16,540 research outputs found
Simulation of an Intra-Pulse Interaction Point Feedback for Future Linear Colliders
In future normal-conducting linear colliders, the beams will be delivered in
short bursts with a length of the order of 100 ns. The pulses will be separated
by several ms. In order to maintain high luminosity, feedback is necessary on a
pulse-to-pulse basis. In addition, intra-pulse feedback that can correct beam
positions and angles within one pulse seem technically feasible. The likely
performances of different feedback options are simulated for the NLC (Next
Linear Collider) and CLIC (Compact Linear Collider).Comment: LINAC2000 Conference, Paper ID MOA0
Beam Dynamics Simulation for the CTF3 Drive-Beam Accelerator
A new CLIC Test Facility (CTF3) at CERN will serve to study the drive beam
generation for the Compact Linear Collider (CLIC). CTF3 has to accelerate a 3.5
A electron beam in almost fully-loaded structures. The pulse contains more than
2000 bunches, one in every second RF bucket, and has a length of more than one
microsecond. Different options for the lattice of the drive-beam accelerator
are presented, based on FODO-cells and triplets as well as solenoids. The
transverse stability is simulated, including the effects of beam jitter,
alignment and beam-based correction.Comment: LINAC2000 Conference, Paper No MOA0
Beam Loading Compensation in the Main Linac of CLIC
Compensation of multi-bunch beam loading is of great importance in the main
linac of the Compact Linear Collider (CLIC). The bunch-to-bunch energy
variation has to stay below 1 part in 1000. In CLIC, the RF power is obtained
by decelerating a drive beam which is formed by merging a number of short bunch
trains. A promising scheme for tackling beam loading in the main linac is based
on varying the lengths of the bunch trains in the drive beam. The scheme and
its expected performance are presented.Comment: LINAC 2000, paper ID MOA0
Beam-induced backgrounds in the CLIC 3 TeV CM energy interaction region
Luminosity spectrum and accelerator background levels strongly influence the
experimental conditions and have an important impact on detector design. The
expected rates of the main beam-beam products at CLIC 3 TeV CM energy, taking
into account for machine imperfections, are computed. Among the other
machine-induced background the photon fans from the Incoherent Synchrotron
Radiation (ISR) photons emitted in the final doublet are evaluated.Comment: Proceedings of LCWS1
First Evaluation of Dynamic Aperture at Injection for FCC-hh
In the Hadron machine option, proposed in the context of the Future Circular
Colliders (FCC) study, the dipole field quality is expected to play an
important role, as in the LHC. A preliminary evaluation of the field quality of
dipoles, based on the NbSn technology, has been provided by the magnet
group. The effect of these field imperfections on the dynamic aperture, using
the present lattice design, is presented and first tolerances on the b and
b multipole components are evaluated
Multi-Bunch calculations in the CLIC Main LINAC
In the main linac of the compact linear collider (CLIC [1]) , wakefield induced multi-bunch effects are important. They have a strong impact on the choice of accelerating structure design. The paper presents the limit for the wakefield that one bunch exerts on the next. It also gives estimates for the allowed level of persistent wake fields and on the resistive wall wakefield
Beam-based alignment in the new CLIC Main LINAC
In the main linac of the compact linear collider (CLIC) the beam induced wakefield and dispersive effects will be strong. In the paper the reference beam-based alignment procedure for the new CLIC parameters is specified and the resulting tolerances for static imperfections are detailed
Beam Dynamics Studies for the CLIC Main Linac
The implications of long-range wakefields on the beam quality are
investigated through a detailed beam dynamics study. Injection offsets are
considered and the resulting emittance dilution recorded, including systematic
sources of error. These simulations have been conducted for damped and detuned
structures (DDS) and for waveguide damped structures-both for the CLIC
collider.Comment: 3 pages, 6 figures, IPAC1
Regular Incidence Complexes, Polytopes, and C-Groups
Regular incidence complexes are combinatorial incidence structures
generalizing regular convex polytopes, regular complex polytopes, various types
of incidence geometries, and many other highly symmetric objects. The special
case of abstract regular polytopes has been well-studied. The paper describes
the combinatorial structure of a regular incidence complex in terms of a system
of distinguished generating subgroups of its automorphism group or a
flag-transitive subgroup. Then the groups admitting a flag-transitive action on
an incidence complex are characterized as generalized string C-groups. Further,
extensions of regular incidence complexes are studied, and certain incidence
complexes particularly close to abstract polytopes, called abstract polytope
complexes, are investigated.Comment: 24 pages; to appear in "Discrete Geometry and Symmetry", M. Conder,
A. Deza, and A. Ivic Weiss (eds), Springe
Infrared spectroscopic study of phonons coupled to charge excitations in FeSi
From an investigation of the optical conductivity of FeSi single crystals
using FTIR spectroscopy in the frequency range from 30 to 20000 wavenumbers we
conclude that the transverse effective charge of the Fe and Si ions is
approximately 4e. Of the five optical phonons which are allowed by symmetry we
observe only four, three of which have a Fano line shape presumably resulting
from an interaction of these modes with the electronic continuum. We show that
the large oscillator strength of the phonons results from a relatively weak
coupling (lambda of the order of 0.1) of the lattice degrees of freedom to an
electronic resonance above the semiconductor gap, which is also responsible for
the large electronic polarizability of the medium.Comment: Revtex, 10 pages, 2 postscript pictures, to be published in Phys.
Rev. B Rapid Comm
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