News and Events

U.S. Burning Plasma Organization eNews

Jul 31, 2018 (Issue 132)


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.

CONTENTS

Announcements  
Request from the Editor  
Director’s Corner
C.M. Greenfield
U.S. Fusion Outreach Team  
Research Highlight
T.M. Wilks1
Schedule of Burning Plasma Events  
Contact and Contribution Information  

Announcements

ITER internships

An announcement for ITER internship opportunities for undergraduate and graduate students was recently posted. Please see the following link for a description: https://www.iter.org/jobs/internships

The proposed topics can be found here:

https://www.iter.org/doc/www/content/com/Lists/WebText_2014/Attachments/321/Call_for_topics-Internship_2018_V3.pdf

 


Request from the Editor

Dear USBPO eNews readers,

In years past, previous editors of the US BPO eNews occasionally provided an “Image of the Month” that displayed eye-catching graphics related to research (e.g. an illustration of LHCD propagation and damping) or fun facts (e.g. a comparison of budgets between US FES funding vs. Hollywood films referencing fusion). I would like to ask our readers to send ideas and contributions for similar content. In addition to the above graphics, I would also like to ask people to help develop, or share already-available, eye-grabbing visuals that could be used for outreach efforts. (See announcement by C. Collins regarding the US Fusion Outreach activity in this month’s issue.) I ask our readers to send ideas or suggestions for such graphics to: wgutten@pppl.gov. Thank you.

 

Director’s Corner By C.M. Greenfield

Working at or for ITER

As you all know, preparing ITER for its research program is a huge task, with people from all seven ITER Members coming together at the ITER site as well as at laboratories and industries in the Members’ home countries. There are many avenues for participation. The most obvious of these is to work directly as part of the ITER Organization (IO). The IO maintains a list of available jobs at https://www.iter.org/jobs, and this list is almost always changing. There are currently 16 opening (mostly not aimed at scientists), with application deadlines ranging from early August through mid-September.

I should also call your attention to the ITER Project Associate (IPA) Scheme (https://www.iter.org/jobs/IPA). IPAs work at the ITER site, but continue to be employed by their home institutes rather than the IO. There are currently 20 IPA openings listed. If you’re interested in one of these, please consider the following advice from the DOE Office of Fusion Energy Sciences (FES): 

·         Your institution should be agreeable

·    If you are funded by DOE, the proposed work at ITER should be consistent with your FES-funded work and not prevent that work from being accomplished, and

·         FES can not provide additional financial support

My advice here (at least to U.S. personnel) is that if you are interested in one of the open FPA positions you should consult with your employer and FES before proceeding.

In the United States, the U.S. ITER Project Office (https://www.usiter.org) may also provide some opportunities. Of course, there are numerous contractors throughout the country also working on providing ITER components, these can be found at https://www.usiter.org/publications/us-iter-participants.

The U.S. Fusion Outreach Team

Elsewhere in this issue, you’ll see a message about the formation of the U.S. Fusion Outreach Team. This group is being organized under the auspices of the USBPO, with Cami Collins (Deputy Leader of the Energetic Particles Topical Group) having graciously agreed to serve as leader. This is a very important undertaking, not only for the USBPO, but for our entire field. I hope you’ll consider joining and contributing to the work of this group.

Coming soon: The annual changing of the guard

In the coming weeks, we will be beginning the process of selecting replacements for several members of the USBPO Council, whose terms are ending this summer. Please watch for an announcement, soliciting nominations.

Following the Council selection, we will move on to the annual rotation of topical group leadership. This year, we will select new leadership for five topical groups as their leaders’ terms come to an end:

·         Diagnostics (Max Austin)

·         Pedestal and Divertor/SOL (John Canik)

·         Confinement and Transport (Saskia Mordijck)

·         Integrated Scenarios (Francesca Poli)

·         MHD, Macroscopic Plasma Physics (Steve Sabbagh)

It isn’t too early to be thinking about people you might want to nominate to serve on the leadership team of these topical groups.

Burning Plasmas at the upcoming APS Division of Plasma Physics Conference

As promised, the agenda for the USBPO-organized “Research in Support of ITER” contributed oral session, to be held as part of the annual APS-DPP conference, is below. This will be the eleventh consecutive year for this session, and we were quite pleased with the overwhelming response – there were 32 excellent submissions from the U.S. and abroad. Paring those down to 15 talks was a very challenging process.

1

T. Luce (ITER)

The New Stable ITER Baseline Scenario With Zero Torque

2

X. Gong (ASIPP)

Advances in EAST Long Pulse H-Mode Experiment and Contributions to Steady State Operation of ITER

3

A. Lvovsky (ORAU)

Impact of Initial Plasma Current and Injected Argon Quantity on the Runaway Electron Seed Distribution

4

A. Tinguely (MIT)

Synchrotron Spectra, Images, and Polarization Measurements from Runaway Electrons in Alcator C-Mod

5

N. Eidietis (GA)

First Demonstration of Disruption Mitigation Using Shell Pellets for Core Impurity Deposition on DIII-D

6

M. Kriete (Wisconsin)

Effect of Radial Magnetic Perturbations on Turbulence-Flow Dynamics at the L-H Transition on DIII-D

7

T. Wilks (MIT)

Advancement of the Wide Pedestal Quiescent H-Mode Scenario in DIII-D Towards ITER-Relevant Shape

8

E. Militello-Asp (CCFE)

Coupling Core and Edge Transport Simulations in Support of ITER

9

D. Brunner (MIT)

Unified Scaling of Divertor Heat Flux Widths Across Confinement Regimes to Reactor-Relevant Magnetic Fields in The Alcator C-Mod Tokamak

10

C.-S. Chang (PPPL)

Gyrokinetic Prediction of The Divertor Heat-Load Width for ITER

11

A. Lasa (UTK)

Integrated, Multi-Physics Modeling Of Erosion, Redeposition And Gas Retention In The Iter Divertor

12

P. Manas
(IPP Garching)

Experimental and Theoretical Characterization of He Plasmas Confinement in View of the ITER Pre-Fusion Power Operation Phase

13

V. Duarte (PPPL)

Prediction of The Likelihood of Alfvénic Mode Chirping in ITER Baseline Scenarios

14

T. Vu (SPC-EPFL)

A Tokamak-Agnostic Control System for Actuator Management and Integrated Control with Application to ITER and TCV

15

J. Snipes (ITER)

The Development of First Plasma Operations on ITER

We have also arranged for Tim Luce, the new Director of ITER’s Science and Operations Division, to speak about the ITER Research Plan at an evening town meeting.

U.S. Fusion Outreach Team Cami Collins

The U.S. Fusion Outreach Team is a new group organized by the U.S. Burning Plasma Organization to provide a platform for national fusion outreach efforts to unite. Whether you think fusion outreach is important to help recruit the next generation of researchers, raise interest in the general scientific community, or gain support from the taxpayers and decision makers that fund our research, the U.S. Fusion Outreach Team is here to help. Some of our initial efforts will be to:

·     make it easier to give general presentations about fusion energy research by providing material for talk content and connecting speakers to venues

·   collect and make new visual media (colorful pictures or simulations, 3D images or CAD models, movies) to communicate highlights in fusion research

·      improve Wikipedia pages for fusion devices.

We welcome your contributions at any level; maybe you’d like to give a talk or know a student who would be great at giving outreach presentations. Maybe you need help creating an image that could be used to communicate your research to people outside of plasma physics.  Maybe you have an idea for a cool plasma physics demonstration. You can find more information, post your ideas, receive updates, and volunteer to help by joining the U.S. Fusion Outreach Team Google Group. Anyone is welcome to join!

Research Highlight

Integrated Scenarios (Leaders: Francesca Poli & Francesca Turco)

One of the challenges for ITER operation will be the presence of Edge Localised Modes (ELMs), a type of instability that is beneficial for the plasma core (as it flushes out excess impurities and D2), but it can be detrimental to the PFC and the divertor plates. In this month's Research Highlight, Theresa Wilks and her colleagues at M.I.T. and DIII-D explore the option to use an alternative design for ITER plasmas tasked to reach fusion gain of Q=10, without ELMs or other harmful MHD instabilities.

Exploring Quiescent H-modes for ITER Operation

T.M. Wilks1, K.H. Burrell2, Xi Chen2, A.M. Garofalo2, J.W. Hughes1, J.R. King3, and the DIII-D Team

1MIT Plasma Science and Fusion Center

2General Atomics

3Tech-X Corporation

Author e-mail: twilks@psfc.mit.edu

Economical and reliable fusion reactor designs require plasma operating regimes that sustain density control via particle transport, while maintaining high thermal confinement. High confinement (H-mode) plasmas [1] in current machines can maintain these characteristics, with the particle transport periodically enhanced by edge localized modes (ELMs) [2-3], which are quasi-periodic edge relaxation events thought to develop from magnetohydrodynamic (MHD) instabilities in the edge pedestal region of tokamak plasmas [4]. ELMs can be detrimental to plasma facing components due to the large transient heat and ion fluxes they may produce, and thus represent a significant challenge for the design and operation of future fusion reactors such as ITER [5]. As a result, interest has grown significantly in obtaining high confinement regimes without ELMs [6].

There has been considerable progress on developing an alternative to the ELMy H-mode regime, called the quiescent H-mode (QH-mode) [7-11]. While initially discovered in the DIII-D tokamak, it has subsequently been observed in ASDEX-U [12], JT60-U [13-14], and JET [15]. In QH-mode, edge fluctuations maintain a quasi-steady edge plasma without ELMs by generating the extra particle transport needed to relax gradients below typical MHD stability limits. QH-mode can operate over broad operational regimes at reactor relevant values of important normalized quantities such as confinement enhancement factors [16] (H98 > 1), ratio of plasma pressure to magnetic pressure ( ), and electron collisionality ( < 0.1). Further development for QH-mode operation is still required, specifically its compatibility with low rotation (associated with low net injected torque) and ITER values of safety factor, because ITER and future reactors without neutral beam systems will have little capability of external torque injection. With research geared towards addressing these challenges, QH-mode is considered to be a promising candidate for a naturally ELM free stationary target plasma for fusion power generation [17-18].

The edge pedestal region in QH-mode plasmas consists of about the last 5-15% of enclosed normalized poloidal flux. Pedestal stability with respect to peeling-ballooning driven instabilities such as ELMs can be visualized using a phase space defined by normalized pressure gradient and normalized edge current as seen in Figure 1a. The standard QH-mode has an edge harmonic oscillation (EHO), which is a coherent, low-n dominated current driven MHD mode usually accessed under high torque conditions, as seen in Figure 1b. The plasma operating point with respect to the peeling-ballooning limit is usually at or just below the kink boundary.

Figure 1: a) Reproduced from T.M. Wilks et. al. NF accepted 2018. Contour plot of the ratio of the growth rate of the dominant mode calculated by ELITE to half of the ion diamagnetic frequency, , where the horizontal axis is the normalized peak pressure gradient and the vertical axis is the ratio of the average pedestal current to volume averaged current density [21-23] b) Frequency spectra for the edge harmonic oscillation typically observed in standard QH-modes versus broadband MHD typically seen in WPQH-mode plasmas.

Another type of QH-mode is the wide pedestal QH-mode (WPQH), which has a broader pedestal than is predicted by theory, and has increased edge turbulence. The increased turbulence is thought to produce more transport, allowing the pedestal gradients to relax. The less steep gradients improve pedestal stability, enabling the pedestal to grow higher and wider without reaching peeling-ballooning limitations, shifting the experimental operating points in the peeling-ballooning diagram in Figure 1a farther from the stability boundary than standard QH-modes [19-21]. The pedestal turbulence is characterized by a broadband spectrum similar to that in Figure 1b and can be access at lower torque than the QH-modes with an EHO.

The WPQH is compared to the standard QH-mode in Figure 2 and is seen to have a broader pedestal and radial electric field, smaller pressure gradient, and different ExB profile structures as compared to the standard QH-mode. The different pedestal profile structures cause a variety of turbulent drive and suppression mechanisms, allowing a range of possible edge MHD and turbulence signatures. The coherent EHO and broadband MHD shown in Figure 1b represent two example spectra, but often a mixture of coherent and broadband modes are observed in experiment, which are capable of providing the necessary particle transport to remain naturally ELM free.

Text Box:  
Figure 2: Reproduced from Xi Chen et. al., NF 57, 086008 (2017). Experimental profiles comparing standard QH-mode with wide pedestal QH-mode for a) electron pressure, b) total pressure gradient, c) radial electric field, and d) ExB shear.
Though the physical mechanisms driving the QH-mode edge turbulence are still not completely understood, theoretical models and simulations are beginning to capture some of the physical processes involved. Theoretical models for the standard QH-mode identify the EHO to be a saturated kink-peeling mode, destabilized by ExB shear, with some calculations predicting ITER operation within this parameter space [24-25]. Additional theories advance the understanding of scaling required for ExB shear necessary for EHO onset [21,26]. Nonlinear 3D single fluid simulations using the NIMROD code have reproduced the low-n saturated dominant mode similar to the EHO, which can only be reproduced with rotation present in the model, consistent with experimental observations. The particle transport in the NIMROD simulation is larger than the heat transport due to density fluctuations that have both a larger amplitude and a cross-phase more conducive to convective transport relative to temperature fluctuations. [27-28]. Research in theory and simulation of the wide pedestal QH-mode broadband edge turbulence is still under development.

Recent DIII-D experiments have extended the operational range of QH-modes toward more ITER relevant parameters in torque, safety factor, ion/electron heating mix, and shape. One of the primary actuators for developing the ITER Baseline Scenario in DIII-D plasmas is the application of n=3 non-axisymmetric magnetic field perturbations. These perturbations are utilized to drive the extra ExB shear in the edge necessary for EHO onset and allow for ELM free operation [29]. While QH-mode has been demonstrated with many of the dimensionless scaling parameters within the range projected for ITER operation, the ability to sustain the ELM free regime at zero torque and low rotation with an ITER relevant q95~3 remains a key question. It is currently possible to operate QH-modes at net zero injected NBI torque and higher q95~5, as well as the ITER q95 with larger net injected edge torque, but operation with both parameters at ITER predicted levels remains elusive. Additionally, there is still research required for more accurate predictions on what the ITER rotation and radial electric field profiles will be. In the near future, further modeling and experiments focused on developing the QH-mode scenario into a reactor relevant target plasma regime are planned with a specific focus on ITER.

Acknowledgements

Support from the DIII-D team was essential to this work and greatly appreciated. This research was supported by the U.S. Department of Energy, Office of Science, and Office of Fusion Energy Sciences using the DIII-D National Fusion Facility under award DE-FC02-04ER54698 and MIT cooperative agreement DE-SC0014264.

Disclaimer: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

References

[1] F. Wagner et. al., PRL 49, 1408 (1982)

[2] A. Leonard, PoP 21, 090501 (2014)

[3] D.N. Hill, Journ. Nucl. Mater., 241-243, 182 (1997)

[3] P.B. Snyder et. al., Nucl. Fusion 44, 320 (2004)

[4] A. Loarte et. al., PPCF 45, 1549 (2003)

[5] R. Maingi, Nucl. Fusion 54, 114016 (2014)

[6] K.H. Burrell et. al., PPCF 44, A253 (2002)

[7] K.H. Burrell et. al., PoP 5, 2153 (2001)

[8] K.H. Burrell et. al., PoP 12, 056121 (2005)

[9] K.H. Burrell et. al., Nucl. Fusion 53, 073038 (2013)

[10] E. Viezzer, Nucl. Fsion accepted 2018. https://doi.org/10.1088/1741-4326/aac222

[11] W. Suttrop et. al., Nucl. Fusion 45 721 (2005)

[12] Y. Sakamoto et. al., Plasma Phys. Control. Fusion 46 A299 (2004)

[13] Oyama N. et al 2005 Nucl. Fusion 45 871

[14] E.R. Solano et. al., Phys. Rev. Lett. 104, 185003 (2010)

[15] ITER Physics Basis Expert Groups on Confinement and Transport and Confinement Modelling and Database, ITER Physics Basis Editors 1999 Nucl. Fusion 39 (2175)

[16] A.M. Garofalo et. al., PoP 22, 056116 (2015)

[17] W.M. Solomon et. al., Nucl. Fusion 55, 073031 (2015)

[18] K.H. Burrell et. al., PoP 23, 056103 (2016)

[19] Xi Chen et. al., Nucl. Fusion 57, 086008 (2017)

[20] T.M. Wilks et. al., NF accepted 2018. https://doi.org/10.1088/1741-4326/aad143

[21] H.R. Wilson et. al., Phys. Plasmas 9, 1277 (2002)

[22] P.B. Snyder et. al., Phys. Plasmas 9, 2037 (2002)

[23] P.B. Snyder et. al., Nucl. Fusion 47, 961–968 (2007)

[24] P.B. Snyder et. al., Nucl. Fusion 51, 103016 (2011)

[25] Z.B. Guo and P.H. Diamond, PRL 114, 145002 (2015)

[26] J.R. King et. al., Nucl. Fusion 57, 022002 (2017)

[27] J.R. King et. al., Phys. Plasmas 24, 055902 (2017)

[28] A.M. Garofalo et. al., Nucl. Fusion 51, 083018 (2011)

 

Calendar of Burning Plasma Events

2018

August 27-31

Theory of Fusion Plasmas, Joint Varenna-Lausanne International Workshop

Varenna, Italy

Sept 3-5

ITPA Energetic Particles Topical Group meeting

Lisbon, Portugal

Sept 11-14

EU Transport Task Force (EU-TTF) meeting

Seville, Spain

Sept 17-20

ITPA Transport & Confinement Topical Group meeting

ITER HQ, France

Sept 30 – Oct 3

6th International Symposium on Liquid Metals Applications for Fusion (ISLA-6)

University of Illinois at Urbana-Champagne, IL

October 1-3

ITPA MHD Disruptions & Control Topical Group meeting

Napoli, Italy

October 8-12

ITPA Diagnostics Topical Group meeting

ITER HQ, France

October 22-27

IAEA Fusion Energy Conference

Gandhinagar, Gujarat, India

October 29-31

ITPA Integrated Operation Scenarios Topical Group meeting

ITER HQ, France

October 29-31

ITPA Pedestal & Edge Physics Topical Group meeting

ITER HQ, France

November 5-9

60th Annual Meeting of the APS Division of Plasma Physics

Portland, OR

November 11-15

ANS 23rd Topical Meeting on the Technology of Fusion Energy (TOFE)

Orlando, FL

November 12-14

21st MHD Stability Control Workshop

UCLA, CA

November 12-18

2nd Asia-Pacific Conference on Plasma Physics

Kanazawa, Japan

December 4-5

Fusion Power Associates 39th Annual Meeting & Symposium, Fusion Energy: Strategies & Expectations through the 2020s

Washington, DC

December 6-7

Meeting of the Fusion Energy Sciences Advisory Committee (FESAC)

Washington, DC

January 15-17

ITPA Coordinating Committee & CTP ExComm

ITER HQ, France

2019

JET DT-campaign (https://www.euro-fusion.org/newsletter/jet-full-throttle/)

April 15-17

Sherwood Theory conference

Princeton, NJ

October 21-25

61st Annual Meeting of the APS Division of Plasma Physics

Fort Lauderdale, Florida

2020

JT60-SA First Plasma (http://jt60sa.org/)



Contact and Contribution Information

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: Walter Guttenfelder (wgutten@pppl.gov)

 

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