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Leonid Sukhikh

Analytical calculation of the spectral-angular characteristics of coherent Smith-Purcell radiation generated by the short bunches with THz repetition rate. Leonid Sukhikh. Contents. Introduction Polarization radiation theory Super-radiant Smith-Purcell radiation model Calculation results

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Leonid Sukhikh

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  1. Analytical calculation of the spectral-angular characteristics of coherent Smith-Purcell radiation generated by the short bunches with THz repetition rate Leonid Sukhikh

  2. Contents • Introduction • Polarization radiation theory • Super-radiant Smith-Purcell radiation model • Calculation results • Conclusion

  3. Introduction

  4. Coherent Radiation from a single bunch • Coherent radiation from a single bunch: • Bunch form-factor:

  5. Gaussian form-factors

  6. Coherent Radiation from a train of bunches ~1ps ~0.2ps

  7. CR spectrum Radiation line width is proportional to Nb-1

  8. Gaussian form-factors for several bunches

  9. Frequency-locked CTR

  10. Smith-Purcell Radiation

  11. Frequency-locked CSPR

  12. Bunched CSPR power measurement

  13. Bunched CSPR power measurement Bunch charge 4.67 pC

  14. Smith-Purcell radiation models Includes It is a big challenge to compare all models with known experimental data and to find/create the best one

  15. Polarization radiation Theory

  16. Polarization radiation

  17. Theory 1 • Polarization radiation theory was developed by D. V. Karlovets and A.P. Potylitsyn: • D.V. Karlovets and A.P. Potylitsyn, JETP Lett. 2009, Volume 90, Number 5, Pages 326-331 • D. V. Karlovets, JETP, 2011, Volume 113, Number 1, Pages 27-45

  18. Theory 2 For non magnetic media a polarization current is a linear function of the full field where: Maxwell equations may be written as: Unwanted term

  19. Theory 3 For the simplest case of the flat vacuum-medium boundary: And where - Surface normal Due to boundary conditions: The unwanted term disappears.

  20. Theory 3 The exact solution of the Maxwell equations may be written as following: where This is exact field of polarization radiation inside the target with arbitrary permittivity. Additional manipulations are required to find the field outside the target. One should use the reciprocity theorem and Fresnel coefficients.

  21. Super-radiant smith-purcell radiation model

  22. Smith-Purcell radiation model In the case of ideal-conducting thin grating the radiation field in far field assumption may be written as:

  23. Smith-Purcell radiation spectrum Smith-Purcell radiation spectrum

  24. Smith-Purcell radiation gain due to several microbunches Smith-Purcell radiation spectrum

  25. Radiation gain strongly depends on bunching frequency… Smith-Purcell radiation spectrum

  26. Tilted grating • For the first time was calculated by P. Karataev et al. • The developed model allows calculation of spectral-angular parameters of super-radiant Smith-Purcell radiation generated by a tilted grating

  27. Line shift

  28. Conclusion

  29. Conclusion • Smith-Purcell radiation intensity significantly increases due to beam microbunching at the frequencies that correspond to the microbunching frequency. • Microbunching frequency control and diagnostics is really important. • One may try to use the grating tilt for such control.

  30. Thank you for your attention

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