174 research outputs found
Benchmarking of a 1D Scrape-off layer code SOLF1D with SOLPS and its use in modelling long-legged divertors
A 1D code modelling SOL transport parallel to the magnetic field (SOLF1D) is
benchmarked with 2D simulations of MAST-U SOL performed via the SOLPS code for
two different collisionalities. Based on this comparison, SOLF1D is then used
to model the effects of divertor leg stretching in 1D, in support of the
planned Super-X divertor on MAST. The aim is to separate magnetic flux
expansion from volumetric power losses due to recycling neutrals by stretching
the divertor leg either vertically or radially.Comment: 31 pages, 17 figures. This is an author-created, un-copyedited
version of an article accepted for publication in Plasma Physics and
Controlled Fusion. IOP Publishing Ltd is not responsible for any errors or
omissions in this version of the manuscript or any version derived from i
Investigation of conventional and Super-X divertor configurations of MAST Upgrade using SOLPS
One of the first studies of MAST Upgrade divertor configurations with
SOLPS5.0 are presented. We focus on understanding main prospects associated
with the novel geometry of the Super-X divertor (SXD). This includes a
discussion of the effect of magnetic flux expansion and volumetric power losses
on the reduction of target power loads, the effect of divertor geometry on the
divertor closure and distribution of neutral species and radiation in the
divertor, the role of the connection length in broadening the target wetted
area. A comparison in conditions typical for MAST inter-ELM H-mode plasmas
confirms improved performance of the Super-X topology resulting in
significantly better divertor closure with respect to neutrals (the atomic flux
from the target increased by a factor of 6, but the atomic flux from the
divertor to the upper SOL reduced by a factor of 2), increased radiation volume
and increased total power loss (a factor of 2) and a reduction of target power
loads through both magnetic flux expansion and larger volumetric power loss in
the divertor (a factor of 5-10 in attached plasmas). The reduction of the
target power load by SXD further increases with collisionality (high density or
detached regimes) thanks to larger importance of volumetric power losses. It is
found that a cold divertor plasma leads to stronger parallel temperature
gradients in the SOL which drive more parallel heat flux, meaning that the
effectiveness of perpendicular transport in spreading the power at the target
can be reduced, and this needs to be taken into account in any optimisation.Comment: 32 pages, 23 figures. This is an author-created, un-copyedited
version of an article accepted for publication in PPCF. IOP Publishing Ltd
and IAEA are not responsible for any errors or omissions in this version of
the manuscript or any version derived from i
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A revision of the grasshopper genus Orthochtha and its allies (Orthoptera: Acrididae: Acridinae)
This revision concerns the genera Orthochtha, Euprepoptera, Lobopoma, Pamacris and Xerophlaeoba, which are diagnosed and redescribed, plus three others erected here: Shabacris for Lobopoma robusta, Nimbacris for Lobopoma longicornis and Xenocymochtha for a new species, barkeri, here described. As now recognized, Orthochtha comprises 25 species and 11 subspecies of which 12 species and five subspecies respectively are described here as new, while the identity of another species, O. angustata, remains uncertain. Of the other genera, two species are now recognized within Euprepoptera, one of which is new, three within Lobopoma (two new) and two within Pamacris, with carterocera transferred from Lobopoma. In all, 36 species and 11 subspecies are diagnosed, illustrated, keyed and their distributions mapped. Six new synonymies are established and four specific names recalled but given new status as subspecies; two other species are reduced to the rank of subspecies. Six lectotypes and one neotype are designated. The affinities of the taxa are discussed on the basis of classical taxonomic criteria and also by numerical analysis. Their biogeographies are assessed, notably in terms of the postulated environmental influences on their evolution. A synopsis of the available information on the biology, ecology and economic importance is given for each species
Toroidal modelling of plasma response and RMP field penetration
The penetration dynamics of the resonant magnetic perturbation (RMP) field is sim-
ulated in the full toroidal geometry, under realistic plasma conditions in MAST experiments.
The physics associated with several aspects of the RMP penetration - the plasma response
and rotational screening, the resonant and non-resonant torques and the toroidal momentum
balance - are highlighted. In particular, the plasma response is found to significantly amplify
the non-resonant component of the RMP field for some of the MAST plasmas. A fast rotating
plasma, in response to static external magnetic fields, experiences a more distributed electro-
magnetic torque due to the resonance with continuum waves in the plasma. At fast plasma
flow (such as for the MAST plasma), the electromagnetic torque is normally dominant over
the neoclassical toroidal viscous (NTV) torque. However, at sufficiently slow plasma flow,
the NTV torque can play a significant role in the toroidal momentum balance, thanks to the
precession drift resonance enhanced, so called superbanana plateau regime
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