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Description
In the J-PARC LINAC, the beam monitor and LLRF systems utilize independent RF references. The LLRF system operates at 312-MHz and 960-MHz LO frequencies and includes active environmental compensation, whereas the monitor’s 324-MHz RF reference distribution system lacks this capability, leading to humidity-dependent phase drift at downstream stations. To reduce environmental dependency and enhance stability, a feedback-based compensation system based on μTCA.4 technology is implemented. The system performs IF phase correction by down-converting the 324-MHz monitor reference tapped from the SSA output to 12-MHz on μRTM, followed by fast feedback calculations in FPGA, enabling real-time compensation of phase drift. The resulting 324-MHz IQ-modulated output is sent via the μRTM to drive the SSA for distribution to monitor systems in klystron gallery. The developed system is designed to mitigate environmental phase fluctuations to enhance reference stability, improve beam monitoring reliability, and support future beam power upgrades at J-PARC. Moreover, the new system leverages the existing LLRF infrastructure, installed in μTCA.4 crate at MEBT1, allowing a fully synchronized, cost-effective, and compact system, contributing to more sustainable operation. This paper presents design methodology, long-term reference comparison and initial feedback implementation results.
| Abstract Category | Measurement and Control |
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