Showing papers in "Fusion Science and Technology in 2004"
TL;DR: In this article, short transient thermal pulses with deposited energy densities on the order of several tens of MJ/m2 are a serious concern for next-step devices, in partic...
Abstract: Beside quasi-stationary plasma operation, short transient thermal pulses with deposited energy densities on the order of several tens of MJ/m2 are a serious concern for next-step devices, in partic...
73 citations
TL;DR: A model of bubble nucleation, growth and release for aging metal tritides is described in this article, which accounts for major features of the tritide database and the evolution of the bubble nucleations.
Abstract: A continuum-scale, evolutionary model of bubble nucleation, growth and He release for aging metal tritides is described which accounts for major features of the tritide database. Bubble nucleation,...
71 citations
TL;DR: The relevant equations that are used in these codes are established, and on the basis of these equations, the necessary calculations needed to resolve them are pointed out.
Abstract: This paper gives a brief introduction on numerical transport codes. The relevant equations which are used in these codes are established, and on the basis of these equations, the necessary calculations needed to resolve them are pointed out. Finally, some examples are given, illustrating their application.
55 citations
TL;DR: In this article, the current power consumption in different parts of the world and an estimate of the future energy needs for the world are given, as well as the present energy supplies and prospects, the possible consequences of a continued massive fossil fuel consumption, and the potential of non-fossil candidates for long-term energy production.
Abstract: The current power consumption in different parts of the world and an estimate of the future energy needs of the world are given. The present energy supplies and prospects, the possible consequences of a continued massive fossil fuel consumption, and the potential of non-fossil candidates for long-term energy production are outlined. An introduction to possible fusion processes in future fusion reactors is given. The inexhaustibility, safety, environmental and economic aspects of magnetic fusion energy are discussed.
52 citations
TL;DR: In this paper, a compact quasi-poloidally symmetric stellarator (QPS) plasma and coil configuration is described that has desirable physics properties and engineering feasibility with a very low aspect ratio plas...
Abstract: A compact quasi-poloidally symmetric stellarator (QPS) plasma and coil configuration is described that has desirable physics properties and engineering feasibility with a very low aspect ratio plas...
42 citations
TL;DR: In this article, the effect of edge biasing on plasma potential was investigated in the TJ-II stellarator and the T-10 tokamak, and the results showed that the potential response has the same polarity and scale as the biasing voltage, and fluctuations are suppressed near the electrode/limiter region.
Abstract: The effect of edge biasing on plasma potential was investigated in the TJ-II stellarator and the T-10 tokamak The Heavy Ion Beam Probe (HIBP) diagnostic, a unique tool for studying the core potential directly, was used in both machines Experiments in TJ-II show that it is possible to modify the global confinement and edge plasma parameters with limiter biasing, illustrating the direct impact of radial electric fields on TJ-II confinement properties For the first time it was shown that the plasma column in a stellarator can be charged as a whole for a hot, near-reactor-relevant plasma The plasma potential and electric fields evolve on two different characteristic time scales Although the experimental conditions in the two machines have many important differences, the basic features of plasma potential behavior have some similarities: The potential response has the same polarity and scale as the biasing voltage, and the fluctuations are suppressed near the electrode/limiter region However, whereas both edge and core plasma potential are affected by biasing in TJ-II, the potential changes mainly near the biased electrode in T-10
42 citations
TL;DR: In this paper, the authors discuss recent progress towards converting this process into a high yield, production scale process, and show that fabrication of a mandrel which met the symmetry and surface finish requirements was feasible using this technique.
Abstract: All planned National Ignition Facility (NIF) capsule targets except machined beryllium require a glow discharge polymer (GDP) mandrel upon which the ablator is applied. This mandrel, {approx}2 mm in diameter, must at least meet if not exceed the symmetry and surface finish requirements of the final capsule. Such mandrels are currently produced by the three-step depolymerizable mandrel technique. The quality of the final mandrel depends upon precise optimization and execution of each of the three steps. We had shown previously that fabrication of a mandrel which met the symmetry and surface finish requirements was feasible using this technique. In this paper we will discuss recent progress towards converting this process into a high yield, production scale process.
40 citations
TL;DR: In this paper, the magnetic field configuration of the Large Helical Device (LHD) was changed from a classical heliotron configuration to a magnetar configuration, and the authors investigated the financement of energetic ions from neutral beam injection heating.
Abstract: Confinement of energetic ions from neutral beam injection heating is investigated by changing the magnetic field configuration of the Large Helical Device from a classical heliotron configuration t...
38 citations
TL;DR: In this paper, an open divertor was chosen as the first step in divertor development for the expected extended magnetic and plasma parameter range for the Wendelstein 7-X stellarator.
Abstract: For the Wendelstein 7-X stellarator, an open divertor was chosen as a first step in divertor development for the expected extended magnetic and plasma parameter range. Particularly, the three-dimensional (3-D) geometry of the boundary and the provided stationary operation are challenges for the design. So far, simplified models have been used to specify the geometry of the divertor and the performance of the high-heat-load surfaces. By applying the 3-D codes that are now available, the results concerning local heat load and particle exhaust can have more detailed evaluation and can be confirmed generally. Together with the development of improved high-heat-load components, a significant reduction of the target area in comparison with the previous design is possible. The new specifications will be characterized.
37 citations
TL;DR: In this article, the authors used Resorcinol-formaldehyde (R/F) as the selected foam material due to its transparency in the optical region and provided extensive characterization of the wall uniformity of these shells.
Abstract: OAK-B135 New high gain designs for direct drive ignition on NIF require foam shells. Scaled down versions of these designs are needed for near term experiments on the OMEGA laser facility at the Laboratory Laser Energetics (LLE). These shells need to be about 1 mm in diameter and 50-100 {micro}m wall thickness and densities of 100-250 mg/cc. In addition, a full density permeation seal needs to be deposited for retention of the fill gas at room temperature or the ice at cryogenic temperatures. They have fabricated such shells using Resorcinol-formaldehyde (R/F) as the selected foam material due to its transparency in the optical region. Extensive characterization of the wall uniformity of these shells has been performed. The foam shells have {approx} 5%-6% non-concentricities on the average. A full density permeation seal has been deposited on the R/F shells using two different techniques. In the first technique R/F shells are coated directly with plasma polymer to thicknesses of 3-4 {micro}m. In the second technique, R/F shells are coated with polyvinylphenol, using a chemical interfacial polymerization technique. Data on surface finish and gas retention for R/F shells coated by both methods are provided.
37 citations
TL;DR: The Frascati Tokamak Upgrade (FTU) has been operating for more than 12 years since its first plasma in 1990 and has played an important role in several aspects of the tokamak research as mentioned in this paper.
Abstract: The Frascati Tokamak Upgrade (FTU) has been operating for more than 12 yr since its first plasma in 1990 and has played an important role in several aspects of the tokamak research. As the first paper of this special issue containing papers on all aspects of FTU, this paper briefly summarizes the main dates, the general description of the facility, the objectives, and the major achievements in FTU.
TL;DR: The Columbia Nonneutral Torus as mentioned in this paper is a stellarator experiment being built at Columbia University, New York, to study the confinement of nonneutral and electron-positron plasmas.
Abstract: The Columbia Nonneutral Torus is a new stellarator experiment being built at Columbia University, New York, to study the confinement of nonneutral and electron-positron plasmas. It will be a two-period, ultralow aspect ratio classical stellarator configuration created from four circular coils. The theory of the confinement and transport of pure electron plasmas on magnetic surfaces is reviewed. The guiding principles behind the experimental design are presented, together with the actual experimental design configuration.
TL;DR: In this paper, indirect drive ignition target simulations are described as they are used to determine target fabrication specifications, and a new target with radially dependent Cu dopant in Be is described.
Abstract: Indirect drive ignition target simulations are described as they are used to determine target fabrication specifications. Simulations are being used to explore options for making the targets more robust, and to develop more detailed understanding of the performance of a few point designs. The current array of targets is described. A new target is described with radially dependent Cu dopant in Be. This target has significantly looser specifications for high-mode perturbations than previous targets. Current estimates of size limitations for fill tubes, holes, and isolated defect are discussed. Recent 3D simulations are described.
TL;DR: Inertial confinement fusion shells have been evaluated on the basis of microscopic examination for local defects and limited surface profiling to represent their average fluctuation in this article, and they have been shown to have good performance.
Abstract: Inertial confinement fusion shells have previously been evaluated on the basis of microscopic examination for local defects and limited surface profiling to represent their average fluctuation powe...
TL;DR: In this article, the dependence of impurity transport on plasma parameters in the modular stellarator Wendelstein 7-AS was investigated by means of a laser blow-off technique.
Abstract: The dependence of impurity transport on plasma parameters in the modular stellarator Wendelstein 7-AS was investigated by means of a laser blow-off technique. An increased impurity transport at higher heating power and lower magnetic field strength as well as no effect of the isotope composition on the impurity confinement was observed. The most critical scaling with respect to stationary operation at high density is the improved confinement of impurities at high densities, leading to a degradation of plasma energy by increasing radiation and to a loss of density control. This was attributed to a reduction of the impurity diffusion coefficient with density. After installation of island divertor modules, a transition from normal confinement into the high-density H-mode (HDH) at a certain power-dependent threshold density appeared. This transition is characterized by a strong reduction of the impurity confinement time and an increase in energy confinement time. In the HDH operational regime, access to even higher densities (4 x 10{sup 20} m{sup -3}) than achieved before became possible under stationary operation conditions. Impurity transport measurements and model predictions indicate that the reduction of the impurity confinement in HDH is caused by not only a reduction of the inward convection in the coremore » plasma but also possibly by changes in the edge transport. Comparison of experimental data with an axisymmetric transport model should elucidate the role of stellarator-specific transport aspects.« less
TL;DR: In this paper, the analysis of Thomson scattering data is discussed, and capabilities for assessing diagnostic setups are outlined, as well as technical issues resulting from desired on-line capabilities are discussed.
Abstract: Steady-state fusion devices, such as Wendelstein 7-X, require new approaches for data analysis. These efforts are motivated by both the physics and the technical requirements of steady-state operation. Diagnostic data and physics information, such as modeling results, are linked to arrive at an integrated data analysis. For this purpose, methods of Bayesian probability theory are employed. The analysis of Thomson scattering data is discussed. Capabilities for assessing diagnostic setups are outlined. Extension to more complex analyses are presented. Technical issues resulting from desired on-line capabilities are discussed.
TL;DR: A blanket tritium recovery system that uses an electrochemical hydrogen pump with a protonic conductor membrane is proposed in this article, where one of the advantages of this system is the potential for processing the...
Abstract: A blanket tritium recovery system that uses an electrochemical hydrogen pump with a protonic conductor membrane is proposed. One of the advantages of this system is the potential for processing the...
TL;DR: In this article, ultralow density (2~10 mg/cm3) hydrocarbon plastic (CH2) foams with a controllable micro- or nano-meter-sized lamella structure are described.
Abstract: The present report describes ultralow density (2~10 mg/cm3) hydrocarbon plastic (CH2) foams with a controllable micro- or nano-meter-sized lamella structure. These foams are prepared from a poly(4-...
TL;DR: In this article, Tungsten and carbon are considered as armor for IFE dry-wall chambers based on their high-temperature and high-heat-flux accommodation capabilities.
Abstract: The chamber wall armor is subject to demanding conditions in inertial fusion energy (IFE) chambers. IFE operation is cyclic in nature, and key issues are (a) chamber evacuation to ensure that after each shot the chamber returns to a quiescent state in preparation for the target injection and the firing of the driver for the subsequent shot and (b) armor lifetime that requires that the armor accommodate the cyclic energy deposition while providing the required lifetime. Armor erosion would impact both of these requirements. Tungsten and carbon are considered as armor for IFE dry-wall chambers based on their high-temperature and high-heat-flux accommodation capabilities. This paper assesses the requirements on armor imposed by the operating conditions in IFE, including energy deposition density, time of deposition, and frequencies; describes their impact on the performance of the candidate armor materials; and discusses the major issues.
TL;DR: The design of diagnostics for the Frascati Tokamak Upgrade (FTU) is challenging because of the compactness of the machine and the low operating temperatures requiring the presence of a cryostat.
Abstract: The design of diagnostics for the Frascati Tokamak Upgrade (FTU) is challenging because of the compactness of the machine (8-cm-wide ports) and the low operating temperatures requiring the presence of a cryostat. Nevertheless, a rather complete diagnostic system has been progressively installed. The basic systems include a set of magnetic probes, various visible and ultraviolet spectrometers, electron cyclotron emission (ECE) for electron temperature profiles measurements and electron tails monitoring, far-infrared and CO{sub 2} interferometry, X-ray (soft and hard) measurements, a multichord neutron diagnostics (with different type detectors), and a Thomson scattering system. Some diagnostics specific to the FTU physics program have been used such as microwave reflectometry for turbulence studies, edge-scanning Langmuir probes for radio-frequency coupling assessment, oblique ECE, and a fast electron bremsstrahlung (FEB) camera for lower hybrid current drive-induced fast electron tails.These systems are briefly reviewed in this paper. Further developments including a scanning CO{sub 2} laser two-color interferometer, two FEB cameras for tomographic analysis, a motional Stark effect system, and a collective Thomson scattering system are also described.
TL;DR: In this paper, high-frequency wave systems with high-power density launching capability have been the preferred choice to heat the Frascati Tokamak Upgrade (FTU) because of physics arguments (electron heating at...
Abstract: High-frequency wave systems with high-power density launching capability have been the preferred choice to heat the Frascati Tokamak Upgrade (FTU) because of physics arguments (electron heating at ...
TL;DR: In this article, the authors compared the LHD results with the Wendelstein 7-AS high-beta properties and showed the relationship between the experimentally achieved parameters and theoretical predictions.
Abstract: Recently, dramatic progress has been achieved in the study of helical systems with high-beta experiments. Discharges with more than 3% beta plasmas have been achieved in Large Helical Device (LHD) and Wendelstein 7-AS (W7-AS). Although magnetohydrodynamic (MHD) instabilities affect local pressure gradients, the global transport property does not seem to limit the achieved beta value in either device. We summarize the LHD high-beta properties in MHD stability, equilibrium, and transport, and we show the relationship between the experimentally achieved parameters and theoretical predictions. We contrast the LHD results with the W7-AS high-beta properties. In both devices, stationary discharges in the definitely MHD unstable region have not been observed. We mention the key issue for achievement of the beta values >5%.
TL;DR: The ARIES-IFE study as mentioned in this paper was an integrated study of inertial fusion energy (IFE) chambers and chamber interfaces with the driver and target systems, and detailed analysis of various subsystems was performed parametrically to uncover key physics/technology uncertainties and to identify constraints imposed by each subsystem.
Abstract: The ARIES-IFE study was an integrated study of inertial fusion energy (IFE) chambers and chamber interfaces with the driver and target systems. Detailed analysis of various subsystems was performed parametrically to uncover key physics/technology uncertainties and to identify constraints imposed by each subsystem. In this paper, these constraints (e.g., target injection and tracking, thermal response of the first wall, and driver propagation and focusing) were combined to understand the trade-offs, to develop operational windows for chamber concepts, and to identify high-leverage research and development directions for IFE research. Some conclusions drawn in this paper are (a) the detailed characterization of the target yield and spectrum has a major impact on the chamber; (b) it is prudent to use a thin armor instead of a monolithic first wall for dry-wall concepts; (c) for dry-wall concepts with direct-drive targets, the most stringent constraint is imposed by target survival during the injection process; (d) for relatively low yield targets (<250 MJ), an operational window with no buffer gas may exist; (e) for dry-wall concepts with indirect-drive targets, a high buffer gas pressure would be necessary that may preclude propagation of the laser driver and require assisted pinch transport for the heavy-ion driver; andmore » (f) generation and transport of aerosols in the chamber is the key feasibility issue for wetted-wall concepts.« less
TL;DR: Tearing modes often limit the performance of tokamak plasmas, because the magnetic islands which they generate lead to a loss of confinement, or even a disruption.
Abstract: Tearing modes often limit the performance of tokamak plasmas, because the magnetic islands which they generate lead to a loss of confinement, or even a disruption. A particularly dangerous instabil...
TL;DR: It is getting more and more rewarding to deal with the problems related to the ignition and burning of plasmas.
Abstract: After more than 50 years of fusion research the time has arrived when fusion processes in experimental plasmas are increasingly getting important. In JET the genuine fuel (deuterium-tritium) of a fusion reactor was used for the first time in late 1991, in TFTR the same happened in 1993, and in JET an extended period of experiments of this kind was performed in 1997. Therefore, it is getting more and more rewarding to deal with the problems related to the ignition and burning of plasmas.
TL;DR: Energy-resolved neutral particle fluxes are studied in the TJ-II stellarator by using measurements from a neutral particle analyzer in this paper, where the average ion energy can be deduced up to positions outside the positions outside th...
Abstract: Energy-resolved neutral particle fluxes are studied in the TJ-II stellarator by using measurements from a neutral particle analyzer. The average ion energy can be deduced up to positions outside th...
TL;DR: The Wendelstein 7-X (W7-X) stellarator is the largest fusion experiment presently under construction as discussed by the authors, and the first superconducting nonplanar coil is undergoing acceptance testing, the first sector of the plasma vessel has been leak tested, the main parts for the outer vessel have been fabricated, and many rigs for the assembly are already installed.
Abstract: The Wendelstein 7-X (W7-X) stellarator is the largest fusion experiment presently under construction. The main objective of W7-X is to prove the reactor relevance of a stellarator, based on the HELIAS principle, as an alternative to the tokamak. Details of the optimization criteria and the scientific and technical objectives can be found in several publications. At present, the construction of W7-X is close to the start of the assembly. The first superconducting nonplanar coil is undergoing acceptance testing, the first sector of the plasma vessel has been leak tested, the main parts for the outer vessel have been fabricated, the first ports are close to delivery, and many rigs for the assembly are already installed. The assembly started at the end of 2003 with the attachment of saddle coils for magnetic diagnostics on the plasma vessel and will last until 2009 when the torus will be closed. Start of plasma operation is scheduled for the middle of 2010.
Abstract: Double shell targets have been built by Lawrence Livermore National Laboratory (LLNL) for inertial confinement fusion (ICF) experiments on the Omega laser at the University of Rochester and as a prelude to similar experiments on NIF. Of particular interest to ICF studies are high-precision double shell implosion targets for demonstrating thermonuclear ignition without the need for cryogenic preparation. Because the ignition tolerance to interface instabilities is rather low, the manufacturing requirements for smooth surface finishes and shell concentricity are particularly strict. This paper describes a deterministic approach to manufacturing and controlling error sources in each component. Included is the design philosophy of why certain manufacturing techniques were chosen to best reduce the errors within the target. The manufacturing plan developed for this effort created a deterministic process that, once proven, is repeatable. By taking this rigorous approach to controlling all error sources during the manufacture of each component and during assembly, we have achieved the overall 5 {micro}m dimensional requirement with sub-micron surface flaws. Strengths and weaknesses of the manufacturing process will be discussed.
TL;DR: In this article, the authors examined how the FTWR design concept would change if superconducting magnets were used and developed a design concept for a FTWR based on normal conducting magnets.
Abstract: We are developing a Fusion Transmutation of Waste Reactor (FTWR) concept—a subcritical, metal fuel, liquid metal cooled fast reactor driven by a tokamak DT fusion neutron source. An emphasis is placed on using nuclear, separation/processing and fusion technologies that either exist or are at an advanced state of development and on using plasma physics parameters that are supported by the existing database. We have previously discussed the general capabilities of DT tokamak neutron sources for driving transmutation reactors [1] and developed a design concept for a FTWR [2] based on normal conducting magnets. The concept has been further developed in papers dealing with nuclear design and safety [3] and with the evaluation of the potential impact on radioactive waste management [4]. The purpose of this paper is to examine how the FTWR design concept would change if superconducting magnets were used.
TL;DR: In this article, the feasibility of heating TJ-II plasmas by electron Bernstein waves (EBWs) is studied, using the Clemmov-Mullaly-Allis diagram to explore the possible heating regimes, and the TRUBA ray-and beam-tracing code is used to perform detailed calculations.
Abstract: The feasibility of heating TJ-II plasmas by electron Bernstein waves (EBWs) is studied. As a first approach, the Clemmov-Mullaly-Allis diagram is studied to explore the possible heating regimes, and the TRUBA ray- and beam-tracing code, which has been adapted to the complicated TJ-II geometry, is used to perform detailed calculations. The final result is that it is possible to heat plasmas by overcoming the cutoff density of electromagnetic modes by injecting the O mode and X mode at the first harmonic, exploiting the O-X-B1 and the X-B1 schemes. Transport simulations are performed to estimate the plasma parameters that are expected in those regimes and to study the transition from the X mode at the second harmonic to EBW heating at the first harmonic.