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 Research Highlight C. Paz-Soldan, et al. Schedule of Burning Plasma Events Contact and Contribution Information
Webinar on Runaway electron generationDate: Thursday, October 6th, 1pm EDT (noon CDT, 11:00 am MDT, 10:00am PDT)
Speaker: Dr. Dylan Brennan, Princeton University
Topic: Recent theoretical progress in understanding runaway electron generation and dynamics
Dr. Brennan is a lead PI for the Simulation Center for Runaway Electron Avoidance and Mitigation, a new FES/ASCR collaborative center focussed on this critical topic for burning plasmas.Connection information: We will use Zoom for audio, video and slides (http://zoom.us/)
Join from PC, Mac, Linux, iOS or Android:
iPhone one-tap (US Toll): +1 408 638 0968, +1 617 253 0886, +1 646 558 8656, +1 617 253 0886
Telephone: +1 408 638 0968 (US Toll) or +1 646 558 8656 (US Toll) Meeting ID: 617 253 0886 International numbers available: https://mit-psfc.zoom.us/zoomconference?m=_U0mTBNJfes5dmmP1cqt7F_tpLGPHG2p
Director's CornerC.M. Greenfield
Last time you heard from me, we had recently concluded the annual election for the US Burning Plasma Organization Council. At that time we were still working on identifying two new appointed members, and that process has now concluded. Cary Forest (Wisconsin) and Gary Staebler (General Atomics) have agreed to join the Council, with Cary also taking over as Vice Chair. The outgoing (2015-16) and incoming (2016-17) Councils are shown below.
|USBPO Council 2015-16||USBPO Council 2016-17|
|Larry Baylor||Ted Biewer (ORNL)|
|David Brower||David Brower (UCLA)|
|Stan Kaye (PPPL)||Cary Forest (Vice Chair, Wisconsin)|
|Chuck Kessel (Vice Chair, PPPL)||Stan Kaye (PPPL)|
|Mark Koekpe(Chair, West Virginia)||Chuck Kessel (Chair, PPPL)|
|Earl Marmar (MIT)||Earl Marmar (MIT)|
|David Maurer (Auburn)||David Newman (U Alaska)|
|David Pace (GA)||David Pace (GA)|
|Juergen Rapp (ORNL)||Juergen Rapp (ORNL)|
|Susana Reyes (LLNL)||Susana Reyes (LLNL)|
|Jim Terry (MIT)||Gary Staebler (GA)|
|Dan Thomas (GA)||Jim Terry (MIT)|
|François Waelbroeck (U Texas)||François Waelbroeck (U Texas)|
We also recently completed the selection of six new topical group leaders and deputies, as follows:
Confinement and Transport Topical Group: Gary Staebler (GA) completed his term, and previous deputy Saskia Mordijck (William and Mary) became the new leader. Walter Guttenfelder (PPPL) is the new deputy.
Diagnostics Topical Group: Ted Biewer (ORNL) and Brent Stratton (deputy, PPPL) completed their terms. Brent elected to not continue as leader, so we had two positions to fill. Max Austin (Texas) has agreed to take over leadership of the group, with Luis Delgado-Aparicio (PPPL) becoming the new deputy.
Integrated Scenarios Topical Group: Chris Holcomb (LLNL) completed his term, and previous deputy Francesca Poli (PPPL) became the new leader. Francesca Turco (Columbia) is the new deputy.
MHD and Macroscopic Plasma Physics: Bob Granetz (MIT) completed his term, and previous deputy Steve Sabbagh (Columbia) became the new leader. Carlos Paz-Soldan (GA) is the new deputy.
Modeling and Simulation: Xianzhu Tang (LANL) completed his term, and previous deputy Lang Lao (GA) became the new leader. Xueqiao Xu (LLNL) is the new deputy.
A big thank you goes to all of the outgoing leaders, as well as to the incoming leaders. With these changes, the 2016-17 Research Committee includes:
|Topical Group||Leader||Deputy Leader|
|Confinement and Transport||Saskia Mordijck (W&M)||Walter Guttenfelder (PPPL)|
|Diagnostics||Max Austin (Texas)||Luis Delgado-Aparicio (PPPL)|
|Integrated Scenarios||Francesca Poli (PPPL)||Francesca Turco (Columbia)|
|MHD, Macroscopic Plasma Physics||Steve Sabbagh (Columbia)||Carlos Paz-Soldan (GA)|
|Modeling and Simulation||Lang Lao (GA)||Xueqiao Xu (LLNL)|
|Energetic Particles||Nikolai Gorelenkov (PPPL)||Eric Bass (UCSD)|
|Fusion Engineering Science||David Rasmussen (ORNL)||Jean Paul Allain (Illinois)|
|Operations and Control||Jim Irby (MIT)||Eugenio Schuster (Lehigh)|
|Pedestal and Divertor/SOL||John Canik (ORNL)||Mike Jaworski (PPPL)|
|Plasma-Wave Interactions||Robert Pinsker (GA)||Greg Wallace (MIT)|
Activities at the APS-DPP Conference
The USBPO is organizing two events on Thursday, November 3, during the upcoming annual meeting of the APS Division of Plasma Physics in San Jose.
We will also host a town meeting on ITER on Thursday evening at 7:30PM in room 230B. The featured speaker will be David Campbell, Director of the ITER Science and Operations Department. Dr. Campbell will speak about Progress in ITER Construction and Strategy Towards the Operations Phase.
The ninth annual Research in Support of ITER contributed oral session will be held on Thursday morning in room 230A. This year's agenda is as follows:
|W. Suttrop||IPP Garching||AUG/DIII-D RMP ELM Suppression Similarity Experiment|
|P. Snyder||GA||Prediction and OPtimization of the ITER Pedestal|
|Larry Baylor||ORNL||ELM Mitigation in Low-rotation ITER Baselin Scenario Plasmas on DIII-D with High Frequency Deuterium Pellet Injection|
|L. Cui||PPPL||Transport modeling of DIII-D RMP ELM controlled plasmas|
|y.-K. Oh||NFRI||Highlights of the KSTAR Research relevant to ITER|
|D. Brennan||Princeton U||Progress and challenges in predictive modeling of runaway electron generation in ITER|
|A. Tinguely||MIT||Analysis of Runaway Electron Synchroton Emission in Alcator C-Mod|
|E. Kolemen||Princeton U||Transient-Free Operations With Physics-Based Real-time Analysis and Control|
|A. Hassanein||Purdue||Secondary radiation damage effects during transient events on ITER divertor and nearby|
|T. Abrams||ORAU||Characterizing the intra-ELM tungsten erosion profile in the DIII-D divertor in different ELM regimes|
|W. Choi||Columbia||Feed-back control of 2/1 locked mode phase: experiment on DIII-D and modeling for ITER|
|J. Wright||MIT||Application of the three ion species ICRF scenario to ITER operations|
|F. Poli||PPPL||EC power management for NTM control in ITER|
|M. Brookman||U of Texas||Experimental Evidence of ECH Deposition Broadening on DIII-D|
|J. McGlenaghan||ORAU||Extrapolations of the high betaP scenario to ITER using TGYRO modeling|
We are once again preparing for a meeting of the ITER Science and Technology Advisory Committee (STAC), which will be held in Nara, Japan, the week prior to the IAEA Fusion Energy Conference. This will be the first time the STAC meeting is held away from the ITER site. The US participants, as in recent meetings, will be Rob Goldston (PPPL), Chuck Greenfield (GA and USBPO), Earl Marmar (MIT), Juergen Rapp (ORNL), and Jim Van Dam (USDOE). The STAC has only two charges for this meeting, but each has a very large scope:
- Evaluate the technical aspects of the plan for staged operation (three stages and four stages) including:
- availability of heating, fuelling and diagnostics systems and machine capabilities for each of the operational stages;
- the objectives of scientific research in each of the operational stages and the associated outline Research Plan up to DT Operation.
- Evaluate the technical aspects of the Risk Management Plan in the context of the resource loaded schedule to First Plasma.
The first charge will be informed by a study of the ITER Research Plan that was conducted in late July. This study was a first step in developing a self-consistent hardware and research plan to progress from first plasma to high-fusion-gain DT operation. I expect this work will continue through next year, but the STAC is asked to comment on the plan in its current form to the ITER Council at their next meeting in November. US participants in the ITER Research Plan activity are Max Fenstermacher (LLNL), Tim Luce (GA), Rajesh Maini (PPPL), and Steve Sabbagh (Columbia).
Where to find more information about ITER
There are several sources of information about ITER that might be of interest to you. The ITER website, at http://www.iter.org, is a great source of information. Among other things, you can find the ITER Newsline weekly newletter at http://www.iter.org/news/whatsnew, and the ITER Magazine, published about twice a year, at http://www.iter.org/news/mag. You can subscribe to each of these and have them show up in your mailbox as they are published. Those of you who might have an interest in living in France and working at the ITER site might want to also keep an eye on the ITER jobs website at http://www.iter.org/jobs.
The US ITER Project Office has its own website, at http://www.usiter.org. There you can find information about US efforts to produce components of the ITER project.
And of course there's our own US Burning Plasma Organization website at http://burningplasma.org.
Pedestal and Divertor/SOL Topical Group, Leaders: John Canik and Mike Jaworski
The control of edge-localized modes (ELMs) is critical to the success of future fusion devices, including ITER, as the repetitive release of plasma to the tokamak walls can rapidly damage plasma-facing components. While the control of ELMs via externally applied three-dimensional magnetic perturbations has been observed experimentally for more than a decade, a full understanding of the processes involved has remained elusive. In this month's Research Highlight, by Carlos Paz-Soldan, a set of recent DIII-D ELM control experiments and related modeling are described that have yielded significant insight into the complex response of the plasma to applied perturbations, and point to possible means to improve ELM control
Multi-mode Plasma Response and its Application to Edge Localized Mode Control
1 General Atomics, San Diego, CA 92186-5608, USA
In the tokamak H-mode regime a boundary layer in the outer ≈ 5% of the plasma radius exhibits an extremely steep pressure gradient that elevates the core pressure profile onto a `pedestal'. Unfortunately, there are limits imposed by magneto-hydrodynamic (MHD) stability on the pressure built up in this pedestal, which if exceeded can result in the growth of an edge-localized mode (ELM) that releases a potentially damaging flux of energy to the tokamak wall. The size of the pedestal should thus be regulated to avoid the ELM, with several techniques under study. One promising technique is the application of weak ( < 0.1 %) symmetry breaking (3D) fields to locally increase transport at the pedestal top, thus preventing the expansion of the pedestal to its stability limit and suppressing the ELMs.
Recent experimental and modeling work by DIII-D scientists has identified new signatures in the tokamak magnetic fields when ELM suppression is achieved, connected these observations to 2D equilibrium conditions, and developed new techniques to optimize the spatial structure of the applied 3D fields. These advances were enabled by new diagnostics and experimental techniques. The number of magnetic sensors on DIII-D was recently doubled, with the tokamak high-field side (HFS) in particular receiving magnetic probe coverage for the first time. Further, longer spatial wavelength 3D fields were applied (toroidal periodicity n of 2 vs. 3), allowing spatial rotation of the applied field and larger spatial scale effects which together enabled unique measurements.
Figure 1(a) demonstrates the DIII-D coil geometry and the technique of scanning the differential phase between an upper and lower row of 3D coils (denoted ∆ϕUL). Scanning ∆ϕUL changes the spatial structure of the applied perturbations over time. Comparing Fig. 1(b)-(c) it can be seen that the shape of the deformations in the plasma magnetic field (called the `plasma response') is not rigid and takes on a different structures as different ∆ϕUL excite the plasma. The non-rigid plasma response is referred to as a multi-mode response because multiple Eigenmodes of the plasma response (each of fixed shape) must be superimposed to allow the response to be non-rigid. Observation of a multi-modal response is of fundamental importance because it opens the possibility to tune the plasma response by preferentially exciting the desired mode spectrum with a well designed applied field structure. For example, were the plasma response modes associated with a loss of energetic fusion alphas from the plasma core different than those controlling ELMs at the edge, the latter could be maximized relative to the former.
Figure 1: Slowly scanning ∆ϕUL (a) modulates the structure of plasma response (here plotting perturbed radial magnetic field) excited (b-c). The strength of the measured magnetic fields on the HFS wall (d), the suppression of ELMs (e), and the strength of the coil drive for `resonant' fields vary together (f). Adapted from Refs.
In these experiments, as the plasma response field measured with the newly installed high-field side (HFS) magnetic sensors trends to its maximum [Fig. 1(d)] ELM suppression occurs [Fig. 1e)]. Experiment and modeling here indicates that the plasma response is peaked throughout the HFS, as well as at the top and bottom. This shape of plasma response is also maximized during peak ELM mitigation in the MAST and AUG tokamaks in Europe. The working hypothesis for ELM suppression relies on the presence of `resonant' components of the total 3D field driving enhanced transport at the pedestal top. While any plasma response mode could in principle enhance the resonant components, calculations indicate this shape of response is well coupled to edge resonant surfaces and thus closely connected to ELM control, as seen by the correlation in Fig. 1(d)-(f).
Figure 2: Variation of the n=2 LFS and HFS magnetic response with βN and ν*e. The LFS is primarily sensitive to βN while the HFS is primarily sensitive to ν*e.
Follow up experiments studied the dependence of these plasma response structures on basic 2D plasma equilibrium parameters such as the normalized plasma pressure (βN) and the collisionality at the pedestal-top (ν*e). Results shown in Fig. 2 demonstrate that the plasma response measured at the tokamak low-field side (LFS) is very sensitive to βN, but not ν*e [Fig. 2(a)]. In contrast, HFS measurements are insensitive to βN but very sensitive to ν*e [Fig. 2(d)]. The pressure scan results were expected - pressure driven `kink' modes tend to balloon out on the LFS and their Eigenfunctions are very weak on the HFS. Raising ν*e at fixed βN interestingly decreased the HFS response three-fold. This was thought to be due to reduction of the edge `bootstrap' current magnitude, though MHD modeling indicates more subtle effects are at play. This drop at high ν*e is certainly interesting as there is often a ν*e threshold for achieving ELM suppression - perhaps due in part to the MHD mode drive becoming weaker. These scans also highlight the essential reason the HFS response is so sensitive to pedestal-top features: it is not overwhelmed by the much larger core pressure driven modes that typically dominate the LFS signal and blind it to the pedestal.
Figure 3: Eigenvalue (a), mode structure (b,c), stability (d), and resonant drive (e), of reluctance Eigenmodes for the discharge of Fig. 1. Negative reluctance modes are most stable, have significant amplitude on the HFS side, and can drive resonant fields. Positive reluctance Eigenmodes are LFS localized, least stable, and can also drive resonant fields.
Modeling efforts to better understand the multi-mode plasma response also led to a new appreciation of the plasma `reluctance' and a path to ELM control with highly stable modes. The plasma reluctance is a Hermetian basis of plasma MHD modes (allowing Eigenmode decomposition) and is a fundamental property of the 2D equilibrium. Each reluctance Eigenmode is ranked by the amount of perturbed (3D) current driven in the plasma, and sorting by the sign of the reluctance Eigenvalue separates modes into `shielding' and `amplifying' types (Fig. 3[a]). Positive reluctance modes add to the applied field (thus amplifying it), while negative reluctance modes subtract (and thus shield). The amplifying modes are LFS localized and βN driven while the shielding modes have strong contributions on the HFS (Fig. 3[b,c]), consistent with the results in Fig. 2. Amplifying modes are the least stable (smallest perturbed energy, δW) and shielding modes are the most stable (largest δW) (Fig. 3[d]). The ability of pressure driven modes to amplify resonant fields is reproduced, but interestingly the stable shielding modes are also found to drive resonant fields (Fig. 3[e]). As each reluctance mode is orthogonal, an applied field structure could be designed to only couple to the shielding modes without driving the most amplifying modes, showing a potential path to improved ELM control.
Beyond the work at DIII-D highlighted above, it is also an exciting time for this topic due to the recent achievement of ELM suppression with 3D fields on international tokamaks. ELM suppression has recently been reported on the EAST tokamak in China[and it has very recently been achieved on the AUG tokamak in Germany. Together with the KSTAR tokamak in Korea, nearly all major tokamaks equipped with in-vessel coils have now succeeded in suppressing ELMs with 3D fields. This opens new opportunities to compare observations across different tokamaks and plasma regimes.
Work supported by US DOE under DE-FC02-04ER54698. DIII-D data shown in this paper can be obtained in digital format by following the links at https://fusion.gat.com/global/D3D_DMP.
ReferencesA. W. Leonard, Physics of Plasmas, 21(9):090501, 2014.
T. E. Evans, et al., Physical Review Letters, 92(23):235003, jun 2004.
B. Snyder, et al., Physics of Plasmas, 19(5):056115, 2012.
C. Paz-Soldan, et al., Phys. Rev. Lett., 114:105001, 2015.
R. Nazikian, et al., Phys. Rev. Lett., 114:105002, 2015.
C. Paz-Soldan, et al., Nuclear Fusion, 56(5):056001, 2016.
N. C. Logan, et al., Physics of Plasmas, 23(5):056110, 2016.
J. D. King, et al., Review of Scientific Instruments, 85:083503, 2014.
A. Kirk, et al., Nuclear Fusion, 55(4):043011, 2015.
J.-K. Park, et al., Physical Review Letters, 99:195003, nov 2007.
Y. Sun, et al., Physical Review Letters, 117(11):115001, 2016.
W. Suttrop, et al., First observation of ELM suppression by magnetic perturbations in ASDEX Upgrade in a shape-matching identity experiment with DIII-D. (in preparation), 2017.
Y. M. Jeon, et al., Physical Review Letters, 109(3):035004, jul 2012.
October 13-15, ITER STAC Meeting, Kizu, Japan
October 17-22, 26th IAEA Fusion Energy Conference, Kyoto, Japan
October 24-26, 17th ITPA Transport and Confinement, JAEA, Naka, Japan
October 24-26, 30th ITPA Pedestal & Edge Physics, JAEA, Naka, Japan
October 24-26, 28th ITPA MHD Disruptions and Control, Kyoto, Japan
October 24-26, 28th ITPA Energetic Particle Physics, Kyoto, Japan
October 24-27, 17th Integrated Operation Scenarios ITPA meeting, JAEA, Naka, Japan
October 24-27, 23rd Scrape-Off-Layer & Divertor ITPA meeting, JAEA, Naka, Japan
October 31 - November 4, 58th APS Division of Plasma Physics, San Jose, California, United States
November 7-9, 21st MHD workshop, La Jolla, California, United States
November 7-10, 31st Diagnostics ITPA meeting, ITER Organization, St. Paul Lez Durance, France
December 6-8, 7th Coordinating Committee meeting, ITER Organization, St. Paul Lez Durance, France
December 8, 7th Executive Coordinating Committee ITPA meeting, ITER Organization, St. Paul Lez Durance, France
December 13-14, 37th Fusion Power Associates Annual Meeting and Symposium, Fusion Power Development: An International Venture
June 4-8, 27th IEEE Symposium on Fusion Engineering (SOFE2017), Shanghai, China
June 24-28, 2018 IEEE International Conference on Plasma Science (ICOPS), Denver, Colorado, USA
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.
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Editor: Saskia Mordijck (firstname.lastname@example.org)