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Timing Controls Using Enhanced SASE Technique *)

Timing Controls Using Enhanced SASE Technique *). A. Zholents. or *) towards absolute synchronization between “visible” pump and x-ray probe pulses. SLAC XFEL short bunch measurement and timing workshop July 26 – 30, 2004. Pump-probe experiment concept. X-ray probe pulse.

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Timing Controls Using Enhanced SASE Technique *)

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  1. TimingControls UsingEnhanced SASE Technique*) A. Zholents or *) towards absolutesynchronization between “visible” pump and x-ray probe pulses SLAC XFEL short bunch measurement and timing workshop July 26 – 30, 2004

  2. Pump-probe experiment concept X-ray probe pulse Laser excitation pulse sample X-ray detector ∆t ion or e- detector • Requires control/measure of Dt with a resolution better than x-ray pulse duration (possibly as small as 100 attoseconds)

  3. Pump-probe experiment concept con’t Multicolor excitation Near IR sample X-ray probe pulse X-ray detector XUV ion or e- detector

  4. Pump-probe experiment concept con’t • One can hope to get a required synchronization if all sources are linked to a common origin controlled delay Master laser source Near IR XUV Courtesy H. Kapteyn X-ray probe pulse laser - e-beam manipulation and “seeding” • 90o Thomson scattering: Schoenlein, R.W., et al., Science, 274, (1996)236. • “Slicing”: Schoenlein, R.W., et al., Science,. 287, (2000 )2237. • Harmonic Cascade FEL: L.-H. Yu, et al., Science, 289, (2000)2237.

  5. Near IR pump Master source Enhanced Self Amplified Spontaneous Emission (ESASE) • Required: • Laser peak power ~ few GW • Wiggler with 10 – 20 periods Energy modulation in the wiggler at 2 - 4 GeV • Assumed: • Electron energy spread ~ 1.2 MeV Only one optical cycle is shown

  6. acceleration bunching Only one optical cycle is shown Acceleration to 14.35 GeV and bunching at the laser wavelength 50 fs laser pulse lL= 2 microns Peak current z /lL Energy spread Peak current Peak current and energy distribution within one micro-bunch

  7. SASE in the undulator producing x-rays synchronized to the modulating laser 70 as The output x-ray radiation from a single micro-bunch Power at saturation (estimate for bunching~0.5), P0~200 GW • Each spike is nearly temporary coherent and Fourier transform limited. • Carrier phase for an x-ray wave is random from spike to spike.

  8. Peak power z /lL The x-ray radiation output from the entire electron bunch Shaping of a temporal profile of the laser pulse is a tool for shaping of a temporal profile of the x-ray pulse.

  9. e-beam based timing reference Near IR pump Master source Near IR pump SH correlator one period wiggler isochronous bend wiggler radiation, ~0.5 GW ESASE x-rays

  10. Single shot measurement of a time jitter using Second Harmonic intensity correlation laser pulse, I1(t) F. Salin, et al., Applied Optics, 26, (1987)4528 filter wiggler pulse, I2(t) KDP detector I1(t) x w0 SH 2w0 2F S(x) = w0 KDP I2(t) ~0.3 mm

  11. Demonstration of the detector calibration by inserting 0.36 mm glass plate in either arm. (from C. Rempel and W. Rudolph, Experimentell Technik der Physic, 37, (1989)381.)

  12. Summary 1) Synchronization between pump and probe pulses is obtained by linking all pulses to the common origin. 2) ESASE provides a time mark for the x-ray pulse and allows absolute synchronization between laser pulse and x-ray pulse. 3) ESASE allows control over the duration of x-ray pulse and its temporal shape. X-ray pulses less than 100 attoseconds are feasible. 4) ESASE allows beam based monitoring for a time jitter with better than fs resolution.

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