| 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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| 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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| 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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