Abstracts Brochure - CERN

THPCH100
THPCH101
THPCH102
29-Jun-06 16:00 - 18:00 THPCH — Poster Session
PC reads out the boards and transfers data to a fileserver. Matlab-based data analysis software allows to present the
raw data but also higher-level functions like spectra, modal analysis, spectrograms and other functions. The system
has been instrumental in diagnosing beam instabilities in PEP. This paper will describe the architecture of the system
and its applications.
New Fast Dither System for PEP-II
S.M. Gierman, S. Ecklund, R.C. Field, A.S. Fisher, K.E. Krauter,
E.S. Miller, M. Petree, K.G. Sonnad, N. Spencer, M.K. Sullivan, K.K.
Underwood, U. Wienands (SLAC)
416
The PEP-II B-Factory uses dithering techniques
to maximize the luminosity of its colliding
beams. The effect of small dither steps
applied to the High Energy Beam (HEB) at
the interaction point is monitored with a lu-
minosity detector, and the HEB trajectory is subsequently adjusted to maximize the luminosity signal. Dither steps
and corrections are performed serially in the x, y, and yprime directions. A new, faster system is now being implemented,
with the goal of speeding the tuning process and thereby increasing the integrated luminosity. Rather than
stepping serially the HEB in the three directions of interest, the new design calls for simultaneous, small amplitude
oscillations at frequencies distinct in each direction. Lock-in detection on the luminosity signal is then used to separate
the individual effects, and simultaneous corrections are applied at each cycle of the dither loop. This paper describes
the new dither system and its performance.
Modeling and Simulation of Longitudinal Dynamics for LER-HER PEP II Rings
C.H. Rivetta, J.D. Fox, T. Mastorides, D. Teytelman, D. Van Winkle
(SLAC)
A time domain dynamic model and simulation
tool for beam-cavity interactions in LER
and HER rings at PEP II is presented. The
motivation for this tool is to explore the sta-
bility margins and performance limits of PEP II LLRF systems at higher currents and upgraded RF configurations. It
also serves as test bed for new control algorithms and to define the ultimate limits of the architecture. The tool captures
the dynamical behavior of the beam-cavity interaction based on a reduced model. It includes nonlinear elements
in the klystron and signal processing. The beam current is represented by macro-bunches. Multiple RF stations in
the ring are represented via one or two single macro-cavities. Each macro-cavity captures the overall behavior of
all the 2 or 4 cavity RF stations. This allows modeling the longitudinal impedance control loops interacting with
the longitudinal beam model. Validation of simulation tool is in progress by comparing the measured growth rates
for both LER and HER rings with simulation results. The simulated behavior of both machines at high currents are
presented comparing different control strategies and the effect of non-linear klystrons and the linearizer.
Fast Global Orbit Feedback System in SPEAR3
New digital global orbit feedback system
A. Terebilo, T. Straumann (SLAC)
is under commissioning in SPEAR3 light
source. The system has 4kHz sampling rate
and 200Hz bandwidth. Correction algorithm is based on Singular Value Decomposition (SVD) of the orbit response
matrix. For performance tuning and additional flexibility when adding or removing correctors and BPMs, we implemented
an independent PID control loop for every orbit eigenvector used. This paper discusses performance of the