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 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!

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Presentation on theme: " 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!"— Presentation transcript:

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2  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!

3 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 , 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…  ?

4 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, (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

5 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 Journal of Electron Spectroscopy and Related Phenomena, Vol. 75 (1995), pp J. Galayda Construction Phase (2001 – present) Scope expands to user facility, construction, commissioning, + user op’s. First light: April 9, 2009

6  nC C. Pellegrini, X. Ding, J. Rosenzweig, “ Output Power Control in an X-Ray FEL”, PAC-99, New York, NY, March  nC  0.1 nC P. Emma, “ LCLS Accelerator Parameters and Tolerances for Low Charge Operations”, SLAC-TN , May,  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  0.2 nC (resistive wakes under control)  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).  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, (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).

7 Y. Ding 15 Å, z = 25 m, 2.4  ph’s, I pk = 2.6 kA,   0.4 µm 15 Å, z = 25 m, 2.4  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.

8 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), 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.

9 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)

10 52 m 43 m eeee 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

11 PRL 92, (2004). Idea grew out of meetings with Max and Claudio in : Thanks to Clive Field, Mark Petree, et al.

12 OTR screen in BC2 (1 ft up-beam of foil) FEL X-ray Pulse Energy (mJ) Scan only the single-slot section

13 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!

14 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…

15  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

16 Heater OFF  -bunching on dump screen in over- compression bunchlength

17 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 !

18 1 Å (  m) 30  m eeee 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?

19 So was it a crazy idea … ? Yes, I must agree… …completely bonkers! But thanks Claudio, for such a wonderfully crazy idea !


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