A. Zholents, July 28, 2004 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

A. Zholents, July 28, 2004 Pump-probe experiment concept ion or e - detector Laser excitation pulse X-ray probe pulse ∆t ∆t X-ray detector sample Requires control/measure of  t with a resolution better than x-ray pulse duration (possibly as small as 100 attoseconds)

A. Zholents, July 28, 2004 Pump-probe experiment conceptcon’t Near IR X-ray probe pulse ion or e - detector X-ray detector sample XUV Multicolor excitation

A. Zholents, July 28, 2004 One can hope to get a required synchronization if all sources are linked to a common origin Master laser source Pump-probe experiment conceptcon’t controlled delay Near IR XUV Courtesy H. Kapteyn laser - e-beam manipulation and “seeding” X-ray probe pulse 90 o 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.

A. Zholents, July 28, 2004 Energy modulation in the wiggler at GeV Enhanced Self Amplified Spontaneous Emission (ESASE) Only one optical cycle is shown Required: Laser peak power ~ few GW Wiggler with 10 – 20 periods Assumed: Electron energy spread ~ 1.2 MeV Master source Near IR pump

A. Zholents, July 28, 2004 Acceleration to GeV and bunching at the laser wavelength acceleration bunching Only one optical cycle is shown Peak current z / L Peak current Energy spread Peak current and energy distribution within one micro-bunch 50 fs laser pulse L = 2 microns

A. Zholents, July 28, 2004 SASE in the undulator producing x-rays synchronized to the modulating laser The output x-ray radiation from a single micro-bunch Power at saturation (estimate for bunching~0.5), P 0 ~200 GW 70 as Each spike is nearly temporary coherent and Fourier transform limited. Carrier phase for an x-ray wave is random from spike to spike.

A. Zholents, July 28, 2004 The x-ray radiation output from the entire electron bunch Peak power z / L Shaping of a temporal profile of the laser pulse is a tool for shaping of a temporal profile of the x-ray pulse.

A. Zholents, July 28, 2004 e-beam based timing reference Master source Near IR pump one period wiggler isochronous bend x-rays wiggler radiation, ~0.5 GW ESASE SH correlator Near IR pump

A. Zholents, July 28, 2004 KDP filter detector laser pulse, I 1 (t) wiggler pulse, I 2 (t) I 2 (t) I 1 (t) KDP x S(x) =  SH ~0.3 mm     Single shot measurement of a time jitter using Second Harmonic intensity correlation F. Salin, et al., Applied Optics, 26, (1987)4528

A. Zholents, July 28, 2004 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.)

A. Zholents, July 28, 2004 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.