Dale M. Meade

50 years of fusion research

Fusion energy research began in the early 1950s as scientists worked to harness the awesome power of the atom for peaceful purposes. There was early optimism for a quick solution for fusion energy as there had been for fission. However, this was soon tempered by reality as the difficulty of producing and confining fusion fuel at temperatures of 100 million ◦ C in the laboratory was appreciated. Fusion research has followed two main paths— inertial confinement fusion and magnetic confinement fusion. Over the past 50 years, there has been remarkable progress with both approaches, and now each has a solid technical foundation that has led to the construction of major facilities that are aimed at demonstrating fusion energy producing plasmas.

FIRE, a next step option for magnetic fusion

Abstract The next major frontier in magnetic fusion physics is to explore and understand the strong non-linear coupling among confinement, MHD stability, self-heating, edge physics and wave-particle interactions that is fundamental to fusion plasma behavior. The Fusion Ignition Research Experiment (FIRE) design study has been undertaken to define the lowest cost facility to attain, explore, understand and optimize magnetically confined fusion-dominated plasmas. FIRE is envisioned as an extension of the existing advanced tokamak (AT) program that could lead to an attractive magnetic fusion reactor. FIRE activities have focused on the physics and engineering assessment of a compact, high-field tokamak with the capability of achieving Q≈10 in the Elmy H-mode for a duration of ∼1.5 plasma current redistribution times (skin times) during an initial burning plasma science phase, and the flexibility to add AT hardware (e.g. lower hybrid current drive) later. The configuration chosen for FIRE is similar to that of ARIES-RS, the US Fusion Power Plant study utilizing an AT reactor. The key ‘AT’ features are: strong plasma shaping, double null pumping divertors, low toroidal field (TF) ripple ( 5) for a duration of one to three current redistribution times.

Fusion ignition research experiment

Understanding the properties of high gain (alpha-dominated) fusion plasmas in an advanced toroidal configuration is the largest remaining open issue that must be addressed to provide the scientific foundation for an attractive magnetic fusion reactor. The critical parts of this science can be obtained in a compact high field tokamak which is also likely to provide the fastest and least expensive path to understanding alpha-dominated plasmas in advanced toroidal systems.

Physics basis and simulation of burning plasma physics for the fusion ignition research experiment (FIRE)

The FIRE design for a burning plasma experiment is described in terms of its physics basis and engineering features. Systems analysis indicates that the device has a wide operating space to accomplish its mission, both for the ELMy H-mode reference and the high bootstrap current/high-β advanced tokamak regimes. Simulations with 1.5D transport codes reported here both confirm and constrain the systems projections. Experimental and theoretical results are used to establish the basis for successful burning plasma experiments in FIRE.

Physics basis for the fusion ignition research experiment plasma facing components

Abstract A design study of a fusion ignition research experiment (FIRE) is underway to investigate and assess near term opportunities for advancing the scientific understanding of self-heated fusion plasmas. The emphasis for the FIRE program is on understanding the behavior of plasmas dominated by alpha heating ( Q ≥5). Study activities have focused on the technical evaluation of a compact, high field, highly shaped tokamak. One of the key issues for the design is to find suitable plasma facing components (PFCs). We have investigated a variety of plasma edge and divertor conditions ranging from reduced recycling high heat flux conditions (attached) to reduced heat flux detached operation. The inner divertor detaches easily while impurities must be added to the outer divertor to achieve detachment. The outer divertor and private space baffle will have to be actively cooled. The plasma-facing surface of the divertor is tungsten bonded to a CuCrZr heat sink. The remainder of the PFCs are beryllium coated copper attached to the vacuum vessel. Plasma current disruptions impose strong constraints on the design. Appreciable PFC surface melting and evaporation and onset of ‘plasma shielding’ are expected. The forces induced on the PFC due to disruptions determine the size of the attachment of the PFC to the vacuum vessel.

Recent progress on the Tokamak Fusion Test Reactor

The deuterium-tritium (D-T) experiments on the Tokamak Fusion Test Reactor (TFTR) have yielded unique information on the confinement, heating and alpha particle physics of reactor scale D-T plasmas as well as the first experience with tritium handling and D-T neutron activation in an experimental environment. The D-T plasmas produced and studied in TFTR have peak fusion power of 10.7 MW with central fusion power densities of 2.8 MWm−3 which is similar to the 1.7 MWm−3 fusion power densities projected for 1,500 MW operation of the International Thermonuclear Experimental Reactor (ITER). Detailed alpha particle measurements have confirmed alpha confinement and heating of the D-T plasma by alpha particles as expected. Reversed shear, highli and internal barrier advanced tokamak operating modes have been produced in TFTR which have the potential to double the fusion power to ∼20 MW which would also allow the study of alpha particle effects under conditions very similar to those projected for ITER. TFTR is also investigating two new innovations, alpha channeling and controlled transport barriers, which have the potential to significantly improve the standard advanced tokamak.

TFTR experience with D-T operation

Abstract Temperatures, densities and confinement of deuterium plasmas confined in tokamaks have been achieved within the last decade that are approaching those required for a D-T reactor. As a result, the unique phenomena present in a D-T reactor plasma (D-T plasma confinement, alpha confinement, alpha heating and possible alpha-driven instabilities) can now be studied in the laboratory. Recent experiments on the Tokamak Fusion Test Reactor (TFTR) have been the first magnetic fusion experiments to study plasmas with reactor fuel concentrations of tritium. The injection of ≈20 MW of tritium and 14 MW of deuterium neutral beams into the TFTR produced a plasma with a T/D density ratio of ≈1 and yielded a maximum fusion power of ≈9.2 MW. The fusion power density in the core of the plasma was ≈1.8 MW m −3 , approximating that expected in a D-T fusion reactor. A TFTR plasma with a T/D density ratio of ≈1 was found to have ≈20% higher energy confinement time than a comparable D plasma, indicating a confinement scaling with average ion mass, A , of τ E ≈ A 0.6 . The core ion temperature increased from 30 keV to 37 keV due to a 35% improvement in ion thermal conductivity. Using the electron thermal conductivity from a comparable deuterium plasma, about 50% of the electron temperature increase from 9 keV to 10.6 keV can be attributed to electron heating by the alpha-particles. The ∼5% loss of alpha-particles, as observed on detectors near the bottom edge of the plasma, was consistent with classical first orbit loss without anomalous effects. Initial measurements have been made of the confined energetic alphas and the resultant alpha ash density. At fusion power levels of 7.5 MW, fluctuations at the toroidal Alfven eigenmode frequency were observed by the fluctuation diagnostics. However, no additional alpha loss due to the fluctuations was observed. These D-T experiments will continue over a broader range of parameters and higher power levels.

Engineering Status of the Fusion Ignition Research Experiment (FIRE)

FIRE is a compact, high field tokamak being studied as an option for the next step in the US magnetic fusion energy program. FIREs programmatic mission is to attain, explore, understand, and optimize alpha-dominated plasmas to provide the knowledge necessary for the design of attractive magnetic fusion energy systems. This study began in 1999 with broad participation of the US fusion community, including several industrial participants. The design under development has a major radius of 2 m, a minor radius of 0.525 m, a field on axis of 10T and capability to operate at 12T with upgrades to power supplies. Toroidal and poloidal field magnets are inertially cooled with liquid nitrogen. An important goal for FIRE is a total project cost in the

Road map for a modular magnetic fusion program

1B range. This paper presents an overview of the engineering details which were developed during the FIRE preconceptual design study in FY99 and 00.

Tokamak Fusion Test Reactor D-T results

During the past several decades magnetic fusion has made outstanding progress in understanding the science of fusion plasmas, the achievement of actual fusion plasmas and the development of key fusion technologies. Magnetic fusion is now technically ready to take the next step: the study of high gain fusion plasmas, the optimization of fusion plasmas and the continued development and integration of fusion technology. However, each of these objectives requires significant resources since the tests are now being done at the energy production scale. This paper describes a modular approach that addresses these objectives in specialized facilities that reduces the technical risk and lowers cost for near term facilities needed to address critical issues.