News and Events


U.S. Burning Plasma Organization eNews
May 31, 2016 (Issue 108)


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
A. Tinguely, et al.
Schedule of Burning Plasma Events  
Contact and Contribution Information

Announcements

DOE recommedation for US-ITER participation/strong>

The FY 2016 Budget Appropriations Acts directed the Secretary of Energy to submit a report recommending either that the United States remain a partner in the ITER project after October 2017 or terminate participation, which shall include, as applicable, an estimate of either the full cost, by fiscal year, of all future Federal funding requirements for construction, operation, and maintenance of ITER or the cost of termination.

This report is now publicly available at http://science.energy.gov/fes/.

Director's Corner

by C.M. Greenfield

Happy birthday to us!

This year marks the tenth anniversary of the beginning of operations of the US Burning Plasma Organization. The first USBPO Council meeting was held in April 2006 and the first Research Committee meeting in June, but the genesis of the organization goes back to May of 2005, when OFES commissioned Ray Fonck to form the USBPO with a mission to:

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.

The path that got us to that point, of course, goes back to the beginning of fusion research in the 1950s, but for many of us, it really started moving ahead in 2002. That was when the U.S. fusion research community gathered at Snowmass, Colorado for a Fusion Summer Study. That assembly concluded the study of burning plasmas, in which self-heating from fusion reactions dominates plasma behavior, is at the frontier of magnetic fusion energy science. The next major step in magnetic fusion research should be a burning plasma program, which is essential to the science focus and energy goal of fusion research. A year later, a decision was taken for the United States to rejoin the ITER project, reflecting optimism that ITER would provide a superb laboratory for studies of the burning plasma state.

The USBPO's beginnings in 2005 looked forward to the opportunities that we anticipated from ITER, both with the new challenges presented by the self-heating nature of a burning plasma and the promise of a major step toward fusion energy. In December, 2005, we gathered at Oak Ridge National Laboratory for a Burning Plasma Workshop, dedicated to identifying scientific and technical questions needing resolution as we prepared for ITER.

Following this workshop, the USBPO undertook its first task group, developing a community response to the Energy Policy Act of 2005, specifically identifying how the U.S. Fusion Community anticipated participating in the ITER program. This is a topic that has been repeatedly revisited by the USBPO, most recently with last year's Modes of Collaboration in ITER report. The early USBPO also took a leading role in coordinating U.S. participation in the ITER design review.

Moving forward to today, the mission of the U.S. Burning Plasma Organization has not changed, and I believe the conclusion made at the 2002 Snowmass Fusion Summer Study is as true today as it was then. As we all know, our burning plasma has not yet been delivered, and has suffered delays. But, as we just heard from Secretary Moniz, there is reason for confidence that ITER can and will be successful, albeit at a somewhat later date than originally anticipated.

With this in mind, we are reevaluating the goals and activities of the USBPO. We are not reevaluating the mission, which we believe is still appropriate. But with ten years of experience under our belts, and a rather longer than anticipated lead-time for ITER, it is time for an update of what we're doing with our hands and feet to accomplish that mission, together.

Happy birthday to us!

Progress at ITER

As promised, I attended the ITER STAC-20 meeting this month, along with Rob Goldston (PPPL), Earl Marmar (MIT), Juergen Rapp (ORNL), Jim Van Dam (DOE), and our counterparts representing each of the other ITER parties. Although it's difficult to tell from the photo, visible progress on the ITER site has increased so that there's something new to see every time I'm there. Unfortunately, we held this meeting in a rather compressed two days, and did not have an opportunity to go out on the construction site for a tour.

At this meeting, the STAC responded to the following three charges (condensed version) with our report going to the ITER Council during their meeting on June 15-16.

  1. Assess progress in the design and R&D for the in-vessel coils (Vertical Stabilization and ELM control coils)
  2. Review the development of disruption mitigation scenarios with the support of the ITER Members' community of experts and progress on the design of the DMS including specifications, manufacturing and commissioning plan for possible testing in JET, etc.
  3. Review the status of the vacuum vessel pressure suppression system design.

As I told you last month, the first two charges are heavily informed by research performed at US facilities on RMP ELM control (charge 1) and disruption mitigation (charge 2). Significant progress has been made in all three areas, but, as you might expect, open areas remain and some of these issues will be revisited later.

Figure 1: The ITER site in May, 2016. The large building in the center-right is the Assembly Hall.

Perhaps the biggest issue we've all been hearing about is the schedule. The STAC was given a report on this, but was not asked to comment. We anticipate the ITER Council adopting the schedule at its June meeting, and that the STAC will be asked to comment on implementation of the plan at its October meeting in Japan. USBPO activities at the APS-DPP Conference

For the eighth time, last year's APS Division of Plasma Physics annual meeting included a contributed oral session on "Research in Support of ITER," which included 15 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 58th Annual Meeting of the Division of Plasma Physics, which will take place in San Jose, California, on October 31-November 4. 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 ßtandard" 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. 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 27) to Amanda Hubbard (hubbard@psfc.mit.edu). 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 July 1, 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 July 15. If your talk is accepted for this session, please indicate "Research in Support of ITER" in the placement requests box.

Thank you for your help in arranging a strong session on Burning Plasma research.

We are also hoping to once again organize a Town Meeting on ITER as we have in the past. We are not always able to do this due to competition from the November ITER Council meeting and IAEA (in even years). We have made some invitations for excellent speakers; watch for an announcement later.

US Burning Plasma Organization Council election

We ask your help to identify nominees for new members of the USBPO Council. As described in the bylaws, each year two new Council members will be elected by the USBPO regular membership, and two will be appointed by the USBPO Director (Chuck Greenfield, GA). The members each serve a three-year term. Four Council members are now completing their terms: Larry Baylor (ORNL), Mark Koepke (chair, West Virginia U), David Maurer (Auburn), and Dan Thomas (GA). The continuing Council members are David Brower (UCLA), Stan Kaye (PPPL), Chuck Kessel (vice chair, PPPL), Earl Marmar (MIT), David Pace (GA), Juergen Rapp (ORNL), Susana Reyes (LLNL), Jim Terry (MIT), and François Waelbroeck (U Texas). The terms of the continuing members as well as a list of ex-officio members can be found at /organization/?article=Council. The following Council members have agreed to serve on the nominating committee: Dan Thomas [chair], David Maurer, Susana Reyes, Francesca Poli, and Jim Irby.

Note that the bylaws prohibit having more than two members from a single institution. As we already have two continuing members from each of PPPL and MIT, we will not be able to consider any candidates from those institutions. As background, the USBPO bylaws (/organization/?article=Charter%20and%20Bylaws) define the role of the Council: "The Council represents the U.S. MFE research community in providing oversight of the USBPO activities, and, working with the Directorate, is the primary USBPO element responsible for long-term strategic planning of burning plasma research. The Council is responsible for setting the policies and procedures of the USBPO, including establishing the by-laws governing USBPO operations. It will receive regular reports on USBPO activities from the Director, and will provide feedback and assessment on those activities to the Director regarding progress, issues, priorities, and opportunities. When required, a simple majority vote of the Council shall serve to designate Council approval of a decision. When Council comment and recommendations are required, the Council Chair and/or Vice-Chair will work to convey the sense of the Council to the Director and the OFES."

Your nominations are critically important to guide the USBPO and its contribution to the U.S. Fusion Energy Sciences Program. Nominees for Council must come from among the USBPO regular membership.

Schedule for this year's election process:

  1. By close of business June 10: Email your nomination(s) to Dan Thomas thomas@fusion.gat.com
  2. June 20-July 1: Election by USBPO regular members from a slate of candidates using web-based poll software (to be described in a later email)
  3. July 14: USBPO announces the new Council members, both elected and appointed

Please participate in this nomination process, and later in the election.



Research Highlight

Topical Group, Leaders: Bob Granetz and Steve Sabbagh

Disruptions at full performance in ITER are predicted to generate damaging beams of relativistic electrons. In order to qualify mitigation strategies, it is necessary to understand the basic physics of runaway electrons in tokamaks, particularly the maximum energy they may achieve. Research on this issue is being carried out on Alcator C-Mod, by studying the synchtrotron radiation that runaways emit.

Analysis of Runaway Electron Synchrotron Emission in Alcator C-Mod


A. Tinguely 1, R. Granetz 1 and A. Stahl 2
1 MIT Plasma Science and Fusion Center, Cambridge, Massachusetts, 02139, USA
2 Department of Applied Physics, Chalmers University of Technology, SE-41296, Gothenburg, Sweden

Figure 1. Synchrotron emission (bright blob on right side of image) from relativistic electrons during a very low density discharge in Alcator C-Mod. The lack of symmetry between the left and right sides of the image proves that the emission is forward-peaked (Ip is CCW), and therefore not due to other radiation mechanisms such as bremsstrahlung, recombination, or line radiation.

In a plasma, particles "run away" at relativistic speeds when the acceleration due to the toroidal electric field overcomes their collisional friction with the background plasma. In tokamaks, so-called runaway electrons (REs) can occur during the current quench of a disruption, or in very low density discharges. The runaway electrons (RE) can gain energies of tens of MeV and carry as much as 60   % of the total plasma current [1]. If confinement of an RE beam is lost, plasma-facing components can be severely damaged, interrupting operations and requiring repairs. Thus, understanding the evolution of REs as a function of plasma parameters is of interest not only to basic plasma physics, but also for the prevention and mitigation of REs in magnetic fusion devices.

In Alcator C-Mod, REs created during low-density discharges have been observed to reach energies up to  ∼ 30   MeV, emitting forward-peaked synchrotron radiation (SR) in the visible wavelength range (Fig 1). Two spectrometers, with spectral ranges of  ∼ 350–1020   nm, have been absolutely calibrated to measure SR brightness, which increases with RE energy and background magnetic field, among other factors. Recent theoretical studies [2-4] predict that REs will accelerate to a maximum energy at which the SR reaction force and collisional friction balances the electric force, forming a "bump" on the tail of the energy distribution function. Our goal is to experimentally determine whether or not these predictions that SR power really is limiting the maximum energy of the RE energy distribution are true.

Figure 2. Measured synchrotron spectrum (after applying absolute calibration) is shown in blue. Red and green curves show the best fits for synthetic spectra calculated for a theoretically-derived mono-energetic RE distribution, and for a theoretically-derived continuum distribution, respectively.

We are analyzing our measured SR spectra and comparing the observed SR spectra to the spectra calculated from both mono-energetic and continuum distributions to see if we can determine whether or not our RE energy distributions are monotonically continuous (no bump on tail), or mono-energetic (large bump on tail). So far, we are finding that both models fit the data equally well (Fig 2). For a C-Mod plasma in a toroidal magnetic field of 5.4   T, REs are determined to have energies as high as 28 MeV, and carry a current of only  ∼ 100  A in a 1.0   MA flattop plasma current. However, although the analytic spectral fits done so far have not been able to discriminate between the different models, we are looking into other aspects of the SR spectral data, such as its temporal evolution during a discharge, and comparisons between spectra in different discharges. These additional observations seem to support the conjecture that synchrotron emission may be limiting the maximum RE energy.

As a result, we are continuing to work closely with the theory community to better understand the validity of these models. Later this summer we plan to generate runaways and synchrotron emission spectra at different magnetic field strengths (2.7, 5.4, and 8.0 T) to further compare theoretical predictions to experiment.

References

[1] V.V. Plyusin et al. Nucl. Fusion 46 271, 2006.
[2] P Aleynikov and B.N. Breizman Phys. Rev. Lett. 114 155001, 2015.
[3] J. Decker et al. Plasma Phys. Control. Fusion 58 025016, 2016.
[4] E. Hirvijoki et al. Journal of Plasma Physics 81 3, 2015.


Schedule of Burning Plasma Events

USBPO Public Calendar: View Online or Subscribe

2015  - NSTX-U First Plasma - August 10 - W7-X First Plasma - December 10 -
2016  - 10th Anniversary of USBPO Formation -
May 30 - June 3, PSI Conference, Rome, Italy
June 5 - 9, High Temperature Plasma Diagnostics Conference, Madison, Wisconsin, USA
June 19-23, International Conference on Plasma Sciences, ICOPS, Banff, Alberta, Canada
June 27- July 1, 18th International Congress on Plasma Physics (ICPP2018), Kaohsiung, Taiwan
July 4-8, European Physical Society Conference on Plasma Physics (EPS), Leuven, Belgium
September 4-8, Joint EU-US Transport Task Force Meeting, Leysin, Switzerland
October 13-15, ITER STAC Meeting, Kizu, Japan
October 17-22, 26th IAEA Fusion Energy Conference, Kyoto, Japan
October 24-26, ITPA T&C, 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
December 13-14, 37th Fusion Power Associates Annual Meeting and Symposium, Fusion Power Development: An International Venture
2019  - JET DT-campaign - JT60-SA First Plasma

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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: Saskia Mordijck (mordijck@fusion.gat.com)

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