1. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC LCLS Undulator Alignment and Motion Review Beam-Based Alignment (BBA) Paul Emma, SLAC Oct. 21, 2005 LCLS Undulator Alignment and Motion Review Beam-Based Alignment (BBA) Paul Emma, SLAC Oct. 21, 2005 Brief Review of Method Simulations Drift Tolerances Brief Review of Method Simulations Drift Tolerances LCLS

2. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Motivation For SASE FEL at 1.5 Å: Electron trajectory through undulator needs to be straight to <5  m over ~10 m, Traditional survey methods inadequate here, BPM data acquired for several beam energies (14, 7.0, 4.5 GeV) can resolve this level, Beam-based, energy-variation method is sensitive to all fields, not just misaligned quadrupole magnets For SASE FEL at 1.5 Å: Electron trajectory through undulator needs to be straight to <5  m over ~10 m, Traditional survey methods inadequate here, BPM data acquired for several beam energies (14, 7.0, 4.5 GeV) can resolve this level, Beam-based, energy-variation method is sensitive to all fields, not just misaligned quadrupole magnets

3. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC The Method BPM readings, m i, written as sum of upstream kicks + offset, b i Kicks are sensitive to momentum, p k, while offsets, b i, are not BPM readings, m i, written as sum of upstream kicks + offset, b i Kicks are sensitive to momentum, p k, while offsets, b i, are not s b i > 0  E = 0  E < 0 quad offsets and/or pole errors i th BPM  j  j

4. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Reference line defined by incoming x 0, x 0 launch conditions...The Method 1/p mimimimi offset =  b i (15 GeV/c)  1 (7.0 GeV/c)  1 (4.5 GeV/c)  1 p  linear only if C ij independent of p

5. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Schematic layout before BBA (cartoon example) ~300  m UNDULATOR (132 m) LINAC best final trajectory steering elements x0x0x0x0 x0x0x0x0 initial incoming launch error Undulator misaligned w.r.t. linac axis with uncorrelated and correlated* (‘random walk’) component * suggested by C. Adolphsen BPMsquads

6. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Final trajectory after BBA (cartoon example) LINAC Beam is launched straight down undulator, with possible inconsequential kink at boundary dispersion generated is insignificant Quadrupole magnets moved onto straight line and BPM offsets subtracted in software, while undulators track quadrupoles

7. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Input errors used for simulation 100 100 0.04  0.5 200 200

8. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Initial BPM and quad misalignments (w.r.t. linac axis) + Quadrupole positions positions  BPM offsets quad positions BPM offsets Now launch beam through undulator 

9. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Initial trajectory before any correction applied + Quadrupole positions positions o BPM readback e  trajectory e  trajectory ‘real’ trajectory quad positions BPM readings

10. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC After weighted steering – prior to BBA procedure + Quadrupole positions positions o BPM readback e  trajectory e  trajectory

11. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC After 1 st pass of BBA (13.6 GeV) + Quadrupole positions positions o BPM readback e  trajectory e  trajectory   3322°  x  44  m  y  33  m

12. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Steering coils used for small, final corrections…  7  m Use steering coils for final iterations (quad move equivalent down to 0.5  m) BPM

13. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC After 3 rd pass of BBA (13.6 GeV) + Quadrupole positions positions o BPM readback e  trajectory e  trajectory RON (FEL-code) simulation shows L sat increased by <1 gain-length; R. Dejus, N.Vinokurov   98°  x  3.2  m  y  2.5  m rms beam size:  36  m

14. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Run BBA on 25 Different Random Seeds 1-  m BPM resolution + 100-  m initial BPM & quad offsets x,yx,yx,yx,y x & y mover distrib.

15. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC FEL code evaluation of BBA simulation results... B. Fawley, H.-D. Nuhn, S. Reiche, PE FEL Saturation Power at 1.5 Å FEL Saturation Length at 1.5 Å

16. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Alignment drift during BBA procedure… Quadrupole and BPM alignment may change during BBA procedure. One iteration of BBA procedure will require <1 hr after full development and experience. Simulate alignment drift during BBA, using  2.5-  m quad and BPM (separately) changes, which are uncorrelated 

17. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC  2.5-  m uniform quad and BPM changes during BBA procedure + Quadrupole positions positions o BPM readback e  trajectory e  trajectory   167° REQUIRE: <  2  m quad/BPM stability over 1 hr

18. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Allow  5-  m uniform quad and BPM drift over long term (24 hrs) After beam-based alignment  10  m quad and BPM drift MICADO steering applied Tolerance set at  5  m over 24 hrs

19. Emma@SLAC.Stanford.edu Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center LCLS Undulator Alignment and Motion Review, Oct. 21, 2005 Paul Emma, SLAC Summary LCLS BPMs resolve trajectory to 1-2  m rms Quad positions and BPM readings ‘drift’ <2  m over 1-hr procedure Trajectory is stable to <20% of beam size (already demonstrated in FFTB) BBA procedure repeated no more than once per week given  5  m drift tolerance Alignment can be achieved at adequate level using beam-based technique, given that…