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LCLS Linac Coherent Light Source Update John N. Galayda LCLS Project Manager Basic Energy Sciences Advisory Committee Meeting 2-3 August 2001.

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Presentation on theme: "LCLS Linac Coherent Light Source Update John N. Galayda LCLS Project Manager Basic Energy Sciences Advisory Committee Meeting 2-3 August 2001."— Presentation transcript:

1 LCLS Linac Coherent Light Source Update John N. Galayda LCLS Project Manager Basic Energy Sciences Advisory Committee Meeting 2-3 August 2001

2 LCLS R&D progress Gun Bunch compression Undulator X-ray optics FEL experiments Near-term R&D goals Determine baseline gun performance Improve understanding of coherent synchrotron radiation effects Sub-Picosecond Photon Source (SPPS)

3 LCLS National Synchrotron Light Source, Brookhaven National Lab Advanced Photon Source, Argonne National Lab

4 LCLS L INAC C OHERENT L IGHT S OURCE I-280 Sand Hill Rd

5 LCLS Peak and time averaged brightness of the LCLS and other facilities operating or under construction Performance Characteristics of the LCLS ~ TESLA Performance

6 LCLS Electrons are bunched under the influence of the light that they radiate. The bunch dimensions are characteristic of the wavelength of the light. Excerpted from the TESLA Technical Design Report, released March 2001 Self-Amplified Spontaneous Emission

7 LCLS At entrance to the undulator Exponential gain regime Saturation(maximum bunching) Excerpted from the TESLA Technical Design Report, released March 2001

8 LCLS R&D progress – Gun BNL Accelerator Test Facility Measurement of 0.8 mm-mrad emittance with 0.5 nC of charge Such high performance could make shorter LCLS pulses possible Details to be published in NIM-A, 2001 FEL Conference Proceedings

9 LCLS Charge, picocoulombs  mm-mrad R&D progress – Gun SLAC gun test facility Comparison of computed and measured emittances Agreement is good for configurations tested thus far Facility upgrades planned to study configurations with lower emittance LCLS Specification

10 LCLS Producing short bunches At low energy, space charge repulsion degrades the beam properties Accelerate the bunch, then compress it. SLAC linac tunnelundulator hall Linac-0 L  6 m Linac-1 L  9 m  rf  38° Linac-2 L  330 m  rf  43° Linac-3 L  550 m  rf  10° BC-1 L  6 m R 56  36 mm BC-2 L  24 m R 56  22 mm DL-2 L  66 m R 56 = 0 DL-1 L  12 m R 56  0 undulator L  120 m 7 MeV  z  0.83 mm    0.2 % 150 MeV  z  0.83 mm    0.10 % 250 MeV  z  0.19 mm    1.8 % 4.54 GeV  z  mm    0.76 % GeV  z  mm    0.02 %...existing linac new RF gun 25-1a 30-8c 21-1b 21-1d 21-3b 24-6d X Linac-X L  0.6 m  rf = 

11 LCLS  z z z V = V 0 sin(  ) z0z0z0z0 zzzz  z = R 56  Under- compression Over- compression RF Accelerating Voltage Voltage Path Length-Energy Dependent Beamline Path Length-Energy Dependent Beamline

12 LCLS Coherent Synchrotron Radiation (CSR)      R    e–e– Free space radiation from bunch tail at point A overtakes bunch head, a distance s ahead of the source, at the point B which satisfies... s = arc(AB) – |AB| = R  – 2Rsin(  /2)  R  3 /24 and for s =  z (rms bunch length) the overtaking distance is... L 0  |AB|  (24  z R 2 ) 1/3, ( LCLS: L 0 ~ 1 m) Free space radiation from bunch tail at point A overtakes bunch head, a distance s ahead of the source, at the point B which satisfies... s = arc(AB) – |AB| = R  – 2Rsin(  /2)  R  3 /24 and for s =  z (rms bunch length) the overtaking distance is... L 0  |AB|  (24  z R 2 ) 1/3, ( LCLS: L 0 ~ 1 m) Coherent radiation for: r  z r  z Coherent radiation for: r  z r  z r zzzz...from Derbenev, et. al.

13 LCLS CSR Effects  Bunch Energy Gradient  z Charge distribution ~CSR wakefield HEAD TAIL (mean loss) zzzz

14 LCLS CSR Effects  Emittance Growth   s Radiation in bends Energy loss in bends causes transverse position spread after bends  x-emittance growth Energy loss in bends causes transverse position spread after bends  x-emittance growth

15 LCLS R&D Progress – Coherent Synchrotron Radiation CSR sets a lower limit on LCLS as a laser LCLS could produce ~50 fsec pulses of spontaneous radiation New ANL model fits latest data – is the model accurate? LCLS bunch compression can be retuned to accommodate energy spread [%] rms bunch length [ps ] emittance [mm-mrad] minimum compression Elegantmodel Courtesy M. Borland, J. Lewellen, ANL Q  0.3 nC M. Borland, PRST-AB v.4, (2001) Borland, Braun, Doebert, Groening, & Kabel, CERN/PS (AE)

16 LCLS R&D Progress – Prototype Undulator Titanium strongback mounted in eccentric cam movers Magnet material 100% delivered Poles >90% delivered Assembly underway

17 LCLS Helmholtz Coil – magnet block measurement Translation stages for undulator segment Poletip alignment fixture Magnet block clamping fixtures

18 LCLS Planned beam diagnostics in undulator include pop-in C(111) screen To extract and observe x-ray beam, and its superposition on e-beam

19 LCLS R&D Progress – Undulator diagnostics P. Krejcik, W. K. Lee, E. Gluskin Exposure of diamond wafer to electron beam in FFTB- Same electric fields as in LCLS No mechanical damage to diamond Tests of crystal structure planned Before After

20 LCLS R&D Progress – X-ray optics LLNL tests of damage to silicon crystal Exposure to high- power laser with similar energy deposition Threshold for melting 0.16 J/cm 2, as predicted in model Fabrication/test of refractive Fresnel lens Made of aluminum instead of carbon Machined with a diamond point Measurements from SPEAR presently under analysis

21 LCLS Focusing Optic Incident Beam Monitors Back-scatter x-ray spectrometer Spectrometer Laser Outgoing Beam Monitor FEL Beam 100 mm thick sample  m aperture Variable beam attenuator 250  m aperture Imaging detector Optics Tank Sample Tank WDM Shielded Room PPS beam stops 13 m Warm Dense Matter Experiment

22 LCLS R&D Progress – FEL physics More complete analysis of HGHG A. Doyuran, et al. PRL vol. 86, Issue 26, pp , June 25, 2001 LEUTL experiments ongoing Milton, et al. Science vol. 292, Issue 5524, , June 15, 2001 VISA experiment saturation To be published in proceedings of 2001 FEL conference Data from BNL/ANL High-Gain Harmonic Generation(HGHG) Experiment

23 LCLS Distance Traversed in Undulator (m) Radiated Energy (a.u.) LEUTL Gain 530 nm on March 10, October,2000

24 LCLS Preliminary recent results (unpublished) from VISA showing large gain ( ) in SASE FEL radiation and evidence of saturation at 830 nm. Visible to Infrared SASE Amplifier Enclosure for 4-m long VISA undulator Pop-In Diagnostics Data Points taken along VISA Undulator Direction of Electron Beam Wavelength 830 nm Onset of Saturation VISA Pulse Energy vs. Position Wavelength830nm RMS Bunch Length:900 fs Average Charge:170 pC Peak Current:~200 A Measured Projected Emittance:1.7 mm mrad Energy Spread:7×10 -4 Gain Length18.5 cm Equivalent Spontaneous Energy:5 pJ Peak SASE Energy:10  J Total Gain: 2× March 2001 BNL-LLNL-SLAC-UCLA

25 LCLS Near-term R&D goals Gun R&D Thorough investigation of gun operation at LCLS parameters Laser upgrade Linac energy upgrade Experiment/model comparison at 1 mm-mrad emittance, nC Bunch compression, coherent synchrotron radiation Install a bunch compressor in the SLAC linac Continue start-to-end modeling

26 LCLS Bunch compression studies with SLAC linac in 2003 Compatible with PEP-II injection Capable of producing 80 fsec electron bunches Goal: first studies in 1/2003, 1 year of tests pump/probe techniques Accelerator physics opportunities to study wake fields Of great importance to LCLS Short bunches are ideal for advanced accelerator R&D; Strong SLAC support

27 LCLS LCLS – X-ray Laser Physics The “sixth” experiment – Produce < 230 fsec pulses of SASE radiation LCLS will be used to explore means of producing ultra short bunches (< 50 fs). Alternative techniques will be investigated: Stronger compression of the electron bunch No new hardware is required Photon bunch compression or slicing Principle: spread the electron and photon pulses in energy; recombine optically or select a slice in frequency z  Seeding the FEL with a slice of the photon pulse Principle: select slice in frequency, then use it to seed the FEL

28 LCLS Two-Stage Chirped-Beam SASE-FEL for High Power Femtosecond X-Ray Pulse Generation C. Schroeder*, J. Arthur^, P. Emma^, S. Reiche*, and C. Pellegrini* ^ Stanford Linear Accelerator Center *UCLA Strong possibility for shorter-pulse operation

29 LCLS Two-stage undulator for shorter pulse 52 m 43 m eeee 30 m SASE gain (P sat /10 3 ) SASE Saturation (23 GW) Si monochromator (T = 40%) time Energy time Energy  E FW /E = 1.0% time  t FW = 230 fsec x-ray pulse 1.0  10  4 time  t FW < 10 fsec Mitigates e  energy jitter and undulator wakes Also a DESY scheme which emphasizes line-width reduction (B. Faatz) UCLA

30 LCLS LCLS Construction FY2003: $6M for project engineering and design, $3M for R&D Prepare bid packages FY2004: Start of Construction Injector construction and installation Bunch compressor construction Start construction of near hall Undulator procurement FY2005: Injector commissioning Bunch compressor installation Start construction of far hall Undulator, experiment construction FY2006: Installation Linac commissioning Undulator and experiment installation LCLS commissioning

31 LCLS LCLS research activities span the full range of challenges to be met in creating and exploiting an x-ray laser SLAC has supplemented its extraordinary capabilities with the expertise and resources at partner labs to make LCLS possible LCLS can be a reality by 2007

32 LCLS End of Presentation


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