1,373 research outputs found
Massive liquid Ar and Xe detectors for direct Dark Matter searches
A novel experiment for direct searches of the Dark Matter with liquid argon
double-phase chamber with a mass of liquid Ar up to several hundred tons is
proposed. To suppress the b-, g- and n0- backgrounds, the comparison of
scintillation and ionization signals for every event is suggested. The addition
in liquid Ar of photosensitive Ge(CH3)4 or C2H4 and suppression of triplet
component of scintillation signals ensures the detection of scintillation
signals with high efficiency and provides a complete suppression of the
electron background. For the detection of photoelectrons and ionization
electrons, highly stable and reliable GEM detectors must be used.Comment: 8 pages, 2 figures, 1 tabl
Wire GEM detector
A wire GEM (WGEM) detector with a gas gap between meshes was constructed. The
detector provides the amplification 5x10E5 for the gas mixture of Ar +20% CO2
at atmospheric pressure. As compared with well-known GEM detectors produced by
perforation the plastic plate metalized on both sides the WGEM does not suffer
from breakdowns between its electrodes and the effect of accumulation of
charges on holes walls is absent. As a result the WGEM has high reliability and
stability.Comment: Presented at the RD51 Collaboration Meeting, CERN, November 2009,
submitted to the Prib. Tech. Expe
RETGEM with polyvinylchloride (PVC) electrodes
This paper presents a new design of the RETGEM (Resistive Electrode Thick
GEM) based on electrodes made of a polyvinylchloride material (PVC). Our device
can operate with gains of 10E5 as a conventional TGEM at low counting rates and
as RPC in the case of high counting rates without of the transit to the violent
sparks. The distinct feature of present RETGEM is the absent of the metal
coating and lithographic technology for manufacturing of the protective
dielectric rms. The electrodes from PVC permit to do the holes by a simple
drilling machine. Detectors on a RETGEM basis could be useful in many fields of
an application requiring a more cheap manufacturing and safe operation, for
example, in a large neutrino experiments, in TPC, RICH systems.Comment: Presented at the RD51 Collaboration Meeting, CERN, November 200
Double Quantum Dots in Carbon Nanotubes
We study the two-electron eigenspectrum of a carbon-nanotube double quantum
dot with spin-orbit coupling. Exact calculation are combined with a simple
model to provide an intuitive and accurate description of single-particle and
interaction effects. For symmetric dots and weak magnetic fields, the
two-electron ground state is antisymmetric in the spin-valley degree of freedom
and is not a pure spin-singlet state. When double occupation of one dot is
favored by increasing the detuning between the dots, the Coulomb interaction
causes strong correlation effects realized by higher orbital-level mixing.
Changes in the double-dot configuration affect the relative strength of the
electron-electron interactions and can lead to different ground state
transitions. In particular, they can favor a ferromagnetic ground state both in
spin and valley degrees of freedom. The strong suppression of the energy gap
can cause the disappearance of the Pauli blockade in transport experiments and
thereby can also limit the stability of spin-qubits in quantum information
proposals. Our analysis is generalized to an array of coupled dots which is
expected to exhibit rich many-body behavior.Comment: 14 pages, 11 pages and 1 table. Typos in text and Figs.4 and 6
correcte
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