【摘要】 针对合肥红外自由电子激光（Infrared Free-Electron Laser,IR-FEL）装置因宏脉冲串内束团参数无法独立测量而导致的辐射性能优化瓶颈问题，开展了新型束流诊断方法研究。本研究旨在建立60 MeV直线加速器上宏脉冲逐束团三维位置及电荷量同步测量系统。基于系统响应函数重建与波形互相关的方法，获得不同测量点处数据。通过多测量点数据的关联分析，构建束团串核心参数表征模型。束流实验结果表明：宏脉冲内逐束团横向位置分辨率好于30μm，纵向位置分辨率好于1 ps，满足装置调束优化需求。首次明确界定了对FEL辐射具有主要贡献的束团串核心区域（横向边界<200μm），该区域束团占比达到宏脉冲总束团数的66%。基于逐束团参数测量结果对加速器运行参数进行优化后，束团串内能量不一致性得到明显改善，束团串核心区域的中心能量偏差峰峰值从1.1%降低至0.3%,FEL辐射光谱的相对半高宽从2%提高到1%。该方法为合肥IR-FEL装置性能提升及后续升级改造提供了关键诊断技术支撑。更多还原

【Abstract】 [Background] The Hefei Infrared Free-Electron Laser(IR-FEL) facility faces optimization bottlenecks due to the inability to independently measure individual bunch parameters within macropulse trains, which limits radiation performance improvement. [Purpose] This study aims to establish a synchronous measurement system for 3D position and charge of individual bunches within macropulse trains on the 60 MeV linear accelerator. [Methods] Firstly, multi-measurement point data were acquired using button electrode beam position monitors(BPMs) coupled with high-speed oscilloscopes operating at 16 GHz sampling rate. Then, system response functions were reconstructed using equivalent sampling principles adapted for linear accelerator bunch trains, where the macropulse containing N bunches with repetition frequency f was treated equivalently to a single bunch circulating N turns in a storage ring with revolution frequency f. Finally, bunch-by-bunch 3D position and charge parameters were extracted through correlation analysis between measured waveforms and reconstructed response functions, enabling characterization of bunch train core parameters through multi-measurement point data correlation analysis. [Results] The beam experiment results show that the measurement system achieves transverse position resolution better than 30 μm and longitudinal position resolution better than 1 ps for individual bunches within macropulse trains. The bunch train core region contributing mainly to FEL radiation is clearly defined with transverse boundaries less than 200 μm, accounting for 66% of the total bunches in the macropulse train. After optimizing accelerator operation parameters based on bunch-by-bunch measurement results, energy inconsistency within the bunch train is significantly improved, with the peak-to-peak central energy deviation in the core region reduced from 1.1% to 0.3%, and the relative full width at half maximum(FWHM) of FEL radiation spectrum improved from 2% to 1%. [Conclusions] This method proposed in this study provides crucial diagnostic technology support for performance improvement and subsequent upgrades of the Hefei IR-FEL facility. The technique enables quantitative optimization of accelerator parameters and significantly enhances FEL radiation quality through precise bunch-by-bunch parameter control, demonstrating its potential for widespread application in similar linear accelerator facilities.更多还原