154
edits
TJ-II:PelletFuelling: Difference between revisions
→Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)
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In all cases, pellet ablation is monitored across the plasma radius using photodiodes, and a fast camera. Furthermore, using multiple Thomson Scattering profiles, it has been possible to study particle diffusion, deposition and confinement. However, fast radial drift that leads to large particle losses, and hence low efficiency, remains to be evaluated. In addition, using the Doppler Reflectometer, which is sensitive to a local density perturbation, it may be possible to study the plasmoid that extends toroidally out from the neutral cloud surrounding an ablated pellet along magnetic field lines. if successfull this will be important for studying pellet particle deposition in stellarator devices. | In all cases, pellet ablation is monitored across the plasma radius using photodiodes, and a fast camera. Furthermore, using multiple Thomson Scattering profiles, it has been possible to study particle diffusion, deposition and confinement. However, fast radial drift that leads to large particle losses, and hence low efficiency, remains to be evaluated. In addition, using the Doppler Reflectometer, which is sensitive to a local density perturbation, it may be possible to study the plasmoid that extends toroidally out from the neutral cloud surrounding an ablated pellet along magnetic field lines. if successfull this will be important for studying pellet particle deposition in stellarator devices. | ||
In the first instance, it is intended to broaden the current pellet fuelling database by performing injections into a broad range of magnetic configurations in order to determine efficiencies, as well as pellet penetration, ablation processes, particle drift and diffusion, plus the possible role of magnetic islands and magnetic well/hill. In parallel, is intended to determine if it is possible to increase fuelling efficiency by firstly injecting a small pellet (or using a gas puff) to pre-cool the outer plasma core just prior to injecting a fuelling pellet (here Δt | In the first instance, it is intended to broaden the current pellet fuelling database by performing injections into a broad range of magnetic configurations in order to determine efficiencies, as well as pellet penetration, ablation processes, particle drift and diffusion, plus the possible role of magnetic islands and magnetic well/hill. | ||
In parallel, is intended to determine if it is possible to increase fuelling efficiency by firstly injecting a small pellet (or using a gas puff) to pre-cool the outer plasma core just prior to injecting a fuelling pellet (here Δt ≥ 1 ms for sequential pellet injections). The TJ-II pellet injector is unique for undertaking this study as up to 4 pellets can be injected simultaneously.This will allow us to perform the first experimental comparison between pre-cooling by pellet injection and by gas puff in a magnetically confined plasma device. In parallel, it is intended to determine if the Doppler Reflectrometer measurements can provide insight into plasmoid elongation and location. | |||
== If applicable, International or National funding project or entity == | == If applicable, International or National funding project or entity == | ||