Comparison of fast ion collective Thomson scattering measurements at ASDEX Upgrade with numerical simulations

Salewski, M.; Méo, F.; Stejner, M.; Asunta, O.; Bindslev, H.; Furtula, Vedran; Korsholm, S. B.; Kurki-Suonio, T.; Leipold, F.; Leuterer, F.; Michelsen, Poul; Moseev, D.; Nielsen, S. K.; Stober, J.; Tardini, G.; Wágner, D.; Woskov, P.

doi:10.1088/0029-5515/50/3/035012

Cited by 79 publications

(104 citation statements)

References 54 publications

(79 reference statements)

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“…Our tomographic and theoretical results contradict the conventional wisdom that at least two CTS or FIDA views would necessarily be required for tomography of fast-ion velocity distribution functions [12,[22][23][24][25][26][27][28][29][30][31][32]. In an idealized situation in fact just one single CTS or FIDA view suffices to compute an accurate tomography.…”

Section: Discussioncontrasting

confidence: 56%

“…In [24] reconstructions from two and three synthetic CTS views have been shown to contain salient features of the underlying 2D fast-ion velocity distribution functions in idealized situations. It has since become conventional wisdom that a 2D velocity distribution function could not be found from one single 1D CTS or FIDA view and that at least two CTS or FIDA views with different projection directions would be necessary for that [12,[22][23][24][25][26][27][28][29][30][31][32]. We demonstrate that in fact just one single 1D CTS or FIDA view theoretically suffices to compute tomographies of almost the entire discrete 2D velocity distribution function under idealized conditions.…”

Section: Introductionmentioning

confidence: 91%

See 1 more Smart Citation

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

Salewski¹,

Geiger²,

Nielsen³

et al. 2012

Nucl. Fusion

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122

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We compute tomographies of 2D fast-ion velocity distribution functions from synthetic collective Thomson scattering (CTS) and fast-ion D α (FIDA) 1D measurements using a new reconstruction prescription. Contradicting conventional wisdom we demonstrate that one single 1D CTS or FIDA view suffices to compute accurate tomographies of arbitrary 2D functions under idealized conditions. Under simulated experimental conditions, single-view tomographies do not resemble the original fast-ion velocity distribution functions but nevertheless show their coarsest features. For CTS or FIDA systems with many simultaneous views on the same measurement volume, the resemblance improves with the number of available views, even if the resolution in each view is varied inversely proportional to the number of views, so that the total number of measurements in all views is the same. With a realistic four-view system, tomographies of a beam ion velocity distribution function at ASDEX Upgrade reproduce the general shape of the function and the location of the maxima at full and half injection energy of the beam ions. By applying our method to real many-view CTS or FIDA measurements, one could determine tomographies of 2D fast-ion velocity distribution functions experimentally.

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Section: Discussioncontrasting

confidence: 56%

Section: Introductionmentioning

confidence: 91%

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

Salewski¹,

Geiger²,

Nielsen³

et al. 2012

Nucl. Fusion

Self Cite

122

View full text Add to dashboard Cite

show abstract

“…ASDEX Upgrade is also equipped with a suite of fast-ion diagnostics: fast-ion loss detectors (FILDs) [4][5][6], fast-ion D α (FIDA) [7], collective Thomson scattering (CTS) [8][9][10][11][12][13], neutron spectrometry [14,15], neutral particle analysers (NPA) [16,17] and γ -ray spectrometry [18]. These auxiliary heating systems and fast-ion diagnostics give unique opportunities to study fast ions in tokamak plasmas.…”

Section: Introductionmentioning

confidence: 99%

Combination of fast-ion diagnostics in velocity-space tomographies

et al. 2013

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Fast-ion D α (FIDA) and collective Thomson scattering (CTS) diagnostics provide indirect measurements of fastion velocity distribution functions in magnetically confined plasmas. Here we present the first prescription for velocity-space tomographic inversion of CTS and FIDA measurements that can use CTS and FIDA measurements together and that takes uncertainties in such measurements into account. Our prescription is general and could be applied to other diagnostics. We demonstrate tomographic reconstructions of an ASDEX Upgrade beam ion velocity distribution function. First, we compute synthetic measurements from two CTS views and two FIDA views using a TRANSP/NUBEAM simulation, and then we compute joint tomographic inversions in velocity-space from these. The overall shape of the 2D velocity distribution function and the location of the maxima at full and half beam injection energy are well reproduced in velocity-space tomographic inversions, if the noise level in the measurements is below 10%. Our results suggest that 2D fast-ion velocity distribution functions can be directly inferred from fast-ion measurements and their uncertainties, even if the measurements are taken with different diagnostic methods.

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“…Higher frequency bands are also of interest but the diagnostic solutions for these bands are technologically difficult and expensive. An example of a receiver operating at 100-110 GHz is that of the collective Thomson scattering (CTS) diagnostic at ASDEX Upgrade [1,2,[6][7][8][9][10][11]. It can detect spectral power densities of a few eV against the electron cyclotron emission (ECE) background on the order of 100 eV under presence of gyrotron stray radiation that is many orders of magnitude stronger than the signal to be detected.…”

Section: Introductionmentioning

confidence: 99%

Waveguide Bandpass Filters for Millimeter-Wave Radiometers

Furtula

Zirath

Salewski

2013

J Infrared Milli Terahz Waves

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A fundamental requirement for most mmwave heterodyne receivers is the rejection of the input image signal which is located close to the local oscillator frequency. For this purpose we use a bandpass filter, which for heterodyne receivers is also called an image rejection filter. In this paper we present a systematic approach to the design of a waveguide bandpass filter with a passband from 100 to 110 GHz and upper rejection bandwidth in the range from 113 to 145 GHz. We consider two non-tunable filter configurations: the first one is relatively selective with 11 sections (poles) whereas the second one is simpler with 5 sections. We used established design equations to propose an initial guess for the geometries of the filters, optimized the geometries, constructed the filters using two different milling methods, measured their transmission and reflection characteristics, and compared the measurements with numerical simulations. Measurements of both filters agree well with simulations in frequency response and rejection bandwidth. The insertion loss of the 11-pole filter is better than 10 dB and that of the 5-pole filter is better than 5 dB. The 11-pole filter has a sharper attenuation roll-off compared with the 5-pole filter. The upper out-of-band rejection is better than

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Comparison of fast ion collective Thomson scattering measurements at ASDEX Upgrade with numerical simulations

Cited by 79 publications

References 54 publications

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

Tomography of fast-ion velocity-space distributions from synthetic CTS and FIDA measurements

Combination of fast-ion diagnostics in velocity-space tomographies

Waveguide Bandpass Filters for Millimeter-Wave Radiometers

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