Longitudinal bunch profile diagnostics with coherent radiation at FLASH

Eugen Hass; Christopher Gerth; Bernhard Schmidt; Stephan Wesch; Minjie Yan

doi:10.1117/12.2021531

3 May 2013 Longitudinal bunch profile diagnostics with coherent radiation at FLASH

Eugen Hass, Christopher Gerth, Bernhard Schmidt, Stephan Wesch, Minjie Yan

Proceedings Volume 8778, Advances in X-ray Free-Electron Lasers II: Instrumentation; 87780M (2013) https://doi.org/10.1117/12.2021531
Event: SPIE Optics + Optoelectronics, 2013, Prague, Czech Republic

Abstract

The required high peak current in free-electron lasers (FELs) is realized by longitudinal compression of the electron bunches to sub-picosecond length. A novel in-vacuum polychromator (CRISP4) has been developed for measuring coherent radiation in the THz and infrared range. The polychromator is equipped with five consecutive dispersion gratings and 120 parallel readout channels. It can be operated either in short (5-44 μm) or in long wavelength mode (45-430 μm). Fast parallel readout permits the monitoring of coherent radiation from single electron bunches. Due to the large wavelength range covered and the absolute calibration of the device, Kramers-Kronig based phase retrieval allows to online reconstruct a longitudinal bunch profile from the measured coherent radiation spectrum. The device is used as a bunch length monitoring and tuning tool during routine operation at the Free-electron Laser in Hamburg (FLASH). Comparative measurements with the transverse deflecting structure show excellent agreement of both methods.

Citation Download Citation

Eugen Hass, Christopher Gerth, Bernhard Schmidt, Stephan Wesch, and Minjie Yan "Longitudinal bunch profile diagnostics with coherent radiation at FLASH", Proc. SPIE 8778, Advances in X-ray Free-Electron Lasers II: Instrumentation, 87780M (3 May 2013); https://doi.org/10.1117/12.2021531

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