Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Physics

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  • Slide 1
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Physics Requirements and Alignment Heinz-Dieter Nuhn, SLAC / LCLS April 7, 2005 Final Break Length Choice Mitigation of AC Conductivity Wakefield Effects Undulator Tolerance Budget Considerations Cradle Component Arrangement and Alignment Earth Magnetic Field Compensation Radiation Damage Calculations Final Break Length Choice Mitigation of AC Conductivity Wakefield Effects Undulator Tolerance Budget Considerations Cradle Component Arrangement and Alignment Earth Magnetic Field Compensation Radiation Damage Calculations
  • Slide 2
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Break Lengths Old Strategy Characteristic Lengths Length of Undulator Strongback (Segment): L seg = 3.4 m Distance for 113 x 2 Phase Slippage: L 0 = 3.668 m Distance for 2 Phase Slippage in Field Free Space: L inc = u (1+K 2 /2) = 0.214 m Standard Break Lengths Used Use parameter n to characterize different phase length choices L n = L 0 - L seg +(n-1)L inc Use 2 Short Breaks Followed by 1 Long Break in n-Pattern 2 2 4 [0.482 m 0.482 m 0.910 m] Fine Tuning of Initial Break Length Suggested by N. Vinokurov based on Simulations by R. Dejus and N. Vinokurov using Linear Simulation Code, RON Small length increases for first 3 break lengths [0.045 m 0.020 m 0.005 m] Total Undulator Length (from beginning of strongback 1 end of strongback 33): L und = 131.97 m Characteristic Lengths Length of Undulator Strongback (Segment): L seg = 3.4 m Distance for 113 x 2 Phase Slippage: L 0 = 3.668 m Distance for 2 Phase Slippage in Field Free Space: L inc = u (1+K 2 /2) = 0.214 m Standard Break Lengths Used Use parameter n to characterize different phase length choices L n = L 0 - L seg +(n-1)L inc Use 2 Short Breaks Followed by 1 Long Break in n-Pattern 2 2 4 [0.482 m 0.482 m 0.910 m] Fine Tuning of Initial Break Length Suggested by N. Vinokurov based on Simulations by R. Dejus and N. Vinokurov using Linear Simulation Code, RON Small length increases for first 3 break lengths [0.045 m 0.020 m 0.005 m] Total Undulator Length (from beginning of strongback 1 end of strongback 33): L und = 131.97 m
  • Slide 3
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Break Lengths GINGER Simulation Summary As undulator gets closer to construction phase lock-down of segment spacing is required. R. Dejus requests checking of RON results with nonlinear FEL simulation codes before break length distances are being frozen. Phase correction scheme was tested recently by Bill Fawley and Sven Reiche using non-linear FEL codes, GINGER and GENESIS, respectively. With canted poles, phase corrections can be implemented with K adjustments rather than break lengths adjustments. The simulations used changes in break length. As undulator gets closer to construction phase lock-down of segment spacing is required. R. Dejus requests checking of RON results with nonlinear FEL simulation codes before break length distances are being frozen. Phase correction scheme was tested recently by Bill Fawley and Sven Reiche using non-linear FEL codes, GINGER and GENESIS, respectively. With canted poles, phase corrections can be implemented with K adjustments rather than break lengths adjustments. The simulations used changes in break length.
  • Slide 4
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Break Lengths GINGER Simulations Time Domain Results GINGER Simulations for three different applications of the Vinokurov/Dejus correction Reduced [-0.045 m, -0.020 m, -0.005 m] Nominal Increased [+0.045 m, +0.020 m, +0.005 m] Increased lengths produce slightly more power but no significant change in gain length. GINGER Simulations for three different applications of the Vinokurov/Dejus correction Reduced [-0.045 m, -0.020 m, -0.005 m] Nominal Increased [+0.045 m, +0.020 m, +0.005 m] Increased lengths produce slightly more power but no significant change in gain length. William Fawley
  • Slide 5
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Break Lengths GENESIS Simulations Time Domain Results GENESIS results comparable to those from GINGER. Sven Reiche
  • Slide 6
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Break Lengths GINGER Simulations Spectrum During linear regime uncorrected break pattern gives best results. Towards end of undulator no significant effect of corrections General outcome: No need for break in regular break pattern. New break pattern will consist of 22 short and 10 long break lengths only. During linear regime uncorrected break pattern gives best results. Towards end of undulator no significant effect of corrections General outcome: No need for break in regular break pattern. New break pattern will consist of 22 short and 10 long break lengths only. William Fawley
  • Slide 7
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Break Lengths (Old Strategy) New Strategy Characteristic Lengths Length of Undulator Strongback (Segment): L seg = 3.4 m Distance for 113 x 2 Phase Slippage: L 0 = (3.668 m) 3.656 m Distance for 2 Phase Slippage in Field Free Space: L inc = u (1+K 2 /2) = 0.214 m Standard Break Lengths Used Use parameter n to characterize different phase length choices L n = L 0 - L seg +(n-1)L inc Use 2 Short Breaks Followed by 1 Long Break in n-Pattern 2 2 4 ([0.482 m 0.482 m 0.910 m]) [0.470 m 0.470 m 0.898 m] Fine Tuning of Initial Break Length Suggested by N. Vinokurov based on Simulations by R. Dejus and N. Vinokurov using Linear Simulation Code, RON Small length increases for first 3 break lengths [0.045 m 0.020 m 0.005 m] Total Undulator Length (from beginning of strongback 1 end of strongback 33): L und = (131.97 m) 131.52 m Characteristic Lengths Length of Undulator Strongback (Segment): L seg = 3.4 m Distance for 113 x 2 Phase Slippage: L 0 = (3.668 m) 3.656 m Distance for 2 Phase Slippage in Field Free Space: L inc = u (1+K 2 /2) = 0.214 m Standard Break Lengths Used Use parameter n to characterize different phase length choices L n = L 0 - L seg +(n-1)L inc Use 2 Short Breaks Followed by 1 Long Break in n-Pattern 2 2 4 ([0.482 m 0.482 m 0.910 m]) [0.470 m 0.470 m 0.898 m] Fine Tuning of Initial Break Length Suggested by N. Vinokurov based on Simulations by R. Dejus and N. Vinokurov using Linear Simulation Code, RON Small length increases for first 3 break lengths [0.045 m 0.020 m 0.005 m] Total Undulator Length (from beginning of strongback 1 end of strongback 33): L und = (131.97 m) 131.52 m
  • Slide 8
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Mitigation of AC-Conductivity Wakefield Effects Change Vacuum Pipe Properties (See Bane talk) Change Surface Material from Copper to Aluminum Change Cross Section from Round to Oblong (10x5 mm) Move to Low-Charge Operating Point (see Emma talk) Use Tapering to Enhance Gain (see Huang talk) Change Vacuum Pipe Properties (See Bane talk) Change Surface Material from Copper to Aluminum Change Cross Section from Round to Oblong (10x5 mm) Move to Low-Charge Operating Point (see Emma talk) Use Tapering to Enhance Gain (see Huang talk)
  • Slide 9
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Revisiting the Undulator Tolerance Budget Separate budgets exist for undulator tolerances Undulator Field Tuning Segment Alignment BBA Floor Stability A Monte Carlo model is being developed which simultaneously includes all of the above errors Calculates the cumulative phase error with MC statistics Shows the relative importance of different tolerances Next step is to test putative tolerance budgets against FEL code, including beam tolerances. Answer the question: For a give overall tolerance budget, what is the probability that the FEL flux will be above 10 12 photons/pulse? Separate budgets exist for undulator tolerances Undulator Field Tuning Segment Alignment BBA Floor Stability A Monte Carlo model is being developed which simultaneously includes all of the above errors Calculates the cumulative phase error with MC statistics Shows the relative importance of different tolerances Next step is to test putative tolerance budgets against FEL code, including beam tolerances. Answer the question: For a give overall tolerance budget, what is the probability that the FEL flux will be above 10 12 photons/pulse? Jim Welch
  • Slide 10
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Undulator Segment Alignment Tolerance Based on K Tolerance K depends on vertical distance from mid-plane. Canted poles make K also dependent on horizontal position Tolerance Amplitudes Horizontal +/- 180 microns Vertical +/- 70 microns Based on K Tolerance K depends on vertical distance from mid-plane. Canted poles make K also dependent on horizontal position Tolerance Amplitudes Horizontal +/- 180 microns Vertical +/- 70 microns
  • Slide 11
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Cradle Component Arrangement and Alignment Problem Characterization Two-Fold Problem for Segment Alignment Initial installation and alignment to a straight line Alignment maintenance in the presence of ground motion Two Strategies under Consideration Cradle Coupling (Train-Link) Upstream-Downstream Beam Position Monitors Two-Fold Problem for Segment Alignment Initial installation and alignment to a straight line Alignment maintenance in the presence of ground motion Two Strategies under Consideration Cradle Coupling (Train-Link) Upstream-Downstream Beam Position Monitors
  • Slide 12
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Cradle Component Arrangement and Alignment Problem Description BBA will only correct alignment of quadrupoles. Undulator segment alignment is not affected. Additional alignment strategy needed. BBA will only correct alignment of quadrupoles. Undulator segment alignment is not affected. Additional alignment strategy needed. Quad Vertical Before BBA After BBA Before BBA After BBA Horizonal
  • Slide 13
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Cradle Component Arrangement and Alignment Solution 1: Cradle Coupling (CLIC) Coupling will be adjusted on appropriately designed setup in MMF. Quadrupole motion during BBA will through coupled cradle motion. Cradles will be aligned in the process. Coupling will be adjusted on appropriately designed setup in MMF. Quadrupole motion during BBA will through coupled cradle motion. Cradles will be aligned in the process. Quad Vertical Before BBA After BBA Before BBA After BBA Horizonal
  • Slide 14
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Cradle Component Arrangement and Alignment Solution 2: Downstream Monitor Monitor downstream of the undulator, fiducialized to the strongback, will be used to correct undulator alignment after BBA. Monitor could be RF Cavity BPM (either the one used for BBA or additional) or a pair of wire scanners. Use of BBA BPM for the strongback alignment restricts freedom in BPM positioning. Monitor downstream of the undulator, fiducialized to the strongback, will be used to correct undulator alignment after BBA. Monitor could be RF Cavity BPM (either the one used for BBA or additional) or a pair of wire scanners. Use of BBA BPM for the strongback alignment restricts freedom in BPM positioning. Quad Vertical Before BBA After BBA Before BBA After BBA Horizonal Monitor
  • Slide 15
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Cradle Component Arrangement and Alignment Winning Candidate Monitor (wire scanner) upstream of the undulator fiducialized the strongback to control undulator alignment after BBA. RF Cavity BPM for BBA mounted next to quadrupole. Monitor (wire scanner) upstream of the undulator fiducialized the strongback to control undulator alignment after BBA. RF Cavity BPM for BBA mounted next to quadrupole. Quad Vertical Before BBA After BBA Before BBA After BBA Horizonal Monitor BPM Beam
  • Slide 16
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Cradle Component Arrangement and Alignment Undulator to Quad Tolerance Budget Individual contributions are added in quadrature See R. Ruland Talk for discussion
  • Slide 17
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Earth Magnetic Field Compensation Strategy Earth Magnetic Field along Beam Trajectory in Undulator requires compensation. Estimated strength 0.430.06 Gauss : (0.180.03, -0.380.07,0.080.05) Gauss Based on Measurements by K. Hacker. (see LCLS-TN-05-4) Compensation Strategy: Position the Undulator on Magnetic Measurement Bench in same direction as in Undulator Tunnel. Add correction field if necessary. Compensate Earth Field Component in Undulator in Shimming Process Scheduling Issues Earth Magnetic Field along Beam Trajectory in Undulator requires compensation. Estimated strength 0.430.06 Gauss : (0.180.03, -0.380.07,0.080.05) Gauss Based on Measurements by K. Hacker. (see LCLS-TN-05-4) Compensation Strategy: Position the Undulator on Magnetic Measurement Bench in same direction as in Undulator Tunnel. Add correction field if necessary. Compensate Earth Field Component in Undulator in Shimming Process Scheduling Issues
  • Slide 18
  • Undulator Physics Requirements April 7, 2005 Heinz-Dieter Nuhn, SLAC / LCLS Facility Advisory Committee Meeting Nuhn@slac.stanford.edu Earth Magnetic Field Co...

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