LCLS Linac Coherent Light Source Update John N

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

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)

LCLS 1977 -1990 National Synchrotron Light Source, Brookhaven National Lab 1990 -2001 Advanced Photon Source, Argonne National Lab

LCLS LINAC COHERENT LIGHT SOURCE I-280 Sand Hill Rd

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

LCLS Self-Amplified Spontaneous Emission 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

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

LCLS R&D progress – Gun BNL Accelerator Test Facility • Measurement of 0. 8 mm-mrad emittance with 0. 5 n. C of charge • Such high performance could make shorter LCLS pulses possible • Details to be published in NIM-A, 2001 FEL Conference Proceedings

LCLS R&D progress – Gun ge, mm-mrad 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 Charge, picocoulombs

LCLS Producing short bunches At low energy, space charge repulsion degrades the beam properties Accelerate the bunch, then compress it. 4. 54 Ge. V z 0. 022 mm 0. 76 % w ne 250 Me. V 7 Me. V 150 Me. V z 0. 19 mm z 0. 83 mm 1. 8 % 0. 2 % 0. 10 % Linac-X RF L 0. 6 m gun rf=180 Linac-1 Linac-2 Linac-0 L 9 m L 330 m L 6 m rf -38° rf -43°. . . existing linac DL-1 L 12 m R 56 0 21 -1 b 21 -1 d X BC-1 L 6 m R 56 -36 mm 21 -3 b 24 -6 d SLAC linac tunnel BC-2 L 24 m R 56 -22 mm 14. 35 Ge. V z 0. 022 mm 0. 02 % Linac-3 L 550 m rf -10° 25 -1 a 30 -8 c undulator L 120 m DL-2 L 66 m R 56 = 0 undulator hall

LCLS DE/E Overcompressi on 2 z 0 z z Undercompressi on z 2 z V = V 0 sin(wt) RF Accelerating Voltage Dz = R 56 DE/E Path Length-Energy Dependent Beamline

LCLS Coherent Synchrotron Radiation (CSR) z A Coherent radiation for: lr >> z lr |AB | B e– <<1 R. . . from Derbenev, et. al. 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 – 2 Rsin( /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)

LCLS CSR Effects Bunch Energy Gradient Charge distribution DE/E z TAIL HEAD (mean loss) ~CSR wakefield z

LCLS Energy loss in bends causes transverse position spread after bends x-emittance growth Radiation in bends s DE/E = 0 DE/E < 0 CSR Effects Emittance Growth

LCLS [ps ] minimum compression emittance [mm-mrad] rms bunch length energy spread [%] 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 Elegant model Q 0. 3 n. C Courtesy M. Borland, J. Lewellen, ANL M. Borland, PRST-AB v. 4, 074201(2001) Borland, Braun, Doebert, Groening, & Kabel, CERN/PS 2001 -027(AE)

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

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

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

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

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

LCLS Warm Dense Matter Experiment 250 mm aperture Back-scatter x-ray spectrometer Incident Beam Monitors Laser FEL Beam Spectrometer 100 mm Variable beam attenuator Focusing Optic 50 -100 mm aperture thick sample Sample Tank Outgoing Beam Monitor PPS beam stops Optics Tank WDM Shielded Room 13 m Imaging detector

LCLS R&D Progress – FEL physics • More complete analysis of HGHG • A. Doyuran, et al. PRL vol. 86, Issue 26, pp. 5902 -5905, June 25, 2001 • LEUTL experiments ongoing • Milton, et al. Science vol. 292, Issue 5524, 2037 -2041, 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

LCLS LEUTL Gain Curve @ 530 nm on March 10, 2001 107 Radiated Energy (a. u. ) 106 105 104 103 October, 2000 102 101 100 0 5 10 15 20 Distance Traversed in Undulator (m) 25

LCLS 16 March 2001 Visible to Infrared SASE Amplifier BNL-LLNL-SLAC-UCLA VISA Pulse Energy vs. Position Wavelength 830 nm Onset of Saturation Data Points taken along VISA Undulator Pop-In Diagnostics Enclosure for 4 -m long VISA undulator Direction of Electron Beam Preliminary recent results (unpublished) from VISA showing large gain (2 106) in SASE FEL radiation and evidence of saturation at 830 nm. Wavelength RMS Bunch Length: Average Charge: Peak Current: Measured Projected Emittance: Energy Spread: Gain Length Equivalent Spontaneous Energy: Peak SASE Energy: Total Gain: 830 nm 900 fs 170 p. C ~200 A 1. 7 mm mrad 7× 10 -4 18. 5 cm 5 p. J 10 m. J 2× 106

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, 0. 5 -1 n. C • Bunch compression, coherent synchrotron radiation • Install a bunch compressor in the SLAC linac • Continue start-to-end modeling

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

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: DE/E Stronger compression of the electron bunch • No new hardware is required z Photon bunch compression or slicing • Principle: spread the electron and photon pulses in energy; recombine optically or select a slice in frequency Seeding the FEL with a slice of the photon pulse • Principle: select slice in frequency, then use it to seed the FEL

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

LCLS Energy Two-stage undulator for shorter pulse Dt. FW =time 230 fsec x-ray pulse Energy DEFW/E = 1. 0% 1. 0 10 -4 Dt. FW < time 10 fsec Si monochromator (T = 40%) time Mitigates e- energy jitter and undulator wakes time UCLA e 30 m 43 m SASE gain (Psat/103) 52 m SASE Saturation (23 GW) Also a DESY scheme which emphasizes line-width reduction (B. Faatz)

LCLS Construction • FY 2003: $6 M for project engineering and design, $3 M for R&D • Prepare bid packages • FY 2004: Start of Construction • Injector construction and installation • Bunch compressor construction • Start construction of near hall • Undulator procurement • FY 2005: • Injector commissioning • Bunch compressor installation • Start construction of far hall • Undulator, experiment construction • FY 2006: Installation • Linac commissioning • Undulator and experiment installation • LCLS commissioning

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

LCLS End of Presentation