Abstracts Brochure - CERN

THOAFI01
THOAFI02
THOAFI03
29-Jun-06 09:30 - 10:30 THOAFI — Beam Dynamics and Electromagnetic . . .
THOAFI — Beam Dynamics and Electromagnetic
Fields
The Development of Computational Tools for Halo Analysis and Study of Halo Growth in
the Spallation Neutron Source Linear Accelerator
D.A. Bartkoski, A.V. Aleksandrov, S.M. Cousineau, S. Henderson,
J.A. Holmes (ORNL)
Computational tools have been developed to
quantify the halo in a beam by analyzing
beam profiles and identifying the halo particles
using the Gaussian area ratio and kurto-
sis methods. Simulations of various injection quadrupole magnet configurations using three types of initial simulated
distributions, along with an analysis of their phase space and rms properties, provides insight into the development
of halo in the Spallation Neurton Source linear accelerator. Finally, comparisons with machine beam profile data,
taken at the same conditions as that of the simulated data, show how accurately the simulations model the beam and
its halo development and provide a better understanding of the best machine configuration with which to minimize
beam halo and losses.
Ion Instability Observed in PLS Revolver In-vacuum Undulator
Revolver In-Vacuum X-ray Undulator which
H.-S. Kang, J. Choi, M. Kim, T.-Y. Koo, T.-Y. Lee, P.C.D. Park (PAL) was designed and fabricated at Spring-8 is
under commissioning at PLS. This planar undulator
whose permanent magnet array structure is a revolving type with 90-degree step provides 4 different undulator
wavelengths of 10, 15, 20, and 24 mm. The minimum gap of the undulator is as small as 5 mm. It was observed that
the trailing part of a long bunch train was scraped due to ion instability when the undulator gap was closed below
6 mm. At that time the vacuum pressure in the undulator, which is estimated to be about one order of magnitude
lower than that of the undulator gap, increased from 1.4 x 10 -10 (gap 20 mm) to 7.9 x 10 -10 Torr (gap 6 mm) at the
stored beam current of 100 mA. This high vacuum pressure causes fast beam-ion instability: trailing part of a long
bunch train oscillates vertically. It was also confirmed that adjusting the orbit along the undulator has improved the
situation to some extent. The ion instability measured with a pico-second streak camera and a one-turn BPM as well
as the result of orbit adjustment and chromaticity control will be described in this paper.
Global and Local Coupling Compensation Experiments in RHIC using AC Dipoles
Compensation of transverse coupling during
R. Calaga (BNL) F. Franchi (GSI) R. Tomas (CERN)
the RHIC energy ramp has been proven to be
non-trivial and tedious. The lack of accurate
knowledge of the coupling sources has initiated several efforts to develop fast techique using turn-by-turn BPM data
to identify and compensate these sources. This paper aims to summarize the beam experiments performed to measure
the coupling matrix and resonance driving terms with the aid of RHIC ac dipoles.
382 Chair: T. Weiland (TEMF, Darmstadt)