Table of Contents

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1 Executive Summary  
1.1 Introduction 1-1
1.2 The Scientific Case 1-3
1.3 FEL Physics and Simulations 1-3
1.4 The Injector 1-4
1.5 Acceleration and Compression 1-4
1.6 The Undulator 1-5
1.7 Undulator-to-Experimental Area 1-6
1.8 Take-off Optics and Beamline Layout 1-7
1.9 Instrumentation and Controls 1-7
1.10 Alignment 1-8
1.11 Radiation Protection 1-8
1.12 Basic Parameters 1-9
1.13 Estimated Costs, Proposed Schedule, and Project Execution 1-10
2 Overview  
2.1 Introduction 2-1
2.2 Principle of Operation 2-1
2.3 Overall Layout 2-2
2.4 Performance Characteristics 2-3
2.5 The Photoinjector 2-5
2.6 Compression and Acceleration 2-6
2.7 The Undulator 2-6
2.8 The X-ray Optics and Experimental Areas 2-6
2.9 Applications of the LCLS 2-7
2.10 Summary 2-8
2.11 References 2-8
3 The Scientific Case  
  Technical Synopsis 3-1
3.1 History of Scientific Interest in X-ray Free Electron Lasers 3-1
3.2 Unique Features of X-ray FEL Radiation 3-3
  3.2.1 Fundamental Quantum Mechanics 3-5
  3.2.2 Atomic, Molecular, and Plasma Physics 3-6
  3.2.3 Chemical Physics 3-7
  3.2.4 Condensed Matter Physics and Materials Science 3-7
  3.2.5 Biology 3-8
3.3 The Role of the LCLS 3-9
3.4 References 3-9
4 FEL Physics  
  Technical Synopsis 4-1
4.1 Introduction 4-1
  4.1.1 Spontaneous Radiation from the LCLS Undulator 4-3
4.2 FEL Radiation 4-7
4.3 References 4-11
5 FEL Parameters and Performance  
  Technical Synopsis 5-1
5.1 Introduction 5-1
5.2 Parameter Optimization 5-2
5.3 Electron Beam Focusing 5-4
  5.3.1 Lattice Design Criteria 5-5
  5.3.2 Focusing Method (Lattice) 5-5
  5.3.3 Optimum Beam Size 5-6
  5.3.4 Tolerable Beta-Function Modulation Amplitude 5-7
5.4 Undulator Sections 5-9
5.5 Parameter Sensitivities 5-9
5.6 Temporal Structure of Laser Power 5-11
5.7 Effect of Deviations from the Ideal Electron Trajectory 5-12
  5.7.1 Undulator Steering and Corrector Description 5-12
  5.7.2 Magnetic Field Errors 5-12
  5.7.3 Trajectory and Error Control Requirement from Simulations 5-12
  5.7.4 Magnetic Field Error Tolerances 5-13
  5.7.5 Steering Algorithm 5-13
  5.7.6 Steering Error Tolerance 5-14
  5.7.7 Optimum Steering Station Separation 5-14
  5.7.8 Undulator Matching Tolerances 5-16
5.8 Emission of Spontaneous Radiation 5-16
  5.8.1 Average Energy Loss 5-16
  5.8.2 Energy Spread Increase 5-17
  5.8.3 Emittance Increase 5-18
5.9 Output Power Control 5-18
  5.9.1 Peak Current 5-18
  5.9.2 Phase Shifter at Saturation 5-19
5.10 Initial Phase Space Distribution (Coupling to Linac Simulation Results) 5-19
  5.10.1 Transverse Halo 5-20
5.11 Optical Klystron 5-20
5.12 Summary 5-21
5.13 References 5-21
6 Photoinjector  
  Technical Synopsis 6-1
6.1 Electron Source 6-2
  6.1.1 RF Photocathode Gun 6-2
    Gun Description 6-2
    Field Balance 6-3
    Symmetrization 6-4
    Emittance Compensation 6-5
    Summary of Experimental Results at ATF 6-5
    Photocathode 6-7
    RF System 6-7
    Emittance Compensating Solenoid 6-8
    Beamline 6-8
    Vacuum System 6-8
  6.1.2 Laser System 6-9
    System Description 6-10
    Temporal Pulse Shaping 6-13
    Fourier Relay Optics 6-14
    Spatial Pulse Shaping 6-14
    Frequency Conversion 6-15
    Grazing Incidence 6-15
    Stability of Laser Pulse 6-16
    Diagnostics 6-18
  6.1.3 Choice of Laser System 6-21
6.2 Linac 0 6-24
  6.2.1 Comments on Emittance Compensation 6-24
  6.2.2 System Description 6-26
  6.2.3 Emittance Compensation in Linac 0 6-27
6.3 References 6-30
7 Accelerator  
  Technical Synopsis 7-1
7.1 Introduction and Overview 7-1
7.2 Compression and Longitudinal Dynamics 7-3
  7.2.1 Bunch Compression Overview 7-3
  7.2.2 Parameters 7-5
  7.2.3 Longitudinal Wakefields and Non-linearities 7-7
    Geometric Wakefields 7-7
    Resistive Wall Wakefields 7-8
  7.2.4 Beam Jitter Sensitivities 7-11
  7.2.5 Energy Management and Overhead 7-12
7.3 Transverse Linac Beam Dynamics 7-13
  7.3.1 The L0 Linac 7-14
  7.3.2 The L1 Linac 7-14
  7.3.3 The L2 Linac 7-16
  7.3.4 The L3 Linac 7-19
7.4 Design of the Second Bunch Compressor 7-21
  7.4.1 Overview and Parameters 7-21
  7.4.2 Momentum Compaction 7-23
  7.4.3 Incoherent Synchrotron Radiation (ISR) 7-24
  7.4.4 Coherent Synchrotron Radiation (CSR) 7-24
    Unshielded Radiation 7-24
    Shielded Radiation 7-26
    Transverse Forces 7-28
    Calculations with a Transient Model 7-29
  7.4.5 Resistive Wall Longitudinal Wakefields in the Bends 7-31
  7.4.6 Beam Size, Aperture and Field Quality 7-32
  7.4.7 Tuning and Correction 7-32
7.5 Design of the First Bunch Compressor 7-33
  7.5.1 Overview and Parameters 7-33
  7.5.2 Beam Size, Aperture, and Field Quality 7-34
  7.5.3 Tuning and Correction 7-35
7.6 Beam Transport Lines 7-36
  7.6.1 Low-Energy Dog Leg 7-36
    Parameters 7-37
    Beam Size, Aperture, and Field Quality 7-38
    Tuning and Correction 7-38
  7.6.2 High-Energy Dog Leg 7-39
    Parameters 7-40
    Beam Size, Aperture, and Field Quality 7-41
    Tuning and Correction 7-41
    Coherent Radiation 7-41
7.7 Instrumentation, Diagnostics, and Feedback 7-42
  7.7.1 Transverse Emittance Diagnostics 7-42
    ED0 Emittance Station 7-44
    ED1 Emittance Station 7-44
    L2-ED Emittance Station 7-44
    BC2-ED Emittance Station 7-45
    L3-ED Emittance Station 7-45
    ED2 Emittance Station 7-45
  7.7.2 Bunch Length Diagnostics 7-45
  7.7.3 Beam Energy Spread Diagnostics 7-47
    DL1 Energy Spread Diagnostics 7-47
    BC1 Energy Spread Diagnostics 7-47
    BC2 Energy Spread Diagnostics 7-48
    DL2 Energy Spread Diagnostics 7-48
  7.7.4 Orbit and Energy Monitors and Feedback Systems 7-48
    Orbit Feedback Systems 7-48
    Energy Feedback Systems 7-49
7.8 The Wake Functions for the SLAC Linac 7-49
  7.8.1 Introduction 7-49
  7.8.2 The Calculated Wakefields for the SLAC Linac 7-50
  7.8.3 Discussion 7-51
  7.8.4 Confirmations 7-54
  7.8.5 Resistive Wall Wakefields 7-54
  7.8.6 The Impedance Due to the Roughness of the Iris Surface 7-56
7.9 Summary of Dilution Effects 7-57
  7.9.1 Transverse Emittance Dilution 7-57
  7.9.1 Final Energy Spread 7-58
7.10 References   7-59
8 Undulator  
  Technical Synopsis 8-1
8.1 Overview 8-2
  8.1.1 Introduction 8-2
  8.1.2 Undulator Design Summary 8-2
    Introduction 8-2
    Design Concept History 8-3
    The Undulator 8-3
    Strong Focusing 8-5
    Undulator Tolerances 8-7
    Undulator Construction 8-7
    Mechanical, Thermal, and Geophysical Engineering 8-8
8.2 Undulator Magnetic Design 8-9
  8.2.1 Design of Undulator Segments 8-9
    Basic Considerations 8-9
    Correcting Local Field Errors 8-10
    Initial Sorting Model and Results 8-11
    Use of Shims to Correct Field Errors 8-15
  8.2.2 End Design of Undulator Segments 8-15
8.3 Undulator Mechanical Design 8-17
  8.3.1 Mechanical and Thermal Design 8-17
    Introduction 8-17
    Piers 8-18
    Motors 8-20
    Girder 8-21
    Thermal Considerations 8-23
    Vibration of the Girder 8-24
    Dimensional Stability 8-24
    Magnet Support 8-25
    Conclusions 8-30
  8.3.2 Electron Beam Collimation and Vacuum Chamber Design 8-30
    Beam Parameters Used in These Calculations 8-30
    Permanent Magnet Material 8-30
    Undulator Vacuum Chamber 8-32
    Beam Strikes at the Entrance to the Vacuum Chamber 8-32
    Beam Strikes Inside the Undulator 8-33
    Adjustable Collimators to Protect Undulator and Vacuum Chamber 8-35
    Fixed Aperture Protection Collimators 8-36
    Vacuum Chamber Surface Roughness 8-37
8.4 Undulator Vacuum System 8-37
  8.4.1 System Requirements and Description 8-37
  8.4.2 Gas Load and Vacuum Pressure 8-39
  8.4.3 Thermal Considerations 8-42
8.5 Alignment and Trajectory Control 8-42
  8.5.1 Introduction 8-42
  8.5.2 Undulator Beam Based Alignment 8-43
    Introduction 8-44
    Simulation Results 8-47
    Sensitivities 8-56
    Summary 8-57
  8.5.3 The Singular Value Decomposition (SVD) Technique 8-57
    Description 8-57
    Simulation Results 8-59
    Summary 8-61
8.6 Beam Diagnostics 8-61
  8.6.1 RF Cavity BPMs 8-61
    Review of BPM Technology 8-62
    Evaluation of BPM Options for the LCLS 8-63
    LCLS Stripline BPM 8-64
    LCLS Microwave Cavity BPM 8-65
    Parameters of the LCLS BPM Cavity 8-68
    Microwave Cavity Beam Impedance 8-68
    Microwave Cavity Signal Processing 8-70
  8.6.2 Carbon Wire BPMs 8-71
    Beam Position Measurement 8-71
    Beam Emittance Measurements 8-74
  8.6.3 The Combined Electron and Photon Beam Diagnostic 8-75
  8.6.4 Wire Position Monitors 8-77
8.7 Wakefield Effects in the Undulator 8-77
  8.7.1 Introduction 8-77
  8.7.2 Wakefield Induced Beam Degradation 8-78
  8.7.3 The Resistive Wall Wakefields 8-80
  8.7.4 The Effect of Flange Gaps, Pumping Slots, and Bellows 8-81
  8.7.5 The Effect of Wall Surface Roughness 8-82
  8.7.6 The Effects of the Expected Bunch Shape 8-84
  8.7.7 Conclusion 8-84
8.8 Ion Effects 8-85
  8.8.1 Introduction 8-85
  8.8.2 Ionization Processes 8-85
  8.8.3 Emittance Dilution 8-87
  8.8.4 Conclusion 8-89
8.9 References 8-89
9 Undulator-to-Experimental Area  
  Technical Synopsis 9-1
9.1 Transport System 9-1
9.2 Shielding Enclosures 9-4
9.3 Beam Lines and Experimental Stations 9-5
  9.3.1 Experimental Beam Lines 9-5
  9.3.2 The Long Beam Line 9-6
  9.3.3 Experimental Stations 9-8
9.4 Experimental Hall 9-9
9.5 References 9-9
10 Take-off Optics and Beam Line Layouts  
  Technical Synopsis 10-1
10.1 Coherent Radiation 10-2
10.2 Spontaneous Radiation Calculations 10-8
  10.2.1 Spectral-angular Radiation Profiles 10-10
  10.2.2 Far-field Spontaneous Radiation Peak Power Density 10-18
10.3 Bremsstrahlung Calculations 10-20
  10.3.1 Bremsstrahlung from Halo 10-20
  10.3.2 Gas Bremsstrahlung 10-24
  10.3.3 Muons 10-25
  10.3.4 Future Work: Other Radiation Sources 10-25
10.4 Optical System 10-26
  10.4.1 Differential Pumping Section 10-28
  10.4.2 X-ray Slits (Collimators) 10-30
  10.4.3 Personnel Protection System Beam Stoppers 10-33
  10.4.4 Absorption cell 10-34
  10.4.5 Mirrors 10-39
  10.4.6 Crystals 10-44
10.5 Beam Line Optical Instrumentation 10-46
10.6 References 10-47
11 Instrumentation and Controls  
  Technical Synopsis 11-1
11.1 Control System 11-2
11.2 Undulator Control 11-4
  11.2.1 Undulator Elements 11-4
  11.2.2 Mover Mechanism 11-5
  11.2.3 Stepping Motor Controllers and Position Potentiometers 11-5
  11.2.4 The Wire Position Monitor System 11-6
  11.2.5 The Beam Position Monitors 11-7
  11.2.6 Control System Layout 11-7
11.3 Beam Line Electronics and Controls 11-10
  11.3.1 X-ray Optics and Experimental Stations 11-10
  11.3.2 Control System Objectives 11-10
  11.3.3 Control System Layout 11-10
  11.3.4 Motion Controls 11-11
  11.3.5 Photon Beam Stabilization at the Sample 11-11
  11.3.6 Timing System 11-13
11.4 Personnel Protection 11-16
11.5 Machine Protection 11-20
12 Alignment  
  Technical Synopsis 12-1
12.1 Surveying Reference Frame 12-2
  12.1.1 Network Design Philosophy 12-3
  12.1.2 Network Lay-Out 12-5
    Linac Network 12-5
    Undulator Network 12-5
    Transport Line/Experimental Area Network 12-6
  12.1.3 Alignment Coordinate System 12-6
  12.1.4 Network Survey 12-7
  12.1.5 Data Analysis and Data-Flow 12-9
12.2 Lay out Description Reference Frame 12-9
  12.2.1 Lattice Coordinate System 12-9
  12.2.2 Tolerance Lists 12-10
  12.2.3 Relationship between Coordinate Systems 12-10
12.3 Fiducializing Magnets 12-10
12.4 Absolute Positioning 12-10
  12.4.1 Undulator Absolute Positioning 12-11
    Undulator Anchor Hole Layout Survey 12-11
    Pre-alignment of Girder Supports and Magnet Movers 12-11
    Absolute Quadrupole Positioning 12-12
    Quality Control Survey 12-12
  12.4.2 Transport Line and Experimental Area Absolute Positioning 12-12
12.5 Relative Alignment 12-12
  12.5.1 Relative Undulator Alignment 12-12
    Introduction 12-12
    Relative Quadrupole Positioning 12-12
    Undulator Alignment 12-13
  12.5.2 Linac Smoothing 12-13
    Purpose of Linac Smoothing 12-13
    Linac Straightness Measurement Procedure 12-14
  12.5.3 Relative Alignment of Transport Line and Experimental Area Components 12-15
12.6 Undulator Monitoring System 12-15
12.7 References 12-15
13 Radiation Issues  
  Technical Synopsis 13-1
13.1 Radiation Concerns Downstream of the Undulator 13-1
13.2 Radiation Issues in the Undulator 13-1
  13.2.1 Introduction 13-1
  13.2.2 Beam Scattering on the Residual Gas 13-2
  13.2.3 Spontaneous Radiation 13-2
  13.2.4 Bremsstrahlung from Halo on Collimators 13-5
    Normal Incidence 13-5
    Grazing Angle Incidence 13-6
  13.2.5 Induced Activity 13-8
13.3 References 13-9
A Parameter Tables  
Table Description  
1 Beam Tracking A-1
2 Parameter Summary A-2
3 Gun Laser A-3
4 Injector - rf Photocathode Gun A-4
5 Injector - Accelerator A-5
6 Injector - Dogleg A-6
7 General Linac Parameters A-8
8 Linac-1 A-9
9 Bunch Compressor-1 A-11
10 Linac-2 A-13
11 Bunch Compressor-2 A-15
12 Linac-3 A-17
13 Linac to Undulator Transport A-19
14 Undulator A-21
15 FEL A-25
16 Electron Beam Dump A-27
17 X-ray Optics A-28

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Page last modified by Heinz-Dieter Nuhn, SSRL on April 25, 2003