Design and implementation of the CLAPA-II timing system

The laser proton accelerator achieves an exceptionally high gradient of TV/m, offering a novel approach for the development of compact proton irradiation devices. As the first laser-driven proton radiotherapy device worldwide, the Compact Laser Plasma Accelerator (CLAPA-II) at the Beijing Laser Acceleration Innovation Center faces significant challenges for its timing system. Beyond high-precision synchronization, the system must support complex radiotherapy logic, including multi-subsystem coordination, online operation mode switching, and strict safety interlocks. This paper presents the design and implementation of the CLAPA-II timing system, capable of generating hundreds of synchronized trigger pulses with sub-nanosecond precision and robust resistance to the transient EMP generated during laser-target interactions. Two schemes are introduced: a baseband distribution system based on the Stanford DG645, delivering an RMS jitter of 252.2 ps for early-stage experiments; and an event-driven timing system using the SINAP EVG-EVR architecture, achieving an RMS jitter of 29.6 ps and enabling flexible, event-code-based control of the entire proton therapy workflow. The event system natively synchronizes with the 80 MHz laser oscillator and supports millisecond-level switching between treatment modes, offering a robust and scalable solution for clinical applications. This study offers a comprehensive technical foundation for the integration of laser accelerators into proton therapy.