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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

Director’s Corner	C.M. Greenfield
Research Highlights
Contact and Contribution Information

This will be the last issue of the USBPO eNews in 2020. On behalf of myself and the USBPO leadership, I’d like to wish you all a happy, healthy, and safe holiday!

Congratulations to Amanda Hubbard!

Recently departed USBPO Deputy Director Amanda Hubbard was presented with a 2020 Secretary of Energy’s Appreciation Award for her contributions dating back as far as 2005. The citation reads:

In recognition for your instrumental role in the formation of the U.S. Burning Plasma Organization and over a decade of leadership in several key roles of the organization including the first Council Vice Chair, the Council Chair, and finally as the Deputy Director since 2011. Your contributions have established the BPO as the national organization of scientists and engineers focused on understanding burning plasmas and ensuring the greatest benefit from a burning plasma experiment such as ITER. Your efforts have facilitated effective communication between members of the domestic fusion program and fostered strong interactions with international partners. The Office of Science in the U.S. Department of Energy deeply appreciates your contributions and service as a key member of the U.S. fusion program.

This is a very well-deserved award. Congratulations, Amanda!

FESAC Long-Range Plan presented to community

The process of producing a long-range plan for the entire FES scope of research has been completed, with a report given at a three-day long FESAC meeting by committee chair (and USBPO Council Chair) Troy Carter. The plan, entitled “Powering the Future: Fusion and Plasmas,” is an ambitious proposal including a broad program leading toward a fusion pilot plant (FPP). The ITER research program figures prominently, along with other facilities being described that together provide a basis to move to the FPP. In particular, it echoes the earlier Community Planning Process in proposing formation of a US ITER research team. How the USBPO can help to make this a reality has been a hot topic of discussion in recent Research Committee meetings. More about that in future issues…

Looking for a few good people

Each year, five of our ten topical group leaders’ terms expire. Anticipating that the current deputy leaders will each continue for an additional term, we are looking for one person to fill a leadership position in each group. Usually this would be for a deputy position, with a likely (but not automatic) promotion to leader for a second two-year term.

·       Confinement and Transport: Walter Guttenfelder’s term is ending and I am assuming Nathan Howard will continue

·       Diagnostics: Max Austin’s term is ending and I am assuming Calvin Domier will continue

·       Integrated Scenarios: Francesca Turco’s term is ending and I am assuming Devon Battaglia will continue

·       MHD, Macroscopic Plasma Physics: Carlos Paz-Soldan’s term is ending and I am assuming Nate Ferraro will continue

·       Modeling and Simulation: Xueqiao Xu’s term is ending and I am assuming Sterling Smith will continue

More information about these positions and the process of filling them, is available at https://www.burningplasma.org/organization/?article=Charter%20and%20Bylaws.

If you'd like to nominate somebody (yourself, your friends, or even your enemies!) for one of these positions, please email me at greenfield@fusion.gat.com. A short justification would be helpful. There are a number of items we will consider in selecting a slate, including scientific qualifications and institutional balance. This could also be a good opportunity for an early-career scientist to get involved.

Looking forward to next month, we should be holding a USBPO Council election as well.

The plasma material interface in a fusion reactor represents a grand challenge for fusion. The MPEX device highlighted here will offer the opportunity for rapid testing of materials under near reactor conditions.

Overview and status of the
Material Plasma Exposure eXperiment (MPEX)

Arnold Lumsdaine¹, Juergen Rapp¹, Phil Ferguson¹, and the MPEX team

¹Oak Ridge National Laboratory, Oak Ridge, TN, USA

Author email: lumsdainea@ornl.gov

The availability of future fusion devices such as a Fusion Pilot Plant (FPP) greatly depends on the long operating lifetime of plasma-facing components (PFCs) in their divertors. The development of these PFCs and materials requires facilities for testing them at reactor relevant conditions. This includes relevant divertor plasma parameters (n_e~10²¹ m^-3, T_e=1-15 eV) plasma fluxes of 10²⁴ m^-2s^-1, lifetime relevant fluence of ~10³¹ ions/m², high PFC ambient temperature and relevant displacement damage as a result of neutron irradiation. Unfortunately, no existing facility, whether a toroidal or linear plasma device, can conduct the testing under those conditions. Hence, developing the science of plasma-material interactions and the technology of plasma-facing material components will require new facilities. Because next-stage development of plasma-facing materials, underpinned by a fundamental understanding of how prototypical plasmas interact with surfaces, is critical to future fusion systems, new experimental facilities capable of carrying out this research are required.

The Material-Plasma Exposure eXperiment (MPEX), a superconducting magnet, steady-state device, is currently in preliminary design at Oak Ridge National Laboratory (ORNL) to address these conditions. This device, as designed, will have the unique feature of being able to conduct accelerated lifetime tests of PFCs, including those that have experienced neutron damage. MPEX will utilize a new high-intensity plasma source concept based on RF technology. This source concept will allow coverage of all expected plasma conditions in the divertor of a future fusion reactor, including very high densities. It will be able to study erosion and redeposition in geometries with relevant electric and magnetic fields in front of the target. The source system will consist of a helicon antenna for high-density plasma production. This plasma will be subsequently heated by Electron Bernstein Waves and Ion Cyclotron Resonance heating. The total heating power will be up to 1000 kW. The device is sized based on extensive plasma-neutral modeling with state-of-the-art codes, which are also used for the design of the ITER and the W7-X divertors. The plasma production and heating schemes were modeled as well as tested in the Proto-MPEX facility [1,2], which led to the definition of the magnetic field profile. The target section of the device (surface analysis chamber and target chamber) was designed to allow for impurity contamination control with docking station concepts. MPEX will be a world-leading plasma-material interaction facility for the testing and development of viable plasma-facing components for next step fusion devices.

Figure 1. CAD model of the MPEX device.

The MPEX project is being managed according to DOE Order 413.3b, the order defining the program and project management for the acquisition of capital assets. The order defines a series of Critical Decisions (CD) for the various stages of a project. Requirements on the MPEX systems and components flow down from the function on MPEX that is detailed in the CD-0 Mission Need document. A summary of the functional requirements for the facility are:

·       Steady-state magnetic fields up to 2.5 T

·       Steady-state operation of up to 10⁶ sec

·       Ability to reach adequate neutral pressure in different axial locations to achieve plasma production, electron and ion heating, and simultaneously keep the pressure in the PMI chamber in the range of 1–10 Pa

·       Ability to expose radioactive and hazardous materials such as a priori neutron-irradiated materials (irradiated up to 50 dpa) and liquid metals

·       Ability to expose large PFCs (~60 × 600 mm) at magnetic fields of 1 T at the target

·       Ability to expose targets at an angle as low as 5 degrees

·       Ability to monitor evolution of the surface during high-fluence exposures with a variety of surface diagnostics (some in situ and some in vacuo) including electron microscopy (in vacuo)

MPEX is a steady-state linear plasma device. It has magnetic field coils arranged such that it produces a linear magnetic configuration between the plasma and heat source and the target (see Fig. 1). The magnetic field varies along the linear axis. The magnetic field at the target can reach 1 T. The magnetic field in other parts of the linear system is determined by the plasma production and heating systems. The steady-state magnetic field for most of the device is produced by superconducting magnets placed in several cryostats. The plasma is created by a high-power helicon antenna, which can produce deuterium plasmas with electron densities in excess of 10²⁰ m^-3. The deuterium plasma is heated with microwaves and RF waves in axial locations between the helicon and the target.

The main plasma is a deuterium plasma; however, other gases (and gas mixtures) are expected to be injected as trace impurities or main plasma constituents in special applications. The gas may be fed in several axial locations, close to the helicon antenna and the target. The pumping systems are dimensioned to provide a steady-state neutral pressure in the plasma production, the plasma heating and the target section, which ensures adequate heating conditions and appropriate divertor plasma conditions in front of the target.

Figure 2. MPEX plasma source and heating and vacuum systems components.

The MPEX device with the magnet systems removed is shown in Fig. 2. The PMI chamber is designed such that it optimizes diagnostic access for PMI investigations. The target is introduced by a manipulator from a versatile target exchange chamber, which docks to the PMI chamber. The baseline target exchange chamber is designed to transfer targets from the PMI chamber to a dedicated surface analysis station and is equipped to exchange irradiated material samples via a remote-handling system. The target exchange chamber will be a user-driven system. For example, the baseline target exchange chamber could be swapped out with any other compatible user-supplied target exchange chamber.

The design activities for MPEX are broken down into the following systems:

·       Plasma source and heating system

·       Magnet system

·       Vacuum system

·       Cooling system and in-vessel components

·       Instrumentation and control systems

·       Diagnostics

·       Infrastructure

The MPEX conceptual design was completed in mid-2019 [3]. Details on many MPEX systems and components have been previously published, including the magnet system [4], vacuum systems [5], target [6], helicon plasma source [7], and in-vessel components [8]. MPEX received CD-1 approval in February 2020, and preliminary design began at that time. On October 29, 2020, approval was given to begin the procurement of items that were necessary due to long lead times: the magnet systems, gyrotrons and high-voltage power supply, and facility preparation. According to the current schedule (including contingency), MPEX will complete device commissioning in 2026.

References

[1] J. Rapp, C. Lau, A. Lumsdaine, C.J. Beers, T.S. Bigelow, T.M. Biewer, T. Boyd, J.F. Caneses, J.B.O. Caughman, R. Duckworth, R.H. Goulding, R. Hicks, N. Kafle, P.A. Piotrowicz, D. West and the MPEX Team, “The Materials Plasma Exposure eXperiment (MPEX): Status of the physics basis together with the conceptual design and plans forward,” IEEE Transactions on Plasma Science, Vol. 48, No. 6, pp. 1439-1445, 2020.

[2] J. Rapp, A. Lumsdaine, C.J. Beers, T.M. Biewer, T.S. Bigelow, J.F. Caneses, J.B.O. Caughman, R.H. Goulding, N. Kafle, C. Lau, E. Lindquist, P. Piotrowicz, H.B. Ray, M. Showers, and the MPEX team, “Latest Results from Proto-MPEX and the Future Plans for MPEX,” Fusion Science and Technology, Vol. 75, No. 7, pp. 654-663, October 2019.

[3] J. Rapp, A. Lumsdaine, C. Beers, T. Biewer, T. Bigelow, T. Boyd, J. Caneses, J. Caughman, R. Duckworth, R. Goulding, W. Hicks, C. Lau, P. Piotrowicz, D. West, D. Youchison, and the MPEX team, “The Material Plasma Exposure eXperiment: Mission and Conceptual Design,” Fusion Engineering and Design, Vol. 156, July 2020, 111586.

[4] R.C. Duckworth, E.E. Burkhardt, A. Lumsdaine, J. Rapp, W.R. Hicks, T. Bjorholm, W.D. McGinnis, M. Anerella, R. Gupta, J. Muratore, P. Joshi, J. Cozzolino, P. Kovach, A. Marone, S. Plate, K. Amm, and J.A. Demko, “Conceptual Design and Performance Considerations for Superconducting Magnets in the Material Plasma Exposure eXperiment,” IEEE Transactions on Plasma Science, Vol. 48, No. 6, pp. 1421-1427, 2020.

[5] A. Lumsdaine, S. Meitner, V. Graves, C. Bradley, C. Stone, T. Lessard, D. McGinnis, J. Rapp, T. Bjorholm, R. Duckworth, and V. Varma, “Vacuum System and Modeling for the Materials Plasma Exposure Experiment,” Fusion Science and Technology, Vol. 72, No. 4, pp. 581-587, 2017.

[6] A. Lumsdaine, J.B. Tipton, D.L. Youchison, V. Varma, K. Logan, and J. Rapp, “High Heat-Flux Target Design for the Materials Plasma Exposure eXperiment,” Fusion Science and Technology, Vol. 75, No. 7, pp. 674-682, October 2019.

[7] A. Lumsdaine, S. Chakraborty Thakur, J. Tipton, M. Simmonds, J. Caneses, R. Goulding, D. McGinnis, F. Tynan, J. Rapp, and J. Burnett, “Testing and Analysis of Steady-State Helicon Plasma Source for the Material Plasma Exposure eXperiment (MPEX),” submitted to Fusion Engineering and Design, October 2019.

[8] A. Lumsdaine, C. Luttrell, D. McGinnis, K. Logan, R. Hicks, S. Meitner, J. Rapp and the MPEX team, “Conceptual Design and Analysis of In-Vessel Components for the Materials Plasma Exposure eXperiment (MPEX),” IEEE Transactions on Plasma Science, Vol. 48, No. 6, pp. 1446-1451, 2020.

 

Calendar of Burning Plasma Events

2020

JET DT-campaign (https://www.burningplasma.org/resources/ref/Web_Seminars/Litaudon-JET-%202019-05-02-vf.pdf)

JT-60SA First Plasma (http://www.jt60sa.org/)

 

2021

Jan 24-29, 2021	International Conference on Plasma Surface Interactions	Jeju, South Korea Virtual
May 10-15, 2021	28th IAEA Fusion Energy Conference (FEC2020)	Nice, France
June 21-25, 2021	EPS 47th Conference on Plasma Physics	Sitges, Spain
Sep 7-10, 2021	25th Joint EU-US Transport Task Force Meeting	York, UK
Nov 8-12, 2021	63rd Annual Meeting of the APS Division of Plasma Physics	Pittsburgh, PA, USA