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UKAEA-CCFE-PR(26)4222025
Dedicated experiments were conducted on Alfvénic instabilities in the ion sub-cyclotron frequency range excited by energetic beam ions in the MAST-Upgrade tokamak. Losses of the beam ions associated with plasma instabilities were measured with a scintillator-type fast ion lost detector (FILD), which provided a 2D image of the losses as functions o…
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UKAEA-CCFE-PR(26)4082025
An introductory tutorial on plasma stability theory is presented, focussing on application of the normal mode method to the linearised form of the magnetohydodynamic (MHD), Vlasov and Maxwell equations. Following an illustration of how this method can be applied to a simple mechanical problem, single-fluid stability theory is demonstrated for the c…
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UKAEA-CCFE-PR(25)4002025
The first measurements of energetic particle-driven ion cyclotron emission (ICE) in the Mega-Amp Spherical Tokamak Upgrade (MAST-U) have been obtained by adding a high sampling rate (250MHz) capability to one coil of the existing OMAHA array, oriented to measure fluctuations in the toroidal magnetic field component. All these measurements were carr…
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UKAEA-CCFE-PR(25)3422025
We report the observation and analysis of ion cyclotron emission (ICE) in the Wendelstein 7-X (W7-X) stellarator during discharges without a significant fast-ion population. In these experiments, ICE is observed using the strap of the ICRF antenna, while remaining undetectable on the B-dot probes during ECRH-only phases. At low electron densities, …
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UKAEA-CCFE-PR(25)3362025
A method for determining the fast-ion population density in magnetically confined plasmas as a function of pitch-radius, (λ, R), using a solid-state neutral-particle analyzer (ssNPA) signal and neutral-beam injection (NBI) power-output data has been developed. Oscillations in the NBI power output are replicated only in the active part of the ssN…
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UKAEA-CCFE-CP(26)342024
The MAST-U spherical tokamak (ST) is equipped with on-axis and off-axis neutral beam injectors (NBI), external sources of super-Alfvénic fast ions that provide opportunities for studying a wide range of phenomena relevant to the physics of alpha-particles in future burning plasma devices such as STEP or ITER. High performance of MAST-U plasmas rel…
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UKAEA-CCFE-PR(25)3932024
A Fast-Ion Loss Detector (FILD) was installed for the first time at the MAST-U spherical tokamak during its upgrade in 2021. A CMOS camera was installed in the MAST-U FILD acquisition system to provide high spatial resolution (1.1 MPx) to infer the velocity space of the fast-ion losses. This camera allows up to 3.5 kHz ac…
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UKAEA-CCFE-PR(25)3512024
Fast ion (FI) loss properties in the presence of tearing mode and internal kink perturbations are numerically investigated for discharges in the MAST-U spherical tokamak, utilizing the MARS-F magnetohydrodynamic stability code and the REORBIT test particle guiding-center orbit-following module. Tracing about
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UKAEA-CCFE-PR(25)3442024
By analysing the relative neutron rates measured between multiple fission-chamber (FC) diagnostics – constituting a Fission-Chamber Array (FCA) – the spacial distribution of fusion within a tokamak may be studied. Using the two-FC set-up at MAST-U, analysis methods are presented for both the study of poloidal neutron-emissivity distributions an…
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UKAEA-CCFE-PR(24)2652024
Dedicated experiments were performed on MAST Upgrade to study beam-ion losses caused by charge exchange (CX) with edge neutrals. The fuelling was switched from the high-field side to the low-field side mid-discharge. Direct measurements suggest a strong increase in neutral density around the plasma and a deterioration of the beam-ion confinement…
Showing 1 - 10 of 82 UKAEA Paper Results