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Title |
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| THB006 |
New Automatic Bunch Current Sensitive Fast Attenuator for RF Front-end of Bunch-by-Bunch Feedback System at SPring-8
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659 |
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- K. Kobayashi, T. Nakamura
JASRI/SPring-8, Hyogo-ken
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We currently developing a new bunch current sensitive automatic attenuation system for the RF front-end of the bunch-by-bunch feedback system in the SPring-8 storage ring. It controls the attenuation of high current bunch signal to avoid the saturation of RF front-end and for equalization of the feedback gain for hybrid beam filling modes consist of few-mA singlet bunches and sub-mA bunch trains. We have already developed and installed a bunch current sensitive automatic attenuator with a simple mixer, a discriminator and FPGA based 1-turn delay with the attenuation level of 15 dB. However this attenuation level is not enough for hybrid filling modes with higher bunch current singlets and lower bunch current trains which are recently requested by users. To achieve more attenuation level and more flexible operation, we are now developing an attenuation system with a voltage variable attenuator controlled by a digital bunch current measurement device which is converted from a SPring-8 bunch-by-bunch feedback processor. This paper describes the new attenuation system and its test results.
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| THP072 |
Tune Tracking RFKO Bunch Purification with Bunch-by-bunch Feedback at SPring-8
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803 |
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- T. Nakamura, T. Aoki, K. Fukami, K. Kobayashi, M. Shoji, H. Yonehara
JASRI/SPring-8, Hyogo-ken
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The drift of a betatron tune from a RFKO driving tune reduces the betatron amplitude excited by RFKO. For the booster synchrotron in SPring-8, such tune drift occurs at on-demand operation for the top-up mode injection. To overcome this drift, we are developing a tune tracking RFKO system for bunch purification at the booster. In this system, The betatron motion of the main bunch was excited by positive feedback with which the excited amplitude is much less sensitive to the tune shift. The system is based on SPring-8 FPGA based bunch-by-bunch feedback processor and the kick signal produced by the feedback processor was send to the feedback kicker and the RFKO system for the purification. We describe the system and report some beam test result.
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