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Accueil > EN > Research Areas > Complex Systems Dynamics > Optical Systems > Accelerator-based coherent sources

Spatio-temporal instabilities in relativistic electrons - novel THz Coherent Synchrotron Radiation sources

par Serge BIELAWSKI - publié le , mis à jour le

Clément Evain, Christophe Szwaj, Serge Bielawski
Marc Le Parquier (CERLA lab.)

Relativistic electron bunches circulating in accelerators can present spatial structures either :
- spontaneously, as the result of a spatio-temporal instability (the microbunching instability, due to the interaction of an electron bunch with its own emitted radiation)
- artificially, eg, by "shaping" the electron bunches using an external laser

Recently, it has been possible to "see", directly, spontaneously formed patterns inside electron bunches, using two different methods :
- In UVSOR (Japan), using ultrafast YBCO detectors developed by the IMS group at Karlsruhe
- In SOLEIL (France) using the so-called "photonic time-stretch" strategy
In both works, a main challenge was to acquire extremely fast signals (at picosecond scale) at high repetition rates.

Electron bunch structures typically lead to an intense coherent THz radiation (CSR). See, eg :
- Coherent synchrotron radiation for broadband terahertz_spectroscopy, Rev. Sci. Instrum. 84, 033102 (2013)
- Tunable narrowband terahertz emission from mastered laser–electron beam interaction, Nature Phys. 4, 390 (2008)
Current research :
  • Ultrahigh repetition rate single-shot acquisition systems (of THz pulses, bunch shapes, etc.)
  • Generation of tunable narrowband coherent radiation, in particular in the so-called "THz gap".
  • Modeling of the microbunching instability, development of parallel simulation codes.
  • "Seeding" of the microbunching instability with an external laser.

Publications :