Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 1 LCLS Undulator Diagnostics and Comissioning Workshop Wrap-up John N. Galayda, Stanford Linear Accelerator Center 20 January 2004 Challenges of Commissioning the FEL Alignment Undulator K Undulator Damage Undulator Diagnostics CommissioningOperationCharge Challenges of Commissioning the FEL Alignment Undulator K Undulator Damage Undulator Diagnostics CommissioningOperationCharge

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 2 Beam-Based Alignment, Quad Design Tolerances on Trajectory are Tight for SASE at 1.5Å Beam-based alignment, RFBPMs must deliver a good trajectory Dispersion-free steering delivers a “straight” trajectory But beam is not centered in quads at completion Absolute accuracy is not the crucial requirement- sensitivity is critical Ability to change quad gradient would be a significant advantage Iron/copper quads would be longer than 50mm-long permanent magnet quads New gradient is ~60 T/m, about 11 mm bore: 3,000 gauss on the pole? NLC has struggled with “variable” permanent magnet designs Difficult to vary the gradient without moving the magnetic center Electromagnets still perform best in this regard NLC needs beam centered in quads to 1 micron- we don’t Trim windings may be an acceptable option for LCLS Trim windings still leave a residual uncertainty about actual location of quad center “AC” center is not necessarily the same as the “DC” center Tolerances on Trajectory are Tight for SASE at 1.5Å Beam-based alignment, RFBPMs must deliver a good trajectory Dispersion-free steering delivers a “straight” trajectory But beam is not centered in quads at completion Absolute accuracy is not the crucial requirement- sensitivity is critical Ability to change quad gradient would be a significant advantage Iron/copper quads would be longer than 50mm-long permanent magnet quads New gradient is ~60 T/m, about 11 mm bore: 3,000 gauss on the pole? NLC has struggled with “variable” permanent magnet designs Difficult to vary the gradient without moving the magnetic center Electromagnets still perform best in this regard NLC needs beam centered in quads to 1 micron- we don’t Trim windings may be an acceptable option for LCLS Trim windings still leave a residual uncertainty about actual location of quad center “AC” center is not necessarily the same as the “DC” center

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 3 Challenges for Diagnostics in the Undulator Channel Tolerance on K of an undulator is around 1.5 x At this time, canted undulator poles provide preferred solution for K fine-tuning (3 milliradians) K tolerance equivalent to 300 micron horizontal displacement K tolerance equivalent to 50 micron vertical misplacement Piezo tuners may be deleted This displacement does little to the electron optics Dispersion-free steering gets beam to within 20 microns of quad centers If quads and undulators are aligned to within 25 microns, this tolerance is met This is not quite impossible; still pretty difficult This displacement does little to the spontaneous spectrum of 1 und. No one disputed this Tolerance on K of an undulator is around 1.5 x At this time, canted undulator poles provide preferred solution for K fine-tuning (3 milliradians) K tolerance equivalent to 300 micron horizontal displacement K tolerance equivalent to 50 micron vertical misplacement Piezo tuners may be deleted This displacement does little to the electron optics Dispersion-free steering gets beam to within 20 microns of quad centers If quads and undulators are aligned to within 25 microns, this tolerance is met This is not quite impossible; still pretty difficult This displacement does little to the spontaneous spectrum of 1 und. No one disputed this

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 4 Challenges for Diagnostics in the Undulator Channel Radiation Damage to Undulators is a Concern Interlocks will be implemented but tolerable losses are low ANL-APS actively studying radiation damage to storage ring undulators Can the diagnostics identify a damaged undulator? No one asserts that the LCLS diagnostics suite can do this Radiation Damage to Undulators is a Concern Interlocks will be implemented but tolerable losses are low ANL-APS actively studying radiation damage to storage ring undulators Can the diagnostics identify a damaged undulator? No one asserts that the LCLS diagnostics suite can do this

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 5 Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Charge – Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Commissioning Can diagnostics be used to troubleshoot the new hardware? Can diagnostics be used to guide path to saturation? Draft commissioning document emphasizes easier tolerances at long wavelength Implication is that achievement of saturation at 1.5 nm will lead to easier path to 0.15 nm saturation Implication of implication is reliance on FEE diagnostics Does the commissioning plan bear this out? Do simulations show convergence of K-tweaking and steering to optimum output? Commissioning Can diagnostics be used to troubleshoot the new hardware? Can diagnostics be used to guide path to saturation? Draft commissioning document emphasizes easier tolerances at long wavelength Implication is that achievement of saturation at 1.5 nm will lead to easier path to 0.15 nm saturation Implication of implication is reliance on FEE diagnostics Does the commissioning plan bear this out? Do simulations show convergence of K-tweaking and steering to optimum output?

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 6 Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Charge – Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Operations Will the diagnostics permit simple and speedy troubleshooting? Reliability/Availability goals of the LCLS will be those of a light source Progressive installation of undulators may work for commissioning, but In operation, this would require automated “removal” of undulators Routine replacement/measurement of undulators must be part of plan Operations troubleshooting needs attention Operations Will the diagnostics permit simple and speedy troubleshooting? Reliability/Availability goals of the LCLS will be those of a light source Progressive installation of undulators may work for commissioning, but In operation, this would require automated “removal” of undulators Routine replacement/measurement of undulators must be part of plan Operations troubleshooting needs attention

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 7 Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Charge – Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Light diagnostics are crucial Can the Inter-undulator diagnostics survive at high power? No good solution for 800 eV If not, are we placing too heavy a reliance on data taken with low charge? Will optimization at low charge allow us to reach optimum at higher charge 40 cm looks very tight A lot of work required to develop inter-undulator diagnostics Inter-undulaor diagnostics that work at all wavelengths are challenging Even at shorter wavelength, variable geometry of diagnostics is a mechanical challenge Rollaway undulators? How far must they move to be useful? Variable Gap would require a lot of R&D Light diagnostics are crucial Can the Inter-undulator diagnostics survive at high power? No good solution for 800 eV If not, are we placing too heavy a reliance on data taken with low charge? Will optimization at low charge allow us to reach optimum at higher charge 40 cm looks very tight A lot of work required to develop inter-undulator diagnostics Inter-undulaor diagnostics that work at all wavelengths are challenging Even at shorter wavelength, variable geometry of diagnostics is a mechanical challenge Rollaway undulators? How far must they move to be useful? Variable Gap would require a lot of R&D

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 8 Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Charge – Will the Undulator Diagnostics Serve Commissioning and Operations Needs for the LCLS? Do we have redundant diagnostics capability where appropriate? Diagnostics that check the diagnostics We are heavily dependent on FEE diagnostics I don’t see much redundancy yet FEL/Spont is very bad for the 0.15nm case Nothing to tune on in the first 40 meters What is the smallest PROJECTED energy spread we can produce at any (lower) charge? Can spontaneous radiation serve as our diagnostic? Do we need a hi-res monochromator on day 1? Do we have redundant diagnostics capability where appropriate? Diagnostics that check the diagnostics We are heavily dependent on FEE diagnostics I don’t see much redundancy yet FEL/Spont is very bad for the 0.15nm case Nothing to tune on in the first 40 meters What is the smallest PROJECTED energy spread we can produce at any (lower) charge? Can spontaneous radiation serve as our diagnostic? Do we need a hi-res monochromator on day 1?

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 9 Conclusions Gain versus z can be measured by turning off gain with an orbit kink In early commissioning there may be no measurable gain signal for meters when attempting to lase at 0.15 nm energy resolution is a must, to get rid of spontaneous Gain versus z can be measured by turning off gain with an orbit kink In early commissioning there may be no measurable gain signal for meters when attempting to lase at 0.15 nm energy resolution is a must, to get rid of spontaneous

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 10 Issues to be Addressed It is important to estimate how many gain lengths needed to produce a gain signal above spontaneous background ~10 -3 energy resolution is a must, to get rid of spontaneous investigate whether spontaneous radiation become a diagnostic for undulator alignment and quality Investigate whether roll-away undulators provide a useful degree of freedom for diagnosing problems in commissioning or operations It is important to estimate how many gain lengths needed to produce a gain signal above spontaneous background ~10 -3 energy resolution is a must, to get rid of spontaneous investigate whether spontaneous radiation become a diagnostic for undulator alignment and quality Investigate whether roll-away undulators provide a useful degree of freedom for diagnosing problems in commissioning or operations

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 11 Point of No Return

Wrap-up 20 January 2004 Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Diagnostics Workshop John N. Galayda, SLAC 12 End of Presentation