Summary of 20 pC 13.6 GeV FEL experiments

LCLS 20 pC SASE FEL studies

Z. Huang et al.,

Feb. 25, 2011

HXRSS collaboration meeting1Gain length and FEL intensity at 20 pC (06/01/2009)

Well tuned beam, LTU emittance ~0.9/0.5 um FEL intensity ~140 mJ (linear taper) U28/U14 = 6 FEL intensity @ U15 = 23 uJ, well above 1 GW seed power requirementGain length =2.74 m140 mJ FEL energyFEL intensity after U14 ~ 20 uJ YAGXray gain length measurement2

Gain length and FEL intensity at 20 pC (02/24/2011) Not well tuned beam (limited time), LTU emittance ~1.1/0.9 um Poor FEL intensity ~ 60 mJ (> 5 m gain length!) U28/U14 = 130 FEL intensity @ U15 ~ 0.5 uJ, well below 1 GW seed power requirementGain length = 5.35 m60 mJ FEL energyFEL intensity after U14 ~ 0.5 uJ YAGXray gain length measurement3

Pulling out U15 Missing undulator (U15) affects the FEL intensity (25% drop) Tuning U14 and U16 K values has little effect Missing U15 between two data Power drops after U16 due to phase mismatch4FEL performance improved by machine tuning Running LEM and tweaking undulator matching improves FEL performance in 10 minute! U28/U14 = 50 FEL intensity @ U15 ~ 90 uJ, this ratio means U15 has 0.4 GW of seed power (assumes 5 fs FWHM pulse width)

Gain length = 4.29 mFEL intensity after U14 ~ 1.8 uJ

5

FEL divergence after U14 FEL divergence needs to be