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Beam dynamics in the high gain ring FEL based on ERL

Beam dynamics in the high gain ring FEL based on ERL N. A. Vinokurov, O. A. Shevchenko , A. N. Matveenko Budker Institute of Nuclear Physics. Basic principal of the FEL operation. synchronisme condition which is necessary for the energy transfer. noise. The scheme of the FEL oscillator.

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Beam dynamics in the high gain ring FEL based on ERL

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  1. Beam dynamics in the high gain ring FEL based on ERL N. A. Vinokurov, O. A. Shevchenko, A. N. Matveenko Budker Institute of Nuclear Physics

  2. Basic principal of the FEL operation synchronisme condition which is necessary for the energy transfer

  3. noise The scheme of the FEL oscillator Equivalent scheme of FEL oscillator Narrow bandwidth amplifier with feedback

  4. The scheme of the single-pass FEL amplifier

  5. General scheme and principles of operation of ring FEL The beam microbunching is partly conserved in the isochronous bend

  6. Signal from the old bunch to the fresh one is transferred by radiation

  7. The bunching degree vs. time. Deep drops correspond to the moments of the fresh beam injection. The bunching degree vs. longitudinal coordinate over the ring FEL.

  8. Circuit representation and linewidth of ring FEL

  9. High gain ring FEL Master oscillator for x-ray generation High power radiation source Problems of contemporary FELs, which may be solved by high gain ring FELs Poor quality of SASE FEL radiation Power limitation due to mirror heating in FEL-oscillators

  10. Ring FEL requires ERL as a source of electron beams, as the average beam power can be very high.

  11. Specific problems of ring FEL 1. Isochronous bends are required to conserve microbunching Typical lattice of short isochronous bend bending magnets sextupoles quadrupoles Second order aberrations are compensated by sextupoles

  12. Second order aberrations Energy spread and emittance can cause debunching These terms are negligible compared to the others Twiss parameters Choosing the proper values of sextupoles one can adjust (x|x02) to make T511 zero

  13. Experimental observation of the coherency ofradiation from two undulators A schematic view of the achromatic bend: M – bending magnets, L -lens R5,1 and R5,2 = 0 The scheme to observe radiation coherency at the achromatic bend of electrons in the magnetic system of the optical klystron on VEPP-3: M1-M5 –horizontal bending correctors; L – quadrupole lens focusing in horizontal direction; U1 and U2 undulators; TL and ML – optical telescope lens and imaging lens respectively; RS – registering screen Interference pictures observed at a conventional (nonachromatic) bend (a), at an achromatic bend without the delay compensation (b) and with the delay compensation (c)

  14. 2. Influence of coherent synchrotron radiation and quantum fluctuations in the bend can not be compensated (pointed out by Vladimir Litvinenko) Quantum fluctuations inside the bend create local energy spread which lead to debunching si and wiare random

  15. The probability of the photon emission may be expressed through the spectral power density of synchrotron radiation. If this probability is small it possible to fined explicit expression for the spread of longitudinal coordinates where r0 is the classical electron radius,  = 1/137 is the fine-structure constant, is the relativistic factor. For the simple three-bend isochronous achromat with bending angle 0<<1 This value should be compared with (λ/2π)2 which gives an estimation of the maximum permissible bending angle * * It is assumed that

  16. Simulation scheme of the ring FEL operation GENESIS simulation with zero initial radiation field and particle distribution imported from previous run Nonlinear phase space mapping by external code. CSR wake and quantum fluctuations are applied here. GENESIS simulation with fresh particle distribution and initial radiation field imported from previous run

  17. Soft X-ray ring FEL

  18. Linear lattice functions βx, βy, and Dx of the isochronous bend of the soft x-ray (500 Å) ring FEL. Debunching induced by second-order aberrations is acceptable

  19. Longitudinal dispersion calculated from the coordinate s to the exit of the bend Beam debunching induced by quantum fluctuations Debunching induced by quantum fluctuations is small

  20. Energy average transversal angle variation along the beam induced by CSR in the bend The wake field induced by coherent synchrotron radiation is too large. Further optimization is required.

  21. Simulation results for the soft X-ray FEL (CSR effects are not included) Dependence of average radiation power on turn number of the beam in the ring FEL

  22. Soft X-ray FEL, steady-state regime Beam current profile and beam bunching at the exit of the last undulator (dashed line corresponds to the equivalent SASE FEL)

  23. Soft X-ray FEL, steady-state regime Radiation peak power and spectrum at the exit of the last undulator (dashed line corresponds to the equivalent SASE FEL)

  24. Cost of soft x-ray ring FEL (M$)

  25. Compact infrared ring FEL

  26. Possible layout of the infrared FEL magnetic system

  27. Linear lattice functions βx, βy, and Dx of the isochronous bend of the infrared (6 microns) ring FEL. Debunching induced by second-order aberrations is small

  28. Simulation results for the infrared FEL (all negative effects are included) Dependence of average radiation power on turn number of the beam in the ring FEL

  29. Infrared FEL, steady-state regime Beam current profile and beam bunching at the exit of the last undulator

  30. Infrared FEL, steady-state regime Radiation peak power and spectrum at the exit of the last undulator

  31. Infrared FEL, steady-state regime Dependence of the beam bunching and peak radiation power on longitudinal coordinate in the last undulator

  32. Cost of soft infrared ring FEL (M$)

  33. Conclusion 1.The feasibility of the soft X-ray and infrared ring FEL is shown. 2. Second order aberrations in the lattice, quantum fluctuations of synchrotron radiation and CSR wakes are considered. 3. Further optimization of CSR wake effects in the soft X-ray ring FEL is required.

  34. References 1. N. A. Vinokurov, Nucl. Instr. and Meth. A 375 (1996), p. 264. 2. N. A. Vinokurov and O. A. Shevchenko, Nucl. Instr. and Meth. A 528 (2004), p. 491. 3. A.N. Matveenko, O.A. Shevchenko, N.A. Vinokurov, Proc. Of the 2004 FEL Conference, p. 629 4. N.G.Gavrilov, G.N.Kulipanov, V.N.Litvinenko, I.V.Pinayev, V.M.Popik, I.G.Silvestrov, A.S.Sokolov, P.D.Vobly, and N.A. Vinokurov, IEEE J. Quantum Electron., v.27 (1991), p.2569. 5. S. Reiche, Nucl. Instrum. Methods Phys. Res. A 429, 243 (1999). 6. K.G.Steffen, High Energy Beam Optics, Interscience publishers, New York – London – Sydney, 1965. 7. K.L.Brown, R.V.Servranckx, “First- and second-order charged particle optics”, SLAC-PUB-3381

  35. Thank you for your attention

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