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| TUP90 | Improvements of RF Characteristics in the SDTL of the J-PARC Proton LINAC | simulation, linac, proton, focusing | 489 | ||
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A separated drift tube linac (SDTL)* was selected as an accelerator structure of Japan Proton Accelerator Complex (J-PARC), which follows DTL. The SDTL of J-PARC consists of 32 short tanks, ranging from 1.5 to 2.5 m in length. A design of frequency tuners of the SDTL was performed by taking account of 3-D field distribution calculated with MAFIA. The effects of stems on the resonant frequency and field distribution were also analyzed. An easy and effective compensation method for perturbation by stems of both end cells was proposed and applied to the SDTL tanks.
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* T. Kato. Proposal of a Separated-type Proton Drift Tube Linac for a Medium-Energy Structure. KEK Report 92-10, (1992) |
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| THP41 | Development of High RF Power Delivery System for 1300 MHz Superconducting Cavities of Cornell ERL Injector | coupling, alignment, superconductivity, linac | 694 | ||
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Development of a 150 kW CW RF power delivery system for 1300 MHz superconducting cavities is under way at Cornell University in collaboration with MEPhI. The system is based on a twin-coupler consisting of two identical coaxial antenna-type couplers derived from the TTF-3 input coupler design. Because the average power is much higher than in the TTF-3 coupler, the required coupling is stronger and we wanted to avoid multipacting phenomena, major changes were made to the prototype design. Presented coupler has completely redesigned cold part and significantly improved cooling of warm bellows. The results of thermal and mechanical stress calculations are reported. The magnitudes and phases of RF fields applied to each side of the twin-coupler must be very close to each other. This imposes very strict requirements upon a power dividing system. These requirements and proposed layout of a system satisfying them are discussed.
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| THP64 | Waveguide Stub Tuner Analysis for CEBAF Application | klystron, coupling, simulation, resonance | 757 | ||
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Three-stub WR650 waveguide tuners have been used on the CEBAF superconducting cavities for two changes on the external Qs: increasing the Q from 6·106 to 8·106 on 5-cell cavities to reduce the klystron power at operation gradients and decreasing the Q from 2·107 to 8·106 on 7-cell cavities to ease the control system handling the Lorenz Force detuning. To understand the reactive tuning effects in the machine operations with beam current and mechanical tuning, a network analysis model was developed. The S parameters of the stub tuner were simulated by MAFIA and measured on the bench. We used this stub tuner model to study tuning range, sensitivity, frequency pulling as well as cold waveguide and window heating problems. Detailed experimental results will be compared against this model. Pros and cons of this stub tuner application will be summarized.
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| THP69 | The Tuning Study of the Coupled Cavities for the RF Chopper System of J-PARC | simulation, coupling, linac, proton | 770 | ||
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A 3 MeV medium-energy beam transport line (MEBT) is located between RFQ and DTL in the linac of the Japan Proton Accelerator Research Complex (J-PARC). MEBT accomplishes beam matching and chopping. An rf deflector (RFD), which is a heavily loaded cavity, was adopted as a chopper in J-PARC linac for chopping 500 μs long macropulses from the ion source into sub-pulses for injecting into the following 3 GeV rapid-cycling ring. A coupled RFD system was proposed in the design of chopper system for saving the cost of rf power source. The tuning of the coupled RFD system was successfully performed. The longer rise time of the second RFD and the delay of the second RFD excitation were found during the tuning of the coupled RFD system, and these phenomena were further analyzed and investigated. Both in the high power and beam tests, the chopper worked well without any discharge under 36 kW peak driving power.
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| THP89 | Measured RF Properties of the DTL for the J-PARC | linac, target, synchrotron, quadrupole | 809 | ||
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RF properties of the second DTL tank for J-PARC have been measured in KEK. The required flatness and stability of the accelerating field of the tank have been achieved by the tunung of the post-couplers, whose shape were modified to adjust the resonant frequency ?324 MHz). Because the third DTL tank has assembled, the rf measurement and the post-coupler tuning will be started soon. Thus the measured results for both tanks will be described in the paper.
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