A new FILDSIM model for improved velocity-space sensitivity modelling and reconstructions

Schmidt, Bo S; Poley-Sanjuán, Jesús; Rueda-Rueda, José; Galdon-Quíroga, Joaquín; Baquero-Ruiz, Marcelo; Järleblad, Henrik; Reman, Bernard C G; Rud, Mads; Valentini, Andrea; García-Muñoz, Manuel; Salewski, Mirko

doi:10.1088/1361-6587/ad268f

Cited by 7 publications

(6 citation statements)

References 53 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Notably, the gyroradius resolution limit increases with increasing ρ, and the pitch-angle resolution limit increases with increasing α. Such trends align with prior expectations, given that the width of the 1D strike-point distributions in both ρ and α increases with increasing ρ and α [25,27], leading to higher resolution limits at larger values of the two variables.…”

Section: The Resolution Principle: Examplesupporting

confidence: 87%

“…At ASDEX Upgrade, FILD measurements have traditionally been presented in terms of gyroradius, ρ, and pitch angle, α [5,6,15,20,25,26]. This representation, denoted M f , is obtained by mapping M raw onto velocity space and is termed the 'mapped FILD measurement' [27]. Subsequent discussions pertain solely to M f , hereafter referred to as 'FILD measurements'.…”

Section: Velocity Distributions From Fast-ion Loss Detector Measurementsmentioning

confidence: 99%

“…The relation between a FILD measurement M f and the velocity distribution f is modelled as a Fredholm integral equation of the first kind [25,27]:…”

Section: Reconstructions Of Fild Measurementsmentioning

confidence: 99%

“…Tikhonov regularization is a well-established method for velocity-space tomography [34,[43][44][45][46][47][48][49] and for the reconstruction of velocity distributions from FILD measurements [25][26][27]. The optimal estimate x is obtained by solving…”

Section: Tikhonov Regularizationmentioning

confidence: 99%

See 3 more Smart Citations

Iterative reconstruction methods and the resolution principle for fast-ion loss detector measurements

S. Schmidt,

Galdon-Quíroga,

Rueda-Rueda

et al. 2024

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

Fast-ion loss detectors (FILDs) are crucial for analyzing fast-ion dynamics in magnetically confined fusion plasmas. A core challenge is to derive an accurate ion velocity distribution, requiring treatment of thousands of remapped camera frames for a full discharge. The ill-posed nature of this task necessitates regularization with a well-chosen regularization parameter and computationally efficient methods. In this work, we introduce the `resolution principle,' a novel criterion for selecting the optimal regularization parameter, providing a distinction between genuine features and artefacts smaller than the diagnostic resolution in the reconstruction, thereby preventing misinterpretations. This principle, coupled with three iterative reconstruction techniques--Kaczmarz's method, coordinate descent, and Cimmino's method--demonstrates enhanced reconstruction capabilities compared to conventional methods like Tikhonov regularization. Utilizing these techniques allows rapid processing of measurements from full discharges, removing the computational bottleneck and facilitating between-discharge reconstructions. By reconstructing 6000 camera frames from an ELMy H-mode discharge at ASDEX Upgrade, we capture the temporal evolution of gyroradii and pitch angles, unveiling a direct correlation between pitch-angle behaviour and changes in the toroidal magnetic field for a specific subset of lost ions accelerated by edge-localized modes (ELMs) to energies approximately twice that of the injection energy.

show abstract

Section: The Resolution Principle: Examplesupporting

confidence: 87%

Section: Velocity Distributions From Fast-ion Loss Detector Measurementsmentioning

confidence: 99%

“…The relation between a FILD measurement M f and the velocity distribution f is modelled as a Fredholm integral equation of the first kind [25,27]:…”

Section: Reconstructions Of Fild Measurementsmentioning

confidence: 99%

Section: Tikhonov Regularizationmentioning

confidence: 99%

See 2 more Smart Citations

Iterative reconstruction methods and the resolution principle for fast-ion loss detector measurements

S. Schmidt,

Galdon-Quíroga,

Rueda-Rueda

et al. 2024

Nucl. Fusion

Self Cite

View full text Add to dashboard Cite

show abstract

“…The gross weight function [48,60] of the diagnostic (the sum of all Wαβ shown in equation ( 12)), calculated for the plasma profiles shown in figure 4, can be seen at figure 5(a).…”

Section: Numerical Calculation Of the Inpa Weight Functionmentioning

confidence: 99%

Tomographic reconstructions of the fast-ion phase space using imaging neutral particle analyser measurements

Rueda-Rueda,

Garcia-Munoz,

Viezzer

et al. 2024

Plasma Phys. Control. Fusion

Self Cite

View full text Add to dashboard Cite

In this paper we demonstrate how the inversion, in energy and major radius (E, R) coordinates, of imagingneutral particle analyser (INPA) measurements can be used to obtain the fast-ion distribution. The INPA ismost sensitive to passing ions with energies in the range (20-150) keV and pitches near 0.5 in the core and 0.7near the plasma edge. Inversion of synthetic signals, via 0th -order Tikhonov and Elastic Net regularization,were performed to demonstrate the capability of recovering the ground truth fast-ion 2D phase-space distri-bution resolved in major radius and energy, even in the presence of moderate noise levels (10%). Finally,we apply our method to measure the 2D phase-space distribution in an MHD quiescent plasma at ASDEXUpgrade and find good agreement with the neoclassical fast-ion distribution predicted by TRANSP.

show abstract

Simulation of a scintillator-based fast ion loss detector for steady-state operation in Wendelstein 7-X (invited)

LeViness,

Lazerson,

Jansen van Vuuren

et al. 2024

Review of Scientific Instruments

View full text Add to dashboard Cite

A quantitative theoretical framework has been created to model neutral beam injection and fast ion losses in the Wendelstein 7-X (W7-X) stellarator, including a novel method to develop synthetic diagnostics for fast ion loss detectors (FILDs) of many types, such as scintillating and Faraday Cup FILDs. This is the first time that this has been done in stellarator geometry with this level of fidelity, providing a way for fast ion losses to be predicted more precisely in future stellarator experiments and in W7-X. Simulations of the signal seen by a Faraday Cup FILD have been completed for multiple W7-X plasmas and show close agreement with the measured signals. This method is now applied to an actively water-cooled, scintillator-based FILD, which is currently in development to measure the fast ion loss distribution in W7-X in greater detail. The design makes use of a double slit to measure energy-and-pitch-angle-resolved losses of both co-going and counter-going fast ions. The diagnostic, which can be inserted to different radial positions, has been designed to withstand steady-state heat fluxes of up to 120 kW/m2 along with additional transient heat loads of 100 kW/m2 lasting for up to 20 s at a time. Simulations of W7-X standard magnetic configuration show up to 8 × 1013 (s−1 cm−2) ion fluxes onto the sensor from each neutral beam source and no signal from the counter-going slit. These simulations will help inform experimental proposals for future W7-X campaigns after installation of this diagnostic.

show abstract

A new FILDSIM model for improved velocity-space sensitivity modelling and reconstructions

Cited by 7 publications

References 53 publications

Iterative reconstruction methods and the resolution principle for fast-ion loss detector measurements

Iterative reconstruction methods and the resolution principle for fast-ion loss detector measurements

Tomographic reconstructions of the fast-ion phase space using imaging neutral particle analyser measurements

Simulation of a scintillator-based fast ion loss detector for steady-state operation in Wendelstein 7-X (invited)

Contact Info

Product

Resources

About