x,y = 0.4 m (slice) I pk = 3.0 kA E /E = 0.01% (slice) (25 of 33 undulators installed) L G = 3.3 m IT WORKS!
C. Pellegrini, “A 4 to 0.1 nm FEL based on the SLAC linac”, in Workshop on 4th Generation Light Sources, M. Cornacchia and H. Winick, (Eds), pp. 364-375, 1992. SSRL-Report-92/02. “…one is forced to have high gain, i.e. to use electron beams with large peak current, and at the same time small emittance and energy spread. The road to an X-ray FEL requires the development of electron beams with unprecedented characteristics.” Will show only one simple equation… ?
UCLA 16- m FEL M. Hogan et al., Phys. Rev. Lett., 80, 289–292 (1998). 16 m 16 March 2001 A. Tremaine et al., PRL. 88, 204801 (2002) 840 nm saturationstarts VISA at BNL (LEUTL at ANL Saturates in Sep. 2000) March 2001 BNL-LLNL-SLAC-UCLA VISA LANL/UCLA AFEL M. Hogan et al., PRL, 81, 4867–4870 (1998). 12 m >10 5 gain
H. Winick First Design Study (1992 – 1995) Report describes final LCLS quite accurately M. Cornacchia Design Study Report (1996 – 1999) First funding and collaborations established SLAC-R-521, Dec. 1998 Journal of Electron Spectroscopy and Related Phenomena, Vol. 75 (1995), pp. 1-8. J. Galayda Construction Phase (2001 – present) Scope expands to user facility, construction, commissioning, + user op’s. First light: April 9, 2009
1 - 0.1 nC C. Pellegrini, X. Ding, J. Rosenzweig, “ Output Power Control in an X-Ray FEL”, PAC-99, New York, NY, March 1999. 1 - 0.1 nC 0.1 nC P. Emma, “ LCLS Accelerator Parameters and Tolerances for Low Charge Operations”, SLAC-TN-05-042, May, 1999. 0.1 nC 0.2 nC (resistive wakes under control) P. Emma et al., “ An Optimized Low-charge Configuration of the Linac Coherent Light Source”, PAC-05, Knoxville, TN, May 2005. 0.2 nC (resistive wakes under control) 0.001 nC J. Rosenzweig, …, C. Pellegrini, … et al., “ Generation of ultra-short, high brightness electron beams for single-spike SASE FEL operation ”, Nucl. Instrum. Methods Phys. Res., Sect. A 593, 39 (2008). 0.001 nC 0.02 nC Y. Ding et al., “ Measurements and simulations of ultralow emittance and ultrashort electron beams in the linac coherent light source”, Phys. Rev. Lett. 102, 254801 (2009). 0.02 nC LCLS runs mostly at 0.25 nC, much due to Claudio’s 1999 suggestion We had never even considered <1 nC before this (PE).
Y. Ding 15 Å, z = 25 m, 2.4 10 11 ph’s, I pk = 2.6 kA, 0.4 µm 15 Å, z = 25 m, 2.4 10 11 ph’s, I pk = 2.6 kA, 0.4 µm 1.2 fs 0.14 µm Sliced OTR screen with transverse deflector ON 20 pC, 135 MeV, 0.6-mm spot diameter, 400 µm rms bunch length (5 A) z = 25 m Idea to run with 20 pC was first suggested by Joe Frisch, but it was hastened by discussions with Claudio at SLAC in 2008.
Max and Claudio form a “brain-storming” series of meetings in 2002 with a goal of <10 fs… Transverse RF cavities in the undulator More electron compression Chirped FEL + X-ray compression 1 Chirped FEL + monochromator 2 Slotted foil… Many ideas emerge – some fall by the wayside, and 1-2 look good 1.C. Pellegrini, “High Power Femtosecond Pulses from an X-ray SASE-FEL”, NIM A 445 (2000), 124-127. 2.C. B. Schroeder, C. Pellegrini, et al., “Chirped-beam Two-stage Sase-FEL For High Power Femtosecond X- ray Pulse Generation”, PAC-01, Chicago, IL, 2001.
X-Ray Pulse Energy vs. Pulse Length (2.5 – 3.8 mJ) Peak FEL Power vs. Pulse Length (5-40 GW) e bunch length is quickly adjustable (<1 min) from 60 to 500 fs (hard x-rays: 60 to 100 fs) 1.7 keV, 250 pC, 23 of 33 undulators inserted * for soft x-rays (0.5-2 keV)
52 m 43 m eeee 30 m SASE gain (P sat /10 3 ) SASE Saturation (25 GW) Si monochromator (T = 40%) time Energy time E FW /E ≈ 1.0% time t ≈ 200 fsec x-ray pulse 10 4 Mitigates e energy jitter and undulator wakes Also a DESY scheme which emphasizes line-width reduction (B. Faatz) UCLA C. Schroeder, et al. Self-seeding may soon be added to LCLS (Geloni et al) allowing Claudio’s scheme to be tested Self-seeding may soon be added to LCLS (Geloni et al) allowing Claudio’s scheme to be tested
PRL 92, 074801 (2004). Idea grew out of meetings with Max and Claudio in 2002-2003: Thanks to Clive Field, Mark Petree, et al.
OTR screen in BC2 (1 ft up-beam of foil) FEL X-ray Pulse Energy (mJ) Scan only the single-slot section
Great work was certainly done at SLAC to build this machine, …and we are all, understandably, quite proud of this effort. However, as I get more time to appreciate the novelty, complexity, and history of this amazing machine, I also come to appreciate another side… The performance of this machine was theoretically predicted so accurately that the damn thing worked like a brand new refrigerator just out of the box? Yes, we did a good job, but don’t forget that we were provided with a clear and realistic recipe from Claudio and many others who led the way. I stand in amazement at the FEL theorists who brought us this far, and did it mostly with pencil and paper!
From Herman Winick: “…the great majority of scientists thought that it was a crazy idea and that it would never work.” So let’s look at just a few of the accelerator and FEL physics challenges that stood in the way to see how crazy it really was…
22.0° bunch length Energy loss 23.0° 24.0° 25.0° 25.5° 26.0° 26.5° 27.0° 28.0° CSR Can Ruin Bend-Plane Emittance in Bunch Compressors! OTR12 skew quad skew quad streaks beam on OTR12 Energy-loss induced steering after BC1 BPM X Reading after BC1 (mm) 250 pC Skew quad in BC1 streaks beam vertically on OTR screen Use new skew-quad diagnostic to see time- resolved CSR effects… Actual Measurements
Heater OFF -bunching on dump screen in over- compression bunchlength
1 Å Get additional e /photon slippage (phase error) with imperfect trajectory <5 m Producing a sufficiently straight undulator trajectory requires an empirical beam-based alignment method 5 m e and photons phase matched e vs. photon phase error Trajectory straightness requirements are frighteningly tight !
1 Å (0.0001 m) 30 m eeee FEL -bunching 2 km! 1 mm Now let’s draw this more accurately, choosing a 1-mm period… And we must preserve this over a 130-m long undulator! Aspect ratio?
So was it a crazy idea … ? Yes, I must agree… …completely bonkers! But thanks Claudio, for such a wonderfully crazy idea !