Paper | Title | Page |
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TPPT005 | Dual Harmonic Operation with Broadband MA Cavities in J-PARC RCS | 931 |
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In the J-PARC RCS RF system, the fundamental rf acceleration voltage and the 2nd higher harmonic one are applied to each cavity. This is possible, because the magnetic alloy loaded cavities have a broadband characteristic and require no resonant frequency tuning. The tube amplifier provides both rf components. We calculate the operation of the tube under the condition of the dual harmonic, the non-pure resistive load and the class AB push-pull mode. | ||
WPAT007 | Control Loops for the J-PARC RCS Digital Low-Level RF Control | 1063 |
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The low-level radiofrequency control for the Rapic Cycling Syncrotron of J-PARC is based on digital signal processing. This system controls the acceleration voltages of 12 magnetic alloy loaded cavities. To achive a short overall delay, mandatory for stable loop operation, the data-processing is based on distributed arithmetics in FPGA. Due to the broadband characteristic of the acceleration cavities, no tuning loop is needed. To handle the large beam current, the RF system operates simultaneously with dual harmonics (h=2) and (h=4). The stability of the amplitude loops is limited by the delay of the FIR filters used after downconversion. The phase loop offers several operation modes to define the phase relation of (h=2) and (h=4) between the longitudinal beam signal and the vector-sum of the cavity voltages. Besides the FIR filters, we provide cascaded CIC filters with smoothly varying coefficients. Such a filter tracks the revolution frequency and has a substantially shorter delay, thereby increasing the stable operating region of the phase loops. The adaptive radial loop accumulates the orbit variation over several machine cycles to reduce the effects of measurement errors on the effective acceleration frequency program. | ||
WPAT064 | Low Level RF Control System of J-PARC Synchrotrons | 3624 |
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We present the concept and the design of the low level RF (LLRF) control system of the J-PARC synchrotrons. The J-PARC synchrotrons are the rapid cycling 3-GeV synchrotron (RCS) and the 50-GeV main ring (MR) which require very precise and stable LLRF control systems to accelerate the ultra-high proton beam current. The LLRF system of the synchrotron is a full-digital system based on the direct digital synthesis (DDS). The functions of the system are (1) the multi-harmonic RF generation for the acceleration and the longitudinal bunch shaping, (2) the feedbacks for stabilizing the beam, (3) the feedforward for compensating the heavy beam loading, and (4) other miscellaneous functions such as the synchronization and chopper timing. The LLRF system of the RCS is now under construction. We present the details of the system. Also, we show preliminary results of performance tests of the control modules. | ||
ROAC005 | Present Status of J-PARC Ring RF Systems | 475 |
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The accelerator of the J-PARC complex consists of the 400 MeV (initially 181 MeV) linac, the rapid cycling 3 GeV Synchrotron and the 50 GeV main Synchrotron. To accelerate an ultra-high intense proton beam, the synchrotrons require a high field gradient rf system (~25kV/m). Alleviating space charge effects is a key issue for minimizing beam losses during a cycle. Longitudinal bunch manipulation is also considered as well as acceleration. Magnetic alloy loaded cavities are the most practical choice for the J-PARC. Such system provides high field gradient, and broadband behavior. It is a stable passive system without tuning control. Multi-tone signals can be fed into the same cavity for acceleration and bunch manipulation. However, the harmonics of circulating beam current within the cavity bandwidth must be taken into account. A feed-forward scheme is used for compensating the beam induced voltages. The low level rf system is fully digital to provide precise control. The specification is based on high reliability and reproductivity. The design consideration of the whole rf system will be described and the current status presented. | ||
FPAE010 | Barrier RF System and Applications in Main Injector | 1189 |
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Funding: Work supported by the Universities Research Association, INC. under contract with the U.S. Department of Energy NO. DE-AC02-76CH03000 and by the US-Japan Collaboration in High Energy Physics. A wideband RF system (the barrier RF) has been built and installed in the Fermilab Main Injector. The cavities are made of low Q Finemet cores. The modulators use high voltage fast solid-state switches. It can generate ±7 kV single square voltage pulses. It is used to stack two proton batches to double the bunch intensity for pbar production. The stacked high intensity beams have been successfully accelerated to 120 GeV with small losses. A new test to continuously stack 12 batches for the NuMI experiment is under way. |
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FPAE026 | Development of FFAG Accelerator at KEK | 1943 |
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The 150MeV proton FFAG accelerator is constructed and a beam is extracted at the final energy. This is the prototype FFAG for various applications such as proton beam therapy. We are now in preparation for using an extracted beam in the practical applications. |