Option for Larger Bandwidth above 5 keV for crystallography: TN-15-13 LCLS2 Wednesday seminar J. Zemella / Z. Huang LCLS Menlo Park DESY Hamburg 05-27-2015
Outline • Parameters we are/I am aiming at • Corrugated structure at LCLS1 • Elegant simulations • Genesis simulations J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 2 / 12
Parameters ask for: rough priority order Post Workshop (3) LCLS-II Objective Parameters & Future Operating Modes report on progress to Larger BW ~2%-4% BW covering the parameters (above 5 keV) - crystallography copper linac is used to partiality BW & wavelength control 2.1-5 keV problem generate 5 keV photons (<400 meV BW, ~40 fs) crystallography Polarization HXU - vertical polarization (capacity, beam sharing) LCLS-II 2-pulse XPCS: Harmonics (HXU) • >1 m s ➜ 5 ns (RF buckets) performance & isolation from fundamental • nsec, psec ➜ 10 fs (delay line) Pulse pairs at variable spacing 1 m s t 1 t 2 t 3 t 4 t 5 t 6 (0-1 ns, 5 ns-msec) subject of ongoing discussions & iteration with LCLS-II project J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 3 / 12
wake fields for 1 m long corrugated structure amplitude (kV/nC/mm**2) amplitude (kV/nC/mm) 60 60 long. wake dipole wake Corrugated structure at LCLS1 50 40 quadrupole wake 40 20 30 two cases assumed: 0 20 10 -20 0 -40 1 base line corrugated structure 2x 2 m -10 single mode approx. -60 -20 2 base line corrugated structure; scaled -80 -30 0 1 2 3 4 5 0 1 2 3 4 5 wake fields by factor of 2 (2x 4 m) s (mm) s (mm) Parameter (unit) Value half gap a (mm) 0.5 (lower limit) periode p (mm) 0.5 depth h (mm) 0.5 opening g (mm) 0.25 width w (mm) 12 total length (m) 4 Z. Zhang et al., PRSTAB 18, 010702 (2015) J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 4 / 12
Results of Elegant calculation. initial upstream 4 m structure 8 m structure beam OTR2 ’full’ collimated ’full’ collimated ’full’ collimated beam energy (GeV) 0.135 11.86 11.87 11.86 11.87 11.86 11.87 charge (pC) 250 250 170 250 170 250 170 proj. emittance in x ( μ m) 0.68 1.27 0.97 1.28 0.95 1.62 0.95 proj. emittance in y ( μ m) 0.69 0.69 0.57 1.09 0.57 2.36 0.58 peak current (kA) 0.035 4.0 4.1 3.9 4.5 3.9 4.5 rms energy spread 0.077 0.24 0.16 0.40 0.27 0.56 0.38 rms bunch length (fs) 2310 41.6 15.8 41.6 15.7 41.6 15.7 J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 5 / 12
Some plots for electron bunch upstream of corrugated structure 250 pC charge 170 pC charge, collimated 0.5 0.3 relative energy deviation (%) relative energy deviation (%) a b a b 0.2 0.2 0.1 0.0 0.0 -0.1 -0.2 -0.2 -0.3 -0.5 horizontal norm. emittance horizontal norm. emittance 3.6 c d 1.2 4.2 c d 1.2 vertical norm. emittance vertical norm. emittance norm. emittance (micron) norm. emittance (micron) 3.0 1.0 3.5 1.0 current (kA) current (kA) 2.4 0.8 2.8 0.8 1.8 0.6 2.1 0.6 1.2 0.4 1.4 0.4 0.6 0.2 0.7 0.2 0.0 0.0 0.0 0.0 -100 -50 0 50 100 -100 -50 0 50 100 -45 -30 -15 0 15 30 45 -45 -30 -15 0 15 30 45 time (fs) time (fs) time (fs) time (fs) J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 6 / 12
Some plots for electron bunch downstream of 4 m long corrugated structure 250 pC charge 170 pC charge, collimated relative energy deviation (%) relative energy deviation (%) 0.4 a b a b 0.2 0.2 0.0 0.0 -0.2 -0.2 -0.4 -0.4 -0.6 -0.8 -0.6 -1.0 horizontal norm. emittance horizontal norm. emittance 3.6 c d 1.2 4.2 c d 1.2 vertical norm. emittance vertical norm. emittance norm. emittance (micron) norm. emittance (micron) 3.0 1.0 3.5 1.0 current (kA) current (kA) 2.4 0.8 2.8 0.8 1.8 0.6 2.1 0.6 1.2 0.4 1.4 0.4 0.6 0.2 0.7 0.2 0.0 0.0 0.0 0.0 -100 -50 0 50 100 -100 -50 0 50 100 -45 -30 -15 0 15 30 45 -45 -30 -15 0 15 30 45 time (fs) time (fs) time (fs) time (fs) J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 7 / 12
Some plots for electron bunch downstream of 8 m corrugated structure 250 pC charge 170 pC charge, collimated 0.5 relative energy deviation (%) relative energy deviation (%) a b a b 0.2 0.2 0.0 0.0 -0.2 -0.2 -0.5 -0.4 -0.8 -0.6 -1.0 -0.8 -1.2 -1.5 -1.0 horizontal norm. emittance horizontal norm. emittance 3.6 c d 1.2 4.2 c d 1.2 vertical norm. emittance vertical norm. emittance norm. emittance (micron) norm. emittance (micron) 3.0 1.0 3.5 1.0 current (kA) current (kA) 2.4 0.8 2.8 0.8 1.8 0.6 2.1 0.6 1.2 0.4 1.4 0.4 0.6 0.2 0.7 0.2 0.0 0.0 0.0 0.0 -100 -50 0 50 100 -100 -50 0 50 100 -45 -30 -15 0 15 30 45 -45 -30 -15 0 15 30 45 time (fs) time (fs) time (fs) time (fs) J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 8 / 12
Some plots of SASE FEL performance of a chirped bunch using 4 m corrugated structure SASE pulse at 6.2 keV at 132 m with 250 pC bunch 0.14 8 5 single shot single shot 7 0.12 mean over 10 shots mean over 10 shots 4 6 energy (mJ) 0.1 power (GW) power (a.u.) 1.71% 5 3 0.08 4 0.06 2 3 0.04 2 1 0.02 1 0 0 0 0 25 50 75 100 125 0 10 20 30 40 50 60 0.198 0.2 0.202 z (m) s (micron) wavelength (nm) SASE pulse at 6.2 keV at end of undulator with 170 pC collimated bunch 0.25 30 2 single shot single shot mean over 10 shots mean over 10 shots 25 0.2 1.5 energy (mJ) power (GW) power (a.u.) 20 1.25% 0.15 15 1 0.1 10 0.5 0.05 5 0 0 0 0 25 50 75 100 125 0 5 10 15 20 25 30 0.198 0.2 z (m) s (micron) wavelength (nm) J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 9 / 12
Some plots of SASE FEL performance of a chirped bunch using 8 m corrugated structure SASE pulse at 6.2 keV at 132 m with 250 pC bunch 0.07 8 2 single shot single shot 7 0.06 mean over 10 shots mean over 10 shots 6 1.5 energy (mJ) 0.05 power (GW) power (a.u.) 1.76% 5 0.04 4 1 0.03 3 0.02 2 0.5 0.01 1 0 0 0 0 25 50 75 100 125 0 10 20 30 40 50 60 0.198 0.2 0.202 z (m) s (micron) wavelength (nm) SASE pulse at 6.2 keV at end of undulator with 170 pC collimated bunch 0.25 35 2.5 single shot single shot 30 mean over 10 shots mean over 10 shots 0.2 2 energy (mJ) power (GW) power (a.u.) 25 0.15 1.5 20 1.76% 15 0.1 1 10 0.05 0.5 5 0 0 0 0 25 50 75 100 125 0 5 10 15 20 25 30 0.198 0.2 z (m) s (micron) wavelength (nm) J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 10 / 12
Some plots of SASE FEL performance of a chirped bunch with 0.5 % linear taper (75-132 m) SASE pulse at 6.2 keV at end of undulator with 250 pC bunch for 4 m long structure 1 120 2 single shot single shot 0.9 100 0.8 1.5 energy (mJ) power (GW) power (a.u.) 0.7 80 1.25% 0.6 0.5 60 1 0.4 40 0.3 0.5 0.2 20 0.1 0 0 0 0 25 50 75 100 125 0 5 10 15 20 25 30 35 40 45 50 55 60 0.197 0.198 0.199 0.2 0.201 z (m) s (micron) wavelength (nm) SASE pulse at 6.2 keV at end of undulator with 170 pC collimated bunch for 4 m long structure 1.4 180 2 single shot single shot 160 1.2 140 1.5 power (GW) energy (mJ) 1 power (a.u.) 120 1.3% 0.8 100 1 80 0.6 60 0.4 0.5 40 0.2 20 0 0 0 0 25 50 75 100 125 0 5 10 15 20 25 30 0.197 0.198 0.199 0.2 0.201 z (m) s (micron) wavelength (nm) SASE pulse at 6.2 keV at end of undulator with 170 pC collimated bunch for 8 m long structure 1.2 140 2 single shot single shot 120 1 1.5 energy (mJ) power (GW) power (a.u.) 100 0.8 1.25% 80 0.6 1 60 0.4 40 0.5 0.2 20 0 0 0 0 25 50 75 100 125 0 5 10 15 20 25 30 0.197 0.198 0.199 0.2 0.201 z (m) s (micron) wavelength (nm) J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 11 / 12
Summery/Conclusion • 4 m long corrugated structure is able to generate SASE pulse up to 1.7 % relative bandwidth. • 8 m long corrugated structure is able to generate SASE pulse up to 1.8 % relative bandwidth. � Increasing the length of structure does not improve bandwidth for uncollimated bunch (strong trans. wake fields). Increase of 0.5 % relative bandwidth for collimated case. • Increasing the SASE pulse energy using a undulator taper reduces the bandwidth to 1.3 % for both assumed lengths of corrugated structure. Inreasing length of corrugated structure does not improve bandwidth. � • Reverse taper of undulator increase bandwidth but also reduces SASE pulse energy. • Collimated bunches seem to be better. • Larger charge and collimation (350 pC → 250 pC) may increase the chirp of bunch and therefore bandwidth of SASE pulse. J. Zemella / Z. Huang (DESY) LCLS2 seminar . 05-27-2015 12 / 12
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