USBPO Mission Statement: Advance the scientific understanding of burning plasmas and ensure the greatest benefit from a burning plasma experiment by coordinating relevant U.S. fusion research with broad community participation.
Announcements Director’s Corner C.M. Greenfield ITPA Update Schedule of Burning Plasma Events Image of the Month A Storm of Words Contact and Contribution Information
The Office of Fusion Energy Sciences is seeking candidates for a Program Manager position in the Research Division. The position is posted at USAJobs as Job Announcement Number 14–DE–SC–HQ–018 and will remain open through October 3, 2014.
The focus of this position will be to serve as a recognized scientific authority and expert in magnetic confinement of high-temperature plasmas and the operation of large toroidal magnetic fusion science experimental facilities and other technical areas, and as such has the responsibility to plan, coordinate, implement, and evaluate research programs in plasma and fusion science on a national and international level. Full details are available at the USAJobs listing.
by C.M. Greenfield
As I wrote last month, the terms have ended for five of our topical group leaders. In each case, the deputy leaders of these groups agreed to move up into the leader position. We have now appointed new deputy leaders for each of these groups, so the new topical group leadership organization is:
I would like to thank the outgoing topical group leaders: George McKee (Confinement and Transport), David Brower (Diagnostics), Stefan Gerhardt (Integrated Scenarios), Franc ̧ois Waelbroeck (MHD/Macroscopic Plasma Physics), and David Mikkelsen (Modeling and Simulation) for their years of service to the burning plasma community, and thank and welcome the new members. I note that Saskia, Brent, Francesca, and Steve are all members or experts in their respective ITPA topical groups, and we hope their dual involvement will help to strengthen those ties. Lang is the leader of the ITER Modeling Expert Group (IMEG) and it is hoped that his involvement here will help to strengthen the ties between the US modeling and simulation community and ITER.
The topical group leaders’ and deputy leaders’ terms are two years, which can be renewed once. We will be looking for new leadership in the five groups labeled as “ODD” (that’s for the year, not the topic!) next summer.
Preparations are underway for next week’s seventeenth meeting of the ITER Science and Technology Advisory Committee (STAC-17). Once again, the US participants will be Rob Goldston (PPPL), Earl Marmar (MIT), Juergen Rapp (ORNL), Jim Van Dam (DOE) and myself. We will consider the following charges (condensed version):
- Assess technical aspects of a report on progress of the Design Maturity of ITER systems by the ITER Organization and on the implementation of their action plan.
- Assess the ITER Organization commissioning plans for the ITER’s systems for First Plasma operation and further development of the ITER Research Plan (IRP) including:
• Proposed construction sequence
• Assessment of capabilities for low field/current operation
• Approach for developing methods for runaway control and disruption prediction
• Risk analysis taking into account factors like critical deferred systems, impact of a malfunctioning system and critical experimental milestones
- Assess progress on technology and physics issues related to the full-W divertor, in particular effects of self-castellation, morphological response of tungsten to helium plasma exposure, tile shaping including thickness, modeling of melt-layer motion, and creation and mitigation of Type I ELMs in He H-modes.
- Assess the ITER Organization’s plans and progress on the resolution of outstanding technical issues concerning neutronics, radiation exposure of electronic components, magnets, in-vessel coils, and procurement and application of ECH and NNBI systems.
The STAC-17 meeting will produce a report that will provide input to the ITER Council at its November meeting. Similarly, the Management Advisory Committee (MAC) will meet in a few weeks to develop its own report.
In other ITER news, ITER’s second delivery of components was delivered on September 18. This was equipment for ITER’s Steady State Electrical Network (SSEN). The high voltage disconnectors and earthing switches were procured by the Princeton Plasma Physics Laboratory (PPPL), which serves as the SSEN engineering support subcontractor to the US Domestic Agency, and manufactured by the Italian branch of Alstom.
Note that much of the ITER news reported here comes from sources that are readily available to the public. The weekly ITER Newsline can be found at http://www.iter.org/whatsnew. ITER has also recently begun web publication of the ITER Magazine. It can be found at https://www.iter.org/mag and is updated five times a year. Among other material of interest that can be found at the ITER website is a listing of ITER jobs, at https://www.iter.org/working-for-iter. The US Domestic Agency also maintains information on their website, at https://www.usiter.org/. And, of course, we collect a lot of relevant material on the US Burning Plasma Organization website at /.
The seventh annual Research in Support of ITER contributed oral session will be held during the upcoming annual meeting of the APS Division of Plasma Physics. This year’s agenda is as follows:
|Steve Lisgo||ITER||Time-resolved kinetic modelling of ELM-induced tungsten influx in ITER|
|Thomas Eich||ASDEX-U||Revisited ELM divertor heat load scaling to ITER with JET and ASDEX Upgrade data|
|Peter Stangeby||U. Toronto||Power deposition on the DIII-D inner wall limiter|
|Prashant Valanju||U. Texas||X-Divertors on ITER — with no hardware changes|
|Brian LaBombard||MIT||High resolution edge plasma profiles in L and H-mode|
|Ted Biewer||ORNL||Perspectives on the Final Design Review process from the US ITER DRGA team|
|Rich Hawryluk||PPPL||Control of Plasma Stored Energy for Burn Control Using DIII-D In-Vessel Coils|
|Carlos Paz-Soldan||GA||Progress in Understanding DIII-D Low Input Torque ITER Baseline Scenario Stability|
|Yongkyoon In||KSTAR||Steady-state ELM-suppressed H-modes from KSTAR to ITER and beyond|
|Eugenio Schuster||Lehigh||Physics-model-based Current Profile Control in DIII-D|
|Matt Lanctot||GA||Control Solutions for High Performance in ITER with Test Blanket Modules|
|Steve Wukitch||MIT||ICRF Compatibility with high Z metallic walls: Source and transport studies of conventional and field aligned ICRF antennas|
|David Smithe||Tech-X||Modeling the ITER ICRF Antenna with Integrated Time Domain RF Sheath and Plasma Physics|
|Bob Granetz||MIT||Runaway electrons and disruption mitigation|
|Nicolas Commaux||ORNL||Rapid Shutdown using Large Neon Shattered Pellet in DIII-D|
We look forward to another in a series of well-attended sessions highlighting compelling results that support ITER reaching its technical goals.
The USBPO will not be hosting a town meeting at this year’s conference.
MHD and Macroscopic Plasma Physics Topical Group, Leaders: F. Waelbroeck and R. Granetz
A key problem for ITER is the mitigation of thermal and mechanical loads during disruptions. Mitigation contains three components: mitigation of heat loads during the thermal quench, mitigation of damage from runaway electrons, and mitigation of the forces acting on the vessel and plasma facing components. Massive Gas Injection has received the most attention as a technique for mitigating disruptions.
NIMROD Prediction and Experimental Measurement of Radiation Toroidal Peaking Factor During Massive Gas Injection on DIII-D
Center for Energy Research, University of California at San Diego, La Jolla, CA 92093-0424, USA
Simulations of massive gas injection (MGI) using the 3D MHD code NIMROD have indicated that MHD can play a significant role in the toroidal distribution of radiated power . In particular, the m = 1/n = 1 mode that grows and saturates at the end of the thermal quench (TQ) phase gives rise to a large toroidally asymmetric (convective) heat flux which is responsible for the final collapse of the central temperature. Since this mode preferentially dumps heat toward one side of the torus, radiation toroidal peaking can occur even with toroidally symmetric impurity injection. Recent NIMROD modeling is based on the real two-valve geometry that is employed on DIII-D, and directly compares the radiation toroidal peaking factor (TPF) for one- and two-valve simulations with those measured in the experiment.
DIII-D has two massive gas injection (MGI) systems located above the midplane at φ = 15° (MGI1) and below the midplane at φ = 135° (MGI2) as shown in Fig. 1. Each of these MGI systems is modeled in NIMROD as a source of neutral impurities that is localized radially to the vacuum region of the simulation domain. In DIII-D experiments, radiated power is measured by two diagnostics located at 90° and 210° toroidally, also indicated in Fig. 1.
Figure 1: (a) Diagram showing poloidal locations of two DIII-D MGI systems. (b) Toroidal locations of the two MGI systems and of the two radiated power detectors on DIII-D. (c) Normalized poloidal source distribution of neutral Ne for the simulations with MGI1. (d) Normalized poloidal source distribution of neutral Ne for the simulation with MGI2.
Experiments were performed on DIII-D in which each gas jet was fired individually, and both gas jets were fired together with various delay timings , and the toroidal peaking of radiated energy as measured by two Prad detectors at 90° and 210° was calculated for each case (Fig. 2). The radiated power from each detector was integrated to find the radiated energy during the pre-TQ, TQ and current quench (CQ) phases individually, and an estimated, 2-point TPF for each phase was calculated as the maximum over average of the two radiated energies: TPF2-pt = MAX(W90, W210)/MEAN(W90 , W210 ). This quantity has no inherent sign and a minimum value of 1 (right axis of Fig. 2). It is also useful to calculate the difference over the sum of the two energies (left axis of Fig. 2), such that the sign indicates which of the two detectors the asymmetry is weighted towards. These two asymmetry metrics can easily be related by TPF2-pt = 1 + |∆(W90, W210)/Σ(W90, W210)|. The experimental results showed no significant trend as a function of jet delay timing during any phase of the disruption. In general, if the radiated energy vs. toroidal angle is known with high resolution, the TPF is defined as the maximum over the average of the curve. The calculation based on two measurement locations is clearly an approximation of this that may or may not reflect the true TPF. In the NIMROD simulations, the “resolved” TPF can be calculated using the full toroidal resolution of the simulation (here up to n = 10), and a “synthetic” TPF can also be calculated using only information from the 90° and 210° locations. This latter calculation is the most appropriate comparison to the experiment for validation purposes.
For three NIMROD simulations using only MGI1, only MGI2, and both jets simultaneously, we calculate the TPF during the pre-TQ and TQ phases using both methods, and compare these with the DIII-D data in Fig. 2. The results show that the synthetic TPF values lie within measurement error bars for all three cases during the TQ and two of three during the pre-TQ, with one overprediction for only MGI1. In general, the lack of significant variation is reproduced by the synthetic TPF values. However, the resolved TPF values from NIMROD show a marked trend during both phases. During the pre-TQ, the TPF drops from 2.4 − 2.6 with either single jet to 1.5 with both jets together. During the TQ, the TPF is 1.4 with either single jet and just above 1.1 with both. The NIMROD results and comparison with the DIII-D data suggest that the use of two jets in this configuration does in fact reduce the TPF, and that the lack of any trend in the experiments is an artifact of the two-point measurement. In other words, better diagnostic coverage is needed to accurately measure TPF on DIII-D, and validate the NIMROD model.
Figure 2: NIMROD predictions of “synthetic” and “resolved” TPF for the three cases of only MGI1, only MGI2, and both jets simultaneously during the pre-TQ and TQ phases. Overlaid are DIII-D measurements of TPF (small symbols with error bars) for various delay timings between MGI1 and MGI2, integrated over the pre-TQ, TQ and CQ phases.
This material is based upon work supported in part by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, Theory Program, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-FG02-95ER54309, DE-FC02- 04ER54698, DE-FG02-07ER54917, DE-AC05-00OR22725, DE-FC02-99ER54512 and DE-AC52-07NA27344. This research used resources of the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Phys. Plasmas 20, 056107 (2013)
 N. Commaux, et al., “Understanding the physics of thermal quench mitigation,” Phys. Plasmas (accepted 2014)
|October 13–18, 25th IAEA Fusion Energy Conference (FEC 2014), St. Petersburg, Russia|
|October 20–22, ITPA: Meetings of the Pedestal & Edge Physics and Transport & Confinement Topical Groups, ITER Organization, St. Paul Lez Durance, France|
|October 20–22, ITPA: Scrape-off Layer and Divertor Topical Group Meeting, Prague, Czech Republic|
|October 20–23, ITPA: Integrated Operating Scenarios Topical Group Meeting, CEA/DSM/IRFM (Cadarache), St. Paul Lez Durance, France|
|October 21–23, ITPA: Joint Meeting of the Energetic Particles and MHD, Disruptions & Control Topical Groups, Padova, Italy|
|October 27–31, 56th APS Division of Plasma Physics Conference, New Orleans, LA|
|November 3–5, 19th Workshop on MHD Stability Control, Auburn, AL|
|November 3–7, ITPA: 27th Meeting of ITPA Topical Group on Diagnostics, ITER Organization, St. Paul Lez Durance, France|
— NSTX-U First Plasma —
— W7-X First Plasma —
|January, Due date for report concerning the ten-year strategic plan of the Fusion Energy Sciences division of the US Department of Energy.|
— 10th Anniversary of USBPO Formation —
— JET DT-campaign —
— JT60-SA First Plasma —
A Storm of Words
This month’s image is a histogram in which the frequency of a word as it appears in the Draft FESAC Strategy Panel Report is indicated by its displayed size (position and color are random). Since the draft report includes various materials contributed during public comment sessions, this histogram is not expected to represent the actual recommendations of the FESAC panel, though it may indicate some topics that presently receive attention across the participating research community and are widely considered relevant to the future of fusion development. Such an interpretation may explain the relative rarity of electricity (3) compared to all variants of disruption (34†).
Common English words such as and (1129 appearances) and a (448) are ignored in this tabulation, as are the following series of words: fusion (347), science (275), U.S. (164), energy (123), program (114), research (242), and plasma (378). Plasmas (73) is included and can be seen along the left edge of the image. The tabulation does not consider the meaning or context of the words, which explains the major presence of both facilities (142) and facility (95).
This calculation was performed using Wordle.
†Includes incorrect spelling from public presentation title.
This newsletter provides a monthly update on U.S. Burning Plasma Organization activities. The USBPO operates under the auspices of the U.S. Department of Energy, Fusion Energy Sciences (FES) division. All comments, including suggestions for content, may be sent to the Editor. Correspondence may also be submitted through the USBPO Website Feedback Form.
Become a member of the U.S. Burning Plasma Organization by signing up for a topical group.
Editor: David Pace (firstname.lastname@example.org)