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ABSTRACT: Over the past several years, we have been conducting a design work for a synchrotron light facility with low emittance storage ring in the intermediate energy range at NSRRC. A number of design options with different lattice structure types, circumferences, etc., are explored. We present two design cases, i.e., a 24-cell DBA and a 12-cell QBA structures with 486 m circumference. The associated accelerator physics issues are discussed.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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Y.C. Liu,
H.P. Chang,
J. Chen, P.J. Chou,
K.T. Hsu,
K.H. Hu,
Changhor Kuo,
C.C. Kuo,
K.K. Lin,
M.H. Wang,
G.H. Luo
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ABSTRACT: The Taiwan light source began top-up operation in October 2005 with an initial beam current of 200 mA. This was subsequently raised to 300 mA. In the early phase of top-up operation, the injection efficiency varied markably under different machine operating conditions. A procedure to optimize and maintain the injection efficiency is presented. Future improvements and the prospects for a 400 mA top-up operation are discussed.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: The demanding design features of Taiwan Photon Source (TPS), low emittance and small gap undulator vacuum vessels, cause Touschek scattering and gas scattering to play a major limitation role for beam lifetime. We calculate the Touschek lifetime based on the tracking procedure determining energy acceptance. The nonlinear synchrotron oscillation due to large second- order momentum compaction factor is included in the energy acceptance calculations. Small vertical ID gaps are imposed in the tracking procedure. Besides, the gas scattering lifetime is estimated with varying gas pressure. The possible improvement solutions for lifetime will be addressed.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: The storage ring of Taiwan Light Source (TLS) started to operate fully in top-up mode since October 2005. The beam current has been gradually increased to 300 mA in routine user operation. Phenomena of collective effects were observed at 300 mA in top-up operation mode. Active feedback systems were implemented to stabilize the beam in top-up mode. Results of beam observation and analysis will be presented.
Particle Accelerator Conference, 2007. PAC. IEEE; 07/2007
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ABSTRACT: A quadruple-bend achromatic (QBA) cell, defined as a supercell made of two double-bend cells with different outer and inner dipole bend angles, is found to provide a factor of 2 in lowering the beam emittance relative to the more conventional double-bend achromat. The ratio of bending angles of the inner dipoles to that of the outer dipoles is numerically found to be about 1.5-1.6 for an optimal low beam emittance in the isomagnetic condition. The QBA lattice provides an advantage over the double-bend achromat or the double-bend nonachromat in performance by providing a small natural beam emittance and some zero-dispersion straight sections. A lattice with 12 QBA cells and a preliminary dynamic aperture study serves as an example.
Review of Scientific Instruments 06/2007; 78(5):055109. · 1.37 Impact Factor
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ABSTRACT: An intermediate energy synchrotron light source has been proposed. The goal is to construct a high performance light source in complementary to the existing 1.5 GeV synchrotron ring in Taiwan to boost the research capabilities. A 3 GeV machine with 518.4 m and 24‐cell DBA lattice structure is considered and other options are also investigated. We report the 24‐cell design considerations and its performances. © 2007 American Institute of Physics
AIP Conference Proceedings. 01/2007; 879(1):50-53.
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K. H. Hu,
C. H. Kuo,
W. K. Lau,
M. S. Yeh,
S. Y. Hsu, P. J. Chou,
M. H. Wang,
Demi Lee,
Jenny Chen,
C. J. Wang,
K. T. Hsu,
K. Kobayashi,
T. Nakamura,
M. Dehler
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ABSTRACT: Multi‐bunch instabilities deteriorate beam quality, increasing beam emittance, or even causing beam loss in the synchrotron light source. The feedback system is essential to suppress multi‐bunch instabilities caused by the impedances of beam ducts, and trapped ions. A new FPGA based transverse and longitudinal bunch‐by‐bunch feedback system have been commissioned at the Taiwan Light Source recently, A single feedback loop is used to simultaneously suppress the horizontal and the vertical multi‐bunch instabilities. Longitudinal instabilities caused by cavity‐like structures are suppressed by the longitudinal feedback loop. The same FPGA processor is employed in the transverse feedback and the longitudinal feedback system respectively. Diagnostic memory is included in the system to capture the bunch oscillation signal, which supports various studies. © 2006 American Institute of Physics
AIP Conference Proceedings. 11/2006; 868(1):179-186.
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ABSTRACT: A new longitudinal kicker will be installed into the Taiwan Light Source (TLS) storage ring in the near future. This kicker is part of the new bunch-by-bunch longitudinal feedback system for stabilization of beam dipole-mode longitudinal coupled-bunch instability in the ring. It will serve to provide fast switching kick voltage to each bunch at 500 MHz bunch crossing frequency. This new kicker employed the Swiss Light Source design with modifications on beam pipe geometry. It has been fabricated, baked out and vacuum tested by FMB-Berlin recently. The kicker has been delivered to NSRRC in November 2004. Longitudinal coupling impedance has been measured in house by coaxial wire method with resistive matching networks at input and output ports. The measured peak coupling impedance of the accelerating mode is 684 Ω with FWHM bandwidth at 280 MHz. It corresponds to a shunt impedance of 1368 Ω at centre frequency. These results agree very well with those calculated by GdfidL.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: A superconducting (SC) rf cavity designed by Cornell University [1] was installed in the storage ring at Taiwan Light Source (TLS) in December of 2004. The purpose of rf system upgrade is to increase the stored beam current without collective instabilities caused by higher-order-modes (HOM) of rf cavity. Beam measurements related to collective effects are performed. Results are compared with those measured prior to the rf system upgrade. Theoretical studies on collective effects after the rf upgrade are also presented.
Particle Accelerator Conference, 2005. PAC 2005. Proceedings of the; 06/2005
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ABSTRACT: An operation version of longitudinal feedback baseband processing electronics was implemented. The system consists of a bunch phase detector, a 500‐MS/s analog‐to‐digital converter and demultiplexer module (ADC/DEMUX), DSP modules, a digital‐to‐analog converter and multiplexer module (DAC/MUX), and an RF modulator. The ADC/DEMUX unit has a fast ADC that digitizes the bunch phase signal. The down‐sampled phase error data of each bunch are then distributed to the DSP boards to perform filtering and applied control rule. In the DAC/MUX, bunch kick signals are converted into analog signals for bunch phase feedback. Design and implementation of the system will be summarized in this report. © 2004 American Institute of Physics
AIP Conference Proceedings. 11/2004; 732(1):302-309.
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P.J. Chou
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ABSTRACT: The beam current in the storage ring at Taiwan Light Source (TLS) is limited by the longitudinal coupled-bunch instabilities and the available rf power. Two Doris cavities are currently used for particle acceleration in the storage ring at TLS. The higher-order modes (HOMs) from Doris cavities are the major source of longitudinal impedance in the storage ring at TLS. In order to increase the electron beam current in the storage ring, a superconducting (SC) rf cavity developed by Cornell University will be installed to replace those two Doris cavities. The property of HOMs of SC rf cavity is obtained from numerical simulations by using a three-dimensional parallel code GdfidL. The preliminary results show that the storage ring at TLS will not suffer from the longitudinal coupled-bunch instabilities for a beam current not exceeding 450 mA.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: The correlation between the horizontal beam size vs. the cavity temperature, observed at the Taiwan Light Source (TLS), is explained by the combined effects of (1) cavity resonance frequency shift resulting from temperature change, (2) cavity voltage and synchronous phase angle change resulting from uncompensated beam loading in the low-level rf-feedback system, and (3) rf cavity voltage modulation for alleviating the coupled bunch instability. This experimental method can be used to evaluate the intrinsic resolution of the low-level rf-feedback system
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: The storage ring at Taiwan Light Source has experienced a strong
collective instability since 1994. Various cures have been attempted to
suppress this instability, including the use of damping antenna, tunable
rf plungers, different filling patterns, and rf gap voltage modulation.
So far these cures have improved the beam intensity, but the operation
remains to be limited by the instability. The dominant phenomenon is the
longitudinal coupled bunch instability. The major source of longitudinal
impedance is from rf cavities of Doris type. The high-order modes of the
cavity were numerically analyzed using a 3-D code GdfidL. The
correlation of the observed phenomenon in user operation with high-order
modes of rf cavities will be presented. Results of various attempts to
suppress beam instabilities will be summarized. Proposed cures for beam
instabilities will be discussed.
NASA STI/Recon Technical Report N. 07/2002; 2:92424.
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[show abstract]
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ABSTRACT: The storage ring at Taiwan Light Source has experienced a strong
collective instability since 1994. Various cures have been attempted to
suppress this instability, including the use of damping antenna, tunable
RF plungers, different filling patterns, and RF gap voltage modulation.
So far these cures have improved the beam intensity, but the operation
remains to be limited by the instability. The dominant phenomenon is the
longitudinal coupled bunch instability. The major source of longitudinal
impedance is from RF cavities of Doris type. The high-order modes of the
cavity were numerically analyzed using a 3-D code GdfidL. The
correlation of the observed phenomenon in user operation with high-order
modes of RF cavities will be presented. Results of various attempts to
suppress beam instabilities will be summarized. Proposed cures for beam
instabilities will be discussed
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: The performance of the 1.5-GeV storage ring light source TLS in
SRRC has been limited by a longitudinal coupled-bunch beam instability.
To improve the performance of the TLS, the beam instability has to be
suppressed. One possible way considered for the TLS to suppress its
coupled-bunch instability uses uneven filling patterns according to the
theory of Prabhakar (2000). By knowing the harmful high-order-modes
(HOMs), a special filling pattern can be designed to utilize either mode
coupling or Landau damping to cure the beam instability. In TLS the HOMs
are contributed from the Doris RF cavity installed in the storage ring.
The HOMs of a 3-D Doris cavity was numerically analyzed. The filling
patterns with equal bunch current according to theory had been
calculated to cure the most harmful HOM. A longitudinal particle
tracking program was used to simulate the coupled-bunch beam instability
with both the uniform filling and the specially designed filling. A
filling pattern with unequal bunch current was also studied. The results
of the simulation were discussed and compared to the theory
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: A coupled-field analysis process for a RF cavity structure has
been established. The commercial code ANSYS is used as the solver which
successfully links analyses of different fields, including
electromagnetics, heat transfer, and structure mechanics. The
computation efficiency is thus dramatically improved. The calculated RF
characteristics of a pill-box cavity match the theoretical predictions
pretty well. The following thermal and structural computation based on
the surface power loss are also performed. This coupled-field analysis
process has been applied to a cavity in design. The computed results
associated with RF are compared to the ones calculated by other codes
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: The Taiwan Light Source (TLS) is a third-generation synchrotron
light source located at the Synchrotron Radiation Research Center (SRRC)
in Taiwan. The TLS is now operating routinely for user experiments, and
the highest priorities are increasing user beam time, increasing machine
reliability, and improving the stability of the stored electron beam.
Many current machine upgrades are intended to improve beam stability:
the longitudinal feedback system, orbit feedback systems,
radiofrequency-system improvements (better higher-order-mode
performance), and utilities upgrades. In addition, a major improvement
program to increase the stored beam current is being planned
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
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ABSTRACT: The effects of amplitude modulation of RF cavity voltage on the
longitudinal beam dynamics were studied experimentally at SRRC by using
a streak camera system. The characteristics of parametric resonance in
single bunch beam was investigated both by simulation and measurement.
The formation of beamlets in the bunch helps to damp the coherent bunch
oscillation. This property is employed to provide stable beam in the
user's shift at SRRC
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
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ABSTRACT: A digital feedback control system against longitudinal
coupled-bunch instability is being developed for the Taiwan Light Source
(TLS). This system is designed to stabilize bunch-phase oscillation of
each of the 200 electron bunches in the TLS storage ring, and it
operates at a bunch crossing frequency of 500 MHz. Two innovative
aspects of this system are: (1) the special design of the digital signal
processing (DSP) electronics, which run at a peak data rate of 500
Mbytes per second, and (2) the compact broadband longitudinal kicker for
bunch-phase correction. Recent progress of this work and preliminary
results of associated observations of beam longitudinal-dynamics will
also be reported
Particle Accelerator Conference, 1999. Proceedings of the 1999; 02/1999
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ABSTRACT: The design of Taiwan Photon Source (TPS) has a natural emittance less than 2 nm-rad and low emittance coupling. The nominal rms bunch length is less than 3 mm. Several small-gap undulators are planned to provide x-ray photon beam with extremely high brightness. The vertical gap of these undulators are in the range of 5-7 mm. The TPS ring will be operated at top-up mode with high beam current. Various collective effects due to high beam current are investigated. Impacts of small-gap undulators to the beam lifetime are carefully studied. The results of theoretical analysis are presented. Proposals to overcome deleterious effects due to high beam current and small-gap undulators are also discussed.
