Abstracts Brochure - CERN

THPCH — Poster Session 29-Jun-06 16:00 - 18:00
(SSY* are considered which deal with the CSR via a one-dimensional approximation whereby the electron bunch is
modelled by a line density. Their one-dimensional approach is important because it is used in various CSR codes and
since it serves to some extent as a role model for higher-dimensional models. The present report deals with some
general aspects of the work of SSY. In particular, care is taken of the renormalization procedure and of the statistical
description in terms of the line density. SSY use a renormalized retarded field whereas the present work uses the
radiation field which is defined as half the difference of the retarded and advanced fields. The radiation field came
into prominence when Dirac** introduced the Lorentz-Dirac equation.
*E. L. Saldin, et al. Nucl. Instr. Meth. Phys. Res. A 398, 373 (1997) and 417, 158 (1998).**P.A.M. Dirac, Proc. Roy. Soc.
(London) A167, 148 (1938).
Suppression of Beam Transverse Microwave Instability by a Digital Damper
When a beam phase space density increases,
it makes its motion intrinsically unstable. To A.V. Burov, V.A. Lebedev (Fermilab)
suppress the instabilities, dampers are required.
With a progress of digital technology, digital dampers are getting to be more and more preferable, compared
with analog ones. Conversion of an analog signal into digital one is described by a linear operator with explicit time
dependence. Thus, the analog-digital converter (ADC) does not preserve a signal frequency. Instead, a monochromatic
input signal is transformed into a mixture of all possible frequencies, combining the input one with multiples
of the sampling frequency. Stability analysis has to include a cross-talk between all these combined frequencies.
In this paper, we are analyzing a problem of stability for beam transverse microwave oscillations in a presence of
digital damper; the impedance and the space charge are taken into account. The developed formalism is applied for
antiproton beam in the Recycler Ring at Fermilab.
Transient Beam Loading in the DIAMOND Storage Ring
Harmonic cavity systems have been installed
on several 3rd generation light sources to S. De Santis, J.M. Byrd (LBNL) R. Bartolini (Diamond)
lengthen the bunches and increase the Touschek
lifetime. Apart from this beneficial effect, harmonic cavities are known to increase the transient beam loading
in high-current machines, due to the presence of gaps in the fill pattern. The amplitude of this effect, which is
substantially larger than that caused by the main RF system, can in turn produce considerable variations in bunch
length and phase along the train, which result in a significant reduction of the lifetime increase. We have developed
a tracking simulation, which we have applied to the analysis of the beam loading transients in Diamond, for the case
of passive superconducting harmonic cavities. The influence of beam current, gap amplitude and harmonic cavity
tuning on the final lifetime have been studied, as well as the effects of higher-order modes.
Coherent Synchrotron Radiation Studies at the Advanced Test Facility
Coherent Synchrotron Radiation (CSR) has
been the object of recent experiments and is
a topic of great importance for several accelerator
currently in their design phase (LCLS,
S. De Santis, J.M. Byrd (LBNL) A. Aryshev, T. Naito (KEK) M.C.
Ross (SLAC)
ILC, CIRCE). We present the results of several experimental sessions performed at the Advanced Test Facility - KEK
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