1

LCLSII 5keV FEL SASE simulations

Y. Ding(SLAC)

LCLSII physics meeting 11/6/2013

2

Ideal flat beam check

• 4 GeV, 1kA, 0.4µm emittance, 500keV energy spread;

• Undulator period 2.6cm, K = 0.585 (aw=0.414);• Each section 3.38m (N=130), break 1.17m (N=45). • Total undulator beamline including breaks and

U16( it is a drift in setup) is ~150m.• FEL 5keV (2.486 Angstrom)• Checked emittance, current and beta function

with Genesis simulations using a flat beam.

3

Ideal flat beam: gain curve vs emittance

Gain vs. emittance (beta function 15m, 1kA, 500keV energy spread).

Gain vs. current (beta function 15m, 0.3µm, 500keV energy spread).

1kA

800A0.4µm

0.35µm0.3µm

4

S2E beam from Paul4GeV, 100pC: ~1kA, 500keV energy spread, core slice emittance ~0.3µm.

0.3µm slice emittance

head

5

Match and center the core part

t-x t-xp

head

6

Match and center the Core part

Total pulse energy ~ 18µJ, ~ 35 fs (half of e-beam )

Average beta 20m

head

7

Summary: 5keV, SASE

• Resistive wall wake field from undulator chamber is checked, and negligible at this beam condition.

• With the present S2Ebeam, it barely works at 5keV and the core 0.3um emittance helps.

• CSR limits higher currents. This might be further optimized.

• LSC and mircobunching not included in this S2E beam.