37 research outputs found
Non-parametric inference of impurity transport coefficients in the ASDEX Upgrade tokamak
We present a non-parametric inference of impurity transport coefficients by using charge exchange recombination spectroscopy measurements of Ne X, Ne VIII, O VIII, and C VI lines. Due to their close atomic numbers, neon, oxygen and carbon impurity ions are assumed to have the same diffusion coefficient D and convection velocity v. Unlike conventional techniques that modulate or perturb the impurity contents, we employ a quasi-stationary plasma with static impurity profiles. Since the ratio of v to D only describes the equilibrated profile of the sum of all impurity charge states, steady-state measurements can still decouple D and v if different charge states are simultaneously observed. We have formulated a non-parametric analysis framework based on the Bayesian probability theory and conducted transport coefficient measurements for a Type III ELMy H-mode plasma at ASDEX Upgrade. The charge exchange reactions with the background neutrals, which are known to affect the impurity charge state balance, are taken into account by introducing additional free parameters. While D at the pedestal is close to the neoclassical level ( < 1 m s-2), a large diffusion coefficient and a strong outward convection are inferred right inside the pedestal top.This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053
Improvements in the determination of ISS Ca II K parameters
Measurements of the ionized Ca II K line are one of the major resources for
long-term studies of solar and stellar activity. They also play a critical role
in many studies related to solar irradiance variability, particularly as a
ground-based proxy to model the solar ultraviolet flux variation that may
influence the Earth's climate. Full disk images of the Sun in Ca II K have been
available from various observatories for more than 100 years and latter
synoptic Sun-as-a-star observations in Ca II K began in the early 1970s. One of
these instruments, the Integrated Sunlight Spectrometer (ISS) has been in
operation at Kitt Peak (Arizona) since late 2006. The ISS takes daily
observations of solar spectra in nine spectra bands, including the Ca II K and
H line s. We describe recent improvements in data reduction of Ca II K
observations, and present time variations of nine parameters derived from the
profile of this spectral line
Adsorption of Reactive Particles on a Random Catalytic Chain: An Exact Solution
We study equilibrium properties of a catalytically-activated annihilation reaction taking place on a one-dimensional chain of length () in which some segments (placed at random, with mean concentration
) possess special, catalytic properties. Annihilation reaction takes place,
as soon as any two particles land onto two vacant sites at the extremities
of the catalytic segment, or when any particle lands onto a vacant site on
a catalytic segment while the site at the other extremity of this segment is
already occupied by another particle. Non-catalytic segments are inert with
respect to reaction and here two adsorbed particles harmlessly coexist. For
both "annealed" and "quenched" disorder in placement of the catalytic segments,
we calculate exactly the disorder-average pressure per site. Explicit
asymptotic formulae for the particle mean density and the compressibility are
also presented.Comment: AMSTeX, 27 pages + 4 figure
Dynamical Left-Right Symmetry Breaking
We study a left--right symmetric model which contains only elementary gauge
boson and fermion fields and no scalars. The phenomenologically required
symmetry breaking emerges dynamically leading to a composite Higgs sector with
a renormalizable effective Lagrangian. We discuss the pattern of symmetry
breaking and phenomenological consequences of this scenario. It is shown that a
viable top quark mass can be achieved for the ratio of the VEVs of the
bi--doublet =~ 1.3--4. For a theoretically
plausible choice of the parameters the right--handed scale can be as low as
; in this case one expects several intermediate and low--scale
scalars in addition to the \SM Higgs boson. These may lead to observable lepton
flavour violation effects including decay with the rate close
to its present experimental upper bound.Comment: 51 pages, LaTeX and uuencoded, packed Postscript figures. The
complete paper, including figures, is also available via WWW at
http://www.cip.physik.tu-muenchen.de/tumphy/d/T30d/PAPERS/
TUM-HEP-222-95.ps.g
SOLIS Vector Spectromagnetograph: status and science
The Vector Spectromagnetograph (VSM) instrument has recorded photospheric and chromospheric magnetograms daily since August 2003. Full-disk photospheric vector magnetograms are observed at least weekly and, since November 2006, area-scans of active regions daily. Quick-look vector magnetic images, plus X3D and FITS formated files, are now publicly available daily. In the near future, Milne-Eddington inversion parameter data will also be available and a typical observing day will include three full-disk photospheric vector magnetograms. Besides full-disk observations, the VSM is capable of high temporal cadence area-scans of both the photosphere and chromosphere. Carrington rotation and daily synoptic maps are also available from the photospheric magnetograms and coronal hole estimate images