Larry Baylor (ORNL)	US	Research on Disruption Mitigation Enabled by Shattered Pellet Injection Systems on DIII-D, JET, and KSTAR in Support of ITER
Woong Chae Kim (NFRI)	Korea	Progress of Disruption mitigation with SPI and integration of real-time diagnostics for DECAF in KSTAR
Dmitrii Kiramov (Texas)	US	Pellet sublimation and expansion under runaway electron flux
Yipo Zhang (SWIP)	China	Progress in Disruption Mitigation on the HL-2A tokamak
Charlson Kim (SLS2)	US	NIMROD Shattered Pellet Injection Simulations
Michael Faitsch (MPI)	Germany	Broadening of the power fall-off length in a high density, high confinement H-mode regime in ASDEX Upgrade
Curtis Johnson (Auburn)	US	Diagnosing metastable populations in fusion edge plasmas using collisional-radiative modeling constrained by experimental observations with extrapolation to ITER parameter space
Nikolai Gorelenkov (PPPL)	US	Microturbulence-mediated route for stronger energetic ion transport and Alfvénic mode intermittency in ITER-like tokamaks
Christian Kiefer (MPI)	Germany	ASDEX Upgrade experiments and validation of theoretical transport models for the prediction of ITER PFPO-1 plasmas
Mireille Schneider (ITER)	France	Simulation of heating and current drive sources for various scenarios of the ITER Research Plan using the IMAS H&CD workflow
Emmi Tholerus (CCFE)	UK	Scenario development of ITER ELMy H-mode hydrogen plasma
Kathreen Thome (GA)	US	Changes in Impurity Transport with Applied Torque in DIII-D ELMy H-mode Plasma
Sun Hee Kim (ITER)	France	Assessment of access to ITER steady-state operation using CORSICA
Zhang Bin (ASIPP)	China	The dominant electron heating with low torque towards ITER baseline on EAST
Andrea Garofalo (GA)	US	High betaP for ITER Q=10 and Q=5 missions

USBPO Council

You may remember that we held an election for the USBPO Council a while back, as three members’ terms expired: Ted Biewer (ORNL), David Newman (Alaska), and Gary Staebler (GA). I’d like to express my gratitude to Ted, David, and Gary for their service during their terms. Each year we select four new members; two by election and two by appointment. I’m happy to announce that Emily Belli (GA) and Greg Wallace (MIT) were the winners. In addition, Diane Demers (Xantho Technologies) and David Rasmussen (ORNL) have jointed the Council as appointed members.

With these changes, the 2020 USBPO Council is as follows:

11^th ITER International School: The Impact and Consequences of Energetic Particles on Fusion Plasmas

The 11^th ITER International School has been rescheduled for November 16-20, still at Aix-Marseille University as originally planned. The subject of this year’s school is “The Impact and Consequences of Energetic Particles on Fusion Plasmas.” There is, of course, some uncertainty about whether the school can proceed on this schedule and whether US people will be able to travel to France by November.

As previously announced, we are still hoping to send 16 students from the US, supported by USBPO scholarships. In addition, about a half-dozen US researchers are on the agenda as speakers.

The recipients of the 2020 IIS scholarships are:

Gurleen Bal (UCLA)

Genevieve DeGrandchamp (UCI)

Jonah Duran (U Tenn Knoxville)

Kenneth Gage (UCI)

Alvin Garcia (UCI)

Daniel Lin (UCI)

Gabriel Player (UCI)

Quinn Pratt (UCLA)

Aaron Rosenthal (MIT)

Alex Saperstein (Columbia)

Kamil Sklodowski (UCLA)

Elizabeth Tolman (MIT)

Jeff Lestz (Princeton/UC Irvine)

Philip Bonofiglo (PPPL)

Noah Hurst (Wisconsin)

Alex Tinguely (MIT)

More details on this ITER International School are available or forthcoming at https://iis2020.sciencesconf.org/

ITER tokamak assembly begins

Even with COVID-19 restrictions, work is proceeding on the assembly of the ITER tokamak. For the last few years, I’ve been sharing photos of buildings. It was exciting to watch them going up, but now the tokamak building has been completed and turned over to the ITER Organization to move into the next phase: Tokamak assembly.

The first major component, the cryostat base, was inserted into the tokamak pit on May 26. Many large components, including the first poloidal and toroidal field coils, have already arrived at the ITER site. The first completed vacuum vessel sector is in transit.

Meanwhile, meetings at ITER are either delayed or being held remotely. The ITER Council recently held a remote meeting, and the Science and Technology Advisory Committee, of which I am a member, is preparing to hold a meeting remotely in September.

 

The first piece of the ITER Tokamak, the cryostat base, was lowered into the tokamak pit on May 26. Photo courtesy of the ITER Organization.

 

This month’s highlight is from the diagnostic group at University of California, Davis discussing the latest in state-of-the-art edge microwave plasma diagnostic instrumentation. This team has led the development for more compact and robust elements to use in both passive and active microwave systems to provide electron temperature and density measurements for next step fusion devices.

System-on-chip technology: game changer for burning plasma diagnosis*

Guanying Yu¹, Yilun Zhu¹, and Neville Luhmann¹

¹University of California, Davis

Author e-mail: amzhu@ucdavis.edu

Microwave-based measurements have found broad application in magnetic fusion plasma diagnostics and are expected to be widely employed in burning plasma experiments due to their numerous advantages and applications including minimal port access requirements, co-locating interferometer, reflectometer, radiometer, and scattering systems for burning plasma physics studies and real-time feedback plasma control. In many state-of-the-art systems, each device-level function is performed by a separate component. Diagnosticians then typically assemble a functional instrument by connecting these packages together with short sections of waveguide resulting in the common expression of waveguide “plumbing”. In contrast, the cutting-edge microwave integrated chip (IC) technology provides breakthrough opportunities to enhance diagnostics’ capabilities in fusion science and survive the harsh radiation environment. Integrated circuit technology facilitates combining many bulky microwave components onto a single, tiny piece of semiconductor substrate, as shown in Figure 1. The front-end microwave sensor is built on a square millimeter level chip instead of the suitcase-size waveguide approach. The System-on-Chip approach has demonstrated excellent shielding performance against environmental interference, significant mixing efficiency (over 30x boost), and new accessible physics areas. Furthermore, the IC itself is able to be mass produced, making for a bench-stock of consistent and yet inexpensive replacement circuits that can be swapped out with minimal effort—clearly an advantage in burning plasmas where experimental resources, diagnostic access, and run-time are at a premium!

A demo version of System-on-Chip microwave diagnostics was successfully deployed for DIII-D Electron Cyclotron Emission Imaging (ECEI) measurements in 2019. The new ECEI system is now used for 2D pedestal temperature imaging with high spatial and temporal resolution. High confinement (H-mode) plasmas are accompanied by a quasi-periodic crash event (ELMs) at the plasma edge, which poses a detrimental transient heat load to the plasma facing materials. Resonant Magnetic Perturbations (RMPs) have been widely applied in experimental tokamak devices to control the ELMs, but the physics mechanism of RMP-ELM control is still not fully understood. Enhancing plasma edge transport appears to be key to constraining the plasma edge in this stable operating region that is free from ELMs. RMPs are predicted to drive small magnetic islands in the plasma edge that may enhance edge transport by guiding the electrons parallel to the island magnetic field lines. Additionally, the RMP changes the plasma flow at the edge, which may destabilize certain turbulent phenomena that may also enhance the edge transport. For the latter case, the DIII-D W-band [75-110 GHz] ECEI, upgraded with the latest high signal-to-noise-ratio receivers, has been commissioned to measure the electron radiation temperature () fluctuation excited by low-k (k<0.3) turbulence and reveal clues to understanding the physics of RMP ELM suppression.

In DIII-D discharge 179328, an increasing RMP is applied to the plasma to achieve ELM suppression. RMP strength coil current; and the ELMs are measured via the signal. The significant increase in the ECEI spectrum coherence signifies strong turbulence. The cross phase describes the turbulence phase velocity as ~ 15 km/s in the ion diamagnetic direction in the lab frame. The capability of obtaining the cross power spectrum and cross phase allows us to perform more detailed physics studies to correlate profile changes with fluctuation characteristics.

Benefiting from the system-on-chip mixing technology, ECEI is not only a fluctuation diagnostic, but also measures the equilibrium electron temperature. When the ELMs are suppressed in the same discharge, the plasma edge is not static, but exhibits quasi-periodic pulsations every ~10 . The pulsations, seen in Fig 3(a)(b), are confirmed with both the heat flux diagnostic IRTV and the uncalibrated diagnostic ECEI. Each peak in the IRTV heat flux coincides with one valley in the pedestal temperature in the time domain. Due to the high signal quality of ECEI, the turbulence amplitude (Fig. 3(c)) is separately measured with short time windows at all of the peaks and valleys of the IRTV heat flux. We found that the turbulence is strongly correlated with energy transport in the plasma edge, as the turbulence power is significantly stronger at the IRTV heat flux peaks than that at the valleys.

Implementing microwave diagnostics on reactor plasma will require a slight increase in operating frequencies above 160 GHz, mandating further technology developments. However, there are considerably more serious issues raised by the harsh radiation and high temperature environment. ITER will be the first magnetic confinement fusion machine to produce net fusion power and will generate radiation levels, i.e., neutrons and gamma rays, that are much higher than present-day tokamaks. Consequently, there is a need to develop more robust electronics with higher performance and capability to reliably measure the desired data. A major improvement in robustness, as well as performance and capability, is to switch to gallium nitride (GaN) semiconductor devices, which are wide bandgap materials (3.39 eV versus 1.43 and 1.11 for GaAs and Si, respectively). GaN semiconductor devices have been shown to provide high power, high breakdown voltages, and low noise beyond 200 GHz. UC Davis will develop key strategic GaN based chips (75-110 GHz and above) that will advance the capabilities of microwave diagnostics including radiometers, reflectometers, and scattering. This work will transform current microwave measurement capabilities while ensuring continued U.S. leadership in burning plasma diagnostic expertise.

* This work was supported by the US DoE under Grants DE-FG02-99ER54531 and DE-FC02-04ER54698.

Calendar of Burning Plasma Events

2020

JET DT-campaign (/resources/ref/Web_Seminars/Litaudon-JET-%202019-05-02-vf.pdf)
JT-60SA First Plasma (http://www.jt60sa.org/)
Sep 20-25, 2020	31st Symposium on Fusion Technology (SOFT)	Virtual
Oct 12-16, 2020	Theory of Fusion Plasmas Joint Varenna- Lausanne International Workshop	Varenna or Lausanne
Nov 9-13, 2020	62nd Annual Meeting of the APS Division of Plasma Physics	Remote only
Nov 15-19, 2020	Technology of Fusion Energy (TOFE) 2020	Chicago, IL
Nov 16-20, 2020	ITER International School	Marseille, France
Dec 6-10, 2020	47th International Conference on Plasma Science (ICOPS)	Singapore
Dec 13-17, 2020	High Temperature Plasma Diagnostics Conference	Santa Fe, NM
Dec 16-17, 2020	Fusion Power Associates 41st Annual Meeting and Symposium	Washington, D.C.
Jan 24-29, 2021	International Conference on Plasma Surface Interactions	Jeju, South Korea
May 10-15, 2021	28th IAEA Fusion Energy Conference (FEC2020)	Nice, France