Innovative Confinement Concepts Research Articles

Summary of the 27th IAEA Fusion Energy Conference in the categories of EX/W, EX/D, and ICC

This is a summary paper of the 27th IAEA Fusion Energy Conference which was held from 22–27 October 2018 in Gandhinagar, India. The results in the categories of EX/W (wave–plasma interactions, current drive, heating, energetic particles), EX/D (plasma–material interactions, divertors, limiters, scrape-off layer (SOL)), and ICC (innovative confinement concepts) in magnetic confinement experiments are summarized. In total, 121 papers have been contributed to these categories. Interesting results on the coupling between energetic particles, magnetohydrodynamics (MHD), wave–particle interaction, turbulence, SOL physics, and divertors are presented at this conference. For example, control of energetic particle driven MHD by electron cyclotron heating and resonance magnetic perturbation, mitigation of disruption by energetic particle driven MHD, control of decay length by SOL turbulence, and wave scattering by SOL density fluctuations were discussed in this conference. Deeper understanding of these couplings will be essential for the sustainment of high performance steady-state plasma in ITER.

25th IAEA Fusion Energy Conference: summary of sessions EX/S, EX/W and ICC

This paper provides a summary overview, based on papers presented at the 25th IAEA Fusion Energy Conference (FEC), in the area of magnetic confinement experiments related to stability (EX/S), wave–plasma interactions, current drive, heating, energetic particles (EX/W) and innovative confinement concepts (ICCs). A selection of results that represent progress made since the last FEC in a few important thematic areas that are relevant for the successful and safe operation of future fusion devices like ITER, is highlighted.

23rd IAEA Fusion Energy Conference: summary of sessions EX/C and ICC

An overview is given of recent experimental results in the areas of innovative confinement concepts, operational scenarios and confinement experiments as presented at the 2010 IAEA Fusion Energy Conference. Important new findings are presented from fusion devices worldwide, with a strong focus towards the scientific and technical issues associated with ITER and W7-X devices, presently under construction.

Demonstration of Plasma Start-up in HIT-II and NSTX Using Transient Coaxial Helicity Injection

The method of transient coaxial helicity injection (CHI) first developed on the innovative confinement concepts exploration device HIT-II at the University of Washington has now been successfully applied to the, thirty times larger in plasma volume, NSTX device at PPPL. CHI-started discharges have attained start-up currents in excess of 200 kA and have been successfully coupled to induction. These results from NSTX in combination with the results from HIT-II demonstrate favorable scaling with machine size and the high current capability of this method for solenoid-free plasma startup in future spherical torii and in tokamaks.

Innovative Confinement Concepts (ICC) Program in Fusion Energy Sciences

During the 1990s the Office of Fusion Energy (OFE) restructured and adopted joint goals of science and performance. Many small new experiments were commissioned towards the end of the 1990s and a new program was started: the Innovative Confinement Concepts (ICC) program and has continued into the ITER era. The most basic premise of the ICC Program is to support continued concept innovation in the hunt for an economically attractive fusion reactor while supporting innovation in mainline concepts. This paper summarizes the ICC Program, ICC experiments and outlines some future directions.

Stabilization in the ZaP Flow Z-Pinch

The ZaP flow Z-pinch experiment at the University of Washington investigates the innovative plasma confinement concept of using sheared flows to stabilize an otherwise unstable configuration. The ZaP experiment generates an axially flowing Z-pinch that is 1 m long with a 1 cm radius with a coaxial accelerator coupled to a pinch assembly chamber. Magnetic probes measure the fluctuation levels of the azimuthal modes m = 1, 2, and 3. After assembly, the plasma is magnetically confined for an extended quiescent period where the mode activity is significantly reduced. Experimental measurements show a sheared flow profile that is coincident with the low magnetic fluctuations during the quiescent period. Recent experimental modifications produce more energetic Z-pinch plasmas that exhibit the same general behavior. The plasma equilibrium is characterized with a suite of diagnostics that measure the plasma density, magnetic field, ion and electron temperatures, in addition to plasma flow. The equilibrium is shown to satisfy radial force balance.

Linear Connected Array of Non-Adiabatic Traps

An innovative confinement concept of a linearly connected array of non-adiabatic traps is examined. A non-adiabatic trap unit consists of a cylindrical vacuum chamber with external mirror coils and a pair of inner anti-parallel coils. Positions and currents on these coils are adjusted to achieve zero magnetic fields at the center. The plasma is trapped stably in this configuration due to the “Absolute Minimum B” magnetic configuration that is created. However, like a cusp field, energy confinement of plasma in a trap unit is poor, since particles suffer random pitch-angle scattering near the central zero field region and eventually fall into the loss-cone. However, once these non-adiabatic traps are linearly connected, plasma particles escaping a unit will be effectively re-trapped within the neighboring trap due to collision-free pitch-angle scattering in the zero field region. Since the transition of a charged plasma particle from unit to a next unit is stochastic, a connected array of non-adiabatic fusion core units and similar “leak suppressor” array units with low fusion rate at both ends of the core array improves the plasma confinement sufficient to achieve reactor-grade plasmas.

Conference summary: progress in experiments on innovative concepts, confinement and performance

This paper summarizes the results presented at the 21st IAEA Fusion Energy Conference in the areas of innovative confinement concepts, magnetic confinement experiments and performance.

Status of the Plasma Science and Innovation Center Interfacing Group

The Interfacing Group of the Plasma Science and Innovation Center (PSI-Center— http://www.psicenter.org ), facilitates simulations of collaborating Innovative Confinement Concept (ICC) experiments. This includes assisting experiments in setting up new simulations and in comparison of simulations with experimental data, acquiring and disseminating information about simulations to PSI-Center computational groups, and acting as a conduit of information between experiments.

Equilibrium Reconstruction of Anisotropic Pressure Profile in the Levitated Dipole Experiment

The Levitated Dipole Experiment (LDX) is an innovative confinement concept that uses an internal superconducting dipole field to confine plasma. Plasma equilibrium is calculated by a least-squares fit of an anisotropic pressure model to magnetic measurements constrained by X-ray images. Reconstructions have been done for different heating schemes using two-frequency electron cyclotron heating at 2.45 and 6.4 GHz. Results show that a maximum local β ∼ 20% has been achieved using two frequency heating at a combined full power of 5 kW. Analysis of the reconstruction results shows that the magnetic sensors are sensitive primarily to changes in the plasma dipole moment. This is partly due to the fact that the dipole current decreases as the plasma current increases (as required by flux conservation through the superconducting dipole) and the magnetic sensors detect the sum of these changes. This paper will present details of the reconstruction procedure and describe how new magnetic sensors will aid in resolving the pressure profile more accurately.

Chair Summaries from the 2006 Innovative Confinement Concepts (ICC) Workshop

The goal of the ICC program within the DOE O!ce of Fusion Energy Sciences (OFES) is to improve magnetic and inertial fusion concepts and to advance plasma science. ICC2006 is a continuation of the ICC series, which last year met in Madison, Wisconsin. It provides a forum for an exchange of ideas through presentations and discussions on the science and status of Innovative Confinement Concepts research, and for new ideas. The meeting provides feedback from the ICC community to the DOE OFES. In addition to invited talks on these topics, contributed papers are solicited describing experimental, theoretical, or computational work presently done in the ICC program, and also papers describing new ideas for possible proposals. The contributed papers were presented as posters, which were displayed during the workshop. The program committee also selected a subset of the contributed papers for oral presentation. A ‘‘skunkworks’’ session is included for completely new ideas (and novel twists to old ones).

Observation of an Enhanced Magnetic Helicity Injection Mode by a Rotating Plasma Annulus

Coaxial plasma guns are commonly used to inject magnetic helicity in innovative confinement concepts (ICC’s) for magnetic fusion. One of the key issues in magnetic helicity injection is to maximize the magnetic helicity injection rate. We have identified experimentally an alternative way to increase the magnetic helicity injection rate through rotating plasmas by extending the length of the inner electrode of a coaxial plasma gun so that an additional E × B region interweaves the standard J//B configuration. In the so-called “enhanced helicity injection” mode, the gun voltage is larger compared with the “normal” mode and decays more slowly. Another signature of the enhanced mode is increased edge magnetic field in conjunction with larger edge rotation. The results indicate that tuning plasma rotation is another way to enhance magnetic helicity injection using coaxial plasma guns. An alternative ICC is proposed based on the experimental observations.

Summary of US Fusion Program Planning Documents Relating to Innovative Confinement Concepts (1992–2005)

During the 1990’s approximately 15 planning documents were produced by community consensus and by panels of experts. These documents lead to the restructuring of the Office of Fusion Energy (OFE). The OFE adopted joint goals of science and performance and opened a solicitation for Innovative Confinement Concept (ICC) experiments. This paper summarizes the documents that appeared during this time that relate to the ICCs.

Overview of the Plasma Science and Innovation Center (PSI – Center)

The principal goal of the Plasma Science and Innovation Center (PSI – Center) is to achieve significantly improved computational predictive capability for smaller-scale devices. This is being accomplished through the refinement of existing computational tools through adding sufficient physics modeling, boundary conditions, and geometric capabilities while benchmarking results against experimental data. The work emphasizes the modeling needs of emerging concept (EC) experiments, but improved simulation capabilities for all innovative confinement concepts (ICC) are expected. A special emphasis is placed on physics effects that may extend beyond the standard analysis applied to the mainline programs.

Recent Advances in the SPIRIT (Self-organized Plasma with Induction, Reconnection, and Injection Techniques) Concept

Since its inception at the 1997 Innovative Confinement Concept meeting, the Self-organized Plasma with Induction, Reconnection, and Injection Techniques (SPIRIT) concept has been continuously advanced both theoretically and experimentally. The main features of this concept are: (1) formation of large-flux Field Reversed Configuration (FRC) plasmas by merging two spheromaks with opposite helicities; (2) flexibility to assess FRC stability by varying the plasma shape and kinetic parameter, by using passive stabilizers, and by injecting energetic ions; (3) sustainment of the FRC for a time significantly longer than the energy confinement time using an ohmic transformer and/or neutral beam injection. Experiments carried out in TS-3/4 and SSX and more recently in Magnetic Reconnection Experiment (MRX) have further verified the effectiveness of this formation scheme for large-flux FRCs. An improved understanding of FRC stability over plasma shape and kinetic parameter has been obtained in MRX. New numerical simulations showed that FRC plasmas can be globally stabilized by injecting energetic ions. Many of these aspects of the SPIRIT concept can be further studied in the current MRX device.

Conference summary: progress in experiments on confinement, plasma–material interactions and innovative confinement concepts

This paper summarizes the results presented at the 20th IAEA Fusion Energy Conference 2004 in the sessions on confinement, plasma–material interactions and innovative confinement concepts. The highlights of the presentations are as follows. Long pulse operation has been achieved with high beta and high bootstrap fraction for periods much longer than the current diffusion time. The discharge scenario optimization and its extrapolation towards ITER have progressed remarkably. Significant progress has been made in the understanding of global confinement and transport physics. Progress has also been made in material and retention/migration studies. These results will greatly contribute to ITER and the ultimate goal of fusion power generation.

Compact Toroid and Advanced Fuel - Together to the Moon?!

Magnetic geometries like the field reversed configuration and spheromak are compact toroids, where plasma is enclosed in a linear external magnetic field geometry. To burn advanced fuels requires a high fusion power density compact system and a D-3He field reversed configuration will be considered here. Such innovative confinement concept together with remarkable advantages of compact system and advanced fuels, including direct energy conversion, full lifetime fusion core, fusion space propulsion, nonelectrical application of D-3He fusion energy and space resources including helium-3 fusion fuel is very attractive.

Fusion Innovative Confinement Concepts: 2004

This paper summarizes recent progress in fusion Innovative Confinement Concepts (ICC) as reported at the 2004 ICC Workshop held May 25–28, 2004 in Madison, Wisconsin. This was the third in an annual series of workshops on this topic. The purpose of these workshops is to provide a forum for those who are thinking and working beyond what is considered to be the current state of understanding of fusion concepts.

Innovative Confinement Concepts Workshop—2002: Conference Report

The Innovative Confinement Concepts Workshop, ICC2002, provided a forum for presentations and exchange of ideas on the science and status of innovative concepts in the U.S. Fusion Energy Program. The workshop, held at the University of Maryland on January 22-24, 2002, included oral presentations addressing the important science and status of the concepts, posters focussed on details of the work, a skunkworks for novel ideas, and breakout sessions preparing for the July 2002 fusion energy Snowmass meeting. This report summarizes the oral presentations. A web site (https:// wormhole.ucllnl.org/ICC2002/) has been established with the abstracts and many of the presentations, both oral and poster, from the workshop.

Novel liquid blanket configurations and their hydrodynamic analyses for innovative confinement concepts

Hydrodynamics analyses as a part of the APEX (advanced power extraction) study demonstrates the potential application of applying swirling thick liquid walls to innovative confinement concepts such as field reversed configuration (FRC), spherical torus (ST) and heavy-ion fusion (HIF). This paper addresses the design and the hydrodynamic aspects of fusion relevant swirling flow including 3-D velocity distribution, variations of the flow height in axial and azimuthal directions and hydrodynamic flow stability. Numerical hydrodynamic analyses using a 3-D code with Flibe as the working fluid, shows that a thick liquid first-wall/blanket (>0.6 m) can be maintained in a circular vacuum chamber of 2 m radius by injecting the liquid layer from one side through a swirl flow generating inlet with axial (7 m/s) and azimuthal (10 m/s) velocity components. Parametric computational study indicated that the liquid layer thickness in axial and azimuthal directions is strongly dependent on the inlet axial, azimuthal velocity values and gravitational acceleration. It also shows that a uniform liquid layer thickness can be maintained for axial and azimuthal inlet velocities of 11 and 13 m/s in a cylindrical chamber with a 2 m radius and 12 m length. The swirling liquid wall idea is applied successfully to ST and HIF configurations. A 2D linear stability analysis using potential flow theory (Reynolds number is ∼10 6 for liquid wall thickness of ∼0.5 m) of the swirling flow in the azimuthal flow direction suggested that mean flow is stable when the surface tension, gravitational acceleration, and the centrifugal force effects are considered.