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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.

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Director's Corner

by C.M. Greenfield

Farewell to Jim DeKock

Farewell to Jim DeKock Since the early days of the US Burning Plasma Organization, anybody who looked at the USBPO website, visited the forum, participated in a webinar, or read the newsletter saw the results of the hard work of our Communications Coordinator, Jim DeKock of the University of Wisconsin. Jim is retiring effective the end of July, and his hard work, dedication, and consistent willingness to work above and beyond the call of duty will be missed.

In the coming months, the communications infrastructure of the USBPO will be moving to MIT, with new Communications Coordinator Mark London taking over. In typical “DeKock fashion,” Jim will continue to work in his retirement (for a little while) with Mark to make the transfer as seamless as possible.

From the entire US Burning Plasma Organization: Thank you, Jim!

We’ll miss you, but we sincerely wish you a pleasant retirement. Despite his impending retirement, Jim recently took on and completed a new project; that of a brand new USBPO website at http://burningplasma.org, designed with the help of Wisconsin computer engineering student Carter Peterson and just released this month. More thanks!

ITER News

Some of the news posted here comes from personal sources, but we also relay information from other sources. One of the best sources is the ITER Newsline (http://www.iter.org/newsline), a weekly newsletter containing information about the ITER project and fusion news from our partners. The US ITER Project Office also publishes a newsletter on an occasional basis, which can be found at https://www.usiter.org/media/newsletter.shtml.

For those of you interested in working more closely with ITER, both websites (ITER Organization and US ITER) regularly post job openings. See http://www.iter.org/jobs and https://www.usiter.org/jobs for more information.

Webinars

The USBPO web seminar series continued this month with an overview of diagnostics being provided to ITER by the US given by Dave Johnson (PPPL), with input from Theodore Biewer (ORNL). This is timely as we are entering a new phase of diagnostic development in the US, with design teams being formed to carry out R&D, design, and build the diagnostics for ITER. This seminar was particularly well attended and received, with at least 70 participants from a large number of large and small institutions. Thanks to Dave for his work in preparing this seminar, and USBPO Diagnostics Topical Group Leaders David Brower (UCLA) and Matt Reinke (MIT/ORISE) for arranging it. The slides, which include information on how to get involved in this work, are posted on the USBPO website.

Our next web seminar is being planned for September. Suggestions for topics of interest for fall seminars are welcome and should be sent to Amanda Hubbard.

Plans for APS-DPP conference

For the sixth straight year, the US Burning Plasma Organization has organized a contributed oral session on Research in Support of ITER at the 55th Annual Meeting of the Division of Plasma Physics, which will take place in Denver, Colorado, on November 11-15. The scheduling of this excellent session (along with the entire conference) will be announced very soon.

The USBPO is also organizing a Town Meeting on ITER, scheduled for Thursday evening (November 14) in the Sheraton Denver Downtown Hotel. I will announce the speakers in next month’s column. We will have a compelling program, focusing on two ITER design decisions to be formalized late this year: The first will be a decision on whether to include internal “ELM coils” in the baseline design; the second will be a decision on the materials used to construct ITER’s divertor. We will also have a report on US ITER project status.

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USBPO Topical Group Highlights

[The BPO Confinement and Transport Topical Group works to facilitate U.S. efforts to understand plasma confinement via improved measurements and computational models for existing and future magnetic fusion devices (leaders are George McKee and Gary Staebler). This month's Research Highlight by Z. Yan, et al., combines an array of fluctuation diagnostics to demonstrate the complex evolution of broadband turbulence as heating power reaches the level commonly associated with a transition to high-confinement. -Ed.]

The Dynamics of Turbulence, Turbulent Flows and Energy Transfer at the L-H Transition
Z. Yan¹, J. Boedo², G.R. McKee¹, L. Schmitz³, and G. Tynan²

¹ University of Wisconsin-Madison
² University of California-San Diego
³ University of California-Los Angeles

Comprehensive multi-field fluctuation measurements are revealing the complex dynamics of turbulence and flows that transpire in the edge plasma region before, during and after the Low-Confinement to High-Confinement (L-H) transition. These measurements and detailed analyses are demonstrating the critical changes that occur at the turbulence scale and underlie the transition mechanics and empirical scaling relations that help us predict the power required to induce a transition. The L-H transition has been observed for decades in diverted tokamaks and other toroidal magnetic configurations, and inducing it requires a minimum power flow across the magnetic boundary between closed and open field lines. The transition is characterized by a large increase in the edge radial electric field, reduction in edge neutral recycling and suppression of turbulence. But the detailed behavior of how turbulence evolves and is suppressed is only now being clarified. And in a surprising twist, it turns out that the turbulence itself, through a complex set of nonlinear interactions, is a critical player in insuring its own beneficial demise. While a fascinating scientific topic, L-H dynamics is of considerable practical interest since it will be necessary for fusion reactors to operate in the H-mode regime in order to obtain sufficient energy confinement and pressure to efficiently generate fusion power.

The new measurements revealing the L-H dynamics include optical measurements of density fluctuation images, obtained with Beam Emission Spectroscopy, multipoint Langmuir probe measurements of electrostatic potential, electric field, and density fluctuations, and microwave measurements of turbulence and flows obtained with Doppler Back Scattering on the DIII-D tokamak, and build on earlier work [1-3]. By combining the spatiotemporal measurements of turbulence and turbulent flows, a picture is emerging that as power flow increases across the separatrix, turbulence near the edge gradually increases in amplitude, and through a Reynolds stress mechanism, drives radially-localized, toroidally and azimuthally uniform (zonal) flows, the shearing rate of these flows increases until it competes with the decorrelation rates of turbulence, and the rate of the energy transferred from turbulence into the zonal flow exceeds the effective turbulence recovery rate, ultimately suppressing the turbulence, reducing edge transport and allowing the important H-mode pedestal and corresponding radial electric field shear to develop and sustain the high-performance regime. This dynamical process can be envisioned as the transfer of kinetic energy from the turbulence to the zonal flows under conditions of adequate fluctuation amplitude, turbulent flux and geometry.

Figure 1: Transition from L-mode into the Limit-Cycle-Oscillation (LCO) Phase: (a) recycling Dα emission; (b) poloidal ExB velocity 1 cm inside separatrix; (c) comparison of turbulence decorrelation rate (blue) and energy transfer rate from turbulence to zonal flow (red), measured with reciprocating Langmuir probe.

A series of dedicated experiments were performed on the DIII-D tokamak to study the transition details by developing and operating plasmas near the required L-H power threshold. In one set of experiments, a unique regime is obtained whereby the plasma doesn’t rapidly transition from L-mode to H-mode, but rather enters an intermediate phase characterized by Limit Cycle Oscillations (LCO), whereby a coherent low-frequency oscillation (~1-2 kHz) allows for comprehensive investigation of the turbulence and flow evolution near the transition conditions [4, 5]. The edge turbulence and flow properties in a plasma entering the LCO regime are illustrated in Fig. 1; the D_α emission [1(a)] and measured poloidal zonal flow velocity [1(b)] exhibit a clear transition characterized by a coherent oscillation where the plasma is in a balanced state on the verge of transition to H-mode [4]. Fig. 1(c) shows how the measured energy transfer from turbulent fluctuations to the low-frequency zonal flow oscillations increases markedly and exceeds the turbulence decorrelation rate and the effective turbulence recovery rate, a critical threshold presaging the transition. Radial profiles of the zonal flow and energy transfer rate across the separatrix demonstrate that the critical energy exchange process occurs just inside the boundary. Fig. 2 from a related discharge [5] illustrates the spatially and temporally coherent limit-cycle oscillation from DBS measurements in the edge poloidal flows and corresponding density fluctuations; a clear 90-degree phase relationship is found between the flows and density fluctuations, consistent with a predator-prey relationship between the two, as predicted theoretically [1]. The turbulence suppression reduces particle transport, allowing for increased pedestal density, pressure gradient and equilibrium diamagnetic flow that can sustain and develop into the H-mode pedestal.

Figure 2: Figure 2: Evolution and profiles of the (a) turbulence poloidal velocity, and (b) turbulence amplitude, measured with Doppler Back Scattering.

In a related set of experiments, turbulence and flows are studied at high temporal and spatial resolution during a spontaneous, rapid L-H transition, which is more typical of L-H transitions in a variety of regimes, but challenging to diagnose; the turbulence here is seen to evolve in a generally similar fashion on disparate slow and fast time scales prior to the transition, analogous to a single cycle of the LCO regime. Fig. 3 (a) shows an image of the edge turbulence acquired with BES and demonstrates the velocimetry technique that extracts the time-resolved 2D turbulent eddy flow dynamics (shown as black arrows superimposed on image). Power is stepped up, causing an increase in turbulence. Analysis of velocity dynamics shows that the poloidal velocity is dominated in the lower power phase by a coherent Geodesic Acoustic Mode (GAM) oscillation (which has a relatively low effective shearing rate) well before the transition, which then evolves into a lower-frequency less coherent broad zonal flow structure as power is increased and the L-H transition is approached (Fig. 3 (b,d)). Evaluating the Reynolds Stress, R =⟨v_r v_θ ⟩R =⟨v_r v_θ ⟩ from the measured velocity, it is seen in Figs. 3 (c) and (e) that Reynolds Stress and importantly, its radial gradient (the drive term for zonal flows) is increasing. The poloidal velocity shearing rate increases locally and exceeds the measured turbulence decorrelation rate. Of particular note, a similar evolution in the poloidal flow velocity spectrum, extracted Reynolds and gradient therein, and shearing-decorrelation rate relationship is observed at two different toroidal fields, and correspondingly much different power inputs (lower field has a lower power threshold according to L-H threshold scaling relations,, suggesting a connection between the underlying turbulence dynamics and the empirical power threshold scaling relationship [6].

Figure 3: (a) Image of density fluctuations near edge from BES and superimposed extracted velocity field; (b),(d) poloidal turbulence velocity spectrum before (black) and near (red) L-H transition and (c),(e) profile of the inferred turbulent Reynolds stress, at two toroidal fields: (b),(c) at 2 T and (d),(e) at 1 T.

Continuing efforts in this research area seek to quantify the relationship between plasma parameters (e.g., toroidal field, density, shape, q₉₅, and plasma size), edge turbulence and the nonlinear energy transfer processes that underlie the transition. This will establish a solid scientific basis for predicting the edge and global plasma parameters required to obtain H-mode performance in burning plasma experiments.

This work supported by the U.S. Department of Energy under DE-FG02-89ER53296, DE-FG02-08ER54999, DE-FC02-04ER54698, DE-SC0001961, DE-SC0008378, DE-FG02-07ER54917, and DE-FG02-08ER54984.

References

1. E.-J. Kim, P.H. Diamond, Phys. Rev. Lett. 90, 185006 (2003)
2. T. Estrada, et al., Europhys. Lett. 92, 35001 (2010)
3. G. Conway, C. Angioni, et al. Phys. Rev. Lett, 106, 065001 (2011)
4. G. Tynan, M. Xu, P. Diamond et al., Nuclear Fusion (2013)
5. L. Schmitz, L. Zeng, T. Rhodes et al., Phys. Rev. Lett. 108, 155002 (2012)
6. Z. Yan, G. McKee, J. Boedo et al., Proc. IAEA-Fusion Energy Conf. (2012); submitted to Nuclear Fusion (2013).

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Special Contribution

Highlights from the PPPL Theory and Simulation of Disruptions Workshop
S.P. Gerhardt¹, A. Bhattacharjee¹, and F. Waelbroeck²

¹ Princeton Plasma Physics Laboratory
² Institute for Fusion Studies, U. Texas-Austin

A workshop addressing the theory and modeling of tokamak disruptions was held at PPPL during June 17-19, 2013. This workshop included talks by both theorists and experimentalists assessing all aspects of disruption physics. Participants came from multiple US and European institutions, including two representatives from the ITER organization (IO). The meeting was divided into 6 sessions, highlights from which are presented below.

The detailed agenda for the meeting can be found at https://ext-sweb.pppl.gov/tsd/schedule.html, and individuals looking for additional information are encouraged to directly contact the speakers and/or Amitava Bhattacharjee (amitava@pppl.gov).

Session I: ITER Needs

The first session focused on ITER needs and JET results with the ITER-like-wall (ILW); this latter is a modification of the JET plasma facing components (PFCs) from all carbon to having a beryllium first wall and tungsten divertor. The first talk of the session, by M. Lehnen (IO), identified three critical areas for disruption physics research which were repeatedly discussed in the meeting: halo current loads, thermal loads to the plasma facing components (PFCs) during the thermal quench (TQ), and runaway electron (RE) generation and dynamics.

Halo currents are those currents during a disruption whose path lies partly in the edge plasma and party in the vessel and PFCs. While toroidally asymmetric halo currents are a long-known issue, much recent attention has been paid to so-called asymmetric vertical displacement events (AVDEs), where a significant tilt of the plasma column, asymmetric halo currents, and very large sideways vessel forces are observed. Furthermore, if this asymmetry rotates toroidally at the resonant frequency of the ITER vacuum chamber (1-20 Hz), then significant resonant amplification can arise. Key questions in this area include understanding the physics that determines the rotation frequency of the halo current asymmetry and how to extrapolate sideways force data from ASDEX-Upgrade and JET to ITER.

REs can cause damage to first wall components and might generate water leaks. This problem is expected to be more severe in ITER than present large tokamaks as the avalanche gain, which scales as e^2.5Ip, will be a factor of ~e²⁷ larger in ITER (I_P=15MA) than in JET (I_P=4 MA). A key issue is better understanding of the energy deposition process during RE termination, including the question of how much RE current magnetic energy is converted to RE kinetic energy during termination, as opposed to conversion to wall and thermal Ohmic plasma currents. Furthermore, improved understanding of RE generation and dissipation processes are critical.

The talk also discussed disruption mitigation needs for ITER. Here mitigation refers to generating a comparatively benign triggered disruption in advance of an intrinsic, uncontrolled disruption. All of the mitigation techniques are based on the premise of injecting sufficient mass into the plasma to radiate the plasma thermal energy and control the current quench rate. Mitigation technologies under consideration for ITER include massive gas injection (MGI), shattered pellet injection (SPI), and potentially beryllium (Be) pellet injection. Of particular interest is an apparent conflict: the material injection amounts required for mitigation of thermal loads may result in a very fast current quench (CQ). These fast current quenches would then result in unacceptable electromagnetic loads on the blanket shield modules. These mitigation techniques also appear likely to assist in the production of large RE currents, emphasizing the need for RE control or dissipation strategies following the initial material injection. Finally, toroidally localized radiation at the location of gas jet or shattered pellet entry may locally melt the Be wall, and care must be taken to minimize these asymmetries.

The second talk of the session, by Peter de Vries (JET, EFDA) addressed how the ILW has changed disruption dynamics in JET. With the ILW, the fraction of energy radiated during the TQ has dropped substantially, resulting in higher post-TQ temperatures. This in turn leads to larger conducted energy to the PFCs and longer CQ durations. The larger conducted energy has led to some observed melting of Be PFCs, while the slower current quenches lead to longer halo current durations and larger impulses to the vessel. Hence, on-line disruption mitigation by MGI was required for all operation with I_P>2.5 MA.

The disruption rate in the first campaign with the ILW increased compared to previous operation with carbon walls, though this rate is expected to decrease as operations experience is gained. It was also found than nearly half of all disruptions with the ILW were due to excessive core tungsten radiation. Finally, the lack of a current quench immediately following some thermal quenches with the ILW makes assessment of disruption statistics more challenging.

Session II: Disruption Dynamics

The session on disruption dynamics began with a talk by Dylan Brennan (Princeton Univ.) on the physics of the onset of disruptive instabilities. This talk reviewed theory and simulations of the onset of disruptions as the system parameters are driven through a stability limit. The point was made that a significant effort is needed in understanding the evolution to disruption, in part to support avoidance, in addition to studies focused on the consequences and mitigation of disruptions. It then described NIMROD simulations showing that most of the essential capabilities exist in extended MHD codes to address this problem. The talk concluded by summarizing the physics that has been implemented as well as that which is needed to simulate nonlinear disruptive instabilities in experimentally relevant regimes.

Richard Fitzpatrick (IFS, Univ. Texas) provided an interlude between talks on nonlinear initial value simulations by describing a semi-analytic model of VDEs that takes into account halo currents. This model is based on a sharp-boundary plasma equilibrium evolving quasi-statically under the influence of wall and halo resistivity. A key feature is the determination of the effect of the wall on the halo currents by evaluating the resistance and effective emf of the available current paths and using these in a circuit equation. The circuit equation then yields the growth rate. The model yields TPF a little under two and vertical and horizontal forces of 31 and 12 MN, respectively, for ITER. It also reproduces the experimentally observed inverse relation between the toroidal peaking factor (TPF) and the poloidal halo current fraction.

Roberto Paccagnella (Consorzio RFX) presented the results of M3D simulations of asymmetric VDEs. This talk offered a candid assessment of how the difficulty of achieving the correct proportions between time scales characterizing the VDE, the current and temperature evolution, and the evolution of the resistive modes underlies the computational challenge of performing disruption simulations. One consequence is that for large Lundquist numbers, non-axisymmetry must be seeded through the initial conditions. The resulting simulations can reproduce some, but not all of the experimental observations. In particular, the thermal quench is well before the current quench unless the perpendicular transport is enhanced, but doing so leads to unrealistic peaking factors. The asymmetric evolution is dominated by the 2/1 mode. An important conclusion of the studies was the importance of reproducing the right conditions after the thermal quench, as these determine the subsequent evolution.

Ben Tobias (PPPL) concluded the session with a talk on 3D equilibria with internal island and external perturbation currents. The theme of this talk was the analogy between the resonant response of a plasma and that of a tuning fork. Experimental observations show that the radial eigenfunction of 3/2 modes have two T_e phase-inversion layers, as measured by ECE. The Mirnov signals are well correlated to the amplitude of the response diagnosed in the core, and uncorrelated to the narrow island width, showing that the MHD response is dominated by the kink component. The properties of the kink can be determined from its response to ELM. The line width yields Q=60 as the quality factor of the oscillator. Comparisons of the response of the plasma to internally and externally excited modes showed that the responses were similar, and that the poloidal mode number m significantly exceeded nq. In this respect the experimental observations differ from predictions of linear ideal MHD codes.

Session III: Halo/Hiro Currents and Forces

The third session of the meeting dealt with the topic of halo/Hiro currents and the resulting vessel forces. S. Gerhardt (PPPL) and T. Hender (CCFE) presented experimental results from NSTX, DIII-D, JET, and ASDEX-Upgrade. The observed halo current asymmetries tend to rotate in the counter-IP direction in JET and NSTX, and to typically not rotate in DIII-D and ASDEX-Upgrade. Typical rotation frequencies are ~500-1000 Hz in DIII-D and NSTX, and 100 Hz in JET. However, the rotation can be erratic, even changing sign during a single disruption. Evidence was shown of cases with halo currents flowing in arcs between various places on the NSTX vessel. It was noted that while many machines have some set of halo current diagnostics, no machine can form a complete picture by itself. The talk by S. Gerhardt also presented results on disruption prediction in NSTX. A simple, physics based algorithm can predict ~94% of all disruptions in NSTX, with ~4% false positive rate and 2% late warning rate.

A number of theory related talks followed, largely focusing on the generation of and effects from non-axisymmetric halo currents. The talk by A. Boozer (Columbia University) emphasized that these current must form a particular B⋅n distribution (n is the unit vector pointing out of the wall), while also remaining parallel to B in the zero-pressure halo region. These results imply that the halo current asymmetry will have a broad toroidal spectrum. The idea of modifying the internal conducting structure in ITER to protect against halo currents (“lightening rods”) was discussed.

The talk by L. Zakharov (PPPL) discussed the physics mechanisms behind these halo currents and emphasized the role of “Hiro currents”. This mechanism occurs when surface currents, generated by a kink instability and flowing counter to I_P at the location of wall contact, are transferred to the vessel or PFCs. Data from EAST was shown providing evidence of toroidal currents flowing in tiles in the plasma edge in a direction opposite to the plasma current. The talk also expressed concern that the v_N=0 boundary condition (no flow to the wall) in extended MHD codes is not appropriate.

Finally H. Strauss (NYU) discussed disruption simulations for ITER with the M3D code. He presented analytic calculations and simulations of asymmetric VDEs, indicating that the sideways force is highest with γτ_w=1, where γ is the growth rate of the m/n=2/1 growing mode and τ_w is the resistive wall time. The talk also showed how these M3D simulations can produce both a TQ and a CQ. The direction of the asymmetric currents are in the same direction as the vertical displacement, as in the model by Zakharov. Strauss considered various possible boundary conditions (Dirichlet, Neumann and mixed), and indicated confidence that the v_N=0 boundary condition is acceptable.

Session IV: Runaway Electrons and Thermal Loads

This session focused on critical issues of TQ thermal loads and runaway electron generation, confinement, and loss. The talk by N. Eidietis (GA) provided data from DIII-D for cases where argon pellets are used to trigger disruptions and RE formation, and emphasized areas of potential theory collaboration. The RE issues were broken into formation, anatomy, dissipation, and final loss of the RE beam. It was found that RE formation in DIII-D is very sensitive to details of the target plasma and disruption initiating pellet. The RE beam tends to dissipate more rapidly than expected from electron-electron collisions, indicating some anomalous dissipation. Finally, it was found that for short RE termination times, there tends to be a large conversion of RE magnetic energy to wall and Ohmic plasma currents.

This was followed by a talk by Valerie Izzo (UCSD) discussing modeling of the TQ and RE mitigation, using the coupled NIMROD+KPRAD codes. These simulations showed that even for toroidally symmetric low-field side Neon injection, toroidally asymmetric mixing due to n≥0 MHD modes can result in toroidal peaking of the radiation on the FW. For asymmetric neon injection, the peaking can be even stronger, and it is important to resolve the toroidal phase of the MHD modes with respect to the gas jets. Simulations of RE loss due to surface breakup during the TQ indicate better RE confinement in larger devices. This indicates that while this mechanism may impede the formation of REs in C-MOD and result in sensitivity to equilibrium and pellet parameters in DIII-D, it is unlikely to translate to ITER.

The termination of RE currents, and their re-conversion to Ohmic currents during the termination process, was the focus of a talk by J.R. Martin-Solis (Universidad Carlos III de Madrid). A key conclusion was that the fundamental parameter determining the fraction of a RE beam that is converted to Ohmic current during the loss phase is τ_res/Δt_hxr, where τ_res is the decay time of the Ohmic current and Δt_hxr is the RE conversion time, as defined by hard X-ray measurements. This implies that substantial conversion of magnetic energy into runaway kinetic energy is likely occurring for the slowest terminations.

Session V: Disruption Mitigation

Disruption mitigation was the topic of the fifth session. The talk by R. Granetz (MIT) using C-MOD data showed that during the pre-thermal quench phase, the P_rad asymmetry can be controlled by varying the timing of the two gas jets, and that there was a strong correlation between the P_rad asymmetry, the n=1 MHD growth rate, and the relative timing of multiple jets. However, during the thermal quench, the P_rad asymmetry is not well controlled with two gas jets, with the P_rad asymmetry correlated with the rotation of peaked P_rad feature.

This was followed by a talk by J. Wesley (GA), which emphasized the need to use moderate amounts of gas in present MGI experiments, so as to achieve normalized current quench rates that would be safe for ITER. The talk also emphasized the potential role of MHD mixing in determining the relationship between the injected gas amount and the mitigation results.

The session ended with a talk by M. Okabayashi (PPPL) that demonstrated avoidance of NTM-locking induced disruptions based on feedback driven mode control in DIII-D. Key elements of the control included a forced toroidal shift between the detected mode and feedback field and built in dynamic error field correction.

Session VI: Integrated simulation of disruptions

The final session of the meeting highlighted integrated simulations. The talk by S. Jardin (PPPL) emphasized the use of the advanced extended MHD code M3D-C¹ for the simulation of disruptive instabilities. An NSTX example was shown, where MHD instabilities provide a soft β-limit, but no disruption, and convergence studies were presented. Regimes with thermal and current quenches will be addressed in future simulations.

S. Kruger (Tech-X) gave the following talk, focusing on whole device modeling (WDM) issues for disruption avoidance. WDM codes evaluate the full discharge evolution, including transport and current drive models, and can thus predict the future state of the plasma. A scheme was presented where “clouds” of equilibria centered on the present discharge state would be evaluated for stability, after which the actuators would attempt to drive the plasma towards a more stable configuration. Tools from the applied math community, for instance, uncertainty quantification (UQ), can be useful for this effort.

Following these technical talks, some summary comments were provided. Chuck Greenfield (GA), speaking as head of the USBPO, emphasized the need for coordination between experiments, and between experiments and theory, in order to solve the problems described above. The USBPO task group on disruptions, led by John Wesley (GA) and Bob Granetz (MIT) is a mechanism to provide some of the required coordination. Amitava Bhattacharjee (PPPL) then discussed some possible areas of collaboration between experiment and theory, and the need for a task force-like effort on disruptions leading up to the final design review of the Disruption Mitigation System on ITER in 2017. He announced that a follow-up meeting would be held next summer in order to continue this critical dialog between experiments and theory.

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Contact and Contribution Information

This newsletter provides a monthly update on U.S. Burning Plasma Organization activities. Topical Group Highlight articles are selected by the Leader and Deputy Leader of those groups (burningplasma.org/groups.html). ITPA Reports are solicited by the Editor based on recently held meetings. Announcements, Upcoming Burning Plasma Events, and all comments may be sent to the Editor. Suggestions for the Image of the Month may be sent to the Editor. The images should be photos, as opposed to data plots, though combined graphics are welcome. The goal is to highlight U.S. fusion resources through interesting visualizations.

Become a member of the U.S. Burning Plasma Organization by signing up for a topical group:
burningplasma.org/jointopical

Editor: David Pace (pacedc@fusion.gat.com)
Assistant Editor: Amadeo Gonzales (agonzales@austin.utexas.edu)

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ITPA Update

For information on the proposed agenda, see BPO forum link.

Coordinating Committee
	4th Meeting, ITER Site, France, December 9 - 11, 2013
Diagnostics Topical Group
	25th Meeting, ITER Site, France, October 16 - 18, 2013 (tentative) The 24th ITPA Diagnostic topical group meeting was held June 4th – June 7th at General Atomics in San Diego. While this meeting discusses a wide range of diagnostic topics, including the successful progression of conceptual design reviews of ITER diagnostics, one major theme of continued importance is the survivability of plasma facing optics in ITER. Highlights were presented from the IO Workshop on First Mirror Surface Recovery, held in April of this year, where attempts were made to apply a NASA “Technical Readiness Level” scale to various approaches to in-situ mirror cleaning. On a scale from 1-9, with 1 being “basic principles observed and formulated” to 9 being “actual system proven through successful mission operations”, no technique scored above a 5, “component validation in relevant environment”. The domestic agencies and the IO will continue work in this critical area, agreeing on short and long term plans for coordinated R&D. At this time, multiple approaches are being pursued in parallel, including laser and plasma discharge based cleaning approaches, results of which were also presented in this session. Two task teams have been generated by the IO to study neutron calibration (contact: P. Stott) and divertor integration (contact: R. Reichle). The divertor task team will focus on solving issues of diagnostic integration into the divertor cassettes, having to coordinate a large number of interleaved electrical connections. The neutron calibration team is addressing concerns stemming from a 2010 ITPA neutron working group study which predicted 8 weeks would be needed to complete in-situ calibration of ITER neutron instruments. A preliminary report will be presented by October 2013 and workshop is planned in conjunction with the 25th ITPA diagnostics meeting scheduled for the week of October 14th in Cadarache. A workshop on dust, tritium and erosion requirements and measurements will also accompany this fall’s ITPA meeting. It was also announced that Hyeon Park has stepped down as chair of the diagnostics topical group, having led since 2011. Kawano Yasunori has replaced him and a deputy chair has yet to be named.
Energetic Particle Physics Topical Group
	11th Meeting, Beijing, China, September 22 - 23, 2013
Integrated Operation Scenarios Topical Group
	11th Meeting, Fukuoka, Japan, October 7 - 9, 2013
MHD, Disruptions & Control Topical Group
	22nd Meeting, Hefei, China, October 8 - 11, 2013 http://itpa22mhd.ipp.ac.cn/ The meeting will cover key MHD stability topics for ITER, including disruptions, disruption mitigation, axisymmetric control, sawteeth, tearing modes, resistive wall modes, error fields, and 3D effects.
Pedestal & Edge Physics Topical Group
	25th Meeting, Kyushu University, Japan, October 7 - 9, 2013
Scrape-Off-Layer & Divertor Topical Group
	18th Meeting, Hefei, China, March 19 - 22, 2013
Transport & Confinement Topical Group
	11th Meeting, Fukuoka, Japan, October 7 - 9, 2013 http://www.triam.kyushu-u.ac.jp/QUEST_HP/ITPAMeeting/ Areas to be covered include impurity and particle transport; validation of gyrofluid transport models; momentum transport; transport in the L-mode edge, particularly during the current rise phase of ITER; L-H and H-L transitions; profile stiffness; 3D effects; and the long-term effort to provide a fully validated model of plasma transport for ITER. These areas include topics that have been selected for special reports to the Integrated Operation Scenarios Topical Group.

 

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Schedule of Burning Plasma Events

Click here to visit a list of previously concluded events.

2013
July 1 - 5, EPS Conference on Plasma Physics, Espoo, Finland A satellite conference on Plasma Diagnostics will be held July 6.
June 25 - 28, 20th Topical Conference on Radio Frequency Power in Plasmas, Sorrento, Italy
September 14 - 16, ICNSP: 23rd International Conference on Numerical Simulation of Plasmas, Beijing, China
September 17 - 20, IAEA: 13th TM on Energetic Particles in Magnetic Confinement Systems, Beijing, China
October 1 - 3, IAEA: 7th TM on Electron Cyclotron Resonance Heating Physics and Technology for Large Fusion Devices, Vienna, Austria
October 2-4, 14th International Workshop on H-mode Physics and Transport Barriers, Kyushu University, Fukuoka, Japan
October 7 - 9, ITPA PED Topical Group Meeting, Japan
November 11 - 15, APS DPP Meeting, Denver, United States
November 18 - 20, 18th Workshop on MHD Stability Control, Santa Fe, New Mexico, USA https://fusion.gat.com/conferences/mhd13/
December 9 - 11, ITPA: 4th CC/CTP Meeting, ITER
December 16 - 20, IAEA: 2nd DEMO Programme Workshop, Vienna, Austria
December 11, 4th CTP Ex Com Meeting, ITER
2014 NSTX-U commissioning operations begin	2020 November, First plasma at ITER
2015 First plasma at W7-X	2027 March, Beginning of full DT-operation at ITER
2019 First plasma at JT-60SA

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Click here to visit a Directory of Other Plasma Events

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