Harmonic lasing in the LCLSII SXR beamline G. Marcus, Y. Ding, Z. Huang 11/21/2013

2 Outline Motivation Beamline geometry Steady-state analysis 3 rd harmonic Time-dependent GENESIS 3 rd harmonic of E γ = 1.24 keV Various configurations (intra-undulator phase shifts)

3 Motivation Harmonic lasing can be a cheap and relatively efficient way to extend the photon energy range of a particular FEL beamline In comparison to nonlinear harmonics, can provide a beam that is more Intense Stable Narrow-band Suppression by Phase shifters Spectral filtering

4 Beamline geometry – nominal layout QuadPhase shifterUndulator Modeled in GENESIS using AD parameter in drift

5 Simulation parameters – ideal beam Insert Presentation Title in Slide Master e-beam E = 4 GeV I = 1.0 kA ε n ~ 0.45 μm σ E ~ 500 keV = 12 m Undulator λ u = 39 mm N per = 85 L = m L break = 1.17 m (30 per) -Simulated half for slippage K ~ 2.07 λ r = 1 nm

6 Time-dependent, nonlinear harmonics P sat ~ 2.8 GW FWHM ~ 0.68 eV

7 Time-dependent, nonlinear harmonics P sat ~ 39 MW FWHM ~ 1.76 eV Relative spectral bandwidth is roughly constant 5.4e -4 vs 4.7e -4

8 Harmonic lasing, phase shift of 2π/3 (λ/3), steady-state Phase shifters kill the fundamental

9 Harmonic lasing, time-dependent

10 Beamline geometry – 1 break

11 Beamline geometry – 2 breaks

12 Beamline geometry – 3 breaks

13 Harmonic lasing – 3 rd harmonic P ~ 342 MW FWHM ~ 0.99 eV

14 Spectral comparison at saturation points