1. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Overview of Proposed Parameter Changes Heinz-Dieter Nuhn, SLAC / SSRL October 24, 2003 Calculation of On-Axis Undulator Field Undulator Period Maximum Available Linac Energy Undulator Gap Selection New Break Distances Reduction in Focusing Strength Calculation of On-Axis Undulator Field Undulator Period Maximum Available Linac Energy Undulator Gap Selection New Break Distances Reduction in Focusing Strength

2. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL IntroductionIntroduction Original 6-mm gap height too small Increase in gap can open spectral range to 1 Å 50% Power Reduction of at 1.5 Å Undulator field adjustment comb structure Power tapering after saturation replenishes power Original 6-mm gap height too small Increase in gap can open spectral range to 1 Å 50% Power Reduction of at 1.5 Å Undulator field adjustment comb structure Power tapering after saturation replenishes power

3. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Workshop Focus Undulator Period Reduction of maximum available linac energy Undulator gap \height increase Longer break distances Weaker FODO lattice Undulator Period Reduction of maximum available linac energy Undulator gap \height increase Longer break distances Weaker FODO lattice

4. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL PresentationsPresentations Charge – M. Reichanadter Undulator design requirements – S. Milton Description of new parameters – H.-D. Nuhn Status of field adjustment comb – J. Noonan FEL simulation work using new parameters GENESIS 1.3 – S. Reiche GINGER – W.M. Fawley RON – R. Dejus BBA with new parameters – P. Emma Charge – M. Reichanadter Undulator design requirements – S. Milton Description of new parameters – H.-D. Nuhn Status of field adjustment comb – J. Noonan FEL simulation work using new parameters GENESIS 1.3 – S. Reiche GINGER – W.M. Fawley RON – R. Dejus BBA with new parameters – P. Emma

5. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Expected Workshop Outcome Signed Document: Workshop Summary Target Date: Mid November 2003 Purpose Implement the new parameters Document the changes Signed Document: Workshop Summary Target Date: Mid November 2003 Purpose Implement the new parameters Document the changes

6. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Halbach formula for hybrid undulator is used to estimate relation between gap/period and on-axis field Measured prototype field 5.3% larger than estimated Halbach formula for hybrid undulator is used to estimate relation between gap/period and on-axis field Measured prototype field 5.3% larger than estimated Adjusting Estimate of On-Axis Undulator Field

7. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Undulator Period Present undulator period length of 3 cm is near optimum for shortest gain length Change of undulator period length would require more man-power and time than available before next review Undulator period length will be kept at u = 3 cm Present undulator period length of 3 cm is near optimum for shortest gain length Change of undulator period length would require more man-power and time than available before next review Undulator period length will be kept at u = 3 cm

8. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Maximum Available Linac Energy 14.35 GeV has been nominal energy to reach 1.5 Å Loss of available linac energy due to Removal of linac section Off-crest acceleration New maximum energy set to 14.1 GeV to restore operational overhead Requires change in K value 14.35 GeV has been nominal energy to reach 1.5 Å Loss of available linac energy due to Removal of linac section Off-crest acceleration New maximum energy set to 14.1 GeV to restore operational overhead Requires change in K value

9. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Undulator Gap Selection Undulator gap height changes still possible Present gap height: 6 mm Gap height corrected for measured field: 6.35 mm Parameter correction for reduced maximum energy Larger gap gives access to short wavelength 1.0 Å Undulator gap height changes still possible Present gap height: 6 mm Gap height corrected for measured field: 6.35 mm Parameter correction for reduced maximum energy Larger gap gives access to short wavelength 1.0 Å New Parameters

10. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL 1.5 Å at Reduced Electron Beam Energy With the 8.2 mm gap the 1.5 Å radiation is produced at lower energy (14.35 GeV 11.46 GeV) and smaller undulator parameter (3.711 2.838). FEL output power reduced by 50 %. FEL output power reduced by 50 %. Problem for experiments that need as large a number of photons a possible, such as imaging of bio- molecules. Solution: New Field Adjustment Comb allows tapering the undulator after the saturation point. Tapering by about 0.3 % over the last 30 m more than restores the lost energy With the 8.2 mm gap the 1.5 Å radiation is produced at lower energy (14.35 GeV 11.46 GeV) and smaller undulator parameter (3.711 2.838). FEL output power reduced by 50 %. FEL output power reduced by 50 %. Problem for experiments that need as large a number of photons a possible, such as imaging of bio- molecules. Solution: New Field Adjustment Comb allows tapering the undulator after the saturation point. Tapering by about 0.3 % over the last 30 m more than restores the lost energy

11. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL New Break Lengths Separations between undulator modules (breaks) designed to produce slippage by integer number of optical wavelength. Break increments for adding slippage of 1 optical wavelength is  L B = u (1+K 2 /2).  L B =23.7 cm (old); 15.1 cm (new) Present design uses break pattern 1-1-2 which corresponds to the lengths sequence 18.7 cm – 18.7 cm – 42.1 cm 18.7 cm gives not enough space for quads, BPMs, etc. 42.1 cm gives not enough space for x-ray diagnostics New break pattern 3-3-4 (or 3-3-5) corresponding to length sequence 44.6 cm – 44.6 cm – 55.7 cm (or 44.6 cm – 44.6 cm – 70.8 cm) Separations between undulator modules (breaks) designed to produce slippage by integer number of optical wavelength. Break increments for adding slippage of 1 optical wavelength is  L B = u (1+K 2 /2).  L B =23.7 cm (old); 15.1 cm (new) Present design uses break pattern 1-1-2 which corresponds to the lengths sequence 18.7 cm – 18.7 cm – 42.1 cm 18.7 cm gives not enough space for quads, BPMs, etc. 42.1 cm gives not enough space for x-ray diagnostics New break pattern 3-3-4 (or 3-3-5) corresponding to length sequence 44.6 cm – 44.6 cm – 55.7 cm (or 44.6 cm – 44.6 cm – 70.8 cm)

12. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Special Initial Break Lengths Present design uses special values for the first three break lengths: 28.1 cm – 25.6 cm – 47. 3 cm compared to the regular values of 18.7 cm – 18.7 cm – 42.1 cm Introduced by Nikolay Vinokurov to improve the overall FEL gain. Estimate for new special lengths is 46.6 cm – 45.0 cm – 59.0 cm (74.1 cm) New numbers will be checked by simulation with RON and other codes. Present design uses special values for the first three break lengths: 28.1 cm – 25.6 cm – 47. 3 cm compared to the regular values of 18.7 cm – 18.7 cm – 42.1 cm Introduced by Nikolay Vinokurov to improve the overall FEL gain. Estimate for new special lengths is 46.6 cm – 45.0 cm – 59.0 cm (74.1 cm) New numbers will be checked by simulation with RON and other codes.

13. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL UNDULATOR 3410 446 11599 mm Horizontal Steering Coil Vertical Steering Coil Beam Position Monitor 557 X-Ray Diagnostics Quadrupoles Undulator Schematic (Regular Section) 127184 mmTotal Length (708) (11750 mm) (128845 mm)

14. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL Reduction in Focusing Strength Present focusing lattice uses 5-cm-long permanent quadrupoles with gradient of 106 T/m ( = 18 m at 14.35 GeV) New undulator parameters require reduced gradient. Gradient reduced to 60 T/m ( = 30 m at 14.04 GeV) Transverse quadrupole displacement used for steering Reduced gradients require larger quadrupole displacement for same kick angle. Beam Based Alignment procedure has been checked Present focusing lattice uses 5-cm-long permanent quadrupoles with gradient of 106 T/m ( = 18 m at 14.35 GeV) New undulator parameters require reduced gradient. Gradient reduced to 60 T/m ( = 30 m at 14.04 GeV) Transverse quadrupole displacement used for steering Reduced gradients require larger quadrupole displacement for same kick angle. Beam Based Alignment procedure has been checked

15. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL FODO Lattice Energy Limitations 1.5 Å 15 Å 1.5 Å 1 Å

16. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Operating Points for 1 nC Bunch Charge (Old) LCLS Operating Point at 1.5 Å LCLS Operating Point at 15 Å

17. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Operating Points for 1 nC Bunch Charge (New) LCLS Operating Point at 1.5 Å Operating Point

18. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Operating Points for 1 nC Bunch Charge (New) LCLS Operating Point at 15 Å Operating Point

19. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL LCLS Operating Points for 1 nC Bunch Charge (New) LCLS Operating Point at 1.0 Å Operating Point

20. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL OLDNEW Undulator Typeplanar hybrid planar hybrid Magnet MaterialNdFeB NdFeB Wiggle Planehorizontalhorizontal Gap68.2mm Period Length3.03.0cm Peak On-Axis Field1.3251.014T K3.712.84 Module Length3.413.41m Number of Modules3333 Initial Break Lengths0.281,0.256,0.4730.466,0.450,0.590m Regular Break Lengths0.187-0.4210.406-0.557m Undulator Magnet Length112.5112.5m Undulator Device Length (incl. Breaks)121.1127.2m Undulator Filling Factor 9388% OLDNEW Undulator Typeplanar hybrid planar hybrid Magnet MaterialNdFeB NdFeB Wiggle Planehorizontalhorizontal Gap68.2mm Period Length3.03.0cm Peak On-Axis Field1.3251.014T K3.712.84 Module Length3.413.41m Number of Modules3333 Initial Break Lengths0.281,0.256,0.4730.466,0.450,0.590m Regular Break Lengths0.187-0.4210.406-0.557m Undulator Magnet Length112.5112.5m Undulator Device Length (incl. Breaks)121.1127.2m Undulator Filling Factor 9388% Summary of Nominal Undulator Design Changes

21. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL OLDNEW Lattice TypeFODO FODO Magnet Typepermanent permanent Nominal Magnet Length55cm QF Gradient10761T/m QD Gradient-106-60T/m Average  Function at 1.5 Å18.024.5m Lowest Usable Energy3.171.84GeV OLDNEW Lattice TypeFODO FODO Magnet Typepermanent permanent Nominal Magnet Length55cm QF Gradient10761T/m QD Gradient-106-60T/m Average  Function at 1.5 Å18.024.5m Lowest Usable Energy3.171.84GeV Summary of Nominal Focusing Lattice Changes

22. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL At 1.0 ÅOLDNEW Electron Beam Energy - 14.04GeV  - 27483 - 30m Rms beam radius - 36  m At 1.0 ÅOLDNEW Electron Beam Energy - 14.04GeV  - 27483 - 30m Rms beam radius - 36  m Summary of Electron Beam Parameters At 15 ÅOLDNEW Electron Beam Energy 4.45 3.64GeV  88807096 7.3 8.9m Rms beam radius35 39  m At 15 ÅOLDNEW Electron Beam Energy 4.45 3.64GeV  88807096 7.3 8.9m Rms beam radius35 39  m At 1.5 ÅOLDNEW Electron Beam Energy14.35 11.47GeV  28082 22439 18.024.4m Rms beam radius2836  m At 1.5 ÅOLDNEW Electron Beam Energy14.35 11.47GeV  28082 22439 18.024.4m Rms beam radius2836  m

23. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL ConclusionsConclusions New values have been proposed for undulator gap, maximum electron beam energy, break length pattern, and quadrupole gradients Benefits are more room for vacuum chamber more space for diagnostics components between undulator modules increase of accessible wavelength range Reduction in photon number can be more than compensated by tapering using the new Field Adjuster Comb. New values have been proposed for undulator gap, maximum electron beam energy, break length pattern, and quadrupole gradients Benefits are more room for vacuum chamber more space for diagnostics components between undulator modules increase of accessible wavelength range Reduction in photon number can be more than compensated by tapering using the new Field Adjuster Comb.

24. Overview of Proposed Parameter Changes Nuhn@slac.stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Parameter Workshop, May 21-23, 2003 Heinz-Dieter Nuhn, SLAC / SSRL End of Presentation