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.
Director’s Corner C.M. Greenfield Research Highlight N.J. Fish Schedule of Burning Plasma Events Photograph of the Month Contact and Contribution Information
Remembering Cynthia Phillips
We were extremely saddened this month to learn of the death of Dr. Cynthia
Phillips. For those who had not heard the news, Cynthia died on September 1
after a decade long battle with cancer. She was well known to many around the
world as a leading expert in RF physics, and a wise voice in the fusion
community. A nice description of her career and personal qualities prepared
by her colleagues at PPPL can be found
We would like to add our acknowledgment and appreciation of the many contributions Cynthia made to the U.S. Burning Plasma Organization. She was very involved in its formation and early leadership. Before, during and after the U.S. Burning Plasma Workshop at ORNL, in Dec. 2005, she argued strongly and persuasively for the need for a topical group on Plasma-Wave Interactions, making the case that this is a distinct community of experts that is not adequately represented in ITPA. It is largely thanks to Cynthia that this topical group exists, and so when the USBPO was launched the following year she was, appropriately, appointed as its first leader. At that time Amanda served as Vice Chair of the Council and Chuck served along with Cynthia on the Research Committee. Many formative decisions were made in that period, and Cynthia shared her wisdom and commitment with the organization. Following the end of her term as topical group leader, she was asked to serve on the USBPO Council, where she again provided much valuable input from 2010-2013. Whether at a meeting, or in a private conversation or email, we always appreciated her advice. We will greatly miss her advice and friendship.
by C.M. Greenfield
US Burning Plasma Organization Council Election
I am happy to announce the results of the recent USBPO Council
election, during which Earl Marmar of MIT and David Pace of General
Atomics were elected. Earl and David were selected from an excellent
slate of candidates that had been put together by our nominating
committee (Ted Biewer, Chuck Kessel, Xianzhu Tang, Dan Thomas and Anne
White) based on your suggestions. Following the election, and in
accordance with the USBPO bylaws, I appointed two additional members
to fill out the Council. They are Stan Kaye of Princeton Plasma
Physics Laboratory and Susana Reyes of Lawrence Livermore National
I look forward to serving with the new Council, and wish to thank the
outgoing members: Jon Menard, Anne White, and Clement Wong. In
accordance with the USBPO bylaws, Mark Koepke's term on the Council is
being extended for one more year to allow him to complete his term as
chair. The 2015-2016 USBPO Council is then as follows (last column is
the year their term ends):
|Mark||Koepke||West Virginia U||Chair||2016|
Our selection of new topical group leaders and deputy leaders is
nearly complete, and will be announced in next month's eNews.
Progress at ITER
Visiting the ITER site several times each year gives me a chance to
see occasional snapshots of the facility as it rises from (and below)
the ground. During my last couple of visits I watched as the pillars
that will support the ITER Assembly Building were erected. Since my
last visit in May, the pillars have been completed and, this month,
the roof structure, comprised of 730-tons of steel, was raised into
place. The process took 14 hours, as 22 hydraulic jacks lifted the
roof structure to a height of 50 meters.
The ITER Assembly Building before (left) and after (right) the roof was lifted into place. Photos © ITER Organization.
Preparations are currently underway for the nineteenth meeting of the ITER
Science and Technology Advisory Committee (STAC-19). Once again, the US
participants will be Rob Goldston (PPPL), Earl Marmar (MIT), Juergen Rapp
(ORNL), Jim Van Dam (DOE) and myself. We will consider the following charges
- Assess the technical aspects of the Updated Long-Term Schedule
- Assess progress on the resolution of neutronics issues, including cost and schedule impact
- Assess progress in several aspects of the in-vessel coils (for vertical stabilization and ELM control)
STAC-19 will produce a report that will provide input to the ITER Council at its November meeting. Similarly, the Management Advisory Committee (MAC) will meet in a few weeks to develop its own report.
The eighth annual Research in Support of ITER contributed oral session will be held on Thursday morning, November 19, during the upcoming annual meeting of the APS Division of Plasma Physics. This year's agenda is as follows:
|Joseph Snipes||ITER||ITER Plasma Control System Development|
|Eugenio Schuster||Lehigh University||Nonlinear Control and Online Optimization of the Burn Condition in ITER|
|Menno Lauret||Lehigh University||Sawtooth period control by power modulation|
|Antonius J. Donne||EUROfusion||Risk mitigation for ITER by a prolonged and joint international operation of JET|
|R.A. Moyer||UC San Diego||Testing RMP ELM suppression models in low torque ITER Baseline Scenario|
|Guosheng Xu||Chinese Academy of Sciences||Advances in ELM control towards long-pulse H-mode plasmas on EAST|
|S. Brezinsek||FZJ||ELM-induced W sputtering sources in JET|
|Larry Baylor||ORNL||Application of Pellet Injection to Mitigate Transient Events in ITER|
|R. Granetz||MIT||Disruption Mitigation of Plasmas with Locked Modes|
|R.J. La Haye||General Atomics||Effect of thick blanket modules on neoclassical tearing mode locking in ITER|
|Mike Dunne||IPP-Garching||Predictive modelling of the impact of a radiative divertor on pedestal confinement on ASDEX Upgrade|
|B.A. Grierson||PPPL||Time Dependent Predictive Modeling of DIII-D ITER Baseline Scenario using Predictive TRANSP|
|Junya Shiraishi||Japan Atomic Energy Agency||Status of the ITER plasma modeling activities in JAEA|
|G.M. Staebler||General Atomics||The Impact of Zonal Flows on the Performance Predictions for ITER|
|E.J. Doyle||UCLA||Progress in the Design and Development of the ITER Low-Field Side Reflectometer (LFSR) System|
We look forward to another in a series of well-attended sessions highlighting
compelling results that support ITER reaching its technical goals.
The USBPO will not be hosting a town meeting at this year's conference. However, the Thursday evening slot we would normally fill will instead be devoted to reports on the recent Community Workshops. Please refer to the conference agenda for more information.
ITER International School
This year's ITER International School will be held on December 14-18, at the
University of Science and Technology in Hefei, China. The topic will be
Transport and Pedestal Physics in Tokamaks. More information can be found
We are once again planning to organize a scholarship program for several
postdocs and graduate students. We will announce this soon.
Integrated Scenarios Topical Group, Leaders: D. Green and R. Pinsker
This month's Research Highlight summarizes recent theoretical
work by Nathaniel Fisch on possible applications of the Lower-Hybrid
wave to enable the channeling of power from fusion born alphas to
the fuel ions via wave-particle interactions (Alpha Channeling).
Such channeling may lead to the desirable property of higher ion
temperatures (relative to electron temperatures) in Tokamak
The Alpha Channeling Effect
N.J. Fisch 1
1Princeton Plasma Physics Laboratory, Princeton, New Jersey USA
Alpha particles born through fusion reactions in a tokamak reactor slow down
mainly through collisions with electrons. By collisions also mainly with the
electrons, the fuel ions then reach thermonuclear temperatures, sustaining the
fusion reaction. But, with power flow in this direction, the electrons would
then necessarily be hotter than the fuel ions. It would, however, be highly
desirable in a self-sustained tokamak fusion reactor that ions be hotter than
electrons. After all, without contributing to fusion reactions, the electrons
take up valuable pressure that could otherwise be reserved for ions. With
ions hotter than electrons, the fusion reactivity is higher at constant
confined pressure. Also, the electron heat losses, such as through radiation
or transport, are difficult to control, and the lost energy will not then be
captured by the fuel ions. Thus, it would be highly useful if the fuel ions
might directly capture the alpha particle energy, rather than relying on the
electrons as an intermediary.
Power flow in fusion reactors. The normal power flow follows the green arrows, as α particles predominantly slow down on electrons. The electrons then heat the fuel ions on a collisional time scale. Under α channeling, this flow is disrupted. The red arrows indicate the flow of power when waves channel power from α particles to energetic fuel ions on a collisionless time scale. On a collisional time scale, the energetic fuel ions then equilibrate with the bulk fuel ions, which then heat the electrons.
Fortunately, although the α particles predominantly lose their energy
to electrons, that process could in a tokamak reactor take up to hundreds of
milliseconds. That leaves time for waves to extract energy from the α
particles on a collisionless timescale . Thus, this energy
might instead be channeled into useful energy, catalyzed by injected waves,
so as to heat fuel ions or to drive current. The way that channeling might
happen is depicted schematically in Fig. *. If this can be done
quickly then a further advantage is that the α particle energy would
also not be available to destabilize toroidal Alfven modes and other waves, in
a way deleterious to energy confinement.
The interaction between waves and α particles is expected to be
stochastic; in other words, the α particles randomly gain or lose
energy in interacting with the wave, resulting in diffusion in energy. It is
also possible that the random gain or loss of energy is accompanied by a
change in position related to the energy change, resulting in diffusion in
energy in a way that is strictly coupled to diffusion in space. If these
diffusion paths in energy-position space point from high energy in the center
of the tokamak to low energy on the periphery, then α particles will be
cooled while forced to the periphery. The energy from the α particles
is absorbed by the wave. The amplified wave can then heat ions or drive
current. This process or paradigm for extracting α particle energy
collisionlessly has been called Òα channelingÓ. While the effect is
speculative, the upside potential for economical fusion is
Since α-particles are born at 3.5 MeV, with spatial localization at the center of
the tokamak, there is the opportunity for such an inverted energy
distribution. However, for energy extraction by an electrostatic wave, the
diffusion in energy must be coupled to diffusion in space, since the
projection of an isotropic velocity distribution along any one velocity
direction is not inverted. However, there are few high energy α
particles at the periphery, so diffusion paths in energy-position space can
readily produce the inversion.
There were a number of interesting experiments performed on TFTR in the 1990's
that showed that mode-converted ion Bernstein waves could produce diffusion
paths in energy-position space. However, in those experiments, since there
were few fusion-produced α particles, the wave parameters were chosen
so that the diffusion paths connected cold in the center with hot on the
periphery, diffusing 80 keV beams of deuterium ions so that they could be
detected at 2.2 MeV at the periphery [,]. This was
of course not the cooling effect desired, but it did show that in principle
the diffusion paths could operate as expected. There is reason to expect that
this effect could be extrapolated to reactors using a combination of
Orbit of an α-particle in a uniform z-directed (into the paper) magnetic field. An electrostatic wave, traveling with phase velocity ω/ky in the ∧y-direction gives an impulse at the resonance point ω = ky vy. If the particle gains energy, it moves to the red orbit; if it loses energy, it moves to the green orbit.
To see that diffusion in energy can be strictly correlated to diffusion in
space, consider the α-particle orbits in Fig. *. For simplicity, we
consider cylindrical geometry. Here an electrostatic wave, with phase
velocity in the ∧y-direction diffuses α-particles such that if the particle
gains energy it moves up (larger x), and if it loses energy, it moves down.
The interaction can be repeated, with the guiding center moving up with
increasing energy and down with decreasing energy of the α-particle. By associating
the up direction with the tokamak center, and down with the periphery, this
accomplishes the basic idea of the α-channeling effect.
What are some current trends in α-channeling research?
One is to recognize that the paradigm also operates more generally in other
configurations of magnetically confined plasma. In different machines,
different waves would be appropriate. Alpha channeling can be practiced in
particular in mirror machines, where the concept of plasma periphery now
includes the loss cone in velocity space . In supersonically
rotating plasma, there is additional axial confinement due to the rotation,
and there is also the opportunity to store energy in the plasma potential. A
generalization of the channeling effect, in which some of the particle energy
ends up in electric potential energy, can be useful in such centrifugal
confinement devices for fusion . In fact, waves with low
frequency, which includes a fixed azimuthal perturbation (zero frequency), can
be used instead to support the radial potential .
This (generalized) channeling effect might then be used to replace the
electrodes that produce the radial potential, which would be advantageous
technologically in rotating plasma devices such as plasma
A second trend is to identify how α channeling works together with
other tokamak procedures. For example, oscillating the current drive on a
slow time scale in a tokamak, but fast compared to the L/R timescale, while
varying other parameters, produces extraordinary current drive efficiencies.
It turns out that this prescription for optimizing the current drive
efficiency works synergistically with the α channeling
effect . Here, the α channeling is employed to
produce a hot ion mode in the low density phase of the oscillating
resistivity. A second example of this trend is the extent to which the same
wave used to extract α particle energy can also be used for current
drive. It turns out that there is a strong constraint relating current drive
by lower hybrid waves and α channeling by lower hybrid
waves . It is possible to accomplish both with the same wave, most
readily through inside launch of the lower hybrid wave.
This work was supported by the U.S. DOE under Contract No. DE-AC02-09CH11466.
-  N. J. Fisch and J. M. Rax, Phys. Rev. Lett. 69, 612 (1992).
-  N. J. Fisch and M. C. Herrmann, Utility of Extracting Power from Alpha Particles by Waves, Nucl. Fusion 34, 1541 (1994).
-  N. J. Fisch and M. C. Herrmann, A Tutorial on Alpha Channeling, Plasma Physics and Controlled Fusion 41, A221 (1999).
-  N. J. Fisch, Physics of alpha channelling and related TFTR experiments, Nuclear Fusion 40, 1095 (2000).
-  N. J. Fisch and M. C. Herrmann, Alpha Channeling with Two Waves, Nuclear Fusion 35, 1753 (1995).
-  M. C. Herrmann and N. J. Fisch, Cooling energetic alpha particles in a Tokamak with waves, Phys. Rev. Lett. 79, 1495 (1997).
-  N. J. Fisch, Alpha Channeling in Rotating Plasmas, Phys. Rev. Lett. 97, 225001 (2006).
-  A. J. Fetterman and N. J. Fisch, Alpha Channeling in Rotating Plasmas, Phys. Rev. Lett. 205003, 612 (2008).
-  A. J. Fetterman and N. J. Fisch, Alpha channeling in rotating plasma with stationary waves, Phys. Plasma 17, 042112 (2010).
-  A. J. Fetterman and N. J. Fisch, Wave-particle interactions in rotating mirrors, Phys. Plasma 18, 055704 (2011).
-  N. J. Fisch, Transformer Recharging with Alpha Channeling in Tokamaks, J. Plasma Phys. 76, 627 (2010).
-  I. E Ochs, N. Bertelli and N. J. Fisch, Coupling of alpha channeling to parallel wavenumber upshift in lower hybrid current drive, Phys. Plasma 22, 082119 (2015).
-  N. J. Fisch and M. C. Herrmann, Utility of Extracting Power from Alpha Particles by Waves, Nucl. Fusion 34, 1541 (1994).
C-Mod (Greg Wallace and Bob Mumgaard): Lower hybrid current drive (LHCD) in Alcator C- Mod. The color along the ray trajectories (red to blue) indicates the power remaining in each of the four rays as they propagate around the tokamak starting at the LH antenna (in the back of the tokamak just right of the central column), as calculated by GENRAY [A. P. Smirnov and R.W. Harvey, Bull. Amer. Phys. Soc., 40:1837, 1995.]. The four rays experience different upshifts in kk, and thus damping, as a result of the poloidal launch angle. The green shading represents a “virtual diagnostic camera” view of the LH driven current as calculated by CQL3D [R. W. Harvey and M. McCoy, “The CQL3D Fokker-Planck Code.” Proc. IAEA Tech. Comm. Meeting on Simulation and Modeling of Thermonuclear Plasmas, pages 489526, 1992.].
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 (email@example.com)