D.S. Gahle
A5041039329- Magnetic confinement fusion research
- Fusion materials and technologies
- Ionosphere and magnetosphere dynamics
- Laser-Plasma Interactions and Diagnostics
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Chemical Synthesis and Characterization
- Atomic and Molecular Physics
- Zeolite Catalysis and Synthesis
- Advanced NMR Techniques and Applications
- Laser-induced spectroscopy and plasma
University of Strathclyde
2018-2025
Culham Science Centre
2018-2022
Culham Centre for Fusion Energy
2019-2021
Institut Laue-Langevin
2020
Abstract The tokamak à configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system address critical issues in preparation for ITER a fusion power plant. For the 2019–20 campaign configurational flexibility has been enhanced with installation of removable divertor gas baffles, diagnostic capabilities an extensive set upgrades new dual frequency gyrotrons. baffles reduce coupling between main chamber allow detailed...
Abstract The research program of the TCV tokamak ranges from conventional to advanced-tokamak scenarios and alternative divertor configurations, exploratory plasmas driven by theoretical insight, exploiting device’s unique shaping capabilities. Disruption avoidance real-time locked mode prevention or unlocking with electron-cyclotron resonance heating (ECRH) was thoroughly documented, using magnetic radiation triggers. Runaway generation high- Z noble-gas injection runaway dissipation...
The mega amp spherical tokamak (MAST) was a low aspect ratio device (R/a = 0.85/0.65 ~ 1.3) with similar poloidal cross-section to other medium-size tokamaks. physics programme concentrates on addressing key issues for the operation of ITER, design DEMO and future tokamaks by utilising high resolution diagnostic measurements closely coupled theory modelling significantly advance our understanding. An empirical scaling energy confinement time that favours higher power, lower collisionality...
This paper shows experimental results from the TCV tokamak that indicate plasma-molecule interactions involving $D_2^+$ and possibly $D^-$ play an important role as sinks of energy (through hydrogenic radiation well dissociation) particles during divertor detachment if low target temperatures ($< 3$ eV) are achieved. Both molecular activated recombination (MAR) ion source reduction due to a power limitation effect shown be in reducing flux density ramp. In contrast, electron-ion (EIR) sink...
Abstract Detachment, an important mechanism for reducing target heat deposition, is achieved through reductions in power, particle and momentum; which are induced plasma–atom plasma–molecule interactions. Experimental research how those reactions precisely contribute to detachment limited. Both as well interactions can result excited hydrogen atoms emit atomic line emission. In this work, we investigate a new Balmer Spectroscopy technique Plasma–Molecule Interaction—BaSPMI. This first...
In this work we provide experimental insights into the impact of plasma–molecule interactions on target ion flux decrease during divertor detachment achieved through a core density ramp in TCV tokamak. Our improved analysis hydrogen Balmer series shows that processes are strongly contributing to intensities and substantially alter particle balance. We find Molecular Activated Recombination (MAR) sinks from H2+ (and possibly H−) factor ∼5 larger than Electron–Ion (EIR) significant contributor...
The process of divertor detachment, whereby heat and particle fluxes to surfaces are strongly diminished, is required reduce loading erosion in a magnetic fusion reactor acceptable levels. In this paper the physics leading decrease total ion current (It), or 'roll-over', experimentally explored on TCV tokamak through characterization location, magnitude role various sinks sources including complete analysis power balance. These first measurements profiles ionisation hydrogenic radiation...
Abstract Recent results from MAST Upgrade are presented, emphasising understanding the capabilities of this new device and deepening key physics issues for operation ITER design future fusion power plants. The impact MHD instabilities on fast ion confinement have been studied, including first observation losses correlated with Compressional Global Alfvén Eigenmodes. High-performance plasma scenarios developed by tailoring early current ramp phase to avoid internal reconnection events,...
First of a kind SOLPS-ITER simulations on tokamak á configuration variable (TCV) that include nitrogen have been performed to model recent seeded detachment experiments. Based spectroscopic measurements, recycling coefficient 0.3–0.5 the graphite walls TCV is estimated. The experimentally observed decrease core density with increasing plasma reproduced and linked reduction ionisation mean free path in scrape-off layer. Although influence sputtered carbon impurities from TCV's wall cannot be...
The physics of divertor detachment is determined by power, particle and momentum balance. This work provides a novel analysis technique the Balmer line series to obtain full particle/power balance measurement divertor. supplies new information understand what controls target ion flux during detachment. Atomic deuterium excitation emission separated from recombination quantitatively using ratios. enables analysing those two components individually, providing ionisation/recombination...
A combined study of inelastic neutron scattering and ab initio molecular dynamics simulations has been performed in order to the water–acid site interaction zeolite chabazite with a ratio Si/Al = 16 that corresponds 2 protons/uc two different water coverages number molecules being lower higher than proton sites. These results have provided clear picture interaction, it demonstrated there are regimens adsorption, which depend on loading. (i) At low coverage (water/acid ∼0.5), main...
The impurity concentration in the tokamak divertor plasma is a necessary input for predictive scaling of detachment, however direct measurements from existing tokamaks different conditions are limited. To address this, we have applied recently developed spectroscopic N II line ratio technique measuring to range H-mode and L-mode ASDEX Upgrade JET tokamaks, respectively. results both devices show that as power crossing separatrix, Psep, increased under otherwise similar core (e.g. density),...
Abstract The beams of fast runaway electrons (RE), which are often produced during tokamak discharges, particularly dangerous and can induce serious damages the vacuum vessel internal components machine. proper diagnostics RE is essential for controlling discharge, e.g., by early mitigation disruptions potentially beams. usually based on measurements radiation emitted either these electrons, or as a result their interactions with plasma and/or walls. Such recorded means probes placed outside...
The core transport code, JETTO, coupled to the neutral Monte Carlo EIRENE, has been used examine sensitivity of JET H-mode pedestal flux crossing separatrix. Neutral Penetration Model (NPM) [Groebner et. al., Physics Plasmas 9, 2134 (2002)] predicts width density along path scale with inverse its height: 1/ne,ped. By keeping same physics assumptions in NPM, and setting deuterium atoms cross separatrix at location as synthetic diagnostic line sight (i.e. outer mid-plane, OMP), we were able...
Experimentally, it has been observed in high-confinement (H-Mode) plasmas with Edge Localised Modes (ELMs) on JET that the pressure pedestal (pe,ped) is degraded by approximately a factor of two when there change electron separatrix density, ne,sep, from 1−4×1019m−3. Previous work using stability code EUROPED, able to predict degradation pe,ped but only for ne,sep≤1.5×1019m−3. In this work, we apply coupled JETTO-MISHKA-FRANTIC, self-consistently transport region and neutral source varying...
This paper shows experimental results from the TCV tokamak that indicate plasma-molecule interactions involving $D_2^+$ and possibly $D^-$ play an important role as sinks of energy (through hydrogenic radiation well dissociation) particles during divertor detachment if low target temperatures ($< 3$ eV) are achieved. Both molecular activated recombination (MAR) ion source reduction due to a power limitation effect shown be in reducing flux core density ramp. In contrast, electron-ion (EIR)...