| Paper |
Title |
Page |
| MOPC120 |
J-PARC RCS Non-linear Frequency Sweep Analysis
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346 |
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- A. Schnase, K. Haga, K. Hasegawa, M. Nomura, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
KEK, Ibaraki
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A standard method to measure the S21-transfer function of a system of amplifier and cavity involves a network analyzer and a linear or logarithmic frequency sweep. However, to characterize the transfer function of the broadband (Q=2) RCS RF system, we measure and analyze several harmonics at the same time under high power ramping conditions. A pattern driven DDS system generates frequency and amplitude as in accelerator operation. During the 20ms acceleration part of the cycle, a large memory oscilloscope captures the RF-signals. The data are analyzed off-line with a down-conversion process like in a multi-harmonic LLRF-system, resulting in multi-harmonic amplitude and phase information. Using this setup in the cavity test phase we were able to find and cure resonances before installation into the tunnel. We show examples. RCS is in the commissioning phase and has reached the milestone of acceleration to final energy and beam extraction. 10 RF systems are in operation, and the low-level RF system controls the fundamental h(2) and the second harmonic h(4). Using a multi-harmonic analysis during beam operation allows checking the RF system behavior with and without beam-loading.
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| MOPC126 |
Beam Acceleration with Full-digital LLRF Control System in the J-PARC RCS
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364 |
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- F. Tamura, K. Haga, K. Hasegawa, M. Nomura, A. Schnase, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
KEK, Ibaraki
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In the J-PARC RCS (Rapid Cycling Synchrotron) we employ a full-digital LLRF control system to accelerate an ultra-high intensity proton beam. The key feature is the multi-harmonic RF signal generation by using direct digital synthesis (DDS) technology. By employing a full-digital system, highly accurate, stable and reproductive RF voltages are generated in the wide-band RF cavities loaded by magnetic alloy (MA) cores. The beam commissioning of the J-PARC RCS has been started in October 2007. The accelerators, the linac and the RCS, show good stability. The beam orbit and the longitudinal beam shape and phase are reproductive from cycle to cycle especially thanks to the stability of the linac energy, the RCS bending field and the frequency and voltage of the RCS RF. This reproductivity makes the beam commissioning efficient. We present the examples of the orbit signals and the longitudinal current signals. Also, we discuss the longitudinal beam control performance and future plans.
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| MOPC132 |
Acceleration Voltage Pattern for J-PARC RCS
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379 |
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- M. Yamamoto, K. Hasegawa, M. Nomura, A. Schnase, F. Tamura
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
- S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda, M. Yoshii
KEK, Ibaraki
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The beam commissioning has been started at the J-PARC RCS. Some acceleration voltage patterns are tested to prevent the beam losses. The calculation code for the acceleration voltage pattern is usually based on the differential equation of the longitudinal synchrotron motion. We have developed the code based on the forward-difference equation which satisfies the synchronization with the bending magnetic field ramping accurately. This is very useful especially at the rapid cycling synchrotron where the ramping rate is high. The results of the test are described.
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| MOPC134 |
The Status of the J-PARC RF Systems
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385 |
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- M. Yoshii, S. Anami, E. Ezura, K. Hara, C. Ohmori, A. Takagi, M. Toda
KEK, Ibaraki
- K. Haga, K. Hasegawa, M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
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The first acceleration of a proton beam at the J-PARC Rapid Cycling Synchrotron started in October 2007. The R&D for magnetic alloy (MA) loaded rf-systems to realize a high field gradient accelerating system for a rapid cycling machine has been initiated in 1996 with the aim of surpassing standard ferrite loaded cavities. The RCS RF system is broad-band and designed to cover both the RCS accelerating frequency range and the second harmonic for bunch shape manipulation. The optimum Q value of the RCS cavities is approximately 2. This is realized by combining a high-Q parallel inductor with an un-cut core configuration. The beam commissioning of the 50GeV Main Ring synchrotron will start in May 2008. Acceleration and slow-beam extraction are planned for December 2008. In case of the MR RF system, the accelerating frequency swing is small. The Q-value in the order of 20 has been selected to reduce transient beam loading due to the multiple-batch injection scheme. The MR RF cavities realize the Q-value by a cut-core configuration. The details of the RF systems and the results of beam accelerations are summarized.
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| MOPP102 |
High Field Gradient RF System for a Spiral FFAG, RACCAM
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793 |
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- C. Ohmori
KEK, Ibaraki
- J. Fourrier, J. Pasternak
LPSC, Grenoble
- F. Meot
CEA, Gif-sur-Yvette
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A high field-gradient RF system for a spiral FFAG is described. It is wideband to cover the frequency of 3 to 7.5 MHz. The beam will be accelerated with a high repletion rate of 100 Hz to fit requirements for hadron therapy. The cavity has a wide aperture of 90 cm in horizontal direction to allow a large excursion for beam acceleration. It has less than 40 cm in length to fit a very short straight section.
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| MOPP103 |
High Field Gradient RF System for Bunch Rotation in PRISM-FFAG
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796 |
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- C. Ohmori
KEK, Ibaraki
- M. Aoki, Y. Arimoto, I. Itahashi, Y. Kuno, Y. Kuriyama, A. Sato, M. Y. Yoshida
Osaka University, Osaka
- Y. Iwashita
Kyoto ICR, Uji, Kyoto
- Y. Mori
KURRI, Osaka
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The PRISM project aims to supply a high quality muon beam using a wide aperture FFAG for mu-e conversion experiment. The low energy muon which has a large momentum spread will be manipulated in the FFAG using a bunch rotation technique with a low frequency RF around 3.5 MHz. Because of a short lifetime of muon, the rotation should be end in 5-6 turns in the FFAG and more than 2 MV is needed. The low frequency RF system using a magnetic alloy is designed to achieve a very high field gradient of more than 200 kV/m. The whole system is designed for a very low duty pulse operation to minimize the cost. The system has been modified to operate at 2 MHz for the beam test using alpha particle. A field gradient of more than 100 kV/m has been obtained by the preliminary test.
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| MOPP104 |
Possible Upgrade Scenario for J-PARC Ring RF
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799 |
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- C. Ohmori, K. Hara, A. Takagi, M. Toda, M. Yoshii
KEK, Ibaraki
- K. Hasegawa, M. Nomura, A. Schnase, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
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The whole J-PARC RCS RF system is operational and during beam commissioning in 2007 the beam in RCS was successfully accelerated to final energy and then extracted. The Main Ring RF system has been installed in the tunnel. Both Ring RF systems are based on the new technology using magnetic alloy loaded cavities and have achieved higher field gradient than existing ferrite base RF systems in this frequency region. For the future upgrade of the J-PARC Main Ring, a short accelerating cycle is required to increase the average beam current. In this paper, a possible upgrade scenario for RF cavities based on improvements of the magnetic alloy ring cores will be described.
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| THPP007 |
Six-sector FFAG Ring to Demonstrate Bunch Rotation for PRISM
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3389 |
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- A. Sato, M. Aoki, S. Araki, Y. Arimoto, Y. Eguchi, K. Hirota, I. Itahashi, Y. Kuno, Y. Kuriyama, Y. Nakanishi, M. Y. Yoshida
Osaka University, Osaka
- Y. Iwashita
Kyoto ICR, Uji, Kyoto
- A. Kurup
Imperial College of Science and Technology, Department of Physics, London
- Y. Mori
KURRI, Osaka
- C. Ohmori
KEK, Ibaraki
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A monochromatic muon beam is one of the most important requirements to improve a sensitivity of mu-e conversion experiments. In the PRISM project, which searches for mu-e conversion at a sensitivity of BR~10-18, makes such muon beams by using a bunch rotation technique in an FFAG ring. To demonstrate the bunch rotation, a FFAG ring has been constructed in RCNP, Osaka. The ring has six FFAG magnets and one RF cavity. Alpha particles from a radioactive isotope 241Am will circulate in the ring for the demonstration of bunch rotation.
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| THPP071 |
Construction of Six-sector FFAG Ring for Muon Phase Rotation
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3524 |
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- Y. Arimoto, M. Aoki, S. Araki, Y. Eguchi, K. Hirota, I. Hossain, I. Itahashi, Y. Kuno, Y. Kuriyama, Y. Nakanishi, A. Sato, M. Y. Yoshida
Osaka University, Osaka
- Y. Iwashita
Kyoto ICR, Uji, Kyoto
- A. Kurup
Imperial College of Science and Technology, Department of Physics, London
- Y. Mori
KURRI, Osaka
- C. Ohmori
KEK, Ibaraki
- T. Oki
Tsukuba University, Ibaraki
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PRISM is a next-generation of muon source which provides high purity, high intense and high brightness beam. In PRISM, a PRISM-FFAG is one of key section which make a muon beam narrow energy width by using phase rotation technique. To demonstrate the phase rotation, a six-cell FFAG ring has been constructed; the ring consists of full size of scaling-FFAG magnets and a high gradient rf cavity. The experiment is achieved by injecting alpha particles from a radioisotope source as a beam. Construction of the ring has been started from September, 2007; beam duct has been designed and installed, the six FFAG magnets has been aligned, etc. In this paper, we will present the design of the ring and the construction (alignment, etc) from engineering point of view.
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