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U.S. Burning Plasma Organization e-News
September 18, 2007 (Issue 13)

CONTENTS

Dear Burning Plasma Aficionados:

This newsletter provides a short update on U.S. Burning Plasma Organization activities.  E-News is also available online at http://burningplasma.org/enews.html Comments on articles in the newsletter may be sent to the editor (R. Nazikian rnazikian@pppl.gov) or assistant editor (Emily Hooks ehooks@mail.utexas.edu).

Thank you for your interest in Burning Plasma research in the U.S.!

Director's Corner by J. Van Dam

It’s crunch time for the ITER Design Review Activity, and the USBPO is involved in various US contributions to this vital effort.

Two critically important meetings either have been or are being held recently:  the first STAC Meeting and the second IDR Meeting. (ITER is generating an interesting set of new acronyms.)

The Science and Technology Advisory Committee (STAC) of the ITER Council held its first meeting September 5 and 6 in Cadarache. Recall that the STAC is charged with reviewing the work of the ITER Organization from the scientific and technological points of view and then making recommendations directly to the ITER Council, which has the final say in making decisions about the design for ITER. The September STAC meeting was almost entirely focused on key issues related to the ITER Design Review. After an introduction by Director-General Kaname Ikeda and an overview talk on the new ITER baseline design documents by Principal Deputy Director-General Norbert Holtkamp, there were successive talks about first plasma definition, scenario and sensitivity analysis, magnet R&D, plasma facing components and first wall heat loads, divertor design and remote handling, heating and current drive, diagnostics, building design, plant support systems, and cost and schedule impact. In addition, technical activities related to a test blanket module program and to ITER control, data access, and communication (CODAC) were briefly described. The STAC, under the guidance of its chair, Predhiman Kaw, is now preparing a report about its conclusions from this meeting.

In order to prepare the US members of the STAC for the September 5-6 meeting, the USBPO organized several tele/video-conference briefings. On August 16, the US representatives involved in working with the ITER Organization to develop an integrated research plan (which is Task 1 of Working Group 1 of the Design Review Activity) briefed the US members of the STAC about the progress in this area. On August 29, a number of scientists presented reports to the US members of the STAC about work being done by US experts to answer key issues related to the other tasks (Tasks 2-12) of Working Group 1. Task 1 had had to be handled a week earlier because this working group held a meeting in Cadarache during the week of August 27. Progress on tasks from Working Groups 2-8 had already been reviewed for the US STAC members on August 14 by Brad Nelson of the ITER Project Office.

The second Integrated Design Review (IDR) Meeting is, in fact, being held this week, September 17-19, in Cadarache. This is the follow-up to the first such meeting, held July 16-19, which was described in the August issue of the USBPO eNews. At both of these meetings, the eight Design Review working groups propose Design Change Requests (DCRs) for modifying the baseline design.

In order to prepare the US representatives who would attend the IDR Meeting, the USBPO organized more briefings. On September 13, several of the US participants at the first STAC Meeting summarized what had transpired at that meeting and what the US input would be to the STAC report. Later the same day, the US participants in WG1 Task 1 gave an update about the ITER integrated plan of research.

The design changes to be recommended from this week’s IDR Meeting—along with estimates for how they would impact the cost, schedule, and scope of ITER—will be reviewed at the second STAC meeting, which is scheduled for November 5-7. The recommendations of the STAC from that second meeting will be provided as input to the ITER Council when it meets on November 29 to officially decide on approval of the 2007 Baseline Design.

These high-level meetings are obviously extremely influential in setting the course for the construction phase of the ITER Project. Equally as important, however, is the massive amount of work being done to address the key science and technology issues for the design of ITER. This work provides the essential underpinning for these meetings. In recent weeks a small army of North American technical experts has been extremely busy, on a very urgent time scale, writing summary reports and white papers on a host of critical subjects—e.g., PFCs, ripple, disruptions, start-up and vertical stability, scenario variations, fueling requirements, resistive wall mode and ELM control, heating and current drive options. (Note that I deliberately used the term “North American” in the preceding sentence, in order to acknowledge as well the important contributions of our Canadian USBPO members.) The enormous efforts of all of these technical experts in providing this critical information in a timely fashion are most highly appreciated. Personally I am aware that a number of people put in long hours last week to have reports ready in time for use at the IDR Meeting this week. I’ve also seen comments from scientists in the ITER Organization and from other ITER Partner countries, indicating how impressed they were with these excellent reports. Thanks to all of you, especially since many of you were simultaneously getting ready for the National Tokamak Workshop, which is being held this week.

Let me conclude with a few other upcoming USBPO activities. On September 25, Brad Nelson and I will share in giving talks about the Design Review activities; these talks are to be presented to the Technical Advisory Committee of the US ITER Project Office. On September 28, Chuck Greenfield, USBPO Deputy Director, will give a presentation to the National Research Council concerning the report that was written last year in response to the Congressional 2005 Energy Policy Act; this input will help the NRC as it prepares a “review of the plan for a plan” for how the US will take advantage of the ITER science and technology research program when it begins operation. More about this in a future column.

Table of Contents

Announcements

The DIII-D Research Opportunities Forum for the 2008 experimental campaign will be held on October 16-18 at General Atomics in San Diego. This will provide an opportunity for the burning plasma community, among others, to have input into the content of the 2008 DIII-D research program. Details will be distributed in coming weeks, including instructions for web submission of your ideas. For more information, contact Chuck Greenfield (greenfield@fusion.gat.com).

The NSTX Research Forum for FY2008 research will be held at PPPL on November 27-29, 2007 (Tuesday-Thursday) and will be organized by Michael Bell (mbell@pppl.gov).

Feature Article

ITER finite β rippled equilibria by D. A. Spong, ORNL

In the outer regions of the ITER plasma, the magnetic field structure will become increasingly three-dimensional due to the nearby presence of discrete toroidal field coils, ferritic inserts, ferritic materials in blanket modules, RWM/ELM control coils, etc. Non-axisymmetric magnetic field components are known to enhance alpha particle transport, damp toroidal flows, cause mode-locking, and suppress bootstrap current. For these reasons, it is important to have accurate predictions of such symmetry deviations. In the past this has predominantly been addressed by superimposing vacuum calculations of symmetry-breaking fields upon axisymmetric plasma equilibria. However, it is expected that interactions with plasma equilibrium currents (diamagnetic, Pfirsh-Schlüter, Ohmic) can modify the strength of the symmetry-breaking components internal to the plasma. Also, field ripple introduces low-level corrugations in magnetic surfaces that further influence the effective ripple seen by the plasma. Although these are all small effects, ripple itself is also a small effect and so the plasma-induced modifications of ripple cannot necessarily be ordered away.

As part of an ITER design activity, the VMEC equilibrium code has been adapted and applied to study these effects. A multi-filamentary coil model was created for ITER that consists of 18 toroidal, 6 poloidal, and 6 center-stack coils, as shown in Fig. 1(a). Free boundary, rippled, up-down asymmetric equilibria were then calculated with the use of ITER coil current distributions as determined by the TSC code [Fig. 1(a) and 1(b)]. Work is currently underway to include the effects of ferritic inserts and the TBM’s. This will be done using the vacuum field solutions from the ANSYS code (including ferritic materials) that have been generated by M. Roccella, F. Lucca, L. T. Calcoli, and G. Ramogida of Frascati. Such vacuum fields will be coupled into the external Green’s function model of VMEC.

Field ripple results from the VMEC equilibria have been compared directly with coil-only (no ferritic materials) ANSYS calculations. Such a comparison is shown in Figure 2, where the magnetic field strength has been decomposed into Fourier components and the n = 18 (primary ripple harmonic) term is plotted vs. R and Z. The red regions indicate where B_n=18(R,Z) exceeds 1%. The VMEC data stops at the outermost closed flux surface, while the ANSYS data goes out to the first wall. While there are some differences in the internal structure, the levels of B_n=18(R,Z) near the plasma boundary are at similar levels.

A primary motivation for the VMEC model is to examine the influence of increasing equilibrium <β> on ripple levels; for example, plasma diamagnetic currents, whose strength scales as 1/B, can potentially amplify ripple levels. In order to avoid changes due to shifts in the plasma position, these studies have been carried out based on a fixed boundary model, with the boundary shape determined by the above free boundary calculation. Figures 3 (a) and (b) again show contours of B_n=18, but plotted against the poloidal angle and normalized toroidal flux, in order to enlarge the edge region. The black isoline indicates where B_n=18 = 1%. As can be seen, the contours near θ = 0 and 2π for <β> =  2.4% dip further into the central region than the <β> =  0 contours, indicating some degree of ripple amplification is present even at this <β>.

Similar studies will be continued as the ferritic inserts and TBM’s are included in the VMEC model. Data from this model will also be prepared for further use in alpha Monte Carlo, flow damping and bootstrap current calculations.

(a) Contours of Bn=18(θ ,s) for <β> = 2.4%

(b) Contours of Bn=18(θ,s) for <β> = 0

Acknowledgements – S. Hirshman, L. Berry, B. Nelson, G. Kramer, and C. Kessel have provided data and helpful assistance with the codes used in the above calculations.

Table of Contents

BPO-Related Meetings

Sep 9-15
Energy Conversion Systems in Tokamak Reactor      
Erice - Italy
           
Sep 10 -13
EUROMAT 2007 -Materials for Fusion Applications   
Nuremberg, Germany        
http://www.euromat2007.fems.org/

Sep 17-20
National Tokamak Planning Workshop 
MIT, Cambridge, MA          
E. Marmar    

Sep 24-28
International Conference on Burning Plasma Diagnostics    
Villa Monastero, Varenna, Italy
http://www.ispp.it/
           
Sep 26-28
11th IAEA Technical Meeting on H-mode and Transport Barrier      
Tsukuba, Japan
http://www-jt60.naka.jaea.go.jp/h-mode-tm-11/
           
Sep 30-Oct 5
8th Int’l Symp. on Fusion Nuclear Technology - ISFNT-8       
Heidelberg, Germany        
http://iwrwww1.fzk.de/isfnt/

Oct 1-3
CDBM, Transport physics and Pedestal ITPA topical group  
Naka Fusion Institute, JAEA
http://www-jt60.naka.jaea.go.jp/itpa-07-naka/index.html

Oct 8-10
10th IAEA Technical Meeting on Energetic Particles in Magnetic Confinement Systems           
Kloster Seeon, Germany
http://www.ipp.mpg.de/ippcms/eng/for/veranstaltungen/konferenzen/iaea_2007/index.html

Oct 10-12
20th International Conference on Numerical Simulation of Plasmas
Austin, Texas
http://workshops.ph.utexas.edu/
           
Nov 12-16
49th APS-DPP Meeting     
Orlando, FL
http://www.aps.org/meetings/unit/dpp/index.cfm

Dec 4-5
Fusion Power Associates Annual Meeting
Fusion Energy: Preparing for the NIF and ITER Era    
DoubleTree, Oak Ridge, TN
http://fusionpower.org/       

Dec 10-14    
13th International Conf. on Fusion Reactor Materials 
Nice, France
http://www-fusion-magnetique.cea.fr/icfrm13/index.html

For more 2007 Fusion Research-related events, visit the USBPO Upcoming Events page online at http://burningplasma.org/events.html.