4,336 research outputs found
Hie-Isolde High Beta Cavity Study and Measurements
The upgrade of the ISOLDE machine at CERN foresees a superconducting linac
based on two gap independently phased Nb sputtered Quarter Wave Resonators
(QWRs) working at 101.28MHz and producing an accelerating field of 6MV/m on
axis. A careful study of the fields in the cavity has been carried out in order
to pin down the crucial e-m parameters of the structure such as peak fields,
quality factor and e-m power dissipated on the cavity wall. A tuning system
with about 200kHz frequency range has been developed in order to cope with
fabrication tolerances. In this paper we will report on the cavity simulations.
The tuning plate design will be described. Finally the frequency measurements
on a cavity prototype at room temperature will be presented.Comment: 5 pages, SRF09 Conference in Berli
Beam Dynamics Studies for the HIE-ISOLDE Linac at CERN
The upgrade of the normal conducting (NC) Radioactive Ion Beam EXperiment
(REX)-ISOLDE heavy ion accelerator at CERN, under the High Intensity and Energy
(HIE)-ISOLDE framework, proposes the use of superconducting (SC) quarter-wave
resonators (QWRs) to increase the energy capability of the facility from 3
MeV/u to beyond 10 MeV/u. A beam dynamics study of a lattice design comprising
SC QWRs and SC solenoids has confirmed the design's ability to accelerate ions,
with a mass-to-charge ratio in the range 2.5 < A/q < 4.5, to the target energy
with a minimal emittance increase. We report on the development of this study
to include the implementation of realistic fields within the QWRs and
solenoids. A preliminary error study is presented in order to constrain
tolerances on the manufacturing and alignment of the linac.Comment: 3 pages, 8 figures, 1 table, submitted to the Particle Accelerator
Conference (PAC) 2009 in Vancouver. Page formatting changed to US letter siz
DMRG Simulation of the SU(3) AFM Heisenberg Model
We analyze the antiferromagnetic Heisenberg chain by means of
the Density Matrix Renormalization Group (DMRG). The results confirm that the
model is critical and the computation of its central charge and the scaling
dimensions of the first excited states show that the underlying low energy
conformal field theory is the Wess-Zumino-Novikov-Witten
model.Comment: corrections and improvements adde
Bell inequality violation by entangled single photon states generated from a laser, a LED or a Halogen lamp
In single-particle or intraparticle entanglement, two degrees of freedom of a
single particle, e.g., momentum and polarization of a single photon, are
entangled. Single-particle entanglement (SPE) provides a source of non
classical correlations which can be exploited both in quantum communication
protocols and in experimental tests of noncontextuality based on the
Kochen-Specker theorem. Furthermore, SPE is robust under decoherence phenomena.
Here, we show that single-particle entangled states of single photons can be
produced from attenuated sources of light, even classical ones. To
experimentally certify the entanglement, we perform a Bell test, observing a
violation of the Clauser, Horne, Shimony and Holt (CHSH) inequality. On the one
hand, we show that this entanglement can be achieved even in a classical light
beam, provided that first-order coherence is maintained between the degrees of
freedom involved in the entanglement. On the other hand, we prove that filtered
and attenuated light sources provide a flux of independent SPE photons that,
from a statistical point of view, are indistinguishable from those generated by
a single photon source. This has important consequences, since it demonstrates
that cheap, compact, and low power entangled photon sources can be used for a
range of quantum technology applications
BUILDING PERFORMANCE SIMULATION PROGRAMS: BETWEEN “OPERABILITY” AND “ADEQUACY”
Energy efficiency in Buildings, combined with an efficient use of the energy provided by renewable sources, are essential objectives set by the revision of the European Energy Performance of Buildings Directive. To achieve these objectives, an accurate estimate of the behavior of the system to be built/improved must be available during all stages of the design process or energy audit (if existing). While designing or improving energy efficiency, other important and associated goals must be ad-dressed, such as environmental health (hygrothermal, acoustic and luminous), costs, environmental sustainability, etc. Having to choose a dynamic simulation program to inform the design process it is necessary to analyze the possibilities offered by different available software, in terms of accuracy and completeness, while taking into account ease of use and included facilities aimed at supporting the design process itself. Over the past years, numerous Building Performance Simulation tools (BPSts) have been developed with the ambition of removing some shortages of existing BPSts in addressing today’s users’ requirements, sometimes by underestimating the reasons for those lacks of functionality. A software improvement that is focused only on usability might oversimplifies the complexity of the model used by the tool, or its use, while a focus on rapid prototyping might respond poorly to the requirements of a certain typology of users. A critical review of today’s requirements and available tools is here presented, with the aim of informing a better awareness of possibilities offered or denied by current BPSts
Efficient Coherent Control by Optimized Sequences of Pulses of Finite Duration
Reliable long-time storage of arbitrary quantum states is a key element for
quantum information processing. In order to dynamically decouple a spin or
quantum bit from a dephasing environment, we introduce an optimized sequence of
control pulses of finite durations \tau\pp and finite amplitudes. The
properties of this sequence of length stem from a mathematically rigorous
derivation. Corrections occur only in order and \tau\pp^3 without
mixed terms such as T^N\tau\pp or T^N\tau\pp^2. Based on existing
experiments, a concrete setup for the verification of the properties of the
advocated realistic sequence is proposed.Comment: 8 pages, 1 figur
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