1,029 research outputs found
Impedance Analysis of Bunch Length Measurements at the ATF Damping Ring
We present energy spread and bunch length measurements at the Accelerator
Test Facility (ATF) at KEK, as functions of current, for different ring rf
voltages, and with the beam both on and off the coupling resonance. We fit the
on-coupling bunch shapes to those of an impedance model consisting of a
resistor and an inductor connected in series. We find that the fits are
reasonably good, but that the resulting impedance is unexpectedly large.Comment: 9 pages, 5 figures, presented at 10th International Symposium on
Applied Electromagnetics and Mechanics (ISEM2001
Intrabeam Scattering Analysis of ATF Beam Measurements
At the Accelerator Test Facility (ATF) at KEK intrabeam scattering (IBS) is a
strong effect for an electron machine. It is an effect that couples all
dimensions of the beam, and in April 2000, over a short period of time, all
dimensions were measured as functions of current. In this report we derive a
simple relation for the growth rates of emittances due to IBS. We apply the
theories of Bjorken-Mtingwa, Piwinski, and a formula due to Raubenheimer to the
ATF parameters, and find that the results all agree (if in Piwinski's formalism
we replace the dispersion squared over beta by the dispersion invariant).
Finally, we compare theory, including the effect of potential well bunch
lengthening, with the April 2000 measurements, and find reasonably good
agreement in the energy spread and horizontal emittance dependence on current.
The vertical emittance measurement, however, implies that either: there is
error in the measurement (equivalent to an introduction of 0.6% x-y coupling
error), or the effect of intrabeam scattering is stronger than predicted (35%
stronger in growth rates).Comment: 4 pages, 3 figures, Presented at IEEE Particle Accelerator Conferenc
Yang-Mills fields on CR manifolds
We study pseudo Yang-Mills fields on a compact strictly pseudoconvex CR
manifold.Comment: 52 page
Harmonic G-structures
For closed and connected subgroups G of SO(n), we study the energy functional
on the space of G-structures of a (compact) Riemannian manifold M, where
G-structures are considered as sections of the quotient bundle O(M)/G. Then, we
deduce the corresponding first and second variation formulae and the
characterising conditions for critical points by means of tools closely related
with the study of G-structures. In this direction, we show the role in the
energy functional played by the intrinsic torsion of the G-structure. Moreover,
we analyse the particular case G=U(n) for even-dimensional manifolds. This
leads to the study of harmonic almost Hermitian manifolds and harmonic maps
from M into O(M)/U(n).Comment: 27 pages, minor correction
- âŠ