GINGER Study: Results for New LCLS Undulator Configuration

1. GINGER Results for the NEW LCLS Undulator Configuration William M. Fawley Lawrence Berkeley National Laboratory Presented to LCLS Undulator Parameter Workshop24 October 2003

2. Outline of GINGER Study • First determine best K for peak gain for monochromatic cases at l=1.5, 0.15, and 0.1 nm • Examine taper performance for SASE runs at 0.15-nm, 11.47 GeV base case • SASE performance at 0.1 nm with E=14.04 GeV • Study of taper sensitivity for 1.5 nm case • No wake effects examined --- need ELEGANT time-dependent beam parameters • Some additional S2E SASE results for ICFA03 study –envelope reconstruction looks surprisingly good

3. Study Parameters/Bottom-Line Results SASE results; best taper for 0.15, 1.5 nm

4. Effects of Linear K Taper on LCLS SASE Output Power at =0.15nm • GINGER SASE runs • New drift space/undulator configuration • Quadrupole strengths & Twiss parameters from H.-D. Nuhn • Taper begins at z=75 m; simple linear decrease with z (including drift spaces) • Max power obtained around 0.3 to 0.4% taper; excessively large tapers appear to lead to rapid debunching with z and thus reduced gain

5. GINGER SASE runs for new LCLS drift space/undulator configuration Bunching and Inverse Bandwidth vs Z:0.15-nm LCLS

6. SASE Results at 0.1-nm Wavelength • No taper • “1st” saturation at ~110 m • Output power ~6 GW • No obvious anomalies ---but little margin for any beam degradation

7. 1.5-nm Taper Results • 1.5 nm option is a “cake-walk” for LCLS parameters • “1st” saturation at ~30 m; simple linear tapering begins at z=25 m • Tapering increases power over 6-fold to > 80 GW • 60 m of undulator gives most of output power • More “intelligent” tapers probably could increase power to >100 GW

8. New GINGER Results for ICFA03 “2nd-Order” Simulation Study • Extension of results for ICFA03-Zeuthen S2E study for LCLS • Full SASE simulation extended over full beam head region- results low-pass filtered in time (original res-olution = 12 attoseconds) • In regions where 5D distribution is “simple”, full SASE and envelope reconstruction agree surprisingly well • Similar runs underway for wake case (CSR but no wake fields) Output P for SASE; peak P(z) for no slippage cases

9. Where might we go from here? • Need ELEGANT runs with/without CSR effects to produce time-dependent 5D distributions at undulator entrance • Examine temporal sensitivity of P(z) to taper • Examine “ “ to wakes • One optimization criterion is maximizing product of power times the inverse bandwidth (at least for experiments in which monochromatization will be done) • See if results with taper are more sensitive to undulator errors, beam offset/pointing errors • Perhaps greater sensitivity to phase jitter but does deeper ponderomotive well help? • Develop taper algorithm for undulator with drift spaces & consider effects of “spiky” SASE P(t)