Reliable bunch length measurement for electron beams is critical for the successful development of high-brightness beam injectors. Compared with commonly used schemes involving complicated techniques and dedicated devices, RF-phasing techniques have advantages in low-energy injectors owing to their convenience and low cost. Although previous direct calculation formulas originating from RF-phasing techniques are feasible and efficient in low-energy injectors, non-negligible errors are inevitable in practical operations, which limits application. By recalling the analytical derivation procedure and reconsidering the approximate conditions, compensation methods were explored through theoretical analysis and numerical simulations. Virtual measurements using beam dynamics calculations were used to evaluate reliability, and experimental validations were conducted at the HUST (Huazhong University of Science and Technology) injector to verify the compensation. Both of these efforts demonstrate that the improvements in the RF-phasing-based diagnostics for bunch length are feasible and reliable in typical low-energy injectors in common operating conditions. With compensation, these diagnostic methods are a promising alternative to conventional methods. For beam injectors, there may be a tradeoff among a compact layout, low cost, and complete characterization functions.

可靠的电子束束长测量对于成功开发高亮度电子束至关重要 注射器。与涉及复杂技术和专用设备的常用方案相比，RF 相位技术由于其方便和成本低，在低能量喷射器中具有优势。虽然之前源自射频定相技术的直接计算公式在低能量喷射器中是可行和有效的，但在实际操作中不可避免地存在不可忽略的误差，从而限制了应用。通过回顾分析推导程序并重新考虑近似条件，通过理论分析和数值模拟探索了补偿方法。使用光束动力学计算的虚拟测量用于评估可靠性，并在 HUST（华中科技大学）注入器进行实验验证以验证补偿。这两项努力都表明，在常见操作条件下的典型低能量喷射器中，基于射频相位的诊断改进对于束长度是可行且可靠的。通过补偿，这些诊断方法是传统方法的有前途的替代方案。对于射束注入器，可能需要在紧凑的布局、低成本和完整的表征功能之间进行权衡。