Abstracts Brochure - CERN

THPCH — Poster Session 29-Jun-06 16:00 - 18:00
Wakefields Effects of New ILC Cavity Shapes
The operation of International Linear Collider
(ILC) requires high gradients and qual- I. Zagorodnov (DESY) N. Solyak (Fermilab)
ity factors in accelerating structure. One way
to reach it is to modify the cavity shape to reduce the ratio of peak surface magnetic to accelerating field. Two
candidate shapes are suggested recently: the Re-entrant shape and the Low-Loss shape. In this paper we estimate
numerically longitudinal and transverse short range wake functions for the new shapes. The obtained analytical
expressions are used in beam dynamic simulations for ILC lattice. We show that ILC will tolerate the cavities with
the new shape and the smaller iris diameter.
The PANDA Insertion Impedance in High Energy Storage Ring of FAIR
The PANDA insertion due to the special
shape of the vacuum pipe creates a discon- E. Senicheva, A. Lehrach, D. Prasuhn (FZJ)
tinuity. This was expected to be the main
contribution in the impedance of the vacuum chamber. In this paper we present the results of computations dealing
with this problem. From many published articles it is known that the reliability of the results depends on many
factors and some time they differ from each other significantly. Therefore we have investigated the impedance of the
PANDA insertion using different codes and methods, in particular, MAFIA, ABCI and the analytical estimation with
the formula Yakoya recognized as a most successful theoretical estimation of the tapers. Besides, PANDA has two
symmetrical T-shape insertions, which have been calculated by 3D MAFIA and compared with the results given by
the diffraction theory. We have analysed the longitudinal and the transverse impedance.
Beam Studies with Coherent Synchrotron Radiation from Short Bunches in the ANKA
Storage Ring
In the ANKA storage ring it is possible to
store bunches with RMS lengths of the order
of 1 ps using a dedicated optics with reduced
momentum compaction factor. For
A.-S. Müller, I. Birkel, S. Casalbuoni, B. Gasharova, E. Huttel, Y.-L.
Mathis, D.A. Moss, P. Wesolowski (FZK) C. J. Hirschmugl (UWM)
short bunch operation a beam energy of 1.3 GeV is chosen as a trade-off between low energy longitudinal instabilities
and the increase in natural bunch length with energy. At this medium energy (the energy range of the ANKA storage
ring is 0.5 to 2.5 GeV) steady state emission of coherent synchrotron radiation is observed by the ANKA-IR beamline
below the threshold current defined by the micro-bunching instability. At lower beam energies where the natural
bunch length is significantly shorter, bursts of coherent synchrotron radiation are detected in spite of the longitudinal
oscillation. The far infrared spectrum is sensitive to the dynamics of the charge distribution generating the radiation.
Measurements of the frequency spectrum of the infrared detector signal add information on bunch dynamics. This
paper gives an overview of the studies performed at the ANKA storage ring.
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