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Title |
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| MPPE044 |
Damping Wiggler Study at KEK-ATF
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2809 |
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- T. Naito, H. Hayano, Y. Honda, K. Kubo, M. Kuriki, S. Kuroda, T. Muto, N. Terunuma, J.U. Urakawa
KEK, Ibaraki
- M. Korostelev, F. Zimmermann
CERN, Geneva
- N. Nakamura, H. Sakai
ISSP/SRL, Chiba
- M.C. Ross
SLAC, Menlo Park, California
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The effects by damping wiggler magnets have been studied at KEK-ATF. The damping ring of the KEK-ATF is a 1.3 GeV storage ring capable of producing ultra-low emittance electron beams. It is significant issue to realize fast damping in the damping ring. The tuning method with 4 sets of wiggler was investigated for the ultra-low emittance beam. The performance on the beam quality, which is related to the transverse (x and y) and the longitudinal (z and dp/p), has been measured by the SR monitor, the laser wire, the streak camera and the energy spread monitor at the extraction line. We report on the operation condition and the measurement results.
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| TPPT049 |
Design and Cold Model Test of 500MHz Damped Cavity for ASP Storage Ring RF System
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3076 |
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- J. Watanabe, K. Nakayama, K. S. Sato, H. Suzuki
Toshiba, Yokohama
- M. Izawa
KEK, Ibaraki
- A. Jackson, G. LeBlanc, K. Zingre
ASP, Clayton, Victoria
- T. Koseki
RIKEN/RARF/CC, Saitama
- N. Nakamura, H. Sakai, H. Takaki
ISSP/SRL, Chiba
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TOSHIBA is constructing the storage ring RF system for the Australian Synchrotron Project(ASP). Two pairs of the 500MHz Higher Order Mode(HOM) damped cavities will be applied for this system. The cavities are modified KEK-PF type with silicon-carbide(SiC) microwave absorber and added three HOM anttenas for damping the longitudinal HOM impedance less than 20kOhm/GHz to meet requirement of ASP specification. The shunt impedance has been improved more than 5% in comparison with the original design by reducing the beam bore diameter without degrading HOM damping capability. The design of the cavity and the test results of an Al cold model are described.
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| RPAE040 |
COD Correction at the PF and PF-AR by New Orbit Feedback Scheme
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2613 |
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- K. Harada, T. Obina
KEK, Ibaraki
- N. Nakamura, H. Sakai, H. Takaki
ISSP/SRL, Chiba
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The eigen-vector method with a constraint condition is a new COD correction method that enables us to combine the local orbit correction at the insertion devices with the global COD correction by integrating the local one into the global one as the constraint condition using the Lagrange’s undetermined multiplier method. In order to achieve this method, we only use the new contrived response matrix for the global COD correction where the local correction is involved and done simultaneously. We have tested this correction scheme at the PF ring and the PF-AR. In the machine studies, the new orbit correction method is successfully demonstrated. The RMS COD of the constraint BPMs are sufficiently suppressed and, on the other hand, there is almost no large difference in the RMS COD of all the other BPMs between the new and ordinary methods.
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| TPPT006 |
Development of RF Input Coupler with a Coaxial Line TiN-Coated Against Multipactoring
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1006 |
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- T. Abe, T. Kageyama, H. Sakai, Y. Takeuchi
KEK, Ibaraki
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In one of the normal-conducting RF cavities used in the KEKB operation, we observed an unexpected rise of the vacuum pressure at certain input-power levels with and without a beam current. From the simulation study, we identify the pressure rises as an effect of the multipactoring discharge in the coaxial line of the input coupler. According to the simulation results, we have decided to make TiN coating on the inner surface of the outer conductor to suppress the multipactoring. In this paper, the status of the development of the TiN-coated input coupler is reported including the recent results of the high-power tests.
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| TPPT010 |
HOM Damping of ARES Cavity System for SuperKEKB
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1186 |
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- T. Kageyama, T. Abe, H. Sakai, Y. Takeuchi
KEK, Ibaraki
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The ARES cavity scheme is a decisive edge for KEKB to stably accelerate high-current electron and positron beams. The RF structure is a coupled-cavity system where a HOM-damped accelerating cavity is coupled with a large cylindrical energy storage cavity via a coupling cavity between. The HOM-damped structure is designed to be smoothly embedded into the whole coupled-cavity scheme without any structural or electromagnetic incompatibility. Currently, the total HOM power dissipated in the RF absorbers per cavity is about 5 kW according to calorimetric measurements in the KEKB LER with a beam current of 1.6 A. On the other hand, for SuperKEKB aiming at luminosity frontiers over 1035 cm-2 s-1, the total HOM power per cavity is estimated about 100 kW for the LER with the design beam current of 9.4 A. In this article, a new HOM-damped structure of the ARES cavity system designed for the SuperKEKB LER is reported together with the recent activities and future plans for upgrading the HOM absorbers.
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| TPPT012 |
High Power Testing of Input Couplers for SuperKEKB
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1294 |
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- H. Sakai, T. Abe, T. Kageyama, Y. Takeuchi
KEK, Ibaraki
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In KEKB, 32 ARES cavities have been successfully operated to stably accelerate high-current electron and positron beams. Currently, each ARES cavity is fed with RF power (frequency = 509 MHz) of about 300 kW through an input coupler, which has a ceramic disk window at the coaxial line section following the doorknob transformer section with a capacitive iris at the rectangular waveguide entrance. For SuperKEKB, which is a challenging project to boost the luminosity frontier beyond 1035 cm-2 s-1, the power capability of the input coupler needs to be upgraded to more than 900 kW, while the design power capability for KEKB is 400 kW. Recently, we have constructed a new test stand in order to simulate the actual operating condition for the input coupler to drive the ARES cavity with the maximum beam loading of 9.4 A expected for the SuperKEKB LER. In this article, the key features of the new test stand are described together with the recent results of high-power tests.
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| WPAT009 |
Status of the RF System for the 6.5 GeV Synchrotron Light Source PF-AR
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1168 |
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- S. Sakanaka, K. Ebihara, S. Isagawa, M. Izawa, T. Kageyama, T. Kasuga, H. Nakanishi, M. Ono, H. Sakai, T. Takahashi, K. Umemori, S.I. Yoshimoto
KEK, Ibaraki
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The Photon Factory Advanced Ring (PF-AR) is a 6.5-GeV synchrotron light source at KEK. An rf system comprises two 1.2-MW klystrons, six alternating-periodic-structure (APS) cavities, and other components. It supplies an rf voltage of about 15 MV with a beam current of 60 mA. The system has been working well, except for a trouble (frequent trips with beams) in one of the cavities. We found that the trips were triggered by an irradiation of synchrotron radiation to the cavity wall. In the summer of 2004, we reorganized the rf system, which allows us to install two insertion devices in a part of the rf sections. We replaced the troubled cavity at a time. We report both the operation status and the modification of the rf system.
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| WPAT010 |
RF Dielectric Properties of SiC Ceramics and their Application to Design of HOM Absorbers
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1195 |
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- Y. Takeuchi, T. Abe, T. Kageyama, H. Sakai
KEK, Ibaraki
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The KEKB ARES cavity is equipped with two types of HOM absorbers, which are made of different commercial products of the alpha-type SiC ceramics. Their dielectric responses to the RF frequency show the dielectric relaxation properties. Those properties can be clearly explained by the polycrystal structure model with electrically conductive grains and non-conductive grain boundaries. In this article, the RF dielectric properties of the SiC ceramics are discussed together with the application to HOM absorbers.
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| RPAE044 |
Operation and Recent Developments of the Photon Factory Advanced Ring
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2845 |
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- T. Miyajima, T. Abe, W.X. Cheng, K. Ebihara, K. Haga, K. Harada, Y. Hori, T. Ieiri, S. Isagawa, T. Kageyama, T. Kasuga, T. Katoh, H. Kawata, M. Kikuchi, Y. Kobayashi, K. Kudo, T. Mitsuhashi, S. Nagahashi, T.T. Nakamura, H. Nakanishi, T. Nogami, T. Obina, Y. Ohsawa, M. Ono, T. Ozaki, H. Sakai, Y. Sakamoto, S. Sakanaka, M. Sato, M. Satoh, T. Shioya, M. Suetake, R. Sugahara, M. Tadano, T. Takahashi, S. Takasaki, Y. Tanimoto, M. Tejima, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, N. Yamamoto, S. Yamamoto, S.I. Yoshimoto
KEK, Ibaraki
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The Photon Factory Advanced Ring (PF-AR) is a synchrotron light source dedicated to X-ray research. The PF-AR is usually operated at a beam energy of 6.5 GeV, but a 5.0 GeV mode is also available for medical application. In 6.5 GeV mode the typical lifetime of 15 hrs and the beam current of 60 mA with a single-bunch have been archived. Almost full-time single-bunch operation for pulse X-ray characterize the PF-AR. However, single-bunch high-current caused several problems to be solved, including the temperature rise of the some of the vacuum component, a pressure increase in the ring, and a sudden drop in lifetime. In order to avoid these issues the developments of new methods have been continued. In this paper, the status and the recent developments of the PF-AR will be presented. It concerns: the successful operation with two-bunch high-current in 5.0 GeV mode; varying the vertical beam size for the medical application; modulating the RF acceleration phase in order to elongate the length of bunch; stabilizing temperature in the ring tunnel; the study for medium emittance operation with 160 nmrad; moving the RF cavities in order to install a new insertion device; an innovative injection scheme using a pulsed quadrupole magnet.
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| RPPE040 |
Development of Copper Coated Chamber for Third Generation Light Sources
|
2633 |
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- H. Sakai, I. Ito, H. Kudo, N. Nakamura, S. Shibuya, K. Shinoe, H. Takaki
ISSP/SRL, Chiba
- K. Kobayashi
KEK, Ibaraki
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For the 3rd generation light sources, it is essential to reduce the beam instability in order to produce the highly bright synchrotron light much stably. Especially, to avoid the coupled bunch instability, the resistive wall impedance must be reduced. The copper-coating inner surface of the chamber(especially in insertion device section)is much effective method for the reduction of the resistive wall impedance, whose method was already proposed by our group (N.Nakamura et.al., EPAC 1998 p984). We have already produced the copper coated chamber. In this paper, we describe the measurement of the outgassing from the copper coated chamber to evaluate if this chamber is valid on the ultra-low high vacuum condition.
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