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Publications (6 of 6) Show all publications
Trier, E., Frassinetti, L., Fridström, R., Garcia Carrasco, A., Hellsten, T., Johnson, T., . . . Zuin, M. (2019). ELM-induced cold pulse propagation in ASDEX Upgrade. Plasma Physics and Controlled Fusion, 61(4), Article ID 045003.
Open this publication in new window or tab >>ELM-induced cold pulse propagation in ASDEX Upgrade
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2019 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 61, no 4, article id 045003Article in journal (Refereed) Published
Abstract [en]

In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the plasma current are the main determining parameters for the inward penetration of the T-e perturbations. With increasing plasma current the ELM penetration is more shallow in spite of the stronger ELMs. Estimates of the heat pulse diffusivity show that the corresponding transport is too large to be representative of the inter-ELM phase. Ergodization of the plasma edge during ELMs is a possible explanation for the observed properties of the cold pulse propagation, which is qualitatively consistent with non-linear magneto-hydro-dynamic simulations.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
ELMs, MHD instabilities, stochastic field, magnetic islands, cold pulse
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-245121 (URN)10.1088/1361-6587/aaf9c3 (DOI)000458986000002 ()
Note

QC 20190315

Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2019-05-20Bibliographically approved
Tierens, W., Frassinetti, L., Hellsten, T., Petersson, P., Fridström, R., Garcia Carrasco, A., . . . et al., . (2019). Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments. Nuclear Fusion, 59(4), Article ID 046001.
Open this publication in new window or tab >>Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments
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2019 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 59, no 4, article id 046001Article in journal (Refereed) Published
Abstract [en]

In this paper we validate the finite element code RAPLICASOL, which models radiofrequency wave propagation in edge plasmas near ICRF antennas, against calculations with the TOPICA code. We compare the output of both codes for the ASDEX Upgrade 2-strap antenna, and for a 4-strap WEST-like antenna. Although RAPLICASOL requires considerably fewer computational resources than TOPICA, we find that the predicted quantities of experimental interest (including reflection coefficients, coupling resistances, S- and Z-matrix entries, optimal matching settings, and even radiofrequency electric fields) are in good agreement provided we are careful to use the same geometry in both codes.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
ICRF, finite elements, simulation
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-243928 (URN)10.1088/1741-4326/aaf455 (DOI)000456197200001 ()
Note

QC 20190212

Available from: 2019-02-12 Created: 2019-02-12 Last updated: 2019-02-12Bibliographically approved
Fridström, R., Chapman, B. E., Almagri, A. F., Frassinetti, L., Brunsell, P. R., Nishizawa, T. & Sarff, J. S. (2018). Dependence of Perpendicular Viscosity on Magnetic Fluctuations in a Stochastic Topology. Physical Review Letters, 120(22), Article ID 225002.
Open this publication in new window or tab >>Dependence of Perpendicular Viscosity on Magnetic Fluctuations in a Stochastic Topology
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2018 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 22, article id 225002Article in journal (Refereed) Published
Abstract [en]

In a magnetically confined plasma with a stochastic magnetic field, the dependence of the perpendicular viscosity on the magnetic fluctuation amplitude is measured for the first time. With a controlled, similar to tenfold variation in the fluctuation amplitude, the viscosity increases similar to 100-fold, exhibiting the same fluctuation-amplitude-squared dependence as the predicted rate of stochastic field line diffusion. The absolute value of the viscosity is well predicted by a model based on momentum transport in a stochastic field, the first in-depth test of this model.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-230495 (URN)10.1103/PhysRevLett.120.225002 (DOI)000433425500007 ()2-s2.0-85047758978 (Scopus ID)
Note

QC 20180614

Available from: 2018-06-14 Created: 2018-06-14 Last updated: 2018-06-19Bibliographically approved
Fridström, R., Munaretto, S., Frassinetti, L., Chapman, B., Brunsell, P. R. & Sarff, J. (2016). Estimation of anomalous viscosity based on modeling of experimentally observed plasma rotation braking induced by applied resonant magnetic perturbations. In: 43th European Physical Society (EPS) Conference on Plasma Physics. July 4 – July 8, 2016: . Paper presented at 43th European Physical Society (EPS) Conference on Plasma Physics. July 4 – July 8, 2016. European Physical Society (EPS)
Open this publication in new window or tab >>Estimation of anomalous viscosity based on modeling of experimentally observed plasma rotation braking induced by applied resonant magnetic perturbations
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2016 (English)In: 43th European Physical Society (EPS) Conference on Plasma Physics. July 4 – July 8, 2016, European Physical Society (EPS) , 2016Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
European Physical Society (EPS), 2016
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-203360 (URN)2-s2.0-85013867240 (Scopus ID)
Conference
43th European Physical Society (EPS) Conference on Plasma Physics. July 4 – July 8, 2016
Note

QC 20170321

Available from: 2017-03-15 Created: 2017-03-15 Last updated: 2017-11-21Bibliographically approved
Sweeney, R. M., Frassinetti, L., Brunsell, P. R., Fridström, R. & Volpe, F. A. (2016). Local measurement of error field using naturally rotating tearing mode dynamics in EXTRAP T2R. Plasma Physics and Controlled Fusion, 58(12), Article ID 124001.
Open this publication in new window or tab >>Local measurement of error field using naturally rotating tearing mode dynamics in EXTRAP T2R
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2016 (English)In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 58, no 12, article id 124001Article in journal (Refereed) Published
Abstract [en]

An error field (EF) detection technique using the amplitude modulation of a naturally rotating tearing mode (TM) is developed and validated in the EXTRAP T2R reversed field pinch. The technique was used to identify intrinsic EFs of m/n = 1/-12, where m and n are the poloidal and toroidal mode numbers. The effect of the EF and of a resonant magnetic perturbation (RMP) on the TM, in particular on amplitude modulation, is modeled with a first-order solution of the modified Rutherford equation. In the experiment, the TM amplitude is measured as a function of the toroidal angle as the TM rotates rapidly in the presence of an unknown EF and a known, deliberately applied RMP. The RMP amplitude is fixed while the toroidal phase is varied from one discharge to the other, completing a full toroidal scan. Using three such scans with different RMP amplitudes, the EF amplitude and phase are inferred from the phases at which the TM amplitude maximizes. The estimated EF amplitude is consistent with other estimates (e.g. based on the best EF-cancelling RMP, resulting in the fastest TM rotation). A passive variant of this technique is also presented, where no RMPs are applied, and the EF phase is deduced.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2016
Keywords
error field, EXTRAP T2R, plasma, reversed field pinch, tearing mode, tokamak, Amplitude modulation, Magnetoplasma, Modulation, Pinch effect, Plasmas, Tearing modes, Errors
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-202888 (URN)10.1088/0741-3335/58/12/124001 (DOI)000399802800001 ()2-s2.0-84997785038 (Scopus ID)
Note

QC 20170309

Available from: 2017-03-09 Created: 2017-03-09 Last updated: 2017-05-08Bibliographically approved
Frassinetti, L., Brunsell, P., Setiadi, C., Fridström, R., Khan, W. & Drake, J. (2014). TM locking and unlocking mechanism to an external resonant field. In: Meeting of the Nordic Research Units in EUROfusion: . Paper presented at Meeting of the Nordic Research Units in EUROfusion.
Open this publication in new window or tab >>TM locking and unlocking mechanism to an external resonant field
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2014 (English)In: Meeting of the Nordic Research Units in EUROfusion, 2014Conference paper, Oral presentation only (Other academic)
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-203618 (URN)
Conference
Meeting of the Nordic Research Units in EUROfusion
Note

QCR 20170405

Available from: 2017-03-16 Created: 2017-03-16 Last updated: 2017-04-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-6554-9681

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