839 research outputs found
Microscopic analysis of the chemical reaction between Fe(Te,Se) thin films and underlying CaF
To understand the chemical reaction at the interface of materials, we
performed a transmission electron microscopy (TEM) observation in four types of
Fe(Te,Se) superconducting thin films prepared on different types of substrates:
CaF2 substrate, CaF2 substrate with a CaF2 buffer layer, CaF2 substrate with a
FeSe buffer layer, and a LaAlO3 substrate with a CaF2 buffer layer. Based on
the energy-dispersive X-ray spectrometer (EDX) analysis, we found possible
interdiffusion between fluorine and selenium that has a strong influence on the
superconductivity in Fe(Te,Se) films. The chemical interdiffusion also plays a
significant role in the variation of the lattice parameters. The lattice
parameters of the Fe(Te,Se) thin films are primarily determined by the chemical
substitution of anions, and the lattice mismatch only plays a secondary role.Comment: 30 pages, 9 figur
Calculation of Control Rods Reactivity Worth of RSG-GAS First Core Using Deterministic and Monte Carlo Methods
The control rod worth is a key parameter for the research reactor operation and utilization. Control rod worth computation is a challenge for the fully-deterministic and Monte Carlo calculations, including the few-group cross section generation, and the core analysis. The safe and reliable utilization of research reactor demands the possible accurate information of control rod worth because they are used to compensate the excess reactivity for safe reactor operation and its controlled shut down. The criticality positions of the control rods change with time due to buildup of fission products during the reactor operation. It is therefore important to determine the reactivity worth of control rods. The aim of this article is to obtain reliable control rod worth of the first core of RSG-GAS as a verification and validation result. For this purpose, deterministic and Monte Carlo models of the reactor core were developed and confirmed by the experimental results of excess reactivity, shutdown margin, and combined control rod reactivity worth using the combination of WIMSD-5B and Batan-3DIFF computer codes. WIMSD-5B is a neutron transport theory-based lattice cell modeling code that is used for the generation of group constants for different regions of the reactor core. These are provided as input to the diffusion theory based Batan-3DIFF code which performs the global core calculations for the reactor system. For the Monte Carlo model, to estimate the reactivity worth of control rods, the MCNP6 code is used. The result of this analysis showed that for the integral control rod worth a good agreement was found between experimental data and Monte Carlo simulation results but up to 5 % difference occurred between experimental results and diffusion result
Radiative type-I seesaw model with dark matter via U(1)_{B-L} gauge symmetry breaking at future linear colliders
We discuss phenomenology of the radiative seesaw model in which spontaneous
breaking of the U(1) gauge symmetry at the TeV scale gives the common
origin for masses of neutrinos and dark matter (Kanemura et al., 2012). In this
model, the stability of dark matter is realized by the global U(1)
symmetry which arises by the BL charge assignment. Right-handed neutrinos
obtain TeV scale Majorana masses at the tree level. Dirac masses of neutrinos
are generated via one-loop diagrams. Consequently, tiny neutrino masses are
generated at the two-loop level by the seesaw mechanism. This model gives
characteristic predictions, such as light decayable right-handed neutrinos,
Dirac fermion dark matter and an extra heavy vector boson. These new particles
would be accessible at collider experiments because their masses are at the TeV
scale. The U(1) vector boson may be found at the LHC, while the other
new particles could only be tested at future linear colliders. We find that the
dark matter can be observed at a linear collider with =500 GeV and
that light right-handed neutrinos can also be probed with =1 TeV.Comment: 15 pages, 8 figure
Point-contact Andreev-reflection spectroscopy in Fe(Te,Se) films: multiband superconductivity and electron-boson coupling
We report on a study of the superconducting order parameter in
Fe(TeSe) thin films (with different Se contents: x=0.3, 0.4, 0.5)
by means of point-contact Andreev-reflection spectroscopy (PCARS). The PCARS
spectra show reproducible evidence of multiple structures, namely two clear
conductance maxima associated to a superconducting gap of amplitude and additional shoulders at higher energy that, as we
show, are the signature of the strong interaction of charge carriers with a
bosonic mode whose characteristic energy coincides with the spin-resonance
energy. The details of some PCARS spectra at low energy suggest the presence of
a smaller and not easily discernible gap of amplitude . The existence of this gap and its amplitude are confirmed by PCARS
measurements in Fe(TeSe) single crystals. The values of the two
gaps and , once plotted as a function of the local
critical temperature , turn out to be in perfect agreement with the
results obtained by various experimental techniques reported in literature.Comment: 8 pages, 6 figures. This is an author-created, un-copyedited version
of an article published in Supercond. Sci. Technol. IOP Publishing Ltd is not
responsible for any errors or omissions in this version of the manuscript or
any version derived from it. The Version of Record is available online at
10.1088/0953-2048/27/12/12401
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