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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
Director’s Corner	C.M. Greenfield
Research Highlight	Saskia Mordijck
Schedule of Burning Plasma Events
Contact and Contribution Information

NAS Burning Plasma committee

The NAS committee on “A Strategic Plan for U.S. Burning Plasma Research” held a public meeting on April 11-13 at Princeton Plasma Physics Laboratory. Presentations to the committee and additional public input submitted directly to the committee can be found here:

http://sites.nationalacademies.org/BPA/BPA_184701

 

New plasma book

“Magnetic Helicity, Spheromaks, Solar Corona Loops, and Astrophysical Jets” by professor Paul M. Bellan of Caltech has recently been published.

 

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

 

By C.M. Greenfield

Eleventh Annual APS-DPP Contributed Oral Session on “Research in Support of ITER”

For the tenth time, last year’s APS Division of Plasma Physics annual meeting included a contributed oral session on Research in Support of ITER, which included talks from US and foreign participants. These sessions have become quite popular and are always well attended.

The US Burning Plasma Organization is organizing a similar session for the 60^th Annual Meeting of the Division of Plasma Physics, which will take place in Portland, Oregon, on November 5-9. Once again, we are looking for talks on research that has been done specifically to address ITER design, operation, or physics issues. These brief talks are “standard” contributed orals: 10 minutes in duration, followed by a 2-minute discussion period. We hope to have broad participation once again, so we can highlight the breadth of this work and the institutions performing it, both US and international.

The abstract submission deadlines for this year’s meeting are quite early, so we need to get an early start with this year’s process. If you, or somebody from your institution, are interested in making a presentation in this session, please send a title, brief synopsis (one paragraph is sufficient), and speaker’s contact information as soon as possible (but no later than June 1) to Chuck Greenfield (greenfield@fusion.gat.com). The brief synopsis should provide a sufficient description to understand the work and its importance to ITER.

Note that space in this session is limited to 15 talks, so we may not be able to include all talks nominated. We will inform speakers by June 15, so any not selected for the ITER session may indicate a preference for other sessions, or allow the conference program committee to select an appropriate session. A full abstract would still need to be submitted via the conference website no later than 5:00 PM Eastern Daylight Time on June 29. If your talk is accepted for this session, please indicate “Research in Support of ITER” in the placement requests box.

ITER news

There has been a lot of news lately about ITER’s future being considered by the political class in Washington. I reported last month on a hearing by the House Subcommittee on Energy. This has now been followed up by an op-ed by Representative Lamar Smith, chairman of the full Committee on Science, Space, and Technology, entitled “Fusion Energy Could Bring the Stars' Power to Earth.” You can read the full essay at https://tinyurl.com/y9vj38tw. Mr. Smith’s conclusion is:

It is imperative that the United States uphold its commitment to ITER and fully fund the fusion research program at DOE. To maintain America’s global standing as the leader in science, we must meet our international commitments and support this basic research that will lead to transformative clean energy technologies. Let’s bring the power of the stars to Earth! 

I couldn’t have said it better myself!

Preparations are underway for this month’s ITER STAC-23 (Science and Technology Advisory Committee) meeting at ITER Headquarters. The STAC meets periodically to consider a number of technical charges from the ITER Council. At this meeting, the following four charges (condensed and paraphrased version) will be addressed, with STAC’s findings being reported at the upcoming ITER Council meeting in June:

1. Assess progress on outstanding issues for ITER’s Disruption Mitigation System (DMS)
2. Review adjustments being made to ITER’s construction schedule to maintain the objective of first plasma in 2025
3. Assess the status and plans for heating systems in the early phases of ITER operation
4. Review progress towards the final design of the In-Vessel Vertical Stability

The US STAC participation is changing. Rob Goldston (PPPL), Earl Marmar (MIT), and Juergen Rapp (ORNL) will continue. Since I am now the STAC chair, I don’t “count” as a US STAC member. Max Fenstermacher (LLNL) will take my place. Also, Jim Van Dam (DOE) is now attending the ITER Council meetings, and John Mandrekas (DOE) will take his place at STAC.

General Atomics Creates Free App for Plasma Physicists

Even in the extremely complex world of plasma physics, it turns out there’s an app for that.

General Atomics (GA) is making its first foray into mobile application development, deploying a new app to calculate plasma characteristics on the fly. Called Plasmatica, it incorporates expressions from the NRL Plasma Formulary and The Magnetic Fusion Energy Formulary (MIT-PSFC) and allows comparisons of various plasma parameters across different input values such as magnetic field amplitude or electron density.

“Before this, most of us just would have written a little program on our computers to do these calculations, and in fact a bunch of us have them,” said David Pace, the GA physicist who spurred the development of Plasmatica. “It’s been exciting to get some initial feedback that is guiding us to a new round of improvements.” Pace created a similar widget when he was in graduate school and thought it would be helpful to have GA bring it into the app age and share it with collaborators and the wider plasma community. The app has been tested by researchers and is getting solid reviews. Plasmatica is available for free from both the Android and Apple app stores.

 

Google Play Store: https://play.google.com/store/apps/details?id=com.ga.plasmatica

Apple App Store: https://itunes.apple.com/us/app/plasmatica/id1325455852

 

Confinement and Transport (Leaders: Saskia Mordijck & Walter Guttenfelder)

This month's research highlight by Prof. Saskia Mordijck of The College of William and Mary describes experiments on the DIII-D tokamak that demonstrate how the density profile in DIII-D H-modes is influenced by measured and predicted microturbulence. Fusion reactivity is sensitive to density peaking, so understanding and predicting these mechanisms is critical in burning plasmas such as ITER. These results have been reported in a series of recent papers by Prof. Mordijck and Dr. Xin Wang.

Particle confinement and the role of turbulence in DIII-D H-mode plasmas

S. Mordijck¹

¹ The College of William and Mary, Williamsburg, VA, 23187, USA

¹smordijck@wm.edu

Exploration of particle transport behavior on DIII-D shows the importance of turbulence in determining particle confinement. The density is linearly correlated with the fusion gain and thus achieving high core densities is of vital importance in order to increase the fusion product. However, with plasmas hotter than then sun in current magnetic confinement devices and future burning plasma devices such as ITER, it is impossible to fuel the plasma core directly using neutrals. As such we depend on turbulent plasma transport to fuel the core by moving particles inward from the edge (and up a gradient). In this article we will highlight how turbulence can affect density confinement and thus the eventual ability to reach high fusion gain factors in future burning plasma devices such as ITER.

Turbulent transport is gradient driven in magnetically confined plasmas relevant for fusion applications. Depending on the relative ‘strength’ of each of the gradients, such as the electron and ion temperature gradients as well as the density gradient, the drive to generate turbulence will be altered. One example of how an increase in turbulence drive can reduce confinement is observed when we use Electron Cyclotron Heating (ECH) instead of Neutral Beam Injection (NBI) Heating in DIII-D H-mode plasmas [1,2]. We observe that when ECH is injected deep in the plasma core (ρ~0.2), there is a strong reduction in the electron density which originates at the plasma edge (ρ~0.78), rather than in the core where the dominant electron heating is applied (Fig. 1a). By investigating the changes in turbulence using TGLF (a quasi-linear gyrofluid code) as well as fluctuation measurements, we observe that the reduction in particle confinement is correlated with a strong increase in turbulence activity at various scales (Fig. 1 d & 1e). TGLF modeling shows that this increase is the result of an increase in the turbulence drive (Fig. 1b).

Prior work investigating the role of ECH heating did not include the time-dependent analysis presented in this article. As such, it was concluded that the reduction in particle confinement was the result of a change in turbulence type, not an increase in turbulence drive [2,3]. When the plasma is heated using NBI, typically the Ion Temperature Gradient (ITG) is the dominant drive for turbulence. When the electron temperature gradient increases, for example using ECH, the turbulence drive changes to a combination of the electron temperature and density gradient, which is referred to as Trapped Electron Mode (TEM). This change in turbulence type is accompanied by a change in the mode frequency (or propagation direction of the turbulence). This has an important effect on particle transport through the so-called thermo-diffusive pinch, which changes sign from inward when ITG is unstable to outward when the plasma is TEM unstable. As such, prior research connected changes in confinement and transport to a change in turbulence type, when they compared NBI to ECH heated plasmas. However, the new time dependent analysis given in Figure 1b shows that this change in turbulence frequency occurs on a much slower time scale than the increase in particle transport.

While the change in turbulence type does not cause the reduction in confinement during ECH, it still affects the local electron density gradient in the plasma core. Prior theoretical work by Fable et al. [4] showed that the frequency of the largest unstable mode should correlate with the local density gradient. Fable et al. [4] found that the local density gradient reaches a maximum at the cross-over point between the ITG and TEM regimes. This is linked to the change in direction of the thermo-diffusive pinch component of turbulent particle transport. In DIII-D, we were able to experimentally confirm these results in the plasma core [5]. By adding ECH to NBI heated plasmas, we were able to alter the frequency of the dominant unstable mode from the ITG to the TEM regime. We observe experimentally that the local density gradient reaches a maximum right at the cross-over between the ITG and TEM regimes (Fig. 2).

Both these examples show that turbulence drive as well as turbulence type can strongly affect particle transport in DIII-D. Increasing the velocity shear is one option to reduce turbulence transport and another is reversing the magnetic shear. In DIII-D we can change the velocity shear without affecting the temperature profiles and thus the turbulence drive and gradients by using co- and counter-NBI to alter the injected momentum. The resulting change in the toroidal rotation then affects the E´B shear, and by comparing the turbulence drive to the E´B shearing rate we can test whether the E´B shear is strong enough to suppress and reduce turbulent transport. We find that good particle confinement is achieved when the E´B shear is larger than, or of similar magnitude to, the turbulence drive owing to enhanced decorrelation of turbulent eddies [6]. However, when the E´B shear is much smaller than the turbulence drive, we find that particle confinement is strongly reduced. In DIII-D, this occurred when the NBI injection is balanced between co and counter and thus no net external momentum is injected into the plasma.

These three recent examples indicate the importance of turbulence in determining particle confinement and thus the electron density profile. Currently, without good predictive and validated models for particle transport, the core electron density profile in ITER scenarios is assumed to be flat. These experimental observations motivate the need to development predictive transport models to better predict the electron density profile on ITER. Aside from how this affects the fusion gain, it also affects impurity accumulation in the plasma core and core Helium ash removal. One aspect that we did not address in this work is the role of fueling on the density profile. Current devices such as DIII-D are partly fueled by NBI injection, which can affect the local density gradient in the core. Furthermore, fueling from the plasma edge penetrates beyond the separatrix. However, future burning plasmas will be too opaque, i.e., ‘too dense’ for outside neutrals to penetrate into the core. Future work will focus on understanding the role that fueling plays along with turbulent transport in determining the electron density profile.

Acknowledgements

This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-SC0007880, DE-FG02-08ER54984, DE-AC05-06OR23100, and DE-FC02-04ER54698.

References

[1] S. Mordijck et al. Nucl. Fus. 55 (2015) 113025

[2] X. Wang et al. Nucl. Fus. 57 (2017) 116046

[3] C. Angioni et al. Nucl. Fus. 44 (2004) 827

[4] E. Fable et al. PPCF (2010) 52 015007

[5] X. Wang et al. Nucl. Fus. 58 (2018) 016025

[6] X. Wang et al. PPCF 58 (2016) 045026

More information concerning the ITPA may be found at the Official ITPA Website.

Summary of ITPA Integrated Operating Scenarios Topical Group meeting, April 9-11, 2018, Daejeon, South Korea

Francesca Poli, Francesca Turco

The ITPA-IOS group decided to undertake the task of writing part of the Update to the ITER Physics Basis report, which will contain a critical review of present research since 2006. It has also been proposed to populate a new Advanced Scenario database to update the previous database which is now ~15 years old [1]. During the meeting results from the main operating machines were presented, such as the achievements of the KSTAR advanced scenario development and heating & current drive (H&CD) system upgrades; the JET program in preparation for the DTE2 2020 deuterium-tritium campaign; more advanced scenario development carried out on TCV with the new NBI system, and on DIII-D with the aid of TRANSP simulations; and the new stable zero torque ITER Baseline Scenario in DIII-D. Moreover, sessions dedicated the H&CD focused on off-axis, long pulse ECH and LH systems and the new upward-viewing NBI on KSTAR; the impact of LH antenna frequency in EAST; the progress in the new HFS LH antenna in DIII-D with its impact on the main scenarios; and a comprehensive analysis of the possibilities for plasma initiation and breakdown in ITER with ECH for pre-ionization and burnthrough.

Focus of the joint modeling activities is mostly on the ITER pre-fusion power operation (PFPO) phase. This includes modeling of plasmas in Helium and Hydrogen at 1.8T/5MA for the ITER PFPO-1 with up to 30MW of ECH and assuming up to 10 MW of ICH, although there is high concern that ICH may be not available for the PFPO-1. Modeling of plasmas with 2.65T/7.5MA is still high priority, which should be combined with experiments in Helium to assess H-mode power threshold as a function of the hydrogen dilution and ELM characteristics. Two joint activities have been started, one on the benchmarking of transport solvers that couple the core and the plasma edge and one on benchmarking of models for pellet fueling. ITER is centralizing a database of reference simulations for modelers and experimentalists, for example for diagnostics studies, including development of synthetic diagnostics.

The ITPA-IOS group encourages participation in modeling activities from the US plasma physics community. Individuals and groups interested in getting involved in joint modeling activities should feel free to contact their ITPA US representatives through the USBPO channels.

[1] A.C.C. Sips et al., 20^th IAEA-FEC (Vilamoura, Portugal, 2004), paper IT/P3-36.

USBPO Public Calendar: View online or subscribe

2018                                               

May 7-10	5th IAEA DEMO Programme Workshop	Daejon, South Korea
May 8-11	US Transport Task Force (US-TTF) meeting	San Diego, CA
May 23-25	ITPA Energetic Particles Topical Group meeting	ITER HQ, France
June 17-22	International Conference on Plasma Surface Interactions (PSI)	Princeton, NJ
June 24-28	2018 IEEE International Conference on Plasma Science (ICOPS)	Denver, CO
July 2-6	EPS Conference on Plasma Physics	Prague, Czech Rep.
Sept 11-14	EU Transport Task Force (EU-TTF) meeting	Seville, Spain
Sept 17-20	ITPA Transport & Confinement Topical Group meeting	ITER HQ, Franc
October 1-3	ITPA MHD Disruptions & Control Topical Group meeting	Napoli, Italy
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 12-18	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 4-6	ITPA Coordinating Committee & CTP ExComm	ITER HQ, France

2019

JET DT-campaign (https://www.euro-fusion.org/newsletter/jet-full-throttle/)
October 21-25	61st Annual Meeting of the APS Division of Plasma Physics	Fort Lauderdale, Florida, USA

2020

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

 

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)