4,542 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
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
Two distance-regular graphs
We construct two families of distance-regular graphs, namely the subgraph of
the dual polar graph of type B_3(q) induced on the vertices far from a fixed
point, and the subgraph of the dual polar graph of type D_4(q) induced on the
vertices far from a fixed edge. The latter is the extended bipartite double of
the former
Hidden order in bosonic gases confined in one dimensional optical lattices
We analyze the effective Hamiltonian arising from a suitable power series
expansion of the overlap integrals of Wannier functions for confined bosonic
atoms in a 1d optical lattice. For certain constraints between the coupling
constants, we construct an explicit relation between such an effective bosonic
Hamiltonian and the integrable spin- anisotropic Heisenberg model. Therefore
the former results to be integrable by construction. The field theory is
governed by an anisotropic non linear -model with singlet and triplet
massive excitations; such a result holds also in the generic non-integrable
cases. The criticality of the bosonic system is investigated. The schematic
phase diagram is drawn. Our study is shedding light on the hidden symmetry of
the Haldane type for one dimensional bosons.Comment: 5 pages; 1 eps figure. Revised version, to be published in New. J.
Phy
Paesaggio sacralizzato e militanza ecclesiale
Il contributo focalizza il tema della sacralizzazione del paesaggio nella contemporanità, ponendo la questione in relazione con le dinamiche storico-sociali e politiche del Dopoguerra. Caso-studio è il Getsemani di Casale Corte Cerro, ideato da Luigi Gedda - protagonista della politica italiana degli anni Cinquanta - e realizzato da Ildo Avetta
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