ASTRA Injector Setup 2012

1. ASTRA Injector Setup 2012 Julian McKenzie 17/02/2012

2. Baseline: Simulations using ASTRA (07/04/2008 win32) No intrinsic emittance – could expect up to 1.2 mm mrad from photocathode

3. 7 ps Gaussian vs28 ps flat-top

4. Buncher power scans Red = 7 ps Gaussian Blue = 28 ps flat-top • Bunch length required at entrance to linac to achieve energy spread for FEL ~7ps • We still don’t understand booster to linac longitudinal dynamics... Buncher power [W] Yuri reckons 1.6 mm FWHM

5. BC1 scans For 7 ps Gaussian laser pulse Red = 1 kW buncher power Green = 1.6 kW buncher power

6. For 1kW buncher power, choose +15 BC1 phase • Set SOL-02 to minimise transverse beam size • Set BC2 phase to minimise chirp (-13)

7. But phase space isn’t good: Is RMS bunch length even a good quantity to optimise on?Need to look at phase space plots

8. Phase space plots (longitudinal) Using “nominal” setup detailed on slide 1 Red = 7 ps Gaussian Blue = 28 ps flat-top -10/+10(as per original model) -20/+30 Looks similar to Bruno’s: Lots of charge at the “crossover point” NB// head to the right. z [m] vspz (eV/c)

9. BC1 phase for minimum curvature: For 7 ps Gaussian laser pulse BC1 = 0 BC1 = -6 Buncher = 1 kW Buncher = 1.6 kW

10. Sol2 scans For 7 ps Gaussian laser pulse Red = 1 kW buncher power Green = 1.6 kW buncher power

11. BC2 phase? For 7 ps Gaussian laser pulse Red = 1 kW buncher power Green = 1.6 kW buncher power BC1 at -6 SOL-02 at 220G

12. To do list: • Emittance vs SOL-02 for 7/28ps with identical bunch length from buncher • At minimum emittance from above, BC2 phase scan to look at minimum energy spread • Investigate lowering energy gain from BC1 • Anything else?