U.S. Burning Plasma Organization e-News
June 15, 2008 (Issue 21)

CONTENTS

     -- Director's Corner by Jim Van Dam
    -- Reports
         - Summary of the 14th meeting of the ITPA Pedestal and Edge Physics group by Tom Rognlien
         - 11th meeting of the OTPA topical group on MHD and Disruptions by Ted Strait
     --Feature Article
         -Ripple Induced Alpha Particle Loss Calculations Due to Tritium Breeding Modules by G.J. Kramer & R.B. White
    -- Announcements
     -- Upcoming 2008 Burning Plasma-Related Events

Dear Burning Plasma Aficionados:

This newsletter provides a short update on U.S. Burning Plasma Organization activities. 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

USBPO Council Election: As I write this column, the election to fill two open seats on the USBPO Council is underway. Details about the slate of candidates and the voting procedure have been sent by email to USBPO members. The election is web-based, thanks to our being able to make use of the University of Wisconsin web site, which provides this capability. All US members are eligible to vote and are encouraged to do so.

ITPA Structure: The Contact Persons for the seven ITER Partners have successfully negotiated the selection of the new leadership for the ITPA Topical Groups. It is as follows:

New ITPA Topical Groups	New Leader	New Deputy Leader
Diagnostics	Rejean Boivin (US)	Hyeon Park (KO)
Pedestal	Howard Wilson (EU)	Naoyuki Oyama (JA)
Divertor and SOL	Bruce Lipschultz (US)	Emanuelle Tsitrone (EU)
MHD Stability	Abhijit Sen (IN)	Edward Strait (US)
Energetic Particles	Sibylle Guenter (EU)	Koji Shinohara (JA)
Transport and Confinement	Stan Kaye (US)	Shaojie Wang (CN)
Integrated Operation Scenarios	Shunsuke Ide (JA)	Adrianus Sips (EU)

As noted last month, each ITPA topical group will also have a co-deputy leader who is an ITER Organization staff scientist. The new leadership will participate in the annual meeting of the ITPA Coordinating Committee (June 30-July 1, 2008, in Cadarache). The US members of the Coordinating Committee are Erol Oktay, Ron Stambaugh (who is also the ITPA Chair), Ned Sauthoff, and me. Congratulations to the new topical group leaders, and sincere thanks to those who had been serving in this capacity.

STAC-4 Meeting: The 4th meeting of the ITER Council’s Science and Technology Advisory Committee (STAC) was held May 19-22 in Cadarache. During the meeting the STAC also met jointly with the Management Advisory Committee for a half-day session, in order to discuss issues of mutual interest, such as the Overall Project Cost and the Overall Project Schedule. As with the STAC-3 meeting in April, the purpose of STAC-4 was to review how the ITER Organization and the Domestic Agencies of the seven ITER partners have integrated the results from last year’s Design Review Activity and also the conclusions from the recent STAC Issue working groups into the new ITER baseline design. Specifically, STAC-4 assessed the design optimization by the ITER Organization, reviewed the integration of these solutions into the ITER scope, and evaluated their cost and schedule impacts. Topics of considerable discussion were the poloidal field system and in-vessel coils (for sufficient volt-second capability, vertical stability, and ELM control), vacuum vessel and blanket loading conditions, divertor armor strategy (the choice of materials for plasma-facing components), the mix of heating and current drive systems, test blanket module implementation, coil cold testing, remote handling, and hot cell. A particular highlight of the STAC-4 meeting was the presentation of the first version of a detailed ITER Research Plan, describing the various operational phases for scientific exploitation of ITER. The STAC meeting concluded with a tour of the ITER construction site. The site clearing process and ground leveling is well in progress.

The recommendations from the STAC-3 and STAC-4 meetings, along with recommendations from the Management Advisory Committee, are to be submitted to the ITER Council in June, which is to act on approving the new ITER Design Basis. The new ITER baseline design will then serve as a reference for hardware Procurement Arrangements, for future changes in the design, cost, and schedule, and for project management and configuration control. Further physics analysis and engineering design work is expected to continue on several of the STAC issues, in order to provide underpinning for a more complete project cost and schedule, to be presented to the ITER Council at its next meeting, in November.

ITER Update: Here are a few items of interest concerning recent ITER developments, as reported by Director-General Ikeda at the STAC-4 Meeting:

A delegation from Kazakhstan visited ITER in April. Kazakhstan is interested in becoming a full member of ITER.
ITER has submitted a Construction Permit (“permis de construire”). A two-month period for public consultation began in April. Site preparation is underway; the main platform levelling work has commenced on the ITER site, and preparations for construction of the poloidal field coil winding building are under way. ITER has also submitted a Preliminary Safety Report to the French nuclear regulatory authorities.
In order to provide guest accommodation on site, a private project is underway to build a guesthouse with 33 rooms, each having an individual kitchen, in the area of St. Paul lez Durance (2 km from the ITER site).
An international school opened in September 2007. It is located in Manosques, a town near the ITER site where many ITER families live. As of April 2008, there are 121 children attending the school, 55% of whom are from ITER-connected families. The staff consists of 32 teachers, who are teaching courses in six languages so far (French, English, Japanese, German, Chinese, Italian, and Spanish).
As of April 2008, ITER has 197 professionals on staff, which is about one-third full strength. In addition, it has 68 support staff. Recruitment for 61 new positions is currently underway, and another 20 new positions will be advertised subsequently.

ITER Council: The second meeting of the now official (i.e., no-longer-interim) ITER Council will be held June 17-18, 2008, in Aomori, Japan. At the IC-2 Meeting, the ITER Organization plans to present the updates of the Reference Design, the Integrated Project Schedule, and the Project Resource Estimates, in order to seek approval of the new ITER Baseline.

IUPAP presentation: The International Union of Pure and Applied Physics was established in 1922 in order to foster international collaborations in physics. At the recent annual meeting of the US Liaison Committee for the IUPAP, I was invited to give a status report about the ITER project and US participation therein. The Q&A session following the talk was quite stimulating, with much discussion about the vagaries of the US government’s system for funding large science initiatives. The talk is posted on the USBPO web site.

Reports

Summary of the 14th meeting of the ITPA Pedestal and Edge Physics group (T. Rognlien)

The 14th ITPA Pedestal and Edge Physics topical group meeting was held at General Atomics on April 30 – May 2. Researchers attended the meeting from the EU, Japan, and the U.S. Most major tokamak facilities were represented (Alcator C-Mod, ASDEX-U, DIII-D, JET, JT-60U, MAST, NSTX, Textor, and ITER), as well as edge theory and simulation experts. Two closely related topics dominated the meeting: (1) the character and control of Edge Localized Modes (ELMs), and (2) the temporal and spatial structure of the pedestal between successive ELMs. Controlling ELM size bears directly on possible excessive erosion of divertors/walls and possibly energy confinement, whereas pedestal structure (with ELM stability) is predicted to strongly impact fusion gain, especially via the ion temperature at the top of the between-ELM pedestal.

The importance of the ELM/pedestal-structure issue for fusion is underscored by the recent request by the ITER International Organization (IO) that Pedestal and Edge topical group develop an international research plan to understand and control ELMs to allow successful ITER operation. This specific IO request marks the first made to an ITPA group since the recent modification to the ITPA charter that includes explicit support of ITER as part of the ITPA mission. A draft plan was submitted to the IO following the meeting (contact Tony Leonard [Leonard@fusion.gat.com] for details). Executing elements of this plan in the U.S. will involve active BPO participation.

During the meeting, there were 32 technical presentations followed by thorough discussions and summaries on ELM/pedestal issues. Researchers presented experimental results and analysis for ELM control by Resonant Magnetic Perturbations (RMP), fast-period pellet injection, and understanding naturally occurring small-ELM regimes of operation. Following the DIII-D lead, some variation of the RMP has been, or is about to be, tried on numerous other machines with emerging results. Pellet injection can trigger small ELMs if frequent pellets can be obtained, thereby avoiding large ELMs; sufficient frequency and density control for ITER are active questions. Natural small-ELM regimes include further investigation of the ELM “zoology,” where type II, type III, type V, and “grassy” ELMs are examples. Other possibilities of ELM control include toroidal B-field ripple, plasma rotation, and edge currents. Any successful approach must show that it is able to preserve other aspects of the ITER operational scenario (e.g., density). Theory and modeling included a range of simple models of ELM ejection into the scrape-off layer, advances in fluid (3r) simulations of microturbulence and ELMs, and kinetic (2r, 2v) simulations of edge transport. The next ITPA Pedestal and Edge meeting will be held in a yet-to-be-determined location this fall.

11th meeting of the ITPA topical group on MHD and Disruptions (T. Strait)

The ITPA topical group on MHD and Disruptions held its 11th meeting in Naka, the week of February 25-29. This meeting was held in conjunction with an IEA Large Tokamak workshop on Control of ELMs and RWMs (W68) and a US-Japan workshop on MHD Behavior and Control of Burning Plasma. Together the three meetings filled the week, and covered a wide range of MHD topics including basic MHD physics and experiments in RFPs and helical systems.

Much of the discussion was focused on urgent issues for ITER, with greatest emphasis on edge-localized mode (ELMs), disruptions, and axisymmetric control. ELM control work has focused on theoretical and experimental understanding of ELM mitigation by resonant magnetic perturbations. Modeling of various proposed RMP coil designs for ITER was presented; there was strong (but informal) support for the current concept of 3 rows of coils inside the vacuum vessel.

Disruption modeling suggests that the worst-case vertical forces may approach the limits of the vacuum vessel supports, motivating the need for improved characterization of halo currents in the ITPA disruption database. The large quantity of gas thought necessary to suppress runaway electron avalanches in ITER disruptions may present a challenge to the pumping systems. Experiments to confirm predictions of runaway generation and suppression are in progress.

Axisymmetric control modeling, benchmarked to current experiments, indicates that the original ITER design was not adequate. Several options to remedy this situation are being explored, including power supply upgrades and addition of fast internal control coils in conjunction with the ELM control coils.

Other key MHD topics: Efforts on control of resistive wall modes (RWMs) have focused on possible stabilization by kinetic effects at very low rotation, and realistic 3-D modeling of passive and active stabilization. Theoretical efforts have begun to address the observed influence of plasma rotation or rotational shear on Neoclassical tearing mode (NTM) stability; requirements for NTM stabilization in ITER by modulated electron cyclotron current drive were also discussed. Recent error field experiments and modeling have shown the importance of plasma response and non-resonant braking of rotation. Modeling of observed fast ion loss related to core localized Alfven eigenmodes is in progress.

All of the topics mentioned above are designated as high priority research areas for the topical group, and are the subject of joint experiments that were discussed at the meeting.

The coming reorganization of the ITPA under the ITER organization was discussed briefly, as was the formation of EFDA topical groups similar to the USBPO. The next meeting of this group will be in Lausanne, Oct. 20-22 (immediately following the IAEA Fusion Energy Conference).

Feature Article

Ripple Induced Alpha Particle Loss Calculations Due to Tritium Breeding Modules
By G.J. Kramer and R.B. White

A major technology objective of ITER is to study tritium breeding in Test Blanket Modules (TBMs). Three of these modules will be inserted in the machine along the midplane at toroidal angles of -40, 0 and 40 deg, according to current plans. These TBMs increase the toroidal field ripple significantly at those locations as can be seen in figure 1. The question addressed in this study is whether the low-n field ripple induced by the TBMs may adversely affect alpha particle losses to the machine first wall.

Figure 1. Radial component of the ITER toroidal field ripple at the plasma mid-plane without (left) and with (right) the three test blanket modules. Note the four-fold increase of the color scale for the TBM case on the right.

Two standard ITER configurations were studied: an inductive 15MA H-mode plasma producing 400MW of fusion power with Q=10 for 400s (scenario 2), and a 9MA steady state weakly reversed magnetic shear plasma with a minimum magnetic safety factor of 2.5 producing 300~MW of fusion power with Q=5 for 3000s (scenario 4).

A Monte Carlo method was used to distribute an ensemble of 3.5MeV alpha particles according to the initial alpha particle birth profile given for the two configurations. Two orbit following codes, the ORBIT (guide center) and the SPIRAL (full orbit) code, were used to follow the particles. The SPIRAL code uses the Lorentz force equation to follow the alpha particles in the 3-D toroidal magnetic field in order to determine the localization of the loss and is benchmarked against the ORBIT code for the total loss rate.

For the ripple field without the TBMs (i.e. only including the ripple induced by the 18 toroidal field coils), the ORBIT and SPIRAL codes analysis reveals 0.6% of the fusion alpha power is lost in both ITER scenarios. In Figure 2a, the distribution of the alpha particle power loss on the last closed flux surface for scenario 2 is shown, based on full orbit calculations, and the peak heat load on the last closed flux surface is quite moderate (less than 0.2MW/m2). The TBMs generate larger ripple fields that penetrate deeper into the plasma than the toroidal field coil-induced ripple because of the low toroidal mode number of the TBM ripple. The full orbit calculations with the TBMs reveal that the losses occur at three highly localized spots at the center of the TBMs (Fig. 2b).

Figure 2. Heat loads, for scenario 2, from lost fusion alpha particles at the last closed flux surface for (a) toroidal field ripple only and (b) toroidal field ripple and TBMs, shown as a function of the toroidal and poloidal angle calculated for the 15MA H-mode plasma with Q=10.

In scenario 2 (the inductive high fusion power H-mode regime) the TBMs induce a 1.5% fusion alpha power loss with heat loads around 1 MW/m2. It must be emphasized that these losses represent lower bounds because MHD activity (such as sawteeth, NTMs, Alfvén eigenmodes, etc.) in burning plasmas can possibly broaden the alpha particle profile, giving rise to additional losses.

The TBM ripple fields used in this study were not optimized to reduce the heat loads. The analysis of the losses is preliminary and considerable additional work is needed to quantify the losses in a range of operating conditions. However, the present results indicate that the final TBM design may need to include compensating coils to decrease the magnetic field ripple and hence the heat loads on the TBMs.

Announcements

Submit Burning Plamsa-related announcements for next month’s eNews to Raffi Nazikian at rnazikian@pppl.gov.

Upcoming 2008 Burning Plasma-Related Events

Jun TBD
ITPA CC Topical Group Mtg
Location TBD

Jun 8-12
ANS Annual Meeting
Anaheim, CA

Jun 9-13
35th EPS Conference on Plasma Physics
Hersonissos, Crete, Greece

Jun 15-19
35th IEEE Int'l Conf on Plasma Science (ICOPS2008)
Karlsruhe, Germany

Jun 16-19
23rd Symposium on Plasma Physics and Technology
Prague, Czech Republic

Jun 24-27
Innovative Confinement Concepts
Reno, NV

Jul 6-11
17th Int'l Conf on High-Power Particle Beams (BEAMS'08)
Xi’an, China

Jul 13-20
37th Scientific Assembly of the Committee on Space Research and Associated Events (COSPAR 2008)
Montreal, Canada

Jul 15-19
19th Europhysics Conf on the Atomic and Molecular Physics of Ionized Gases (ESCAMPIG-2008)
Granada, Spain

Jul 27-Aug 2
7th Int’l Wkshp on Strong Microwaves: Sources and Applications
Nizhny Novgorod, Russia

Aug 25-29
24th Summer School & Int’l Symp on the Physics of Ionized Gases
Novi Sad, Serbia

Sep 1-4
13th EU-US TTF Wksp
Copenhagen, Denmark

Sep 8-12
Int'l Congress on Plasma Physics
Fukuoka, Japan

Sep 15-18
ITPA SolDiv Topical Group Mtg
Japan

Sep 15-19
25th Symp on Fusion Technology (SOFT)
Rostock, Germany

Sep 22-27
Int'l Conf & School on Plasma Physics & Controlled Fusion and 3rdAlushta Int'l Wksp on the Role of Electric Fields in Plasma Confinement in Stellarators and Tokamaks
Crimea, Ukraine

Sep 25-27
18th IAEA Technical Mtg on Research using Small Fusion Devices
Crimea, Ukraine

Sep 28-Oct 2
18th ANS Topical Mtg on the Technology of Fusion Energy
San Francisco, CA

Sep 29-Oct 2
coNuSS 2008
Belgrade, Serbia

Oct 12-18
22nd IAEA Fusion Energy Conf - 50th Anniversary of Controlled Nuclear Fusion Research
Geneva, Switzerland

Oct 20-25
11th Int'l Conf on Electrostatic Precipitation (ICESP-XI)
Hangzhou, China

Oct 20-22
ITPA CBDM, Transport, and Pedestal & Edge Physics Mtgs
Milan, Italy

Oct 20-22
ITPA MHD Topical Group Mtg
Lausanne, Switzerland

Oct 20-23
ITPA SSO Topical Group Mtg
Location TBD

Nov TBD
ITPA/IEA Joint Experiment Coordination Mtg
Location TBD

Nov 9-13
ANS Winter Meeting
Reno, NV

Nov 17-21
50th APS-DPP
Dallas, TX

Nov 23-25
MHD Control Workshop
Austin, TX

Nov/Dec TBD
ITPA Diagnostics Topical Group Mtg
IPR, India

Dec 9-12
18Th International Toki Conference
Toki-City, Japan

Please submit your 2008 events to Emily Hooks at ehooks@mail.utexas.edu.

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

U.S. Burning Plasma Organization e-News June 15, 2008 (Issue 21)

CONTENTS