160 research outputs found
Spatiotemporal evolution of runaway electrons from synchrotron images in Alcator C-Mod
In the Alcator C-Mod tokamak, relativistic runaway electron (RE) generation
can occur during the flattop current phase of low density, diverted plasma
discharges. Due to the high toroidal magnetic field (B = 5.4 T), RE synchrotron
radiation is measured by a wide-view camera in the visible wavelength range
(~400-900 nm). In this paper, a statistical analysis of over one thousand
camera images is performed to investigate the plasma conditions under which
synchrotron emission is observed in C-Mod. In addition, the spatiotemporal
evolution of REs during one particular discharge is explored in detail via a
thorough analysis of the distortion-corrected synchrotron images. To accurately
predict RE energies, the kinetic solver CODE [Landreman et al 2014 Comput.
Phys. Commun. 185 847-855] is used to evolve the electron momentum-space
distribution at six locations throughout the plasma: the magnetic axis and flux
surfaces q = 1, 4/3, 3/2, 2, and 3. These results, along with the
experimentally-measured magnetic topology and camera geometry, are input into
the synthetic diagnostic SOFT [Hoppe et al 2018 Nucl. Fusion 58 026032] to
simulate synchrotron emission and detection. Interesting spatial structure near
the surface q = 2 is found to coincide with the onset of a locked mode and
increased MHD activity. Furthermore, the RE density profile evolution is fit by
comparing experimental to synthetic images, providing important insight into RE
spatiotemporal dynamics
Conceptual design study for heat exhaust management in the ARC fusion pilot plant
The ARC pilot plant conceptual design study has been extended beyond its
initial scope [B. N. Sorbom et al., FED 100 (2015) 378] to explore options for
managing ~525 MW of fusion power generated in a compact, high field (B_0 = 9.2
T) tokamak that is approximately the size of JET (R_0 = 3.3 m). Taking
advantage of ARC's novel design - demountable high temperature superconductor
toroidal field (TF) magnets, poloidal magnetic field coils located inside the
TF, and vacuum vessel (VV) immersed in molten salt FLiBe blanket - this
follow-on study has identified innovative and potentially robust power exhaust
management solutions.Comment: Accepted by Fusion Engineering and Desig
On the minimum transport required to passively suppress runaway electrons in SPARC disruptions
In [V.A. Izzo et al 2022 Nucl. Fusion 62 096029], state-of-the-art modeling
of thermal and current quench (CQ) MHD coupled with a self-consistent evolution
of runaway electron (RE) generation and transport showed that a
non-axisymmetric (n = 1) in-vessel coil could passively prevent RE beam
formation during disruptions in SPARC, a compact high-field tokamak projected
to achieve a fusion gain Q > 2 in DT plasmas. However, such suppression
requires finite transport of REs within magnetic islands and re-healed flux
surfaces; conservatively assuming zero transport in these regions leads to an
upper bound of RE current ~1 MA compared to ~8.7 MA of pre-disruption plasma
current. Further investigation finds that core-localized electrons, within r/a
< 0.3 and with kinetic energies 0.2-15 MeV, contribute most to the RE plateau
formation. Yet only a relatively small amount of transport, i.e. a diffusion
coefficient ~18 , is needed in the core to fully mitigate these
REs. Properly accounting for (i) the CQ electric field's effect on RE transport
in islands and (ii) the contribution of significant RE currents to disruption
MHD may help achieve this
Husten, Atemnot und B-Symptome bei einer 40-jährigen Frau
Zusammenfassung: Der Morbus Castleman ist eine seltene polyklonale, lymphoproliferative Erkrankung, bei der Mediatoren von Entzündungsreaktionen, v.a. Interleukin-6, eine wichtige pathophysiologische Rolle spielen. Zur Behandlung dieser Krankheit ist keine Standardtherapie etabliert. Wir berichten über den Fall einer 40-jährigen HIV-negativen Patientin mit primär pulmonaler Manifestation eines HHV-8-negativen, plasmazellreichen multizentrischen Morbus Castleman. Verschiedene Therapieversuche mit Immunmodulatoren wurden durchgeführt, bevor eine Behandlung mit dem Interleukin-6-Rezeptor-Antikörper Tocilizumab begonnen wurde. Seit 5Jahren ist der klinische Verlauf unter fortgesetzter Tocilizumabgabe stabi
MHD stability and disruptions in the SPARC tokamak
SPARC is being designed to operate with a normalized beta of beta(N) = 1.0, a normalized density of n(G) = 0.37 and a safety factor of q(95) approximate to 3.4, providing a comfortable margin to their respective disruption limits. Further, a low beta poloidal beta(p) = 0.19 at the safety factor q = 2 surface reduces the drive for neoclassical tearing modes, which together with a frozen-in classically stable current profile might allow access to a robustly tearing-free operating space. Although the inherent stability is expected to reduce the frequency of disruptions, the disruption loading is comparable to and in some cases higher than that of ITER. The machine is being designed to withstand the predicted unmitigated axisymmetric halo current forces up to 50 MN and similarly large loads from eddy currents forced to flow poloidally in the vacuum vessel. Runaway electron (RE) simulations using GO+CODE show high flattop-to-RE current conversions in the absence of seed losses, although NIMROD modelling predicts losses of similar to 80 %; self-consistent modelling is ongoing. A passive RE mitigation coil designed to drive stochastic RE losses is being considered and COMSOL modelling predicts peak normalized fields at the plasma of order 10(-2) that rises linearly with a change in the plasma current. Massive material injection is planned to reduce the disruption loading. A data-driven approach to predict an oncoming disruption and trigger mitigation is discussed
Management of patients at the hepatopancreatobiliary unit of a London teaching hospital during the COVID-19 pandemic
To mitigate COVID-19-related shortage of treatment capacity, the hepatopancreatobiliary (HPB) unit of the Royal Free Hospital London (RFHL) transferred its practice to independent hospitals in Central London through the North Central London Cancer Alliance. The aim of this study was to critically assess this strategy and evaluate perioperative outcomes. Prospectively collected data were reviewed on all patients who were treated under the RFHL HPB unit in six hospitals between November 2020 and October 2021. A total of 1541 patients were included, as follows: 1246 (81%) at the RFHL, 41 (3%) at the Chase Farm Hospital, 23 (2%) at the Whittington Hospital, 207 (13%) at the Princess Grace Hospital, 12 (1%) at the Wellington Hospital and 12 (1%) at the Lister Hospital, Chelsea. Across all institutions, overall complication rate were 40%, major complication (Clavien-Dindo grade ≥ 3a) rate were 11% and mortality rates were 1.4%, respectively. In COVID-19-positive patients (n = 28), compared with negative patients, complication rate and mortality rates were increased tenfold. Outsourcing HPB patients, including their specialist care, to surrounding institutions was safe and ensured ongoing treatment with comparable outcomes among the institutions during the COVID-19 pandemic. Due to the lack of direct comparison with a non-pandemic cohort, these results can strictly only be applied within a pandemic setting
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