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U.S. Burning Plasma Organization e-News
January 20, 2010 (Issue 40)
CONTENTS
Director's Corner Reports Meeting of the ITPA Pedestal Topical Group
Summary of the US-Japan Workshop on "Interaction between plasma and high Z material towards steady state operation"
Upcoming Burning Plasma-related Events 2010 Events
2011 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 (Tom Rognlien trognlien at llnl.gov) or assistant editor (Rita Wilkinson ritaw at mail.utexas.edu).
Thank you for your interest in Burning Plasma research in the U.S.!
Director's Corner by J. W. Van Dam
Planning for ITPA Joint Experiments
For the past seven years, the International Tokamak Physics Activity (ITPA) has served the
international fusion community by coordinating joint experiments that are carried out on two or
more experimental facilities. The most recent such meeting to coordinate this schedule of
international joint experiments—officially called the Eighth IEA Large Tokamak Workshop (W71)
on “Implementation of the ITPA Coordinated Research Recommendations”—was recently held
December 15 and 16, 2009, in Daejeon, Korea, hosted by the National Fusion Research
Institute. A total of 25 participants attended from the various ITER Member countries.
Participants from the US were Stan Kaye, Bruce Lipschultz (by videoconference), and Ted
Strait, representing the Transport, DivSOL, and MHD Stability topical groups, respectively;
facility representatives Rich Hawryluk (NSTX), Earl Marmar (Alcator C-Mod), and Tony Taylor
(DIII-D); and Ron Stambaugh (ITPA Chair), Erol Oktay, and yours truly from the ITPA
Coordinating Committee.
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Participants at the 8th IEA/ITPA Joint Experiments Workshop in Daejeon, Korea |
Presentations were given from each of the seven ITPA topical groups describing the progress
on last year’s joint experiments, specifying which ones to close out or continue, and proposing
new joint experiments to be added. Then, facility representatives presented brief status reports
covering 12 experimental facilities around the world. Finally, there was a general discussion
(characterized by Stambaugh as an “auction”) of the proposed roster of joint experiments for
2010, with each facility indicating its interest in the various proposed experiments. The result
was a giant spreadsheet. Typically, the ITPA has 60-70 joint experiments on the books each year. This year, approximately 15% of the experiments were marked as being completed. Only
nine new joint experiments were proposed, compared to 23 last year—likely due to the fact that
three of the world’s large facilities (JET, DIII-D, and MAST) will not operate for much of this year
to install upgrades. The ITPA also scheduled half a dozen so-called Joint Activities, in which
theory/modeling/simulation is strongly involved. This part of the meeting concluded with a
discussion of data base access policies.
The agenda for the Joint Experiments Workshop as well as the topical group presentations, the facility presentations, and the joint experiments master list are all posted on the workshop web site at http://ieaw71.nfri.re.kr/html/agenda.htm.
Immediately after the conclusion of the workshop, the meeting segued into an extraordinary
executive committee meeting for the International Energy Agency (IEA) Large Tokamak
Agreement. It was announced that Korea has joined the Large Tokamak Agreement. Also, the
plan to combine the Large Tokamak Agreement and the Poloidal Divertor Agreement into a
single International Agreement for Tokamak Activities is moving forward.
The next Joint Experiments Workshop will be hosted by Japan in mid-December 2010. In the
spirit of “joint experiments,” the participants agreed to consider holding this meeting by
videoconference, with all US participants gathering in one location and likewise for the
European participants and the Asian participants.
ITER Workshop on Plasma Control
The conceptual design activity for the ITER Plasma Control System (PCS) was launched with a
3.5-day workshop held December 8-11, 2009, at Cadarache, France. All seven ITER Members
sent participants to the workshop. The six participants sent by the US Domestic Agency were
David Gates, Bob Granetz, David Humphreys, Egemen Kolemen, Lynda LoDestro, and Mike Walker. Of the 57 total participants, almost half (26 to be precise) were from the ITER
Organization, which indicates the high degree of interest in this activity.
The agenda for the workshop was as follows: The first half-day was devoted to a description of
the system requirements for the ITER Plasma Control System and the time schedule for its
development. The next two half-day sessions reviewed the status of plasma control in existing
experimental devices, the operating experience that has been gained by applying various
approaches to plasma control, their applicability to ITER, and issues that might arise in
implementation for ITER. The remaining four half-day sessions were working group discussions
that focused on specific issues such as framework and architecture; types of control (magnetic,
particle, etc.); event handling; sharing of different actuators; simulation needs; and infrastructure
(code and testing issues).
Within the ITER Organization, the Department for Fusion Science and Technology has the
responsibility to define the requirements for the ITER Plasma Control System. The Department
for CODAC & IT, Heating & CD, Diagnostics will have responsibility for its construction. The
ITER Integrated Modeling Expert Group (IMEG) will help with simulations needed for the
Plasma Control System (see December eNews for a description of IMEG). Tasks to support the
conceptual design of the ITER Plasma Control System will begin this year.
Transport Task Force Meeting
The next meeting of the U.S. Transport Task Force Workshop will be held April 13-16, 2010, in
Annapolis, MD. Information is available at the workshop web site (http://ttf2010.ucsd.edu). Many
physics topics of high relevance to burning plasmas will be discussed at this meeting. We
encourage attendance.
Fusion in the news recently
The December 2009 issue of Physics World was dedicated to the subject of “Fusion Challenges
and Solutions.” The five articles cover JET, laser-driven fusion power, postgraduate training
programs, the new European fusion supercomputer, and ITER and the future of fusion.
The December 4, 2009, issue of EIR Science and Technology features an interview with Gyung-Su Lee, president of the National Fusion Research Institute of Korea, about his vision for the
future. The article is entitled “Fusion in Korea: Energy for the Next Generation.”
Changes in European leadership
Jerome Pamela, Leader of the European Fusion Development Agreement (EFDA), became the new
director of Agence ITER France (CEA) as of January 1, 2010
(http://www.iter.org/newsline/Pages/112/1568.aspx). The December 2009 issue of Fusion
News, which is published by EFDA, contains an interesting interview with him
(http://www.efda.org/news_and_events/downloads/efda_newsletter/nl_2009_12.pdf).
Francesco Romanelli, EFDA Associate Leader for JET, has been asked to serve as EFDA
Leader Ad Interim (http://www.jet.efda.org/jet/news/2009/12/efda-garching/).
Frank Briscoe, Operations Director at UKAEA Culham Fusion Science Center, was appointed
Director Ad Interim of Fusion for Energy (F4E), which is the European Domestic Agency for
ITER, on January 11, 2010. The outgoing director, Didier Gambier, will move to a position in the
European Commission in Brussels. For further information, see the news release
(http://fusionforenergy.europa.eu/documents/press_release/f4e_press_release_11_01_10.pdf).
ITER Booth at AAAS Meeting
The US ITER Project Office will have a display booth at the AAAS Meeting (18-22 February,
San Diego, http://www.aaas.org/meetings/2010/). If anyone plans to be at the meeting and could spare a few hours to help staff the ITER display booth, please contact Bonnie Hebert at
the USIPO (865-574-8381, hebertb@ornl.gov). She will set up the schedule and provide any
instructions.
ITER Workshop on TBM Impact
Breaking news: ITER just announced that it plans to hold a 2.5-day "Workshop on TBM Impact
on ITER Plasma Physics and Potential Countermeasures," April 13-15, in Cadarache. Scientists
who wish to attend this workshop and possibly make a presentation, are asked to contact Joe
Snipes (Joseph.Snipes@iter.org) and Luciano Giancarli (Luciano.Giancarli@iter.org) by
January 22. Anyone interested in participating should indicate how many days you would plan to
attend the workshop, submit a title for your presentation, and estimate how much time you
would like for the presentation.
Happy New Year
As we enter the new decade, we look forward to further exciting developments in burning
plasma science.
Incidentally, this month’s issue is the 40th issue of eNews. I’d like to take the opportunity to
thank our new editor, Tom Rognlien, and our USBPO administrator, Rita Wilkinson, for their dedicated and inspired work in publishing this electronic newsletter each month.
Reports
Meeting of the ITPA Pedestal Topical Group
Compiled by Phil Snyder (General Atomics)
The 17th meeting of the ITPA Pedestal Group was hosted by PPPL on October 5-7, 2009.
There were approximately 35 scientists attending from the Pedestal Group, and a further 30 in
the ITPA Transport and Confinement group, with whom we shared a joint session on the low-to-high
(L-H) confinement transition. The meeting was organized into sessions focused on each of
five urgent tasks: pedestal structure and H-mode physics, impact of magnetic perturbations on
ELMs, L-H transition, impact of magnetic ripple on the pedestal, and pellet pacing. The meeting
concluded with discussion of joint experiments.
Alberto Loarte opened the meeting with an overview of the urgent issues for ITER. He
discussed a number of key H-mode-related issues pertinent to operation with a power
amplification of Q = 10, emphasizing issues that have not received substantial focus in the past.
These issues included: both access to and exit from the H-mode, access to an energy
confinement parameter of H98 ~ 1, pedestal parameters and gradients in edge plasmas “thick” to
neutral penetration, toroidal magnetic field (TF) ripple effects on the pedestal and required ripple “correction,” ELM control compatible with Q = 10 scenario requirements, and H-mode in rampup/down phases. Furthermore, early ITER operation with H/He plasmas requires understanding
the different behavior (compared to D or DT) for access to H-mode and H98 ~ 1, pedestal
plasma characteristics, and ELMs and ELM control. Progress on each of the five urgent task
areas listed in the previous paragraph is given below.
Pedestal Structure
Several talks on transport, stability, and fuelling of the pedestal were presented, including
discussions of recent observations, theoretical progress, and simulations of existing
experiments and ITER. A primary ITER urgent issue in this area is to explore the impact of
heating source on pedestal structure and ELMs. Significant progress was reported on JET, DIIID,
and AUG experiments in which neutral beam power was exchanged for RF or electron beta, both pedestal height and width were approximately constant, independent of power
source. Additional results were discussed on dependence of pedestal width on the ion
gyroradius normalized to the minor radius (rho-star) in JET and DIII-D, which continue to find
that pedestal width is independent of (or perhaps even negatively correlated with) rho-star. Due
to recent progress in extending Quiescent H-Mode (QH) operation to a broader parameter
regime, a subgroup on QH mode has been created. QH mode results on DIII-D were discussed,
including extensions of QH mode to co-rotating plasmas and plasmas with near zero (slightly
negative) input torque, as well as relatively high density, high pedestal, high performance
plasmas.
Impact of Magnetic Perturbations on ELMs
Observations on DIII-D, NSTX, MAST, JET, and LHD were reported, as well as modeling efforts
aimed at quantifying stochastic transport. On DIII-D, the parameter range of Resonant Magnetic
Perturbation (RMP) ELM-suppression has been significantly extended, including highperformance
discharges and studies of suppression dependence on plasma beta, collisionality,
and safety factor (q95). On MAST, initial experiments with internal coils have found density
pump-out, but not ELM suppression. A coordinated effort between the MAST and DIII-D teams
is planned to better quantify necessary criteria for full ELM suppression. NSTX and JET find
mitigation, but not full suppression, of ELMs using external control coils. A planned set of
internal coils for AUG is expected to be available in late 2010, with an extension to 8 coils
available in spring 2011. LHD finds increased particle transport with imposed perturbations
having 1/1 poloidal/toroidal mode numbers. A new subgroup has been formed to explore ELM
pacing using imposed time varying magnetic perturbations. NSTX reported ELM pacing results
using magnetic perturbations and vertical jogs of the magnetic equilibrium, and both NSTX and
DIII-D plan additional experiments to further study magnetic ELM pacing.
L-H Transition
A productive session on L-H transition observations and physics was held in conjunction with
the Confinement and Transport Topical Group. The dependence of the L-H transition power on
a number of parameters was discussed. The dependence on ion species is of special interest
for the initial hydrogen and/or helium operational phase of ITER. While results across machines
are reasonably consistent for the ratio of hydrogen to deuterium threshold power (~2:1), there is
significant variation in the He:D ratio, with JET, MAST, DIII-D, and C-Mod finding a power ratio
of 1.2-1.8, while AUG and NSTX find a ratio ~1. Observed confinement time in H or He is
generally found to be ~20-30% lower than in D for reasons that are not well understood. The
variation in L-H power with several “hidden variables” including magnetic geometry, wall
conditions, rotation, and recycling was also discussed, noting that the strong variation in PLH
with rotation found on DIII-D is not consistently found on all machines (AUG and JET see little
variation in PLH with heating source). A two-stage plan for the L-H transition database was
presented by J. Hughes, starting with a scalar database and progressing to profile data. The
pedestal group plans to focus its efforts on understanding the L-H transition in terms of local
parameters near the separatrix and continuing theory and computational efforts.
Effect of Ripple
Results and plans for studies of the impact of magnetic ripple on the pedestal were reported for
JT-60U, JET, and DIII-D. On JT-60U it has been found that the pedestal height increases ~10-20% when ripple was reduced using ferritic inserts in a high ripple configuration. However, in the
JET/JT-60U similarity configuration, no impact of ripple on the pedestal was found. On JET, a
significant impact of ripple was found at high plasma current (2.6MA), but not at 1.0 or 1.7MA. In
a dedicated JT-60U/JET comparison experiment, no impact was found on pedestal height for
ripple values from 0.1-1%, but rotation was reduced at higher ripple. Plans for upcomingexperiments (now completed in December) using a mock-up Test Blanket Module (TBM) on
DIII-D were described.
Pellet ELM Pace-Making
A progress report on ELM pace-making was presented. Technical difficulties with the JET pellet
injector have allowed only limited progress in recent studies of pace-making. The DIII-D pellet
dropper has not been successfully used in pace-making, and a modification of the existing pellet
fueling system is being considered for ELM pacing. On AUG, the possibility of using solid state
pellets (e.g., C, Be) has been discussed and an injector identified; however, no further steps
have yet been taken due to a lack of manpower.
Status reports were presented for 14 joint experiments in the pedestal topical area. A great deal
of progress was presented here, and at the preceding H-Mode Workshop in Princeton, and
several journal articles are being submitted or are already published. Four topics were closed,
and three new joint experiments planned, all dealing with aspects of the L-H transition (critical
parameters, profile evolution, and X-point height effects).
The next ITPA Pedestal Topical Group is planned for April 21-23, 2010, to be hosted by JAEA
at the Naka Fusion Institute in Naka, Japan.
Further details about the meeting are available in the full report at
http://itpa.ipp.mpg.de/pedestal_edge/PEP17-summary.pdf
Summary of the US-Japan Workshop on “Interaction between plasma and high Z
material towards steady state operation”
Compiled by Mizuki Sakamoto (Kyushu University, Japan) and Bruce Lipschultz (MIT)
The US-Japan Workshop on “Interaction between plasma and high Z material towards steady
state operation” was held November 9-10, 2009, at the Plasma Science and Fusion Center of
MIT. Sixteen scientists participated in the workshop (10 from the US and 6 from Japan). The
purpose of this workshop was to discuss Plasma Surface Interaction (PSI) phenomena of high Z
materials from both microscopic and macroscopic viewpoints (i.e., multiscale) directed towards
understanding steady state operation, and to exchange information on these phenomena. The
main topics were as follows: (1) hydrogen recycling/retention observed in fusion devices, (2)
impact of radiation damage and He bubble on hydrogen retention, (3) erosion and surface
modification including nano-structure formation, arcing, and dust, and (4) material modeling
including H trapping, defect and bubble formation, and others. The details follow.
Fuel retention results from Alcator C-Mod indicate that 1-2% of the ion flux/fluence on the
divertor plates is being retained during normal, non-disruptive discharges. This value is ~5-10x
higher than what the equivalent laboratory data would predict. The difference between lab and
C-Mod data may be due to any of the following: direct creation of traps in the Mo and W by
impurity ions (e.g., B), reduction of the surface recombination rate by impurities, or the high
plasma fluxes on C-Mod. Analysis of real-time particle balance in Alcator C-Mod showed that,
during stationary plasma density conditions, the wall materials had ~zero retention rate globally, i.e., fuel was neither released nor retained. This balance was found in cases where the divertor
plasma was strongly pumped. The result is contrary to the expectations from shot-averaged
retention, and it is unclear if this is an effect of the refractory metal or due to some plasma
physics effect. In TRIAM-1M at Kyushu University, indications are that co-deposition of
hydrogen with eroded Mo produces substantial wall pumping, and the level of hydrogen
retention depends on the grain size of the deposits. Oxygen strongly affects the structure of the
deposits. Comparing particle balance in cases of cold walls and hot walls in TRIAM-1M indicates that wall temperature is a key factor for steady state particle control. Microscopic
modification and particle retention in tungsten exposed to LHD divertor plasmas were also
presented. Analysis of a W divertor tile from LHD showed that many small hydrogen cavities
existed in the tungsten matrix. Because the cavities likely arise from radiation damage, such
radiation is expected lead to a general enhancement of the hydrogen retention in W.
Effects of material damage on retention were shown from laboratory experiments. Tungsten (W)
samples with displacement damage produced by 12 MeV silicon ion irradiation were exposed to
lab deuterium plasmas in PISCES-A and to divertor (D) plasmas in DIII-D. Nuclear reaction
analysis showed that the quantity of trapped D is small due to slow permeation at 200ºC and
below, and that trapping is also small due to weaker binding of D to traps and defect annealing
above 400ºC. The results indicate that the tritium inventory from trapping at neutron-damage
sites in tungsten should be small in ITER. In another experiment, it was shown that the D/W
ratio increased strongly until 0.2~0.3 dpa, and then saturated or increased more slowly with
increasing dpa. Results of tritium plasma exposure were shown from TPE, and bulk tritium
diffusion in W and Mo was discussed. In addition, characterization of H adsorption on W(100)
was reported.
Results of the formation mechanism and properties of a fuzz layer on tungsten due to helium
plasma exposure were presented from PISCES and NAGDIS devices. The response of
tungsten surfaces to bombardment of pure helium and mixed deuterium/helium plasma was
reported from PISCES. The response of the surface varies with the surface temperature. At low
surface temperature (a few 100°C), small nano-bubbles are formed from the helium in the near
surface region. These nano-bubbles appear to inhibit the diffusion of deuterium deep into the
tungsten bulk. At higher surface temperature (800°C–1500°C), surface tungsten nanostructures
appear. The surface fuzz appears to have a reduced sputtering yield, consistent with
an increased probability of the sputtered material redepositing in the highly textured surface
structure. In NAGDIS, it was shown that the fuzz layer formation caused a decrease in optical
reflectivity by changing the surface morphology. For ruby laser irradiation of the W fuzz, the
ablation threshold of W significantly decreased by the synergetic effect of laser and helium
irradiation, leading to W impurity emission and W dust formation. Results of W fuzz exposure to
the TEXTOR edge plasma indicates that a W fuzz layer changes the surface condition so as to
increase carbon deposition. Also, in situ and real time measurement of surface modification of
W due to low energy helium plasma irradiation in the APSEDAS device at Kyushu University
was reported.
Turning to modeling, how ambient hydrogen influences vacancy formation in tungsten crystals
was discussed. Improved understanding of experimental results may be obtained by taking into
account surface-energy corrections for the density-functional calculations in the generalized
gradient approximation. Based on present calculations, it was shown that the di-vacancy states
possess almost zero or negative binding energies. This means that the di-vacancy easily
disintegrates into mono-vacancies. However, formation energies found for a complex of the divacancy
and a hydrogen atom (V2H) were smaller than those for the di-vacancy alone. Thus, in
the presence of hydrogen, the V2H complex would be more stable. It was suggested that
oxygen impurities have a similar effect on the di-vacancy nucleation. Results were also shown
for kinetic Monte Carlo (KMC) simulations of helium bubble evolution in tungsten, which covered
helium bubble diffusion, coalescence, surface pore formation, and helium implantation.
Results of fuel retention in fusion devices are complicated due to the complex circumstances of
PSI processes, and they are often different from the predictions of the equivalent laboratory
data. It was pointed out that cooperation among fusion experiments, laboratory experiments,
and modeling/simulation is important to get a better understanding of high Z material (e.g., tungsten) for use in fusion. Participants agreed to hold another US-Japan workshop to make
additional progress in this key area of steady state plasma operation with high Z wall materials.
Announcements
Submit BPO-related announcements for next month’s eNews to Tom Rognlien at trognlien at llnl.gov.
Upcoming Burning Plasma Events
| 2010 Events |
| January 18-21 Workshop on Opportunities in Plasma Astrophysics (WOPA) Princeton, New Jersey USA |
| February 16-19 Innovative Confinement Concepts Workshop (ICC 2010) (abstracts due Dec. 4) Princeton, New Jersey USA |
| Week of 22 March ITPA Transport & Confinement Topical Group Meeting Oxfordshire, UK |
| April 12-15 16th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating Sanya, China |
April 13-15 ITER "Workshop on TBM Impact on ITER Plasma Physics and Potential Countermeasures" Contributors contact: Joseph.Snipes@iter.org and Luciano.Giancarli@iter.org by Jan. 22 Cadarache, France |
| April 13-16 U.S. Transport Task Force Workshop Annapolis, Maryland USA |
| April 13-16 International Conference on Plasma Diagnostics Pont-à-Mousson, France |
| April 19-21 Sherwood Fusion Theory Conference (abstracts due Feb. 16) Seattle, Washington USA |
April 20-23 Integrated Operational Scenarios ITPA Meeting Princeton, New Jersey USA |
| April 21-23 ITPA Pedestal Topical Group Meeting Naka, Japan |
| May 16-20 18th ITPA Diagnostics & HTPD Topical Group Meetings Wildwood, New Jersey USA |
| May 19-21 STAC-8 Cadarache, France |
| May 24-28 19th International Plasma Surface Interactions Conference (abstracts due Nov. 20, 2009) San Diego, California, USA |
| May 31-June 4 4th ITER International Summer School (abstracts due April 30) Austin, Texas USA |
| June 21-25 37th European Physical Society Conference on Plasma Physics Dublin, Ireland |
| June 21-15 37th IEEE International Conference on Plasma Science (ICPOS 2010) (abstract submission extended to Jan. 23) Norfolk, VA USA |
| Aug 30-Sept 3 Theory of Fusion Plasmas Joint Varenna-Lausanne International Workshop (abstracts due June 18) Varenna, Italy |
| Sept 27-Oct 1 26th Symposium on Fusion Technology (SOFT2010) Porto, Portugal |
| Oct 11-16NOTE DATE CORRECTION 23rd IAEA Fusion Energy Conference (U.S. synopsis due Feb. 8) Daejeon, Korea |
| Oct 24-29 9th International Conference on Tritium Science and Technology Nara, Japan |
| Nov 7-11 19th Topical Meeting on the Technology of Fusion Energy (TOFE) (embedded with 2010 ANS Winter Meeting) Las Vegas, NV |
| Fall ITPA Transport and Confinement Topical Group Meeting (following IAEA) South Korea |
| Fall ITPA IOC Topical Group Meeting (following IAEA) South Korea |
| Fall ITPA Diagnostics Topical Group Meeting (following IAEA) Japan |
| 2011 Events |
| Spring ITPA Transport & Confinement Topical Group Meeting (following US/EU TIF) San Diego, California USA |
Fusion Research-related events can also be seen on the USBPO website at http://burningplasma.org/events.html
Please contact the administrator with additions and corrections.