on the ITER steady state relevant plasmas and hybrid operation relevant ones in more depth.

Task 7: Tritium and Remote Handling

De-tritiation of plasma facing component: With regard to the de-tritiation of plasma facing components, further trials of flash lamp photonic cleaning have been conducted in 2005-2006 in the JET Beryllium Handling Facility using inner divertor tiles with thick deposited films. Using increased power of 500J per pulse in a single lamp, up to 90 microns of a-C:H layers were removed from films deposited in the shadowed region at the JET inner divertor, and ~3GBq tritium were released during the cleaning of a single JET divertor tile. SIMS and Ion Beam Analysis of the tile showed that hydrogen isotopes are desorbed from the film for several microns in advance of the removal front, but that metallic impurities in the deposited films can accumulate at the surface and slow the removal rate. This latter effect requires further investigation.

The equipment for testing laser de-tritiation via layer ablation on tritiated JET tiles has been completed. The trials will take place in the JET beryllium handling facility during the last two weeks of June 2006, and will be followed by IBA and SIMS analysis of the tiles to demonstrate the efficacy of the treatment.

Trials have taken place of a small plasma torch that can access small areas to remove deposited films. Initial tests used an argon plasma, but switching to a nitrogen plasma has proved to increase the power delivered to the sample, thus increasing the surface temperature and removal rate. Future tests will examine whether the torch can be used to remove deposits from within castellations, which represent a very large area in ITER yet are not treated by some of the other candidate de-tritiation techniques.

Surface analysis of plasma facing component: Fuel and impurity particles show complicated behavior on the surface of plasma facing components (PFC) in fusion devices. The study is important for the design of the fuel recycling, plasma control, safety management of the tritium inventory, etc. Quantitative measurements of hydrogen isotope, lithium isotope and other impurities were performed on the PFC surface exposed to D-T plasmas in the Tokamak Fusion Test Reactor (TFTR) to understand the fuel and impurity particle behaviors. The analyzed tile made of carbon-fiber composite was used as the inner bumper limiter at the position KC-16 in D-T experiments from 1993 to 1997. The sample tile was analyzed with the nuclear reaction analysis (NRA) by a deuterium accelerator of Fusion Neutronics Source (JAERI-FNS), imaging plate method, full combustion method and activation analysis. The tritium retention of the side surface of the tile was 2.3 times larger than that of the plasma facing surface and its areal distribution increased toward the plasma facing surface. So co-deposition with hydrogen isotopes occurred on tile surfaces without direct plasma contact. The retained T/D ratio of 1 % fairly agreed with the total injected T/D ratio of 3 %. No other impurities such as carbon-14 or radioactive intermediate mass nuclei were detected.

Erosion/deposition profile and hydrogen isotope distribution in the plasma facing material in JT-60U W-shaped divertor have been investigated in collaboration with Japanese universities. Erosion/deposition analyses showed that deposition was dominant at the inner divertor and the outer dome wing, whereas erosion dominant at the outer divertor. In the plasma shadowed area, thick deposition (~several 10) was observed on the bottom side of the outer dome wing tile, indicating that local transport of eroded carbon to inboard direction plays an important role on the carbon re-deposition process. The highest H+D retention was observed in the re-deposition layers at the bottom of the outer dome wing tile with 16 x 10²² atoms/m² and ~0.13 in (H+D)/C. The amount of the hydrogen isotope retention in such area is still smaller than those observed in JET (louvers at the inner corner: D/C 0.4~0.8).

An experiment of ¹³CH₄ gas puffing from the outer divertor was performed. A deposition layer of more than 200 thick was observed on the outer divertor tile adjacent to the gas puffing port. ¹³C distribution on the plasma-facing wall was measured with SIMS. A large amount of the ¹³C (~10²¹ cm^-2) re-deposited on the outer divertor tiles near the gas puffing port and less ¹³C was detected on the inboard first wall (~10¹⁶ cm^-2) and the inner divertor tiles (10¹⁷~10¹⁹ cm^-2). These results indicate that carbon impurities are transported through SOL.

The characteristics of hydrogen isotope retention and carbon migration on the plasma facing component was discussed between JET and JT-60. It was confirmed that the hydrogen isotope retention and carbon deposition on the remote area of JT-60U was much different from those of JET. The hydrogen retention on the remote area should be investigated taking into account local carbon deposition, which is related to divertor geometry.

Six reports of the JT-60U Surface analysis were presented at the 17^th International conference on PSI (China, Hefei, 2006).

Task 8: Others: "Diagnostics and technical issues such as neutral beam technology"

Neutral Beam Technology
Exchanges in negative ion beam studies have been very active this year (JE143, UJ300-7, 8, 9). In Japan in the past 12 months, progress on negative ion beams continues to be made in many areas through the LTA agreement, resulting in very long pulse operation of NNBI systems, up to 25s on JT-60U. In order to continue this steady progress more work is required under the LTA agreement to develop a deeper understanding of the NNBI physics. Two new insights were obtained this year which will lead to further advances. On JT-60U (also observed on LHD), it was found that during beam extraction there is a rapidly rising neutral cesium component in the discharge, even for discharges as long as 25s. It was previously expected that all the evaporated cesium entering the plasma would be ionized and electrostatically prevented from leaving the source during beam extraction. Understanding the cesium physics and long time stability of the arc is a major goal for the future study. Second, it was also discovered that observable levels of oxygen can play a significant role in the dynamics of the arc. Understanding the physics of Cesium and Oxygen is a high priority for the LTA exchanges aimed at extending the performance of NNBI systems.

In addition to the work in Japan, in the EU at IPP Garching, progress has been made with initial operation of the first large RF H-ion source. Interesting results are expected in the coming year.

Dr. N. Umeda (JAEA) visited JET to discuss current status and future projects of Neutral Beam (NB) injection systems on JET and JT-60U. Significant progress has been achieved in JT-60U by extending the pulse duration of the negative-ion based NB system from 10s to 25s. Key to this achievement is the suppression of the heat load of the acceleration grids by reducing the stripping losses. Dr. T. Jones (UKAEA) described a new activity related to the JET NB system. It is planned to increase the NB power from 23MW to 34MW for 20s in an intervention scheduled for 2008. The key is the utilization of the molecular ion beams (D2+ and D3+), whose neutralization efficiencies are higher than that of D+. The magnetic configuration of the ion source will be modified to increase the molecular ions in the source plasma. Both parties confirmed that steady efforts on JET and JT-60U contribute to progress in NB technologies.

Diagnostics
In the framework of the bilateral collaboration between the EU and US, new diagnostic systems have been installed on JET during the last year. First, a set of nine Faraday cups located in 5 different poloidal positions in the lower outer part of JET allow the spatial resolution in poloidal angle and a rough energy resolution for the alpha/fast particle losses. In addition, a scintillator probe, imaged with a CCD camera, has been installed in the equatorial plane to provide data on the pitch angle of the alpha/fast particles. Preliminary results are being obtained from both diagnostics, with clear correlations between MHD activity and fast particle losses being detected. Second, the JET Charge Exchange Recombination Spectroscopy (CXRS) system has been upgraded for the measurement of helium ash by the installation of new periscopes and additional optical fibres supplied by the EU. ORNL and PPPL provided two high throughput, short focal length, holographic transmission grating spectrometers and two fast CCD cameras. Third, GA provided 21 filter spectrometers and PPPL provided amplifiers (for the detectors) for a new High Resolution Thomson Scattering system on JET. The spectrometers have 4 channels, with seven spectrometers being fitted with filters suitable for low temperatures (50eV ? 5keV) and the remaining being fitted with filters which allow measurements in the range 500eV - 20keV. The detectors are avalanche photo diodes with good spectral sensitivity even at the laser wavelength.

Atomic data for impurity studies were discussed during the visit of H. P. Summers and A. D. Whiteford to JAEA in early 2006 (EJ47). The extensive discussions covered developments in heavy species modeling, the status of ADAS, the JAEA atomic/molecular database and the status of JT60 modeling and spectral analysis activities. Separate discussions were held on atomic data issues for ITER support at the Naka ITPA with A. Costley and T. Sugie.

IEA Large Tokamak Cooperation

Workshop Number: W60
SUBJECT: Burning Plasma Physics and Simulation
Date: July 4-5, 2005
Place: University Campus, Tarragona, Spain Organizer: J. Ferron, B. Goncalves, J.-M. Noterdaeme, T. Ozeki

Name (s) of attendees: (All names of attendees are listed in the attachment.)

Brief description of the activities in the Workshop

The workshop followed the EPS conference in Tarragona, during which the decision to built ITER in Cadarache was announced.
The scope of the workshop was burning plasma research in the areas of Plasma Transport and Confinement, MHD Stability and Fast Particle Confinement, Integrated Modelling of Burning Plasmas, and Diagnostics and Control for Burning Plasmas. The session on MHD stability and fast particle confinement was held in common with the ITPA MHD Group.
In each of the areas, a number of presentations were given. Following those, participants prepared in break-out sessions a summary presentation in those four areas in the spirit of a road map: where are we (review of the status), where do we want to go (identify the needs), and how do we get there (ways and means).
Based on those summary presentations, and the lively ensuing discussion, summaries were written and iterated after the workshop among the participants. Those summaries will be published in the January issue of Fusion Science and Technology, and provide a concise view of the participants on the topics. The views may be subjective, but, precisely because of their frankness and succinctness, could be interesting to illuminate the path ahead. The full presentations and the summary presentations can be found under Workshop W60 on the IEA web site: http://www-jt60.naka.jaeri.go.jp/lt/index.html

This report received by Secretariat on 25day 11mo 2005y

Appel, L. (EURATOM-UKAEA)
Baylor, L. (ORNL)
Bindslev, G. (EURATOM-Riso)
Budny, R. (PPPL)
Coster, D. (IPP-Garching)
Costley, A. ( ITER International Team)
Donne, A. (EURATOM-FOM)
Fasoli, A. (CRPP-EPFL)
Ferron, J. (General Atomics)
Firpo, M. (C.N.R.S. Ecole Polytechnique)
Fisch, N. (PPPL)
Fonck, R. (University of Wisconsin-Madison)
Goncalves, B. (EFDA-JET CSU)
Gorelenkov, N. ( PPPL, Princeton University)
Guenter, S. (EURATOM-IPP Garching)
Hammamatsu, K. (JAERI)
Hawryluk, R. (PPPL)
Hellsten, T. (EURATOM-VR)
Jardin, S. (PPPL)
Jaun, A. (EURATOM-VR)
Kessel, C. Jr (PPPL)
Kritz, A. (Lehigh University)
Lee, W. (PPPL)
Lister, J. (EURATOM-CRPP)
Martin, P. (EURATOM-ENEA)
Meo, F. (EURATOM-Riso)
Miura, Y. (JAERI)
Moreau, D. (EFDA-JET CSU)
Noterdaeme, J-M. (EURATOM-IPP Graching)
Okabayashi, M. (PPPL, Princeton University)
Osborne, T. (General Atomics)
Ozeki, T. (JAERI)
Peng, M. (ORNL, UT-Battelle)
Plyusnin, V. (EURATOM-IST)
Porkolab, M. (MIT)
Raman, R. (University of Washington)
Sasao, M. (Tohoku University)
Schneider, M. (CEA Cadarache)
Snipes, J. (MIT)
Solano, E. (EURATOM-CIEMAT)
Stork, D. (EURATOM-UKAEA)
Strait, E. (General Atomics)
Takenaga, H. (JAERI)
Takechim, (JAERI)
Todo, Y. (NIFS)
Uckan, N. (ORNL)
Vlad, G. (EURATOM-ENEA)
Watkins, M. (EFDA-JET CSU)
Wesley, J. (General Atomics)

IEA Large Tokamak Cooperation

Workshop Number: W62
SUBJECT: Fourth IEA Large Tokamak Workshop on "Implementation of the ITPA Coordinated Research Recommendations" Joint Workshop of Large Tokamak, Poloidal Divertor and TEXTOR IA's
Date: November 1-2, 2005
Place: General Atomics, San Diego, USA

Name (s) of attendees: (All names of attendees are listed in the attachment.)

Brief description of the activities in the Workshop W62
The 4^th annual Workshop for the planning of ITPA/IEA joint experiments to implement the ITPA HPRTs was held at GA on November 1 and 2. About 32 participants (see Attachment #1) included Chairs or Co-Chairs of Executive Committee members of the three tokamak related IEA IAs, Chairs, Co-Chairs, and some members of the ITPA Coordinating Committee and its Topical Groups, Head of ITER Physics Team, and Leaders or their representatives of ~ 15 tokamak programs in the six ITER Parties (CN, EU, JA, KO, RF, and US). Most participants are involved in 2 or more of these organizations (ITPA, IEA, ITER, and the Tokamak programs), which enhanced the coordination among the organizations. The previous workshops for the planning of Joint Experiments were held at MIT, USA (Nov 02), Naka, Japan (December 03), and Oxford, UK (Dec 04).

The meeting agenda is shown in Attachment 2. Erol Oktay made opening comments as the Chair of the IEA LT ExCo and the U.S. Contact person for the ITPA. He suggested several topics for discussion at the closing session of the meeting, based on the information exchange during the meeting. Uli Samm (Chair of IEA TEXTOR ExCo) and Otto Gruber (representing G.S. Lee, the Chair of the IEA Poloidal Divertor IA) made additional comments on this activity. Duarte Borba (JET), representing Jerome Pamela (JET), reported briefly on the 3rd Workshop held at Oxford, UK in December 2004. Ron Stambaugh, Chair of the ITPA Coordinating Committee reported on the status of Joint Experiments that were planned at the Oxford meeting. Of the 67 planned joint experiments, substantial progress is made on 15 experiments, some progress on 25, no progress on 8, and 2 were completed. Since joint experiments rely on experiments on two or more tokamaks, some of the planned experiments were not completed during this year, and these would be continued in the following year. The Topical Groups proposed 12 new joint experiments and updated their proposed research on the experiments to be continued into 2006. Thus there were ~ 75 joint proposals for CY2006 for the participants to review and plan for CY 2006. The TG Chairs or Co-Chairs provided one page summaries of these proposals, including the progress made previously, and their recommendations for tokamaks that should participate in these experiments to provide the parameter range for the experiments.

Michiya Shimada, Head of ITER Physics Team, presented a summary of ITER Design Issues that need urgent ITPA input and description of Major Physics Issues for the Operating Regimes of ITER. The ITER design issues need urgent input from the ITPA Topical Groups on DivSOL, MHD, and Pedestal on the critical issues of disruptions, ELMs, carbon erosion and re-deposition, detriation, divertor material choices, and vertical and RWM stabilization. The major physics issues for ITER operating scenarios, which include inductive high Q, hybrid, improved hybrid, and steady state regime, cover a wide range of physics issues and involve work of all of the seven TGs. Shimada noted that the 75 joint experiments proposed by the TGs cover ~ 95 % of the HPRT�fs in the TGs relevant to these physics issues.

These presentations were then followed with brief presentations by the tokamak leaders or their representatives, updating information on the new hardware capabilities, their operating schedules, and major topical areas of their research programs. In the afternoon, the TG chairs/co-chairs provided brief reports on the technical contents of their proposals.

Thus this information exchange on ITER physics needs, tokamak programs and their schedules, and technical details of proposed joint experiments in the first day provided the necessary basis for the participants to consider the proposed joint experiments for inclusion in the Joint Experiments Program.

The first half of the second day was dedicated to a brief review each proposal, receiving an expression of interest from the tokamak leaders to participate in the specific joint experiment, and to identify spoke-persons for the joint experiments and the names of the contact persons from the participating tokamaks. This activity led to the development of the Joint Experiments Plan for FY 2006, which is shown in Attachment 3. The commitments from some of the tokamaks are not yet firm (indicated in green), pending finalization of Research Forums of the individual programs and their process to finalize their experimental program plans. Most tokamaks (in red) were committed to the experiments. The tokamaks participating in the joint experiments, but completed their experimental runs earlier are shown in black.

The process of developing joint experiments has matured during these past three years, and most proposals were well defined and involved coordinated joint experiments. These are labeled as ready for Experiments (E). Some proposals, categorized as D, required additional discussions for joint experiments, partly because tokamak leaders expressed an interest to join the experiment at the meeting and their participation needed to be defined. Only a few proposals were labeled as P, indicating that this is an ongoing programmatic activity, such as collecting database, with minimal coordination among the participating tokamaks.

There was a good discussion among the participants at the concluding session, which lasted about two hours. These are briefly summarized below:

• ITER/ITPA/IEA interactions: It was very useful to have a presentation at the meeting by the ITER Physics Head, and his participation in the discussion of proposals and planning of experiments. These interactions improve coordination between ITER, ITPA, and IEA in the areas of ITER Design issues and High Priority Research Tasks. There is a need to also include interactions on specific ITER Physics Tasks.
• Remote Participation: The participants discussed the desirability of remote participation and use of televise conferences to enhance communications and to reduce some travel. The need for dedicated sites and the difficulty of time-changes were mentioned as key obstacles. The participants agree that we have to be more proficient in this mode of communication, which will be essential for ITER construction and operation. It was noted that the ITER Participant Teams are planning to enhance this tool. Some also use these communication tools for some regular meetings in EU and US.
• Inclusion of new coordinated experiments, not identified by the TGs: It was noted that this gathering of people for face-to-face meeting provided a new opportunity to identify co-ordinations not included in the TG proposals.
• Inclusion of Coordination of Modeling activity in �eJoint Experimental program' Plans. Triggered by the proposal submitted by the DivSOL TG for coordinated verification of some edge codes, there was substantial discussion on insufficient coordination in modeling activity. It was noted that coordination to validate codes, which require experimental time and data should be included in the Joint Experiments Program. The tokamak leaders have some responsibility in the use of resources for this purpose. There is some coordination in these codes in the Confinement Database and Modeling TG.
• Burning Plasma programs in ITER Parties: There was informal information exchange on how each party is organizing their research effort for ITER and Burning Plasmas. This process is evolving in all Parties as the ITER process progress towards an Agreement.
• Date and Place of Next Meeting: The participants gladly accepted the offer by Japan (JAEA) to hold the next annual meeting in Japan. The tentative date for the meeting is November 30 ? December 1, 2006, pending approvals from the IEA IAs and the ITPA CC.

This report received by Secretariat on   day mo    y

The Twenty first Executive Committee Meeting for the IEA Implementing Agreement on Cooperation among Large Tokamak Facilities was held at Cadarache, 28 - 29 June 2006.

A. MEMBERSHIP AND CHAIR

The Committee elected Dr. F. Romanelli as the chairman until the next meeting. (Dr. D. Meade had been replaced by Dr. R. Hawryluk as a US member, Dr. J. Pamela had been replaced by Dr. F. Romanelli as an EU member, Dr. Y. Miura had been replaced by Dr. S. Ishida as a JA member, and Dr. T. Fujita had been replaced by Dr. H. Kimura as a JA alternate member. The present members of the Executive Committee are shown in Appendix A.)

B. ADOPTION OF AGENDA

The Committee adopted the agenda, which is attached as Appendix B.

C. REPORTS ON THE STATUS AND PLANS OF EACH PARTY

The status and plans of the fusion programs of EFDA-JET, U.S. (DIIID, C-MOD, NSTX), and JT-60 were presented by Drs. M. Watkins, E. Oktay, (T. Taylor, R. Hawryluk, B. Lipschultz), and M. Kikuchi. The status reports are attached as Appendix C.
In general discussion, the following recommendations and encouragement were given by the participants: 1) With regard to Type I ELM mitigation using ergodic magnetic field perturbations, future experiments in JET and AUG would be quite important to extend the research being conducted on DIII-D. 2) The study of a metallic wall is quite important. In particular, the flaking of W-tiles by He is of concern. Dr. M. Kikuchi will distribute the related paper (N. Yoshida et al.) to all members.

D REVIEW OF TASK ACTIVITIES

The present status of the Task Activities in each device was reported; JET (Watkins), AUG (Gruber), JT-60U (Kamada), DIII-D (Gohil), NSTX (Hawryluk), and C-mod (Lipschultz). In addition, Reports on the 8 Task Areas were briefly introduced. The list of Task Coordinators are appended in Appendix D1. The activities of the Tasks (submitted reports) are attached in Appendix D2. The presentations from each device will be uploaded on the LT web page.
Discussion:

• Some ITPA inter-machine experiments need to be defined better. In order to achieve high priority on any device, well-defined proposals are recommended.
• The Chairman of the IEA Large Tokamak Executive Committee will ask the Chair of the ITPA Coordinating Committee to disribute the proposal for inter-machine experiments in 2007 to the tokamak leaders by November 17^th, 2006.
• It is not easy for the Task organizers to collect the reports from each device. It is necessary to identify a national contact person for each Task. The meeting understood that the Chair of the ITPA Coordinating Committee would provide a list of Contact Persons.
• The difficulty of reporting a Task is partly due to that the report date is different from the date at which the inter-machine experiment is reported to the ITPA/IEA meeting which is usually in November of the year.
• Collaboration on rotation between DIIID and JT-60U is quite productive in many areas utilizing co- and counter-NB injection capability.
• Next time, the status of Task 7 & Task 8 should be included in the report from each device.
• US participation to JET with diagnostics contribution is successful. Such diagnostics based collaboration has to be more encouraged also to JT-60U.
• Members should send modifications on the content of the Reports to the Task Organizer and to the Secretary.

E. REPORTS ON THE COMPLETED WORKSHOPS AND PERSONNEL ASSIGNMENTS FOR JUNE 2005 - MAY 2006

Workshops and personnel assignments completed in the period of June 2005 - May 2006 are listed in Appendix E1. Two workshops on "Burning Plasma Physics and Simulation" (W60), and "Fourth Joint Workshop of Large Tokamak, Poloidal Divertor and TEXTOR IA's on Implementation of the ITPA Coordinated Research Recommedations" (W62) were carried out. The total number of personnel assignments completed in the period was 17. 17 PAs were for review tours (less than 4 weeks) (see Appendix E2). Subjects are summarized as follows (see Appendix E3): 4 on Task1: Transport and ITB Physics (23.5%); 0 on Task 2: Confinement database and modeling (0%); 2 on Task 3: MHD, disruptions and control (11.8%); 2 on Task 4: Edge and pedestal physics (11.8%), 2 on Task 5: SOL and divertor physics (11.8%), 0 on Task 6: Steady State Operation (0%), 1 on Task 7: Tritium and RH Technologies (5.9%), and 6 on Task 8: Other (35.2%). The reports on the workshops (FORM C) and the short reports for review tours are attached as Appendices E4 and E5, respectively.
Discussion:

• Nowadays, remote participation in experiments can be carried out effectively. A record of such remote participation should be included.
• A record of publications which result from the collaborations is also important. In order to increase the number of publications, IEA Workshops combined with IAEA workshops may be effective.
• In some cases, the Secretary had not received Form A and/or the initial announcement of some visits. Official procedure should be followed.

F. PROPOSALS OF WORKSHOPS, PERSONNEL ASSIGNMENTS AND REMOTE PARTICIPATION FOR JUNE 2006 - May 2007

Proposed Workshops and Personnel Assignments for June 2006 - May 2007 are listed in Appendix F. These include three new Workshops (W63: "Joint Workshop with PD IA on Real time control for steady state", W64: "Edge Transport in Fusion Plasmas", W65: "Fifth Joint Workshop of Large Tokamak, Poloidal Divertor and TEXTOR IA's on Implementation of the ITPA Coordinated Research Recommedations"). The Committee discussed these proposals and authorized their implementation. With regard to Workshop W63, Dr. O. Gruber will contact the key persons in CODAC/ITER, and discuss the possibility of holding this workshop, and inform the result to the US & JA.

G. GENERAL DISCUSSION ON COOPERATION

Near Term:

• US / JA collaboration on first wall, including first wall tile analyses is encouraged. JET has a strong programme in this area and is open to further collaborations.
• Dr F. Romanelli stressed the importance of increased collaboration on JET as a preparation for working together on ITER.
• Possibility to hold a meeting on JT-60SA was discussed. One candidate for the date is November 27 " 28, 2006. Dr. M.Kikuchi will organize this meeting.

• The Long-term cooperations were discussed. In near future, JT-60U will stop operation for the construction of JT-60SA. The present LT Agreement covers 5 years, starting in 2006. Therefore, the present framework can be continued for another 4 years. However, in view of changes in the world fusion programme, such as the new experiments EAST and KSTAR, a discussion on the new framework/restructuring of the IEA Agreements should be started before March 2007.

H. SCHEDULE FOR ANNUAL REPORT FOR FPCC

The schedule and responsible persons for the production of the annual report for FPCC were discussed. As usual, the Executive Summary will be prepared by the Chairman. He will distribute a draft in the early autumun. The deadline for submission to the FPCC will be the end of November 2006.

I. NEXT MEETING

The next Executive Committee Meeting will be held on May 21(Monday) - 23(Wednesday), 2007 in Naka (JAEA). It will be a joint meeting with PD IA.

J. JOINT SESSION OF TWO EXECUTIVE COMMITTEE

FPCC Study Group on Steady-state issues was discussed. Dr. Jacquinot explained the essential points: Its goal is to identify the issues and to promote collaborations related to steady-state physics and technology including tokamak and helical devices and, in particular, superconducting devices. The charter is now being discussed and comments are requested before September 15^th, 2006. The largest issue raised in the meeting is the difficulty of avoiding overlap among the Agreements. For example, all the existing Implementing Agreements can contribute to steady-state research, and a new Implementing Agreement on steady-state may not be necessary. In addition, the issues of steady-state operation physics are different in each device, depending on its project goal. On the other hand, all agreed that the present Agreements do not cover all the issues related to superconducting devices. From this point of view, a superconducting device Agreement may be better than a topic based agreement.
Related to the PD agreement, the way to invite KSTAR, EAST, SST is also an issue. The members of the PD Executive Committee manifested their unanimous agreement to start the procedure to invite India and China to join that implementing agreement. This decision was supported by the members of the Large Tokamak Implementing Agreement. When JT-60SA starts, it could be part of the Large Tokamak. Poloidal Divertor, or Steady-State Agreements.
The essential difference in the framework between ITPA and IEA is that the former has a structure based on research topics while the latter is based on device type.
More discussion is needed between the different collaboration Agreements. A possible direction in which to proceed is to make one Agreement between all tokamaks and stellarators and introduce sub-groups for specific topics.

K. AMENDMENT OF IEA LT AGREEMENT

The Executive Committee RESOLVED unanimously to approve in its entirety the document entitled "Amendment No. 2 Implementing Agreement on Co-operation on the Large Tokamak Facilities" as prepared by EURATOM (in the version dated 17 May 2006), which amends the Preamble and Articles 3, 4, 9 and 10 of the Implementing Agreement, a copy of which is attached to these minutes (Appendix K).