| 1. |
- Bergkvist, Tommy, et al.
(författare)
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Non-linear Alfvén eigenmode dynamics of a burning plasma in the presence of ion cyclotron resonance heating
- 2006
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Ingår i: EPS Conf. Plasma Phys., EPS. - 9781622763337 ; , s. 1792-1795
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Konferensbidrag (refereegranskat)abstract
- Alfvén eigenmodes (AEs) excited by α particles in a burning plasma can degrade the heating efficiency by spatial redistribution of the resonant α particles. Changes of the orbit invariants in phase space by collisions and other waves, such as magnetosonic waves during ion cyclotron resonance heating (ICRH), lead to changes in the phase between the αs and AEs, causing a decorrelation of the interactions. ICRH lead to an increased decorrelation of the AE interactions and hence a stronger radial redistribution of the thermonuclear α particles by the AEs. Renewal of the distribution function by thermonuclear reactions and losses of α particles to the wall lead to a continuous drive of the AEs and a radial redistribution of the α particles. The redistribution results in a degradation of the heating efficiency.
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| 2. |
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| 3. |
- Dahlin, Jon-Erik, 1977-, et al.
(författare)
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Improved Computer Simulations of Energy Confinement in the Advanced Reversed-field Pinch
- 2006
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Ingår i: 33rd EPS Conference on Plasma Phys. - 9781622763337
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Konferensbidrag (refereegranskat)abstract
- A revised algorithm for numerical simulations of the advanced reversed-field pinch (RFP) is presented. The results show improved scalings of magnetic fluctuations, energy confinement time τE and poloidal beta βθ with basic initial parameters as compared to what has been presented by the authors in earlier studies of the advanced RFP. The improved behaviour of the advanced RFP stems from the introduction of current profile control (CPC), implemented through a scheme of active feedback of the electric dynamo field. The work, which has an optimistic approach and sweeps over a large parameter domain reaching into the reactor relevant region, is theoretical and claims to answer the question of how far CPC can bring the RFP concept in principle. Experimental implementation is thus a later concern. With this scheme, a state with strongly suppressed tearing mode activity is achieved, which allows for a theoretical study of pressure driven resistive g-modes. This is a task that has been very hard to perform in the past, since tearing modes have always dominated the RFP dynamics. Thus it is now possible, for the first time, to investigate whether pressure driven modes, which are persistent in the RFP, are fatal for the confinement of a high-beta RFP configuration or if they can be accepted in a future reactor.
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| 4. |
- Holmström, Kerstin, et al.
(författare)
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On the dynamics of Alfvén eigenmode excitation
- 2006
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Ingår i: EPS Conference on Plasma Physics 2006, EPS 2006. - 9781622763337 ; , s. 1796-1799
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Konferensbidrag (refereegranskat)abstract
- Alfvén eigenmodes (AEs) excited by fast ions can cause losses of fast ions in thermonuclear experiments. To describe the dynamics of the AE excitation, it is necessary to include the decorrelation of the AE interactions and the renewal of the distribution function in the unstable regions on time scales that are short compared to the decorrelation time. For simulation of AE excitation for finite decorrelation times, a Monte Carlo operator describing the phase decorrelation between ions and AEs has been developed for implementation in the SELFO code.
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| 5. |
- Johnson, Thomas, et al.
(författare)
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Numerical Modelling of Ripple Induced Transport
- 2006
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Ingår i: Proceedings of the 33rd EPS Conference on Plasma Physics. - 9781622763337 ; , s. 408-411
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The ASCOT code has been used to analyse transport and calculate the thermal conductivity in plasmas with toroidal field ripple. The scaling of the thermal conductivity with dimensionless plasma parameters is similar to transport in the ripple plateau regime [1]. The ripple in machines with toroidal field coils similar to those in JET and JT-60U are quite different; while the maximum ripple is larger with 16 JET coils, the ripple at the X-point is larger with the JT-60U coils. The results are that the heat conductivity is similar in the two plasmas, while the particle losses are higher with the JT-60U coils.
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