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High-power beyond extreme ultraviolet FEL radiation with flexible polarization at SHINE

Hanxiang Yang, Zhangfeng Gao, Bingyang Yan, Wencai Cheng, Nanshun Huang, Haixiao Deng

TL;DR

This work evaluates the feasibility of high-average-power beyond-EUV (BEUV) radiation at SHINE using a high-repetition-rate SRF linac. By combining undulator tapering with energy-chirp management and a flexible polarization scheme based on an elliptically polarized undulator (EPU) afterburner, the study demonstrates kilowatt-level BEUV output at MHz repetition rates and controllable polarization, including near-pure circular polarization. Baseline simulations show BEUV powers around 0.6–0.8 kW, with tapering raising power to ~1.3–1.6 kW depending on chirp; the BEUV beam also displays a nearly Gaussian transverse profile with good coherence. A polarization-control strategy leveraging reverse-taper planar undulators and the EPU afterburner yields nearly 100% circular polarization with high average power, highlighting SHINE as a realistic platform for next-generation BEUV lithography and science.

Abstract

Linac-based free-electron lasers (FELs) feature high brightness, narrow bandwidth, controllable polarization, and wide wavelength tunability. With the rapid development of superconducting radio-frequency technology, linacs can now operate at MHz-level repetition rates, enabling FELs with both high repetition rates and high average power. Beyond extreme ultraviolet (BEUV) radiation is of great interest for scientific research and industrial applications, especially for next-generation lithography. Owing to the main design parameters of SHINE, the generation of BEUV radiation is a natural capability of the facility. The BEUV characteristics at SHINE are investigated and its achievable performance as a high-average-power light source is evaluated. By applying undulator tapering to enhance the energy extraction efficiency, kilowatt-level BEUV radiation with controllable polarization is shown to be achievable. These results demonstrate that SHINE can provide a high-performance BEUV source, offering a realistic pathway toward a high-average-power light source for next-generation high-resolution lithography.

High-power beyond extreme ultraviolet FEL radiation with flexible polarization at SHINE

TL;DR

This work evaluates the feasibility of high-average-power beyond-EUV (BEUV) radiation at SHINE using a high-repetition-rate SRF linac. By combining undulator tapering with energy-chirp management and a flexible polarization scheme based on an elliptically polarized undulator (EPU) afterburner, the study demonstrates kilowatt-level BEUV output at MHz repetition rates and controllable polarization, including near-pure circular polarization. Baseline simulations show BEUV powers around 0.6–0.8 kW, with tapering raising power to ~1.3–1.6 kW depending on chirp; the BEUV beam also displays a nearly Gaussian transverse profile with good coherence. A polarization-control strategy leveraging reverse-taper planar undulators and the EPU afterburner yields nearly 100% circular polarization with high average power, highlighting SHINE as a realistic platform for next-generation BEUV lithography and science.

Abstract

Linac-based free-electron lasers (FELs) feature high brightness, narrow bandwidth, controllable polarization, and wide wavelength tunability. With the rapid development of superconducting radio-frequency technology, linacs can now operate at MHz-level repetition rates, enabling FELs with both high repetition rates and high average power. Beyond extreme ultraviolet (BEUV) radiation is of great interest for scientific research and industrial applications, especially for next-generation lithography. Owing to the main design parameters of SHINE, the generation of BEUV radiation is a natural capability of the facility. The BEUV characteristics at SHINE are investigated and its achievable performance as a high-average-power light source is evaluated. By applying undulator tapering to enhance the energy extraction efficiency, kilowatt-level BEUV radiation with controllable polarization is shown to be achievable. These results demonstrate that SHINE can provide a high-performance BEUV source, offering a realistic pathway toward a high-average-power light source for next-generation high-resolution lithography.
Paper Structure (9 sections, 3 equations, 8 figures, 1 table)

This paper contains 9 sections, 3 equations, 8 figures, 1 table.

Table of Contents

  1. Introduction
  2. BEUV setup at SHINE
  3. FEL simulation results
  4. Baseline BEUV performance
  5. Effects of energy chirp and undulator tapering
  6. Transverse profile
  7. Multi-shot stability analysis
  8. BEUV polarization control
  9. Conclusion

Figures (8)

  • Figure 1: Schematic layout of the BEUV setup at SHINE.
  • Figure 2: Longitudinal phase space of the electron beam at the undulator entrance (beam head to the right). The color map shows the normalized longitudinal phase-space density, and the white curve represents the current profile. (a) Electron beam with energy chirp. (b) Electron beam after dechirping.
  • Figure 3: Baseline BEUV performance for chirped (red) and unchirped (blue) electron beams. (a) Evolution of the BEUV power along the undulator. (b) Temporal power profiles at saturation. (c) Corresponding FEL spectra.
  • Figure 4: Output average power of the BEUV FEL as a function of the linear undulator taper strength $g$ for chirped and unchirped beams.
  • Figure 5: Transverse power density distribution of the BEUV radiation at saturation.
  • ...and 3 more figures