Abstracts Brochure - CERN

TUPCH — Poster Session 27-Jun-06 16:00 - 18:00
Long-term high-power tests have been performed
for both J-PARC RCS and MR RF systems. Mechanism of local heating, new cutting scheme, and manufacturing
method are presented.
Conceptual Design of a 3rd Harmonic Cavity System for the LNLS Electron Storage Ring
The installation of a second RF cavity in the
UVX electron storage ring at the Brazilian
Synchrotron Light Laboratory (LNLS) at the
end of 2003 brought about longitudinal in-
N.P. Abreu, O.R. Bagnato, R.H.A. Farias, M.J. Ferreira, C. Pardine,
P.F. Tavares (LNLS)
stabilities driven by one of the HOMs of the new cavity. Even though the operational difficulties related to these
unstable modes were successfully overcome by means of a combination of cavity tuning (using temperature and
plunger adjustments) with phase modulation of the RF fields at the second harmonic of the synchrotron frequency,
a more appropriate technique to avoid those problems is the use of higher harmonic cavities, which have the important
advantage of providing damping of the longitudinal modes without increasing the energy spread, i.e., without
compromising the longitudinal emittance. In this work we present the design of a passive higher harmonic cavity
system optimized for operation at the LNLS storage ring. The parameters for a set of cavities as well as the analysis
of some of the effects that they may introduce in the beam dynamics are presented. An overview of the technical
aspects related to the project, construction and installation of the cavities in the storage ring is also presented.
Development of the Feed-forward System for Beam Loading Compensation in the J-PARC
RCS
In the J-PARC Rapid Cycling Synchrotron
(RCS), the heavy beam loading effects due to
the high intensity proton beam must be compensated
for stable acceleration. The beam
F. Tamura, M. Nomura, A. Schnase, M. Yamamoto (JAEA/J-PARC)
S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Yoshii (KEK)
feedforward technique is used to compensate the beam loading in the RCS. We present the development of the feedforward
system. We designed and built the full-digital system with modern FPGAs to realize high accuracy, stability
and predictability of the compensation. Because of the low Q value of each accelerating cavity, the wake voltage
consists of not only the accelerating harmonic component but also higher harmonics. Thus, the system is designed to
compensate the beam loading at several harmonics. The system has two parts. In the first part, vector components of
the selected harmonic are detected from the beam signal picked up by a wall current monitor. The compensation RF
signal is generated from the vector components with proper gain and phase in the latter part. The gain and phase are
set individually for each harmonic and each cavity of the twelve cavities. We also present the preliminary test results
of the newly developed modules.
High Power Test of MA Cavity for J-PARC RCS
We have been constructing the RF system for
the J-PARC RCS. Almost all of the power supplies
and the tube amplifiers have been constructed,
and the cavities are under construc-
M. Yamamoto, M. Nomura, A. Schnase, F. Tamura (JAEA/J-PARC)
S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Yoshii (KEK)
tion. All of them are tested at the experimental hall before installing into the J-PARC RCS building. We test the hybrid
cavity scheme to realize the optimum cavity Q-value. The results of the test are described.
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