1. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Introduction to the LCLS Undulators Heinz-Dieter Nuhn, SLAC / LCLS October 14, 2004 Undulator Overview Requirement Documents Undulator Fields and Tapering Cradle Components and Motion MMF Physics Requirements Undulator Overview Requirement Documents Undulator Fields and Tapering Cradle Components and Motion MMF Physics Requirements

2. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Linac Coherent Light Source Near Hall Far Hall Undulator

3. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu

4. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Undulator Segment Prototype

5. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Undulator Requirement Documents Index URL: http://www-ssrl.slac.stanford.edu/lcls/requirements.html

6. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Undulator Type planar hybrid Magnet Material NdFeB Wiggle Planehorizontal Gap6.8mm Period Length30.0 ± 0.05mm Effective On-Axis Field1.249T Standard Effective K3.49290 ± 0.015% Range of Effective Undulator Parameter K3.5000 - 3.4929 (3.4804) Accumulated Segment Phase Error Tolerance 10degrees (at any point along segment) Module Length3.40m Number of Modules33 Undulator Magnet Length112.2m Standard Break Lengths 48.2 - 48.2 - 94.9 cm Nominal Total Device Length130.954m Quadrupole Magnet Technology EMQ Nominal Quadrupole Magnet Length 7cm Integrated Quadrupole Gradient 3.0T Undulator Type planar hybrid Magnet Material NdFeB Wiggle Planehorizontal Gap6.8mm Period Length30.0 ± 0.05mm Effective On-Axis Field1.249T Standard Effective K3.49290 ± 0.015% Range of Effective Undulator Parameter K3.5000 - 3.4929 (3.4804) Accumulated Segment Phase Error Tolerance 10degrees (at any point along segment) Module Length3.40m Number of Modules33 Undulator Magnet Length112.2m Standard Break Lengths 48.2 - 48.2 - 94.9 cm Nominal Total Device Length130.954m Quadrupole Magnet Technology EMQ Nominal Quadrupole Magnet Length 7cm Integrated Quadrupole Gradient 3.0T Summary of Nominal Undulator Parameters

7. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Micro Tapering V: K values The following list contains the nominal K values for the 33 undulator segments for the 6.8 mm gap height: This amount of tapering requires only a negligible adjustment for break lengths. After achieving goal performance, tapering beyond saturation point is desirable. (up to 0.56% total) This amount of tapering requires only a negligible adjustment for break lengths. After achieving goal performance, tapering beyond saturation point is desirable. (up to 0.56% total) Undulator SegmentK eff 13.5000 23.4998 33.4996 43.4993 53.4991 63.4989 73.4987 83.4984 93.4982 103.4980 113.4978 123.4976 133.4973 143.4971 153.4969 163.4967 173.4964 183.4962 193.4960 203.4958 213.4955 223.4953 233.4951 243.4949 253.4947 263.4944 273.4942 283.4940 293.4938 303.4935 313.4933 323.4931 333.4929 To compensate energy loss from spontaneous radiation

8. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Undulator Pole Canting Canting comes from wedged spacers 4.5 mrad cant angle Gap can be adjusted by lateral displacement of wedges 1 mm shift means 4.5 microns in gap, or 8.2 Gauss B eff adjusted to desired value Source: Liz Moog Suggested by J. Pflueger, DESY

9. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Canting the poles helps in many ways Facilitates final setting of B eff Remote control of position allows run-time adjustment Allows compensating for temperature effect on field strength: ±1.0°C temperature error would require ±1.2 mm lateral shift of undulator Source Liz Moog

10. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Effective B field vs. x Measured slope of 6.6 Gauss/mm agrees with calculations (~ 5.7 Gauss/mm for 3 mrad cant) Field variation allowance between segments is  B/B = 1.5x10 -4, or  B = 2 Gauss, which translates to  x = 0.3 mm ( or 1 micron in gap) Source Liz Moog See I. Vasserman’s Talk for Prototype Measurements

11. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Using Undulator Roll-Away and K Adjustment Function Neutral; K=3.4965;  x=+0.0 mmFirst; K=3.5000;  x=-1.5 mm Last; K=3.4929;  x=+1.5 mmRollAway; K=0.0000;  x=+100 mm PowerTp; K=3.4804;  x=+7.0 mm

12. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Cradle Components Cradle Components include Undulator strongback arrangement mounted on horizontal slides Vacuum chamber support BPM Quadrupole WPM sensors HLS sensors (diagnostics chamber) The undulator strongback arrangement (segment) is mountable on and removable from the cradle with the vacuum chamber in place and without compromising the alignment of the vacuum chamber. Undulator strongback can be taken off the cradle for magnetic measurements Complete cradle assembly will be aligned on Coordinate Measurement Machine (CMM). Cradle Components include Undulator strongback arrangement mounted on horizontal slides Vacuum chamber support BPM Quadrupole WPM sensors HLS sensors (diagnostics chamber) The undulator strongback arrangement (segment) is mountable on and removable from the cradle with the vacuum chamber in place and without compromising the alignment of the vacuum chamber. Undulator strongback can be taken off the cradle for magnetic measurements Complete cradle assembly will be aligned on Coordinate Measurement Machine (CMM).

13. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Motions of the Cradle and of Cradle Components Remotely Controlled Motion: Cradle: x, y, roll x, y motion of cradle ends are coupled roll motion capability is to be used to keep roll constant Undulator: x Horizontal slide stages move undulator strongback independent of cradle and vacuum chamber Manual Adjustment: Cradle Movers to fixed support girder (AMP) Quadrupole and BPM position to cradle. Remotely Controlled Motion: Cradle: x, y, roll x, y motion of cradle ends are coupled roll motion capability is to be used to keep roll constant Undulator: x Horizontal slide stages move undulator strongback independent of cradle and vacuum chamber Manual Adjustment: Cradle Movers to fixed support girder (AMP) Quadrupole and BPM position to cradle.

14. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu MMF Physics Requirements Earth Magnetic Field Compensation Establish environmental magnet field in MMF to be equal to the environmental field at target location in undulator hall to better than 0.01 T. MMF Temperature Average ambient MMF temperature needs be 20.0 ± 0.1 o C to match the ambient undulator hall temperature of 20.0 ± 0.2 o C. Magnetic Undulator Shimming to Reduce phase error below 10 degrees at 0.15 nm. Reduce 1 st Field Integral below ±40×10 -6 Tm Reduce 2 nd Field Integral below ±50×10 -6 Tm 2 Definition of Standard Undulator Axis (SUSA) so that SUSA is Parallel to Undulator Center Line Effective K along SUSA is 3.4965 ± 0.0005 Alignment of Quadrupole on Cradle with respect to CA*. Tolerance: 40  m (rms). Routine Operational Checking of Undulator Segments Remove 3 segments / month from undulator hall and replace with spares Characterize magnetic field of removed segments and prepare for re-installation. Earth Magnetic Field Compensation Establish environmental magnet field in MMF to be equal to the environmental field at target location in undulator hall to better than 0.01 T. MMF Temperature Average ambient MMF temperature needs be 20.0 ± 0.1 o C to match the ambient undulator hall temperature of 20.0 ± 0.2 o C. Magnetic Undulator Shimming to Reduce phase error below 10 degrees at 0.15 nm. Reduce 1 st Field Integral below ±40×10 -6 Tm Reduce 2 nd Field Integral below ±50×10 -6 Tm 2 Definition of Standard Undulator Axis (SUSA) so that SUSA is Parallel to Undulator Center Line Effective K along SUSA is 3.4965 ± 0.0005 Alignment of Quadrupole on Cradle with respect to CA*. Tolerance: 40  m (rms). Routine Operational Checking of Undulator Segments Remove 3 segments / month from undulator hall and replace with spares Characterize magnetic field of removed segments and prepare for re-installation. *Cradle Axis (CA) is identical to SUSA when undulator segment is in neutral horizontal position See J. Welch’s and I Vasserman’s talks for details

15. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu Requirements and Specifications are available from the LCLS WEB site. The main Physics Requirements Document (PRD) outlining the requirements for the undulator system is PRD1.4-001. The MMF specifications are found in PRD1.4-002. Main Physics Task to be done at the MMF are Undulator magnetic field tuning to specifications under same surrounding magnetic field and temperature conditions as at target location in undulator hall. Quadrupole and BPM alignment on cradle with respect to undulator strongback Characterization of undulators that have been used in operation All undulator segments will be tuned identically. Micro-tapering implies that every undulator core be at a slightly different K value, which will be accomplished by horizontal positioning. Requirements and Specifications are available from the LCLS WEB site. The main Physics Requirements Document (PRD) outlining the requirements for the undulator system is PRD1.4-001. The MMF specifications are found in PRD1.4-002. Main Physics Task to be done at the MMF are Undulator magnetic field tuning to specifications under same surrounding magnetic field and temperature conditions as at target location in undulator hall. Quadrupole and BPM alignment on cradle with respect to undulator strongback Characterization of undulators that have been used in operation All undulator segments will be tuned identically. Micro-tapering implies that every undulator core be at a slightly different K value, which will be accomplished by horizontal positioning. Conclusions http://ssrl.slac.stanford.edu/lcls/internals/requirements.html

16. LCLS Undulators October 14, 2004 Heinz-Dieter Nuhn, SLAC / SSRL MMF Review Nuhn@slac.stanford.edu End of Presentation