Development of a Faraday cup fast ion loss detector for keV beam ions

Lazerson, S.; Ellis, R.; Freeman, C; Ilagan, Jessica; Wang, Tianyao; Shao, Lin; Allen, Nicole; Gates, D.; Neilson, H.

doi:10.1063/1.5111714

Cited by 16 publications

(9 citation statements)

References 8 publications

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“…Increased NBI heating power along with a mix of ECRH should allow for higher ion temperatures to be achieved and to investigate the role of ECRH density pump-out. A growing set of fast ion diagnostics (an FC-FILD array [22], ion cyclotron emission [23], spectroscopic beam measurements [6], and collective Thomson scattering [24]) will allow for more detailed studies of the fast ion distribution function. This includes a program to perform fast ion phase space tomography.…”

Section: Discussionmentioning

confidence: 99%

First neutral beam experiments on Wendelstein 7-X

Team¹,

Lazerson²,

Ford³

et al. 2021

Nucl. Fusion

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In the previous divertor campaign, the Wendelstein 7-X (W7-X) device injected 3.6 MW of neutral beam heating power allowing for the achievement of densities approaching 2 × 10 20 m −3 , and providing the first initial assessment of fast ion confinement in a drift optimized stellarator. The neutral beam injection (NBI) system on W7-X is comprised of two beam boxes with space for four radio frequency sources each. The 3.6 MW of heating reported in this work was achieved with two sources in the NI21 beam box. The effect of combined electron-cyclotron resonance heating (ECRH) and NBI was explored through a series of discharges varying both NBI and ECRH power. Discharges without ECRH saw a linear increase in the line-integrated plasma density, and strong peaking of the core density, over the

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Section: Discussionmentioning

confidence: 99%

First neutral beam experiments on Wendelstein 7-X

Team¹,

Lazerson²,

Ford³

et al. 2021

Nucl. Fusion

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“…The nature of this discrepancy points to the rather large uncertainty associated with this method of approximating the fast ion slowing down time. Future work will use proposed fast ion loss diagnostics to measure such quantities in more precise terms [19]. We also note that instabilities in the ion source itself may be influencing the measured data when the beam is first fired.…”

Section: Particle Decelerationmentioning

confidence: 99%

Modeling and measurement of energetic particle slowing down in Wendelstein 7-X

Lazerson

Pfefferlé²,

Drevlak

et al. 2021

Nucl. Fusion

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The energetic particle slowing down model in the BEAMS3D stellarator neutral beam code is compared to analytic models and experimental data from the Wendelstein 7-X experiment (W7-X). Recently, the first neutral beam experiments were performed in W7-X, providing validation of neutral beam deposition codes (Lazerson S.A. et al 2020 Nucl. Fusion 60 076020). This work builds upon that work, and follows the gyro-center orbits of the neutral-beam-generated fast ions to the plasma boundary. Slowing down times based on measurements of diamagnetic energy changes are compared to simulation data. A discharge solely heated by neutral beam injection is used to compare neoclassical heat flux estimates to neutral beam fueling, heating, and current drive. Experimental estimates of electron heat diffusivity suggest that electron turbulence is destabilized by density peaking in the discharge. Neutral beam current drive dominates over bootstrap current, resulting in a reversal of the toroidal current, as seen experimentally. Particle losses and heat flux through the equilibrium boundary are described. The effects of the magnetic configuration and plasma density on such parameters are also assessed. Benchmarking based on analytic estimates and other energetic particle codes is presented.

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“…A prototype Faraday Cup Fast Ion Loss Detector (FC-FILD) mounted on a moveable arm is being developed on Wendelstein 7-X [25]. These detectors are envisioned to provide energy resolved losses through instrumentation of heat shield tiles in the device [7].…”

Section: Resultsmentioning

confidence: 99%

Gyro orbit simulations of neutral beam injection in Wendelstein 7-X

et al. 2023

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Simulations exploring neutral beam operation in Wendelstein 7-X (W7- X) at reduced magnetic field are performed using a newly implemented gyro orbit model in the BEAMS3D code. Operation at field strengths below the nominal 2.5 T are seen as a path to explore both high beta plasmas and as a means to access magnetic configurations not possible at 2.5T. As the field strength becomes smaller, the gyro radius for 55 keV fast protons grows from ∼1 cm at 2.5 T to ∼5 cm at 0.75 T in a device with minor radius ∼50 cm bringing into question the applicability of the gyro center approximation. To address this a gyro orbit model was implemented in the BEAMS3D code. Agreement is found between the gyro center and gyro orbit models in a circular cross section tokamak equilibrium at high field. A set of W7-X equilibria are assessed with fixed density and temperature profiles but decreasing magnetic field strength (increasing plasma beta). Neutral beam deposition is found to be mostly unaffected with changes in the core of the plasma associated with the Shafranov-shift. In general good agreement is found between gyro orbit and gyro center simulations at 2.5 T. Both models indicate increasing losses with decreasing magnetic field strength with the gyro orbit losses being higher at all field strengths. Gyro orbit simulations to the first wall of W7-X show a change in loss pattern with decreasing magnetic field strength. A preliminary assessment of losses to fast ion loss detectors are made.

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Development of a Faraday cup fast ion loss detector for keV beam ions

Cited by 16 publications

References 8 publications

First neutral beam experiments on Wendelstein 7-X

First neutral beam experiments on Wendelstein 7-X

Modeling and measurement of energetic particle slowing down in Wendelstein 7-X

Gyro orbit simulations of neutral beam injection in Wendelstein 7-X

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