Papers by Elisabeth Rachlew
Journal of Physics B, Mar 8, 2005
The npsigma 1Sigma+u and nppi 1Piu states in D2 have been selectively excited using monoenergetic... more The npsigma 1Sigma+u and nppi 1Piu states in D2 have been selectively excited using monoenergetic synchrotron light in the range of 13.97-15.84 eV and the subsequent dispersed emission to the EF 1Sigma+g state was observed using a grating spectrometer. In total, 18 emission bands from the levels n = 3-6 were studied and rotationally analysed. The intensities of the P
Plasma Physics and Controlled Fusion, Jul 5, 2021
Physical Review Letters, Jun 29, 2007
Recent experiments on JET have shown that type-I edge localized modes (ELMs) can be controlled by... more Recent experiments on JET have shown that type-I edge localized modes (ELMs) can be controlled by applying static low n = 1 external magnetic perturbation fields (EMPFs) produced by four external error field correction coils (EFCC) mounted far away from the plasma between the transformer limbs. When an n = 1 EMPF with an amplitude of a few Gauss at the plasma edge (ρ > 0.95) is applied during the stationary phase of a type-I ELMy H-mode plasma, the ELM frequency rises from ~30 Hz up to ~120 Hz and follows the applied perturbation field strength. The energy loss per ELM normalised to the total stored energy, ΔW ELM /W p , decreased from 7 % to below the resolution limit of the diamagnetic measurement (~ 2%). Transport analysis using the TRANSP code shows no or a modest reduction of the thermal energy confinement time because of the density pump-out, but when normalised to the IPB98(y,2) scaling the confinement shows almost no reduction. Stability analysis of mitigated ELMs shows that the operational point moves from intermediate n peeling-ballooning (wide mode) boundary to low-n peeling (narrow mode) boundary with n = 1 perturbation fields. The first results of ELM mitigation with the n = 2 EMPFs on JET demonstrate that the frequency of ELM can be increased by a factor of 3.5, only limited by the available EFCC coil current. During the application of the n = 1, 2 EMPFs, a reduction in the ELM size (ΔW ELM) and ELM peak heat fluxes on the divertor target by roughly the same factor as the increase of the ELM frequency has been observed. The reduction in heat flux is mainly due to the drop of particle flux rather than the change of the electron temperature. Similar plasma braking effect has been observed with n = 1 and n = 2 external fields when a same EFCC coil current was applied. Compensation of the density pump-out effect has been achieved by means of gas fuelling in low triangularity plasmas. An optimised fuelling rate to compensate the density pump-out effect has been identified. Active ELM control by externally applied fields offers an attractive method for next-generation tokamaks, e.g. ITER.
Journal of Physics B, Jul 25, 2011
European Physical Journal Plus, May 1, 2016
EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK' Associ... more EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxon, OX14 3DB, UK' Association EURATOM -CEA, CEA/DSM/DRFC-Cadarache 13108, St Paul Durance, France Assoziationen EURATOM -Forschungszentrum, Jülich D52425 Jülich Germany Laboratorio Nacional de Fusión, Asociación EURATOM-CIEMAT, Madrid, Spain, Associazione EURATOM -ENEA, ENEA Centro Ricerche Frascati C.P. 65, 00044 Italy Association EURATOM-“Belgian State”, ERM/KMS, Brussels, Belgium, Partner in the TEC Association EURATOM-Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany Association EURATOM, Conférédation Suisse, EPFL, 1015, Lausanne, Switzerland Association EURATOM-VR, Department of Physics, SCI, KTH, SE-10691 Stockholm, Sweden # Appendix of M. Watkins et al., Fusion Energy 2006 (Proc. 21st Int. Conf. Chengdu, 2006) IAEA, Vienna
Review of Scientific Instruments, Oct 1, 2010
APS Division of Plasma Physics Meeting Abstracts, Nov 1, 1999
A Motional Stark Effect (MSE) diagnostic is used to measure the magnetic field pitch angle in JET... more A Motional Stark Effect (MSE) diagnostic is used to measure the magnetic field pitch angle in JET discharges. The q-profile is deduced from EFIT magnetic equilibrium reconstructions constrained by MSE data. Measurements have concentrated primarily on the Optimised Shear (OS) regime in which the details of the q-profile play an important role in the formation of internal transport barriers, leading
have investigated the access to high dN for plasmas with H-mode edge and q0‡1. The 1.2MA/1.8T (q9... more have investigated the access to high dN for plasmas with H-mode edge and q0‡1. The 1.2MA/1.8T (q95...5) plasmas were formed by the initial inductive ramp-up phase, similar to experiments developed at DIII-D [1]. LHCD or ICRH was added in some discharges and the initial current ramp rate varied to tailor the q profile shape as the current penetrated towards the plasma centre. The resulting target q profile at the start of the 1.5 1.0 0.5
Journal of Instrumentation, 2019
Convolutional neural networks (CNNs) have found applications in many image processing tasks, such... more Convolutional neural networks (CNNs) have found applications in many image processing tasks, such as feature extraction, image classification, and object recognition. It has also been shown that the inverse of CNNs, so-called deconvolutional neural networks, can be used for inverse problems such as plasma tomography. In essence, plasma tomography consists in reconstructing the 2D plasma profile on a poloidal cross-section of a fusion device, based on line-integrated measurements from multiple radiation detectors. Since the reconstruction process is computationally intensive, a deconvolutional neural network trained to produce the same results will yield a significant computational speedup, at the expense of a small error which can be assessed using different metrics. In this work, we discuss the design principles behind such networks, including the use of multiple layers, how they can be stacked, and how their dimensions can be tuned according to the number of detectors and the desired tomographic resolution for a given fusion device. We describe the application of such networks at JET and COMPASS, where at JET we use the bolometer system, and at COMPASS we use the soft X-ray diagnostic based on photodiode arrays.
Fusion Engineering and Design, 2018
AIP Conference Proceedings, 2003
AIP Conference Proceedings, 2005
Fast wave current drive has been performed in JET plasmas with internal transport barriers, ITBs,... more Fast wave current drive has been performed in JET plasmas with internal transport barriers, ITBs, and strongly reversed magnetic shear. Although the current drive efficiency of the power absorbed on the electrons is fairly high, only small effects are seen in the central current density. The main reasons are the parasitic absorption of RF power, the strongly inductive nature of
In ICRF heated plasmas giant sawteeth (ST) can develop with periods larger than one second. At lo... more In ICRF heated plasmas giant sawteeth (ST) can develop with periods larger than one second. At low ICRH power (<3 MW) a well defined ST period that increases with power is observed. At higher powers a large variation in ST periods is observed with a long ST-free period followed by a phase of shorter ST periods. At higher ICRH powers
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Papers by Elisabeth Rachlew