Undulator Physics Diagnostics / Commissioning Strategy Heinz-Dieter Nuhn, SLAC / SSRL August 11, 2004 Undulator Overview FEL Parameters Diagnostics and Commissioning Strategy

Linac Coherent Light Source Undulator Near Hall Far Hall

Undulator Segment Prototype

Workshops and Meetings Undulator Parameter Workshop October 24, 2003, Argonne URL: http://www-ssrl.slac.stanford.edu/lcls/undulator/meetings/2003-10-24_parameter_workshop/ Undulator Review November 14, 2003, Argonne URL: http://www-ssrl.slac.stanford.edu/lcls/undulator/meetings/2003-11-14_review/ Undulator Diagnostics and Commissioning Workshop January 19-20, 2004, UCLA URL: http://www-ssrl.slac.stanford.edu/lcls/undulator/meetings/2004-01-19_diagnostics_comissioning/ Report: http://www-ssrl.slac.stanford.edu/lcls/workshops/2004-09-22_diag_comm/lcls-tn-04-2.pdf Undulator Systems Review March 3-4, 2004, Argonne URL: http://www-ssrl.slac.stanford.edu/lcls/undulator/meetings/2004-03-03_review/ Undulator Physics and Engineering Meeting June 28-29, 2004, Argonne URL: http://www-ssrl.slac.stanford.edu/lcls/undulator/meetings/2004-06-28_phy_eng/ Undulator Meeting July 23, 2004, Argonne URL: http://www-ssrl.slac.stanford.edu/lcls/undulator/meetings/2004-07-23_und_mtg/ LCLS Diagnostics and Commissioning Workshop September 22-23, 2004, SLAC URL: http://www-ssrl.slac.stanford.edu/lcls/workshops/2004-09-22_diag_comm/

Undulator Design Changes Since May 2003 Canting of Undulator Poles Remote Undulator Roll-Away and K Adjustment Function Increase in Undulator Gap Reduction in Maximum Beam Energy Reduction in Quadrupole Gradient Increase in Beta Function Increase in Break Section Length

Amplitudes of Undulator Parameter Changes May 2003 August 2004 Undulator Type planar hybrid Magnet Material NdFeB Wiggle Plane horizontal Gap 6.0 6.8 mm Gap Canting Angle 0.0 4.5 mrad Period Length 30.0 ± 0.1 mm Effective On-Axis Field 1.325 1.249 T Effective Undulator Parameter K 3.630 ± 0.015% 3.500 ± 0.015% Module Length 3.40 m Number of Modules 33 Undulator Magnet Length 112.2 m Standard Break Lengths 18.7 - 18.7 - 42.1 48.2 - 48.2 - 94.9 cm Total Device Length 121.0 131.9 m Lattice Type FODO Integrated QF Gradient 5.355 3.000 T/m Integrated QD Gradient -5.295 -3.000 T/m Average b Function at 1.5 Å 18 30 m Average b Function at 15. Å 7.3 8.9 m

Performance Impact of Changes (1.5 Å) May 2003 August 2004 Change Electron Beam Energy 14.35 13.64 GeV -5.0 % Emittance 0.043 0.045 nm rad +5.2 % Avg. Electron Beam Radius 27 35 µm +27.5 % Avg. Electron Beam Divergence 1.6 1.3 µrad -17.5 % Peak Beam Power 49 46 TW -5.0 % FEL Parameter (3D) 0.00033 0.00032 -3.5 % Power Gain Length (3D) 4.2 4.3 m +3.6 % Saturation Length (w/o Breaks) 82 86 m +4.9 % Saturation Length (w/ Breaks) 89 101 m +13.5 % Peak Saturation Power 7.4 7.6 GW +2.5 %* Coherent Photons per Pulse 1.4×1012 1.5×1012 +2.5 %* Peak Brightness 1.5×1033 1.5×1033 ** +2.5 %* Average Brightness 4.6×1022 4.7×1022 ** +2.5 %* Peak Spont. Power per Pulse 91 73 GW -19.7 % *Increase due to 3D effects (reduction in diffraction due to beam radius increase) ** [Ph./s/mm2/mr2/.1%]

Undulator Specification Documents Controlled Specification Documents support Inter-Laboratory Communications Global Requirements Document (GRD) GRD 1.1-001 (http://www-ssrl.slac.stanford.edu/lcls/prd/1.1-001-r1.pdf) Physics Requirements Documents (PRDs) PRD 1.4-001 General Undulator System Requirements (http://www-ssrl.slac.stanford.edu/lcls/prd/1.4-001-r0.pdf) PRD 1.4-002 Magnetic Measurement Facility Requirements (http://www-ssrl.slac.stanford.edu/lcls/prd/1.4-002-r0.pdf) PRD 1.4-003 Beam Based Alignments System Requirements (http://www-ssrl.slac.stanford.edu/lcls/prd/1.4-003-r0.pdf) PRD 1.1-314 LCLS Beam Position Measurement System Requirements (http://www-ssrl.slac.stanford.edu/lcls/prd/1.1-314-r0.pdf) Engineering Specification Documents (ESDs) ESD 1.4-100 Undulator Segment Specifications ESD 1.4-101 Undulator Segment Support Specifications ESD 1.4-102 Quadrupole Magnet Specifications ESD 1.4-103 Diagnostics System Specifications ESD 1.4-104 Wire Position Monitor System Specifications ESD 1.4-105 Hydrostatic Leveling System Specification ESD 1.4-106 Vacuum System Specifications ESD 1.4-106 Controls Specifications Interface Control Documents (ICDs) ICD 1.4-500 Undulator Mechanical Interfaces Process of generating these documents is on-going.

FEL Commissioning Workshop 1/19-20/04 Scope Commissioning of the FEL Undulator with Beam Goals End-Of-Construction Goal Defined by DOE to close-off construction project (CD-4) One of the first Commissioning Milestones Commissioning Goal Get LCLS ready for operation Prerequisites Undulator, Diagnostics, Shielding, Beam Dump etc. in Place Commissioning Without Beam for all Components Complete Main Commissioning Tasks Characterization of Electron Beam Up-Stream of Undulator Establishment of a Good Beam Trajectory Through Undulator to Beam-Dump Characterization of Spontaneous Radiation Establishment of SASE Gain Characterization of FEL Radiation Low Charge Single Shot Low Charge, 10 Hz 10 Hz

Workshop Issues Undulator Radiation Protection Measurements of FEL Radiation vs. Z Radiation Power Damage to Inter Undulator X-Ray Diagnostics End-of-Undulator Diagnostics Beam Based Detection of Gain Reducing Errors Using Spontaneous Radiation Using FEL Gain Curve Numerical Simulation Support for Detector Development and Commissioning

Undulator Radiation Protection Two-Phase, Two-Plane Collimation, 1½ Times p/2 ~p/2 3 mm edge scattering 2.5 mm 2 mm halo e- beam undulator beam pipe x1 x2 x3 phase-1 again phase-1 phase-2 (also collimation in y and energy – see next slides)

E1 E2 x1 y1 x2 y2 x3 y3 LCLS Collimation Proposal (2 energy, 3 x, and 3 y adjustable collimators) muon shielding undulator x3 & y3 optional?

well shadowed in x, y, and E 2nd-order tracking with all collimators closed and big halo 2.5 mm 2-phase, 2-plane, and energy collimation in 2nd-order well shadowed in x, y, and E ? - CY3 CX3 2.0 CY2 CX2 CY1 CX1 5.0 CE2 CE1 Dy mm Dx Coll. gex,y = 4000 mm, sE/E = 10% (uniform)

First beam shot through undulator? Track 100 times with: DL2 BPM rms res. = 10 mm DL2 BPM rms misa. = 200 mm DL2 Quad rms misa. = 200 mm Undulator Quad rms misa. = 100 mm Correct und-launch, then open stopper-2 for one beam shot… Just 11 of 100 trajectories exceed 2.5 mm within undulator None exceed 3.5 mm G = 110 T/m First beam shot through undulator?

FEL Gain Measurement Desirable measurements as function of position along undulator : Intensity (LG, Saturation) Spectral Distribution Bunching Saturation Exponential Gain Regime Undulator Regime 1 % of X-Ray Pulse Electron Bunch Micro-Bunching

Dose / Power Considerations Fluence to Melt Energy Density Reduction of a Reflector Be will melt at normal incidence at E < 3 KeV near undulator exit. Using Be as a grazing incidence reflector may gain x 10 in tolerance.

End-of-Undulator Commissioning Diagnostics Measurements Total energy Pulse length Photon energy spectra Spatial coherence Spatial shape and centroid Divergence

4' Muon shield PPS Access Shaft PPS Spectrometer, Total Energy Solid Attenuator Access Shaft Direct Imager Indirect Imager Slit A Slit B Windowless Ion Chamber PPS Gas Attenuator 13' Muon shield Fast close valve

Measurement of SASE Gain along the undulator Direct: Detectors in the Breaks between Undulator Segments. No good solution for x-ray detector in existence, yet. Alternative: End-Of-Undulator Diagnostics Turn-Off Gain at Selectable Point Along Undulator by Introduction of orbit distortion Removal of undulator segments (New roll-away option) Characterize x-ray beam at single station down stream of undulator

Measurement of SASE Gain with end-of-undulator diagnostics GENESIS Simulations by Z. Huang

Spontaneous vs. FEL Radiation -1-

Spontaneous vs. FEL Radiation -2-

Workshop Recommendations No Intra-Undulator-Segment X-Ray Diagnostics in Baseline Design Instead: End-of-Undulator X-Ray Diagnostics to Characterize FEL Radiation vs. z Trajectory Distortion Method Roll-Away Undulator Segments Function Investigation of Spontaneous Radiation as Diagnostics Tools Code Development to Support Commissioning Areas for Follow-Up R&D Study of Spectral and Spatial Distribution of Spontaneous Radiation Diagnostics Prototyping Microbunching Measurement

Requirements for LCLS undulator are well established Conclusions Requirements for LCLS undulator are well established LCLS undulator performance requirements are well understood Risks have been assessed and undulator specifications address the risk Detailed commissioning strategy is being developed. Startup Test Plan exists. PRD 1.1-002 LCLS Start-Up Test Plan (http://www-ssrl.slac.stanford.edu/lcls/prd/1.41002-r1.pdf)

End of Presentation