362 research outputs found
Pedestal and Er profile evolution during an edge localized mode cycle at ASDEX Upgrade
The upgrade of the edge charge exchange recombination spectroscopy diagnostic at ASDEX
Upgrade has enabled highly spatially resolved me
asurements of the impurity ion dynamics during an
edge-localized mode cycle
(
ELM
)
with unprecedented temp
oral resolution, i.e. 65
Ό
s. The increase of
transport during an ELM induces a relaxation of the
ion, electron edge gradients in impurity density
and
fl
ows. Detailed characterization of the recovery
of the edge temperature gradients reveals a
difference in the ion and electron channe
l: the maximum ion temperature gradient
T
i
is
re-established on similar timescales as
n
e
, which is faster than the recovery of
T
e
.Afterthe
clamping of the maximum gradient,
T
i
and
T
e
at the pedestal top continue to rise up to the next ELM
while
n
e
stays constant which means that the temperatur
e pedestal and the resu
lting pedestal pressure
widen until the next ELM. The edge radial electric
fi
eld
E
r
at the ELM crash is found to reduce to
typical L-mode values and its ma
ximum recovers to its pre-ELM conditions on a similar time scale as
for
n
e
and
T
i
. Within the uncertainties, the measurements of
E
r
align with their neoclassical
predictions
E
r,neo
for most of the ELM cycle, thus indicating that
E
r
is dominated by collisional
processes. However, between 2 and 4 ms af
ter the ELM crash, other contributions to
E
B
Ì
fl
ow,
e.g. zonal
fl
ows or ion orbit effects, could not be
excluded within the uncertainties.European Commission (EUROfusion 633053
Effects of strong density fluctuations at the plasma edge on ECEI measurements at ASDEX Upgrade
EUROfusion Consortium 63305
Effects of density gradients and fluctuations at the plasma edge on ECEI measurements at ASDEX Upgrade
Electron cyclotron emission imaging (ECEI) provides measurements of electron temperature (Te) and its fluctuations (ÎŽTe). However, when measuring at the plasma edge, in the steep gradient region, radiation transport effects must be taken into account. It is shown that due to these effects, the scrape-off layer region is not accessible to the ECEI measurements in steady state conditions and that the signal is dominated by the shine-through emission. Transient effects, such as filaments, can change the radiation transport locally, but cannot be distinguished from the shine-through. Local density measurements are essential for the correct interpretation of the electron cyclotron emission, since the density fluctuations influence the temperature measurements at the plasma edge. As an example, a low frequency 8 kHz mode, which causes 10%â15% fluctuations in the signal level of the ECEI, is analysed. The same mode has been measured with the lithium beam emission spectroscopy density diagnostic, and is very well correlated in time with high frequency magnetic fluctuations. With radiation transport modelling of the electron cyclotron radiation in the ECEI geometry, it is shown that the density contributes significantly to the radiation temperature (Trad) and the experimental observations have shown the amplitude modulation in both density and temperature measurements. The poloidal velocity of the low frequency mode measured by the ECEI is 3 km sâ1. The calculated velocity of the high frequency mode measured with the magnetic pick-up coils is about 25 km sâ1. Velocities are compared with the E Ă B background flow velocity and possible explanations for the origin of the low frequency mode are discussed.EUROfusion Consortium 63305
Investigation of inter-ELM ion heat transport in the H-mode pedestal of ASDEX Upgrade plasmas
The ion heat transport in the pedestal of H-mode plasmas is investigated in various H-mode
discharges with different pedestal ion collisionalities. Interpretive modelling suggests that in
all analyzed discharges the ion heat diffusivity coefficient,
Ï
i
, in the pedestal is close to the
neoclassical prediction within the experimental uncertainties. The impact of changing the
deposition location of the electron cyclotron resonance heating on the ion heat transport has
been studied. The effect on the background profiles is small. The pre-ELM (edge localized
modes) edge profiles as well as the behaviour of the electron temperature and density, ion
temperature and impurity toroidal rotation during the ELM cycle are very similar in discharges
with on- and off-axis ECRH heating. No significant deviation of
Ï
i
from neoclassics is
observed when changing the ECRH deposition location to the plasma edge.European Commission (EUROfusion 633053)European Union (EUROfusion Grant WP14-FRF-IPP
Screening a Peptide Library by DSC and SAXD: Comparison with the Biological Function of the Parent Proteins
We have recently identified the membranotropic regions of the hepatitis C virus proteins E1, E2, core and p7 proteins by observing the effect of protein-derived peptide libraries on model membrane integrity. We have studied in this work the ability of selected sequences of these proteins to modulate the LÎČ-Lα and Lα-HII phospholipid phase transitions as well as check the viability of using both DSC and SAXD to screen a protein-derived peptide library. We demonstrate that it is feasible to screen a library of peptides corresponding to one or several proteins by both SAXD and DSC. This methodological combination should allow the identification of essential regions of membrane-interacting proteins which might be implicated in the molecular mechanism of membrane fusion and/or budding
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