| 1. |
- Andersson, Kjell, 1959-, et al.
(författare)
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A flexible chain proposal for winch based point absorbers
- 2018
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Ingår i: Proceedings of the ASME 2018 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2018.
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Konferensbidrag (refereegranskat)abstract
- Ocean wave power is a promising renewable energy source for future energy production. It has however been difficult to find a cost-effective solution to convert the wave energy into electricity. The harsh marine environment and the fact that wave power is delivered with high forces at low speeds makes design of durable mechanical structures and efficient energy conversion challenging. The dimensioning forces strongly depend on the wave power concept, the Wave Energy Converter (WEC) implementation and the actual Power TakeOff (PTO) system. A WEC using a winch as a Power Take-Off system, i.e. a Winch Based Point Absorber (WBPA), could potentially accomplish a low Levelized Cost Of Energy (LCOE) if akey component - a low-cost, durable and efficient winch that can deal with high loads - can be developed. A key problem for achieving a durable winch is to find a force transmitting solution that can deal with these high loads and handle up to 80 million cycles. In this article we propose a design solution for a force transmitting chain in a WBPA system where elastomeric bearings are used as a means to achieve the relative motion between the links in the chain. With this solution no sliding is present and the angular motion is achieved as a deformation in the elastomeric bearing when the chain is winded on a drum. The link was designed primarily to minimize the number of joints in the chain: Thereby the maximum allowed relative angle between the links when rolled up over the drum should be as large as possible within practical limits. The angle is to be handled by the elastomeric bearing. A detailed strength analysis of the link has been performed as well as topology optimization to increase the strength to weight ratio. A test rig for a first proof of concept testing has been developed and the first preliminary test results indicate that this concept with using elastomeric bearings can be a potential solution for a durable chain and should be analyzed further for fatigue conditions and under water operations.
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| 2. |
- Andersson, Kjell, 1959-, et al.
(författare)
-
A Flexible Chain Proposal for Winch-Based Point Absorbers
- 2019
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Ingår i: Journal of mechanical design (1990). - : ASME. - 1050-0472 .- 1528-9001. ; 141:10
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Tidskriftsartikel (refereegranskat)abstract
- Ocean wave power is a promising renewable energy source. It has, however, been difficult to find a cost-effective solution to convert wave energy into electricity. The harsh marine environment and the fact that wave power is delivered with large forces at low speed make design of durable mechanical structures and efficient energy conversion challenging. The dimensioning forces strongly depend on the wave power concept, the wave energy converter (WEC) implementation, and the actual power take-off (PTO) system. A WEC with a winch as a power take-off system, i.e., a winch-based point absorber (WBPA), could potentially enable a low levelized cost of energy (LCOE) if a low-cost, durable and efficient winch that can deal with peak loads can be developed. A key challenge for realizing such a winch is to find a force transmitting solution that can deal with these peak loads and that can handle up to 80 million cycles during its life. In this article, we propose a design solution for a force transmitting chain with elastomer bearings connecting the links of the chain. With this solution no sliding is present, and the angular motion is realized as elastic shear deformations in the elastomer bearings when the chain is wound onto the winch drum. The elastomer bearings were designed for low shear stiffness and high compression stiffness, and the links were designed primarily to minimize the number of joints in the chain. Thereby, the maximum allowed relative angle between the links when rolled up over the drum should be as large as possible within practical limits. Finite element-based topological optimization was performed with the aim to increase the link strength to weight ratio. A test rig for a first proof of concept testing has been developed, and preliminary test results indicate that this chain concept with elastomer bearings can be a potential solution for a durable chain and should be analyzed and tested further for fatigue and sea operations.
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| 3. |
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| 4. |
- Ekergård, Boel, et al.
(författare)
-
Experimental results from a linear wave power generator connected to a resonance circuit
- 2012
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Ingår i: Wiley Interdisciplinary Reviews. - : Wiley. - 2041-8396 .- 2041-840X. ; 2:4, s. 456-464
-
Tidskriftsartikel (refereegranskat)abstract
- The output voltage from a direct-driven permanent magnet linear generator installed in a wave power plant varies both in amplitude and frequency. Electrical conversion is therefore necessary before grid connection can be achieved. The aim of this paper is to present an electrical conversion system based on the electric resonance phenomena. As one of the first steps in the development, and to gain further knowledge and understanding of the proposed resonance circuit, experimental tests with a single-phase permanent magnet linear generator connected to a resonance circuit were performed. The experimental results presented in this paper indicated that a successful resonance between the generator and external circuit was achieved. The research regarding the wave energy converters lies within The Lysekil Wave Power Project at Uppsala University and has been ongoing since 2002.
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| 5. |
- Gustafsson, Johan, 1976, et al.
(författare)
-
Cellular limitation of enzymatic capacity explains glutamine addiction in cancers
- 2022
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Metabolism within the tumor microenvironment, where a complex mixture of different cell types resides in a nutrient-deprived surrounding, is not fully understood due to difficulties in measuring metabolic fluxes and exchange of metabolites between different cell types in vivo. Genome-scale metabolic modeling enables estimation of such exchange fluxes as well as an opportunity to gain insight into the metabolic behavior of individual cell types. Here, we estimated the availability of nutrients and oxygen within the tumor microenvironment using concentration measurements from blood together with a metabolite diffusion model. In addition, we developed an approach to efficiently apply enzyme usage constraints in a comprehensive metabolic model of human cells. The combined modeling reproduced severe hypoxic conditions and the Warburg effect, and we found that limitations in enzymatic capacity contribute to cancer cells’ preferential use of glutamine as a substrate to the citric acid cycle. Furthermore, we investigated the common belief that some stromal cells are exploited by cancer cells to produce metabolites useful for the cancer cells. We identified a total of 233 potential metabolites that could support collaboration between cancer cells and cancer associated fibroblasts, but when limiting to metabolites previously identified to participate in such collaboration, no growth advantage was observed. Our work highlights the importance of enzymatic capacity limitations for cell behaviors and exemplifies the utility of enzyme constrained models for accurate prediction of metabolism in cells and tumor microenvironments.
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| 6. |
- Gustafsson, Johan, 1976, et al.
(författare)
-
Metabolic collaboration between cells in the tumor microenvironment has a negligible effect on tumor growth
- 2024
-
Ingår i: Innovation. - 2666-6758. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- The tumor microenvironment is composed of a complex mixture of different cell types interacting under conditions of nutrient deprivation, but the metabolism therein is not fully understood due to difficulties in measuring metabolic fluxes and exchange of metabolites between different cell types in vivo. Genome-scale metabolic modeling enables estimation of such exchange fluxes as well as an opportunity to gain insight into the metabolic behavior of individual cell types. Here, we estimated the availability of nutrients and oxygen within the tumor microenvironment using concentration measurements from blood together with a metabolite diffusion model. In addition, we developed an approach to efficiently apply enzyme usage constraints in a comprehensive metabolic model of human cells. The combined modeling reproduced severe hypoxic conditions and the Warburg effect, and we found that limitations in enzymatic capacity contribute to cancer cells’ preferential use of glutamine as a substrate to the citric acid cycle. Furthermore, we investigated the common hypothesis that some stromal cells are exploited by cancer cells to produce metabolites useful for the cancer cells. We identified over 200 potential metabolites that could support collaboration between cancer cells and cancer-associated fibroblasts, but when limiting to metabolites previously identified to participate in such collaboration, no growth advantage was observed. Our work highlights the importance of enzymatic capacity limitations for cell behaviors and exemplifies the utility of enzyme-constrained models for accurate prediction of metabolism in cells and tumor microenvironments.
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| 7. |
- Hagnestål, Anders, et al.
(författare)
-
A Compact Non-Planar Coil Design for the SFLM Hybrid
- 2012
-
Ingår i: Journal of fusion energy. - : Springer Science and Business Media LLC. - 0164-0313 .- 1572-9591. ; 31:4, s. 379-388
-
Tidskriftsartikel (refereegranskat)abstract
- A non-planar single layer semiconductor coil set for a version of the Straight Field Line Mirror Hybrid concept with reduced magnetic field has been computed. The coil set consists of 30 coils that are somewhat similar to baseball coils with skewed sides. The coil set has been modeled with filamentary current distributions and basic scaling assumptions have been made regarding the coil widths. This coil set is expected to be considerably cheaper than a previous computed coil set. The coils can probably be produced with technologies known today.
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| 8. |
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| 9. |
- Hagnestål, Anders, 1976-, et al.
(författare)
-
A highly efficient and low-cost linear TFM generator for wave power
- 2017
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Ingår i: Proceedings of the 12th European Wave and Tidal Energy Conference 27th aug - 1st Sept 2017, Cork, Ireland. - : European Wave and Tidal Energy Conference.
-
Konferensbidrag (refereegranskat)abstract
- A force-dense,low-cost and very efficient direct drive transverse flux generator aimed forwave power applications is being developed at the Royal Institute of Technologyin Sweden, and a linear version is currently being built. The machine isspecialized for low speeds, and the project is presented in this paper, wherewe focus on why TFMs are very suitable for low speed applications and why theyare so hard to build. The basic electromagnetic design is given as well as anoverview of the mechanical design. The benefits of such machines at low speedsare described in detail. The challenges that the machine type have are alsopresented, and suggestions are made on how they can be handled. Geometrical andcalculated performance data is given for a prototype machine that is to beconstructed during 2017. The machine is predicted to have an efficiency of about98% at speeds as low as 0.7 m/s, and a shear stress of 100-120 kN/m²,corresponding to 200-240 kN/m² if only half the active area is counted asactive which is custom for such machines.
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| 10. |
- Hagnestål, Anders, 1976-
(författare)
-
A low cost and highly efficient TFM generator for wave power
- 2016
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Ingår i: Proceedings of the 3rd Asian Wave and Tidal Energy Conference. ; , s. 822-828
-
Konferensbidrag (refereegranskat)abstract
- A force-dense and very efficient direct drive transverse flux generator aimed for wave power applications is being developed at the Royal Institute of Technology in Sweden. The machine is specialized for low speeds, and the design of a linear version is presented in this paper. The basic electromagnetic design is given as well as an overview of the mechanical design. The benefits of such machines at low speeds are described in detail. The challenges that the machine type have are also presented, and suggestions are made on how they can be handled. Geometrical and calculated performance data is given for a prototype machine that is to be constructed during 2017. The possibility of using the machine type for control methods such as reactive control is also discussed. The machine is predicted to have an efficiency of 97-98% at speeds as low as 0.7 m/s, and a shear stress of 100-120 kN/m², corresponding to 200-240 kN/m² if only half the active area is counted as active which is custom for such machines.
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| 11. |
- Hagnestål, Anders, et al.
(författare)
-
A study on field and coil designing for a quadrupolar mirror hybrid reactor
- 2011
-
Ingår i: Journal of fusion energy. - : Springer Science and Business Media LLC. - 0164-0313 .- 1572-9591. ; 30:2, s. 144-156
-
Tidskriftsartikel (refereegranskat)abstract
- A vacuum magnetic field from a superconducting coil set for a single cell minimum B fusion-fission mirror machine reactor is computed. The magnetic field is first optimized for MHD flute stability, ellipticity and field smoothness in a long-thin approximation. Recirculation regions and magnetic expanders are added to the mirror machine without an optimizing procedure. The optimized field is thereafter reproduced by a set of circular and quadrupolar coils. The coils are modelled using filamentary line current distributions. Basic scaling assumptions are implemented for the coil design, with a maximum allowed current density of 1.5 kA/cm2. The coils are optimized using a local optimization method and the resulting field is checked for MHD flute stability and maximum ellipticity.
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| 12. |
- Hagnestål, Anders, Forskare, 1976-
(författare)
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Addressing the Magnet Mounting Problem for Double-Sided TFM Machines with Flux-Concentrating Setup
- 2019
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Tidskriftsartikel (refereegranskat)abstract
- Variable reluctance machines such as transverse fluxmachines (TFM) have very suitable properties for slow speedrenewable energy conversion applications such as wave power.The double-sided TFM variant with flux-concentrating magnetsetup has generally better performance than other variants, butis considerably more challenging to build. One of the mostchallenging parts to build for such machines is the magnetstructure, especially for larger machines where the magnetstructure is wide. In this text, the magnet mounting problemof such a structure for a linear wave power generator hasbeen analysed. A mounting method has been proposed and themounting forces involved for that method have been calculated.A mounting tool has been designed and built, and it has beenused to successfully build 12 magnet stacks for two linear wavepower generators that form a test setup. Through this work, ithas been demonstrated that it is fully feasible to construct suchmagnet structures and thereby a reference to how this rathercomplex practical problem can be handled is provided for othersin the field.
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| 13. |
- Hagnestål, Anders, 1976-
(författare)
-
Coil Design and Related Studies for the Fusion-Fission Reactor Concept SFLM Hybrid
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A fusion-fission (hybrid) reactor is a combination of a fusion device and a subcritical fission reactor, where the fusion device acts as a neutron source and the power is mainly produced in the fission core. Hybrid reactors may be suitable for transmutation of transuranic isotopes in the spent nuclear fuel, due to the safety margin on criticality imposed by the subcritical fission core. The SFLM Hybrid project is a theoretical project that aims to point out the possibilities with steady-state mirror-based hybrid reactors. The quadrupolar magnetic mirror vacuum field is based on the Straight Field Line Mirror field and the central cell is 25 m long. A fission mantle surrounds the mirror cell. The fission to fusion power ratio is about 150 with keff = 0.97, implying that almost all the produced energy comes from fission. Beyond each mirror end magnetic expanders are located, which increase the plasma receiving “divertor” area and provide tolerable heat load on wall materials. The plasma is heated with ion cyclotron radio frequency heating and the fission mantle is cooled using a liquid lead-bismuth eutectic. The device is self-sufficient in tritium, and does not seem to suffer from severe material problems. A remaining issue may be the plasma electron temperature, which need to reach about 500 eV for efficient power production. In this doctoral thesis, theoretical work has been done with the magnetic coil system of such a device and also with the overall concept. A new coil type, the fishbone coil, suitable for single cell quadrupolar mirrors, has been invented. Two vacuum field coil sets with satisfying properties have been found, where the most recent coil set consists of fishbone coils. Finite ß effects on the magnetic field have been investigated, showing that the flux tube ellipticity increases with ß. The ellipticity of the vacuum field increases slightly with radius, but with finite ß it decreases with radius. The maximum flux surface radial extensions decrease with ß, which is an unexpected and beneficial result. A radial invariant has also been identified, and particle simulations have been made to emphasize that quadrupolar mirrors must be symmetric or confinement may be lost.
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| 14. |
- Hagnestål, Anders
(författare)
-
Coil Design for a Mirror Based Fusion-Fission Reactor
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The SFLM Hybrid project aims to show that it is probable that a fusion-fission reactor can be constructed with a single-cell minimum B mirror machine as a neutron source. In this licentiate thesis, theoretical work has been done with the magnetic coil system of such a device and also with the overall concept. The magnetic mirror field is based on the Straight Field Line Mirror field and the device has a mirror cell length of 25 m. A fission mantle surrounds the mirror cell, catching almost all fusion neutrons. The energy multiplication of fission to fusion energy is about 150 with keff = 0.97, implying that almost all the produced energy comes from fission. Beyond each mirror end, a magnetic expander is added to the mirror cell. The expanders increase the plasma receiving “divertor” area to an almost arbitrary size, which provides tolerable average heat load on the wall materials. They also add to MHD stability and may be a mean to increase the electron temperature. The device is heated with ion cyclotron radio frequency heating and the fission mantle is cooled using liquid lead or a liquid lead-bismuth eutectic. The device is self-sufficient in tritium. The magnetic field has been optimized for flute stability, low ellipticity and low field gradients in the long-thin approximation. The optimization of the magnetic field components has been made with a local optimizer. A coil set has been calculated which reproduces the selected optimized magnetic field with satisfactory accuracy and within the preliminary geometric constraints imposed by the fission mantle and coolant influx/outflux. Circular coils produce the axisymmetric field component and quadrupolar coils similar to baseball coils produce the quadrupolar field component. The proposed device does not suffer from severe material problems (to our knowledge) or a pulsed mode of operation such as for the ITER project. The main remaining question to be answered seems to be the electron temperature in the plasma, which need to reach about 500 eV for efficient power production.
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| 15. |
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| 16. |
- Hagnestål, Anders, et al.
(författare)
-
Coil design for the straight field line mirror
- 2009
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Ingår i: Fusion science and technology. - 1536-1055 .- 1943-7641. ; 55:2T, s. 127-130
-
Tidskriftsartikel (refereegranskat)abstract
- Coil systems for producing the Straight Field Line Mirror field using axisymmetric and quadrupolar coils are calculated. Two applications are intended, a fusion-fission nuclear waste transmutation device and a small plasma deposition device. Position, size and current for the axisymmetric coils are optimized as well as radial profile and current for the quadrupolar coils for the two applications. Calculations show that such a coil system can produce the Straight Field Line Mirror field for long-thin mirrors with moderate mirror ratio, but some other coil configuration needs to be found for mirrors where the coils cannot reside close to the plasma edge. In this work, the material science experiment mirror can be produced with about 1% error but the fusion-fission device field has not at this moment been reproduced with acceptable errors.
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| 17. |
- Hagnestål, Anders, et al.
(författare)
-
Coil System For a Mirror-Based Hybrid Reactor
- 2012
-
Ingår i: Fusion for Neutrons and Subcritical Nuclear Fission. - : AIP. - 9780735410381 ; , s. 217-223
-
Konferensbidrag (refereegranskat)abstract
- Two different superconducting coil systems for the SFLM Hybrid study - a quadrupolar mirror based fusion-fission reactor study - are presented. One coil system is for a magnetic field with 2 T at the midplane and a mirror ratio of four. This coil set consists of semi-planar coils in two layers. The alternative coil system is for a downscaled magnetic field of 1.25 T at the midplane and a mirror ratio of four, where a higher beta is required to achieve sufficient the neutron production. This coil set has one layer of twisted 3D coils. The 3D coils are expected to be considerably cheaper than the semiplanar, since NbTi superconductors can be used for most coils instead of Nb3Sn due to the lower magnetic field.
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| 18. |
- Hagnestål, Anders, 1976-, et al.
(författare)
-
Durable winch-based point absorbers
- 2017
-
Ingår i: Proceedings of the 12th European Wave and Tidal Energy Conference 27th Aug - 1st Sept 2017, Cork, Ireland. - : European Wave and Tidal Energy Conference.
-
Konferensbidrag (refereegranskat)abstract
- Wave power could give a significant contribution to afuture sustainable energy system if the Levelized Cost Of Energycan be reduced to a competitive level. Winch-based pointabsorbers could potentially accomplish this if a key component –a low-cost, durable and efficient winch that can deal with highloads – can be developed. In this article the possibilities of winchbasedpoint absorbers and the challenges that need to beovercome are described. Further, the possibilities to design suchwinches are explored and several different design approaches areevaluated and compared. At present, we believe that such awinch solution can be found although more research is needed todevelop a full concept, and the most promising solutions so farinvolve inverted tooth chains, flat UHMwPE fiber (Dyneema)bands and flat carbon fibre structures.
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| 19. |
- Hagnestål, Anders, et al.
(författare)
-
Field and Coil Design for a Quadrupolar Mirror Hybrid Reactor
- 2011
-
Ingår i: Journal of fusion energy. - : Springer Science and Business Media LLC. - 0164-0313 .- 1572-9591. ; 30:2, s. 144-156
-
Tidskriftsartikel (refereegranskat)abstract
- A vacuum magnetic field from a superconducting coil set for a single cell minimum B fusion-fission mirror machine reactor is computed. The magnetic field is first optimized for MHD flute stability, ellipticity and field smoothness in a long-thin approximation. Recirculation regions and magnetic expanders are added to the mirror machine without an optimizing procedure. The optimized field is thereafter reproduced by a set of circular and quadrupolar coils. The coils are modelled using filamentary line current distributions. Basic scaling assumptions are implemented for the coil design, with a maximum allowed current density of 1.5 kA/cm(2). The coils are optimized using a local optimization method and the resulting field is checked for MHD flute stability and maximum ellipticity.
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| 20. |
- Hagnestål, Anders, 1976-, et al.
(författare)
-
Finite ß corrections to the magnetic field in the SFLM Hybrid
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Finite effects for the magnetic field in the SFLM Hybrid reactor concept have been studied numerically. The parallel current has been calculated, and it is found to be negligible. The constant pressure surfaces at the midplane are not significantly affected by the parallel current, and have a square-like octupolar distortion near the plasma edge. In most of the plasma region, their cross sections are nearly circular. The flux tube ellipticity is found to increase by the finite effects, but the increase is considerably more pronounced near the z axis where the pressure is high. At the plasma edge, the increase in ellipticity by finite effects is only moderate and the maximum radial extensions of the flux tube are even slightly decreased compared to the vacuum case.
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| 21. |
- Hagnestål, Anders, et al.
(författare)
-
Radial Confinement in Non-Symmetric Quadrupolar Mirrors
- 2013
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Ingår i: Journal of fusion energy. - : Springer. - 0164-0313 .- 1572-9591. ; 32:3, s. 327-335
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Tidskriftsartikel (refereegranskat)abstract
- Charged particles in symmetric quadrupolar mirrors are radially confined and have an associated radial invariant. In a symmetric quadrupolar field the magnetic field modulus satisfies B(z)=−B(z) along the axis if z = 0 defines the field minimum of the mirror, and the quadrupolar field has a corresponding symmetry. The field in the anchor cells of a tandem mirror need not obey a corresponding symmetry. In this paper, the radial confinement of non-symmetric mirrors is examined by tracing sample ions in the magnetic field. It is found that for non-symmetric mirrors, particles are typically not confined, and no radial invariant exists for such devices. Without attention to this effect in the field and coil design, radial confinement of trapped particles may be lost.
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| 22. |
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| 23. |
- Hagnestål, Anders, et al.
(författare)
-
Theoretical field and coil design for a single cell minimum-B mirror hybrid reactor
- 2011
-
Ingår i: Fusion science and technology. - 1536-1055 .- 1943-7641. ; 59:1T, s. 217-219
-
Tidskriftsartikel (refereegranskat)abstract
- A vacuum magnetic field from a superconducting coil set for a single cell minimum-B mirror-based,fission-fusion reactor is computed. The magnetic field is optimized for MHD stability, ellipticity and field smoothness. A recirculation region and wide magnetic expanders on both sides are provided to the central mirror cell. A coil set producing this field is computed which consists of circular and quadrupolar coils. Basic scaling assumptions are made for the coil dimensions, based on a maximum allowed current density of 1.5 kA/cm(2) for superconducting coils. Sufficient space is available for a fission mantle. The field produced by the coils is checked for MHD plasma stability and maximum ellipticity. The resulting confinement region is 25 in long with a 40 cm midplane plasma radius.
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| 24. |
- Hagnestål, Anders, et al.
(författare)
-
Vacuum Field Ellipticity Dependence on Radius in Quadrupolar Mirror Machines
- 2012
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Ingår i: Journal of fusion energy. - : Springer Netherlands. - 0164-0313 .- 1572-9591. ; 31:5, s. 448-454
-
Tidskriftsartikel (refereegranskat)abstract
- The vacuum field flux tube ellipticity dependence on radius for quadrupolar mirror machines has been investigated. A third order expression in the paraxial approximation has been derived for the vacuum field ellipticity. The dependence of ellipticity on midplane radius has been examined in the SFLM Hybrid and the outermost plasma flux tube is 3.5 cm wider than predicted by the first order paraxial approximation, which is within boundaries set by the first wall. The third order approximation has a high accuracy for the ellipticity for long-thin mirrors such as the SFLM Hybrid, and even the first order approximation that is independent of radius is sufficient in many applications. The ellipticity dependence on midplane radius for mirrors with more strongly localized quadrupolar fields than the SFLM Hybrid is also shown to be minor.
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| 25. |
- Moiseenko, V. E., et al.
(författare)
-
Research on stellarator-mirror fission-fusion hybrid
- 2014
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 56:9, s. 094008-
-
Tidskriftsartikel (refereegranskat)abstract
- The development of a stellarator-mirror fission-fusion hybrid concept is reviewed. The hybrid comprises of a fusion neutron source and a powerful sub-critical fast fission reactor core. The aim is the transmutation of spent nuclear fuel and safe fission energy production. In its fusion part, neutrons are generated in deuterium-tritium (D-T) plasma, confined magnetically in a stellarator-type system with an embedded magnetic mirror. Based on kinetic calculations, the energy balance for such a system is analyzed. Neutron calculations have been performed with the MCNPX code, and the principal design of the reactor part is developed. Neutron outflux at different outer parts of the reactor is calculated. Numerical simulations have been performed on the structure of a magnetic field in a model of the stellarator-mirror device, and that is achieved by switching off one or two coils of toroidal field in the Uragan-2M torsatron. The calculations predict the existence of closed magnetic surfaces under certain conditions. The confinement of fast particles in such a magnetic trap is analyzed.
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| 26. |
- Noack, Klaus, et al.
(författare)
-
Comments on the power amplification factor of a driven subcritical system
- 2013
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Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 59, s. 261-266
-
Tidskriftsartikel (refereegranskat)abstract
- The power amplification factor PAF of a driven subcritical system is defined as the ratio of the fission power output of the blanket to the power which the driver must deliver to sustain its neutron source intensity. This parameter decisively determines the effectiveness of the whole system independent of its special purpose as energy amplifier or as transmutation facility. The present note derives a refined analytical expression for the PAF which reveals more physical details than the expressions given by other authors. Moreover, the traditionally used forms of the static reactor eigenvalue equation and of its adjoint equation are rewritten for subcritical systems and used in the derivation of the expression for the PAF. The derived formula and the modified eigenvalue equations are discussed.
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| 27. |
- Noack, Klaus, et al.
(författare)
-
Neutronic model of a mirror based fusion-fission hybrid for the incineration of spent nuclear fuel and with potential for power generation
- 2011
-
Konferensbidrag (refereegranskat)abstract
- In the last decade the Georgia Institute of Technology (Georgia Tech) published several design concepts of tokamak based fusion-fission hybrids which use solid fuel consisting of the transuranic elements of spent nuclear fuel from Light-Water-Reactors. The objectives of the hybrids are the incineration of the transuranic elements and additional net energy production. The paper presents a rough scientific design of the blanket of a mirror hybrid which was derived from the results of neutron transport calculations. The main operation parameters of two hybrid options were specified. One is the analog to Georgia Techs first version of a 'fusion transmutation of waste reactor" (FTWR) and the other is a possible near-term option which requires minimal fusion power.
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| 28. |
- Noack, Klaus, et al.
(författare)
-
Neutronic model of a mirror based fusion-fission hybrid for the incineration of the transuranic elements from spent nuclear fuel and energy amplification
- 2011
-
Ingår i: Annals of Nuclear Energy. - : Elsevier BV. - 0306-4549 .- 1873-2100. ; 38:2-3, s. 578-589
-
Tidskriftsartikel (refereegranskat)abstract
- The Georgia Institute of Technology has developed several design concepts of tokamak based fusion-fission hybrids for the incineration of the transuranic elements of spent nuclear fuel from Light-Water-Reactors. The present paper presents a model of a mirror hybrid. Concerning its main operation parameters it is in several aspects analogous to the first tokamak based version of a "fusion transmutation of waste reactor". It was designed for a criticality keff <= 0.95 in normal operation state. Results of neutron transport calculations carried out with the MCNP5 code and with the JEFF-3.1 nuclear data library show that the hybrid generates a fission power of 3 GWth requiring a fusion power between 35 and 75 MW, has a tritium breeding ratio per cycle of TBRcycle = 1.9 and a first wall lifetime of 12-16 cycles of 311 effective full power days. Its total energy amplification factor was roughly estimated at 2.1. Special calculations showed that the blanket remains in a deep subcritical state in case of accidents causing partial or total voiding of the lead-bismuth eutectic coolant. Aiming at the reduction of the required fusion power, a near-term hybrid option was identified which is operated at higher criticality keff <= 0.97 and produces less fission power of 1.5 GWth. Its main performance parameters turn out substantially better.
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| 29. |
- Noack, Klaus, et al.
(författare)
-
Safety And Power Multiplication Aspects Of Mirror Fusion-Fission Hybrids
- 2012
-
Ingår i: Fusion for Neutrons and Subcritical Nuclear Fission. - : AIP. - 9780735410381 ; , s. 186-198
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Konferensbidrag (refereegranskat)abstract
- Recently, in a research project at Uppsala University a simplified neutronic model for a straight field line mirror hybrid has been devised and its most important operation parameters have been calculated under the constraints of a fission power production of 3 GW and that the effective multiplication factor k(eff) does not exceed 0.95. The model can be considered as representative for hybrids driven by other types of mirrors too. In order to reduce the demand on the fusion power of the mirror, a modified option of the hybrid has been considered that generates a reduced fission power of 1.5 GW with an increased maximal value k(eff) = 0.97. The present paper deals with nuclear safety aspects of this type of hybrids. It presents and discusses calculation results of reactivity effects as well as of driver effects.
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| 30. |
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| 31. |
- Ågren, Olov, et al.
(författare)
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Conceptual study of a straight field line mirror hybrid reactor
- 2011
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Ingår i: Problems of Atomic Science and Technology. - 1562-6016. ; :1, s. 3-7
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Tidskriftsartikel (refereegranskat)abstract
- A hybrid reactor based on the straight field line mirror (SFLM) with magnetic expanders at the ends is proposed as a compact device for transmutation of nuclear waste and power production. Compared to a fusion reactor, plasma confinement demands can be relaxed if there is a strong energy multiplication by the fission reactions, i.e. Q(r)=Pfission/Pfusion >> 1. The values of Q(r) is primarily restricted by fission reactor safety requirements. For the SFLM, computations suggest that values of Q(r) ranging up to 150 are consistent with reactor safety. In a mirror hybrid device with Q(r) > 100, the lower bound on the electron temperature for power production can then be estimated to be around 400 eV, which may be achievable for a mirror machine. The SFLM with its quadrupolar stabilizing fields does not rely on plasma flow into the expanders for MED stability, and a scenario with plasma density depletion in the expanders is a possibility to increase the electron temperature. Efficient power production is predicted with a fusion Q= 0.15 and an electron temperature around 500 eV. A fusion power of 10 MW could then be amplified to 1.5 GW fission power in a compact 25 m long hybrid mirror machine. Beneficial features are that all sensitive equipment can be located outside the neutron rich region and a steady state power production seems possible. Self circulation of the lead coolant, which is useful for heat removal if coolant pumps cease to operate, could be arranged by orienting the magnetic axis vertically. Results from studies on plasma equilibrium and stability, coil designing, RF heating and neutron computations are presented.
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| 32. |
- Ågren, Olov, et al.
(författare)
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Fusion-fission hybrid reactor studies for the straight field line mirror
- 2011
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Ingår i: Fusion science and technology. - 1536-1055 .- 1943-7641. ; 59:1T, s. 166-169
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Tidskriftsartikel (refereegranskat)abstract
- A comparatively small mirror fusion hybrid device may be developed for industrial transmutation and energy production from spent nuclear waste. This opportunity ensues from the large fission to fusion energy multiplication ratio, Q(r) =P-fis/P-fus <= 150, in a subcritical fusion device surrounded by a fission mantle with the neutron multiplicity k(eff) approximate to 0.97. The geometry of mirror machines is almost perfectly suited for a hybrid reactor application, and the requirements for plasma confinement can be dramatically relaxed in correspondence with a high value of Q(r) Steady state power production in a mirror hybrid seems possible if the electron temperature reaches 500 eV. A moderately low fusion Q factor, the ratio of fusion power to the power necessary to sustain the plasma, could be sufficient, i.e. Q approximate to 0.15. Theoretical predictions for the straight field line mirror (SFLM) concept are presented, including results from radio frequency heating, neutron Monte Carlo and magnetic coil computations. Means to achieve an electron temperature of 500 eV are briefly discussed. The basic study considers a 25 m long confinement region with 40 cm plasma radius with 10 MW fusion power and a power production of 1.5 GW thermal.
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| 33. |
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| 34. |
- Ågren, Olov, et al.
(författare)
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Hybrid Reactor Studies Based on the Straight Field Line Mirror
- 2013
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Ingår i: Fusion science and technology. - 1536-1055 .- 1943-7641. ; 63:1T, s. 52-57
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Tidskriftsartikel (refereegranskat)abstract
- The straight field line mirror (SFLM) hybrid reactor studies aim to identify a concept where the safety of fission power production could be enhanced. A fusion neutron source could become a mean to achieve this. The SFLM studies address critical issues such as reactor safety, natural circulation of coolants, steady state operation for a year or more and means to avoid too strong material loads by a proper geometrical arrangement of the reactor components. A key result is that power production may be possible with a fusion Q factor as low as 0.15. This possibility arises from the high power amplification by fission, which within reactor safety margins may exceed a factor of 100. The requirements on electron temperature are dramatically lower for a fusion hybrid compared to a stand-alone fusion reactor. This and several other factors are important for our choice to select a mirror machine for the fusion hybrid reactor studies.
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| 35. |
- Ågren, Olov, et al.
(författare)
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Possibilities for transmutation of nuclear waste and energy production with a "straight field line mirror" neutron source
- 2009
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Ingår i: Fusion science and technology. - 1536-1055 .- 1943-7641. ; 55:2T, s. 46-51
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Tidskriftsartikel (refereegranskat)abstract
- A pure fusion mirror device suffers from the predicted low values of the Q factor (energy gain factor). A much higher energy production may be achieved in a fusion-fission reactor, where the fusion plasma neutron source is surrounded by a fission mantle. The fusion neutrons are capable of initiating energy producing fission reactions in the surrounding mantle. A mirror machine can probably be designed to provide sufficient space for a 1.1 m wide fission mantle inside the current coils, and the power production from the fission reactions can in such a case exceed the fusion power by more than two orders of magnitude ( P-fis / P-fus approximate to 150), suggesting a realistic reactor regime for a mirror based fusion-fission device. An energy producing device may operate with an electron temperature around 1 keV Transmutation of long-lived radio active isotopes (minor actinides) from spent nuclear fuel from fission reactors can reduce geological storage from 100 000 years to only 300 years. Since the energy of D-T fusion neutrons are above the threshold for the most important transmutation reactions desired for treatment of nuclear waste, there may be an interest for a mirror transmutation device even if no net energy is produced. Recent theoretical simulations have considered the possibility to use the Gas Dynamic Trap (GDT) at Novosibirsk as a subcritical burner for transmutation by fusion neutrons. In the present work, possibilities for mirror based fusion-fission machines are discussed Means to achieve sufficient end confinement for a straight field line mirror fusion-fission system with a thermal barrier are briefly analyzed End leakage can alternatively be avoided by connecting the ends of a magnetic mirror with a stellerator tube, while the fusion neutrons are produced in the mirror part where a high energy sloshing ion component is confined. A zero dimensional model for such a mirror-stellarator system has been developed. The computed results indicate some possible parameter regimes for industrial transmutation and power production.
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| 36. |
- Ågren, Olov, et al.
(författare)
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Radial Drift Invariant In Long-Thin Mirrors
- 2012
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Ingår i: Fusion for Neutrons and Subcritical Nuclear Fission. - : AIP. - 9780735410381 ; , s. 255-258
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Konferensbidrag (refereegranskat)abstract
- In omnigenous systems, the guiding centers are constrained to move on magnetic surfaces. Since a magnetic surface is determined by a constant radial Clebsch coordinate, omnigenuity implies that the guiding center radial coordinate (the Clebsch coordinate) is constant. Near omnigenuity is probably a requirement for high quality confinement and in such systems only small oscillatory radial banana guiding center excursions from the average drift surface occur. The guiding center radial coordinate is then the leading order term for a more precise radial drift invariant I-r, where higher order corrections arise from the oscillatory "banana ripple" associated with the excursions from the mean drift magnetic surface. An analytical expression for the radial invariant is derived for long-thin quadrupolar mirror equilibria. The formula for the invariant is then used in a Vlasov distribution function. To model radial density profiles, it is necessary to use the radial invariant (the parallel invariant is insufficient for this). The results are also compared with standard fluid approaches. In several aspects, the fluid and Vlasov system with the radial invariant give analogous formulas. One difference is that the parallel current associated with finite banana widths could be derived from the radial invariant.
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| 37. |
- Ågren, Olov, et al.
(författare)
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Radial Drift Invariant in Long-Thin Mirrors
- 2012
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Ingår i: European Physical Journal D. - : Springer. - 1434-6060 .- 1434-6079. ; 66:28
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Tidskriftsartikel (refereegranskat)abstract
- In omnigenous systems, guiding centers are constrained to move on magnetic surfaces. Sincea magnetic surface is determined by a constant radial Clebsch coordinate, omnigeneity implies that theguiding center radial coordinate (the Clebsch coordinate) is a constant of motion. Near omnigeneity isprobably a requirement for high quality confinement and in such systems only small oscillatory radialbanana guiding center excursions from the average drift surface occur. The guiding center radial coordinateis then the leading term for a more precise radial drift invariant Ir, corrected by oscillatory “bananaripple” terms. An analytical expression for the radial invariant is derived for long-thin quadrupolar mirrorequilibria. The formula for the invariant is then used in a Vlasov distribution function. Comparisons arefirst made with Vlasov equilibria using the adiabatic parallel invariant. To model radial density profiles, itis necessary to use the radial invariant (the parallel invariant is insufficient for this). The results are alsocompared with a fluid approach. In several aspects, the fluid and Vlasov system with the radial invariantgive analogous predictions. One difference is that the parallel current associated with finite banana widths could be derived from the radial invariant.
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| 38. |
- Ågren, Olov, et al.
(författare)
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Studies of a Straight Field Line Mirror with emphasis on fusion-fission hybrids
- 2010
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Ingår i: Fusion science and technology. - 1536-1055 .- 1943-7641. ; 57:4, s. 326-334
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Tidskriftsartikel (refereegranskat)abstract
- The straight field line mirror (SFLM) field with magnetic expanders beyond the confinement region is proposed as a compact device for transmutation of nuclear waste and power production. A design with reactor safety and a large fission-to-fusion energy multiplication is analyzed. Power production is predicted with a fusion Q = 0.15 and an electron temperature of [approximately]500 eV. A fusion power of 10 MW may be amplified to 1.5 GW of fission power in a compact hybrid mirror machine. In the SFLM proposal, quadrupolar coils provide stabilization of the interchange mode, radio-frequency heating is aimed to produce a hot sloshing ion plasma, and magnetic coils are computed with an emphasis on minimizing holes in the fission blanket through which fusion neutrons could escape. Neutron calculations for the fission mantle show that nearly all fusion neutrons penetrate into the fission mantle. A scenario to increase the electron temperature with a strong ambipolar potential suggests that an electron temperature exceeding 1 keV could be reached with a modest density depletion by two orders in the expander. Such a density depletion is consistent with stabilization of the drift cyclotron loss cone mode.
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| 39. |
- Ågren, Olov, et al.
(författare)
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The Hybrid Reactor Project Based On The Straight Field Line Mirror Concept
- 2012
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Ingår i: Fusion for Neutrons and Subcritical Nuclear Fission. - : AIP. - 9780735410381 ; , s. 173-185
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Konferensbidrag (refereegranskat)abstract
- The straight field line mirror (SFLM) concept is aiming towards a steady-state compact fusion neutron source. Besides the possibility for steady state operation for a year or more, the geometry is chosen to avoid high loads on materials and plasma facing components. A comparatively small fusion hybrid device with "semi-poor" plasma confinement (with a low fusion Q factor) may be developed for industrial transmutation and energy production from spent nuclear fuel. This opportunity arises from a large fission to fusion energy multiplication ratio, Q(r) = P-fis/P-fus >> 1. The upper bound on Q(r) is primarily determined by geometry and reactor safety. For the SFLM, the upper bound is Q(r)approximate to 150, corresponding to a neutron multiplicity of k(eff) =0.97. Power production in a mirror hybrid is predicted for a substantially lower electron temperature than the requirement T-e approximate to 10 keV for a fusion reactor. Power production in the SFLM seems possible with Q approximate to 0.15, which is 10 times lower than typically anticipated for hybrids (and 100 times smaller than required for a fusion reactor). This relaxes plasma confinement demands, and broadens the range for use of plasmas with supra-thermal ions in hybrid reactors. The SFLM concept is based on a mirror machine stabilized by qudrupolar magnetic fields and large expander tanks beyond the confinement region. The purpose of the expander tanks is to distribute axial plasma loss flow over a sufficiently large area so that the receiving plates can withstand the heat. Plasma stability is not relying on a plasma flow into the expander regions. With a suppressed plasma flow into the expander tanks, a possibility arise for higher electron temperature. A brief presentation will be given on basic theory for the SFLM with plasma stability and electron temperature issues, RF heating computations with sloshing ion formation, neutron transport computations with reactor safety margins and material load estimates, magnetic coil designs as well as a discussion on the implications of the geometry for possible diagnostics. Reactor safety issues are addressed and a vertical orientation of the device could assist passive coolant circulation. Specific attention is put to a device with a 25 m long confinement region and 40 cm plasma radius in the mid-plane. In an optimal case (k(eff) = 0.97) with a fusion power of only 10 MW, such a device may be capable of producing a power of 1.5 GW(th).
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| 40. |
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| 41. |
- Ågren, Olov, et al.
(författare)
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The straight field line mirror concept and applications
- 2008
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Ingår i: Problems of Atomic Science and Technology. - 1562-6016. ; :6, s. 8-12
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Tidskriftsartikel (refereegranskat)abstract
- The straight field line mirror field is a marginal minimum B field with straight nonparallel field lines. This field gives optimal ellipticity, the drift surfaces lie on a magnetic surface, radiofrequency heating of the plasma is predicted to be efficient and MHD stability is provided by the minimum B property. One intended application of the magnetic field configuration is energy production and transmutation of spent nuclear fuel in a fusion-fission machine, where the mirror confined plasma is surrounded by a fission mantle. Reactor safety can be increased with a subcritical fission mantle, and the fission power can exceed the fusion power by as much as a factor of 150 with a reasonable condition for reactor safety margins, and this provides a basis for a compact reactor design. The straight field line mirror concept can also be of interest as a plasma source for synthesis of sophisticated materials. PACS: 28.52.Av, 28.41.Ak.
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