LINAC2026 - 33rd Linear Accelerator Conference

Single-Shot Extraction Efficiency Evaluation of an Infrared FEL Oscillator via simultaneous measurement of electron energy evolution with and without FEL lasing

Not scheduled

2h

Daejeon Convention Center

Poster Presentation MC2.A04: FELs Poster Session

Speaker

Zhuang Bi (Kyoto University)

Description

Extraction efficiency is a key parameter for oscillator FELs. To evaluate it in a single macro-pulse, both electron beam energy evolution with and without FEL lasing must be known. Previously, we developed a secondary electron emission monitor (SEEM) to measure the temporal energy evolution after the undulator with and without FEL lasing. Since SEEM requires separate measurements with and without FEL lasing, its accuracy is limited. To improve accuracy, we utilize a beam position monitor (BPM) in the dispersive section upstream of the undulator at KU-FEL*, where horizontal beam position strongly correlates with beam energy. Thus the BPM can provides the temporal energy evolution before (or without) FEL lasing. By simultaneously acquiring SEEM and BPM in the same macro-pulse, we can obtain both energy distributions with and without FEL lasing in a single shot. We will present the experimental setup including signal processing, calibration results, and single-shot extraction efficiency measurements. This approach enables high-precision single-shot extraction efficiency measurement and facilitates further optimization of FEL operation.

Funding Agency

JSPS KAKENHI Grant No. JP23K25125

Footnotes

• Z, Bi.; K, Tanaka.; H, Zen.; H, Ohgaki. Development of Array-Type Secondary Electron Emission Monitor Toward Single-Shot Measurement of Extraction Efficiency of FEL Oscillators. Particles 2025, 8, 81.
  ** H, Ohgaki.; H, Zen.; et al. Development of Beam Position Feedback Control System in KU-FEL. Proceedings of IPAC2013, pp. 2968-2970 (2013).