USXR Based MHD, Transport, Equilibria and Current Profile Diagnostics for NSTX. Final Report

The present report resumes the research activities of the Plasma Spectroscopy/Diagnostics Group at Johns Hopkins University performed on the NSTX tokamak at PPPL during the period 1999-2009. During this period we have designed and implemented XUV based diagnostics for a large number of tasks: study of impurity content and particle transport, MHD activity, time-resolved electron temperature measeurements, ELM research, etc. Both line emission and continuum were used in the XUV range. New technics and novel methods have been devised within the framework of the present research. Graduate and post-graduate students have been involved at all times in addition to the senior research personnel. Several tens of papers have been published and lectures have been given based on the obtained results at conferences and various research institutions (lists of these activities were attached both in each proposal and in the annual reports submitted to our supervisors at OFES)

X-VUV spectroscopic imaging with a micropattern gas detector

Abstract An innovative system which combines very fast 2D imaging capabilities with spectral resolution in the X-VUV range 0.2–8 keV has been developed at ENEA-Frascati (Italy) in collaboration with INFN-Pisa (Italy). It is based on a pinhole camera coupled to a micropattern gas detector having a gas electron multiplier as gas amplifying stage. This detector (2.5 cm×2.5 cm active area), equipped with a 2D read-out printed circuit board with 144 pixels in a square matrix geometry (12×12) has been adapted to work at low energy, as far as 0.2 keV, in various configurations. Spectra with different X-VUV laboratory sources, energy calibrations curves and detection efficiency are discussed for all the proposed configurations. Thanks to the high photon flux (10 6 ph/s mm 2 ) detected by this device, high time resolution can be obtained (framing rates up to 100 kHz). The full system has been tested on the Frascati Tokamak Upgrade in 2001 and on the National Spherical Tokamak eXperiments (NSTX) in 2002 as a possible diagnostic tool for magnetic fusion plasmas. Time-resolved 2D images are presented. These results open the way to a new X-VUV imaging technique, where the low definition (limited number of pixels) is highly compensated by the strongly enhanced contrast due to the fine and controlled energy discrimination and by the capability to get images in a selected energy range. The innovative combination of these two major characteristics, make this device a candidate for applications beyond the magnetic plasma physics field

Multi-functional Diagnostic Method with Tracer-encapsulated Pellet Injection

In order to obtain a better understanding of impurity transport in magnetically confined plasmas, a Tracer-Encapsulated Soild PELlet (TESPEL) has been developed. The essential points of the TESPEL are as follows: the TESPEL has a double-layered structure, and a tracer impurity, the amount of which can be known precisely, is embedded as an inner core. This structure enables us to deposit the tracer impurity locally inside the plasma. From experiences of developing the TESPEL production technique and its injection experiments, it became clear that various plasma properties can be studied by the TESPEL injection. There are not only impurity transport in the plasma but also transport both outside and inside of the magnetic island O-point, heat transport and high-energy neutral particle flux. Therefore, the TESPEL injection has a favorable multi-functional diagnostic capability. Furthermore a Tracer-Encapsulated Cryogenic PELlet (TECPEL) has been also developed. The TECPEL has an advantage over the TESPEL in terms of no existence of carbons in the outer layer. The TECPEL injector was installed at LHD in December 2005, and the preliminary injection experiments have been carried out

USXR Based MHD, Transport, Equilibria and Current Profile Diagnostics for NSTX. Final Report

The present report resumes the research activities of the Plasma Spectroscopy/Diagnostics Group at Johns Hopkins University performed on the NSTX tokamak at PPPL during the period 1999-2009. During this period we have designed and implemented XUV based diagnostics for a large number of tasks: study of impurity content and particle transport, MHD activity, time-resolved electron temperature measeurements, ELM research, etc. Both line emission and continuum were used in the XUV range. New technics and novel methods have been devised within the framework of the present research. Graduate and post-graduate students have been involved at all times in addition to the senior research personnel. Several tens of papers have been published and lectures have been given based on the obtained results at conferences and various research institutions (lists of these activities were attached both in each proposal and in the annual reports submitted to our supervisors at OFES)

Beyond Models and Metaphors: Complexity Theory, Systems Thinking and International Relations

The concepts, language and methods of complexity theory have been slowly making their way into international relations (IR), as scholars explore their potential for extending our understanding of the dynamics of international politics. In this article we examine the progress made so far and map the existing debates within IR that are liable to being significantly reconfigured by the conceptual resources of complexity. We consider the various ontological, epistemological and methodological questions raised by complexity theory and its attendant worldview. The article concludes that, beyond metaphor and computational models, the greatest promise of complexity is a reinvigoration of systems thinking that eschews the flaws and limitations of previous instantiations of systems theory and offers an array of conceptual tools apposite to analysing international politics in the twenty-first century

DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

Funding Information: This material is based upon work supported by the US Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Awards DE-FC02-04ER54698 and DE-AC52-07NA27344. Publisher Copyright: © 2022 IAEA, Vienna.DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.Peer reviewe