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| 2. |
- Bykov, Igor, et al.
(författare)
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Transport asymmetry and release mechanisms of metal dust in the reversed-field pinch configuration
- 2014
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 56:3, s. 035014-
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data on dust resident in the EXTRAP T2R reversed-field pinch are reported. Mobile dust grains are captured in situ by silicon collectors, whereas immobile grains are sampled post mortem from the wall by adhesive tape. The simulation of collection asymmetries by the MIGRAINe dust dynamics code in combination with the experimental results is employed to deduce some characteristics of the mechanism of intrinsic dust release. All evidence suggests that re-mobilization is dominant with respect to dust production.
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| 3. |
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| 4. |
- Frassinetti, Lorenzo, et al.
(författare)
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A method for the estimate of the wall diffusion for non-axisymmetric fields using rotating external fields
- 2013
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 55:8, s. 084001-
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Tidskriftsartikel (refereegranskat)abstract
- A new method for the estimate of the wall diffusion time of non-axisymmetric fields is developed. The method based on rotating external fields and on the measurement of the wall frequency response is developed and tested in EXTRAP T2R. The method allows the experimental estimate of the wall diffusion time for each Fourier harmonic and the estimate of the wall diffusion toroidal asymmetries. The method intrinsically considers the effects of three-dimensional structures and of the shell gaps. Far from the gaps, experimental results are in good agreement with the diffusion time estimated with a simple cylindrical model that assumes a homogeneous wall. The method is also applied with non-standard configurations of the coil array, in order to mimic tokamak-relevant settings with a partial wall coverage and active coils of large toroidal extent. The comparison with the full coverage results shows good agreement if the effects of the relevant sidebands are considered.
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| 5. |
- Frassinetti, Lorenzo, et al.
(författare)
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A Technique for the Estimation of the Wall Diffusion Time
- 2012
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Ingår i: 54th Meeting of the APS Division of Plasma Physics, November 2012, Providence, USA.
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Konferensbidrag (refereegranskat)abstract
- Feedback systems are important tools for an advanced control of the MHD instabilities in fusion plasmas, both for the suppression of undesired modes, such as RWMs, and for the generation of external perturbations for ELM suppression. A good knowledge of the diffusion time through the machine wall of each external harmonics is necessary for reaching optimal performances of the feedback algorithms.A correct theoretical estimation is not easy due the presence of three-dimensional mechanical structures in the devices, such as shell cuts and external conductive structures that need to be considered. Identification of differences in the vertical and horizontal diffusion time are not simple from a theoretical point of view.This work will present a relatively simple technique to experimentally estimate the diffusion time for each harmonic. The technique is based on the generation of rotating external magnetic perturbations in vacuum and on the quantification of the wall screening from the measured field inside the wall. The technique will be able to quantify possible differences among the horizontal and vertical diffusion time. In the final part of the work, the comparison with the results obtained with a closed-loop identification algorithm of the machine plant will be discussed.
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| 8. |
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| 9. |
- Frassinetti, Lorenzo, et al.
(författare)
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EXTRAP Coils and Tearing Mode Dynamics
- 2011
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Ingår i: 16th Workshop on MHD stability control, November 20 - 22, 2011 San Diego, CA, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 10. |
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