Undulator Gap Increase Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Meeting, June , 2004 Heinz-Dieter Nuhn, SLAC / LCLS Undulator Gap Increase Heinz-Dieter Nuhn, SLAC / LCLS June 28, 2004 Problem Description Impact on Performance Summary Problem Description Impact on Performance Summary

Undulator Gap Increase Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Meeting, June , 2004 Heinz-Dieter Nuhn, SLAC / LCLS Problem Description Present baseline design includes gap height of 6.5 mm Resulting in 250 microns or less of clearance on top and bottom of the vacuum chamber In order to support the remote roll-away option the APS requests a 200 microns increase in clearance on the top and bottom of the vacuum which corresponds to a gap increase from 6.5 to 6.9 mm If the effect of this gap increase is not compensated by change in magnet design or magnet material it will correspond to a reduction in nominal K value from to Expected performance impact of this reduction in K value is being discussed on the following pages. Present baseline design includes gap height of 6.5 mm Resulting in 250 microns or less of clearance on top and bottom of the vacuum chamber In order to support the remote roll-away option the APS requests a 200 microns increase in clearance on the top and bottom of the vacuum which corresponds to a gap increase from 6.5 to 6.9 mm If the effect of this gap increase is not compensated by change in magnet design or magnet material it will correspond to a reduction in nominal K value from to Expected performance impact of this reduction in K value is being discussed on the following pages.

Undulator Gap Increase Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Meeting, June , 2004 Heinz-Dieter Nuhn, SLAC / LCLS Impact of Gap Change I VARIABLE(Bold=input)UNITSLCLS NOV03LCLS JUN04ChangeLCLS NOV03LCLS JUN04Change Wiggler Typelinear r (Radiation wavelength) nm0.15 0%1.50 0% w (Wiggler period) (used) cm3.00 0%3.00 0% k w (Wiggler wave number)cm % % g w (Wiggler gap)cm % % B w (Wiggler peak field)(used)Tesla % % K (Wiggler parameter, peak) % % awaw % %  x,y,ext. (quad) m % %  n_rms (Normalized rms emittance) mm mrad % %  n,rms /  mm mrad43.56E E-65%286.99E E-65%  x (electron distribution rms  ) mm % %  ' x (electron divergence)  m rad % %  (Electron energy in unit of.511MeV) % % E (Electron Energy)GeV % % I peak (Peak electron beam current)A % % Peak Beam powerGW % % Particle densitiy n e m E E+22-5%3.34E E+21-5%   (rms energy spread) % %    x % % 1.5 Angstrom 15.0 Angstrom

Undulator Gap Increase Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Meeting, June , 2004 Heinz-Dieter Nuhn, SLAC / LCLS Impact of Gap Change II VARIABLE(Bold=input)UNITSLCLS NOV03LCLS JUN04ChangeLCLS NOV03LCLS JUN04Change  j (Radiation Beam Radius) (3D) mm % % Z r (Rayleigh Length) (3D)m % % L G (3D) [as in exp [z /LG(3D)]m % %  (3D) =  w /(4  L G sqrt(3)) E E-6-2%557.64E E-6-3% L E (3D)m % % 2  L c (3D) = 2  L E r / w mm % % 2  L c (3D) fs % % P sat (saturated power, 3D) correctedMW % % L sat (SASE length to saturation, 3D) corm % % Average PowerW244.6E E-3-8%226.7E E-3-10% Peak Photon FluxPh/s6.054E E+24-8%3.011E E+25-10% Average Photon FluxPh/pulse1.539E E+12-8%1.427E E+13-10% Average Photon FluxPh/s1.847E E+14-8%1.712E E+15-10%  ph,x (coherent photon distribution, rms) micron % %  ph,x' (coherent photon distribution, rms) micro-rad % % Repetition RateHz % % Spontaneous Energy per PulseJ21.4E-317.2E-3-20%2.3E-31.8E-3-20% Peak Spontaneous Power per PulseW84.4E+967.6E+9-20%4.8E+93.8E+9-20% Coherent Photons per Pulse1.539E E+12-8%1.427E E+13-10% Coherent Energy per PulsemJ % % Photon EnergykeV8.3E+0 0%826.6E-3 0% Peak Brilliance [Ph./s/mm 2 /mr 2 /.1%]1.639E E+33-8%2.942E E+31-10% Ave. Brilliance [Ph./s/mm 2 /mr 2 /.1%]5.001E E+22-8%1.672E E+21-10% 1.5 Angstrom 15.0 Angstrom

Undulator Gap Increase Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Meeting, June , 2004 Heinz-Dieter Nuhn, SLAC / LCLS ConclusionsConclusions A reduction in nominal K value from to will reduce the FEL output power (8 %) and increase gain length (1 %). Although the reduction of the number of output photons is small, an attempt should be made to minimize it by reviewing the optimization of the undulator design. A reduction in nominal K value from to will reduce the FEL output power (8 %) and increase gain length (1 %). Although the reduction of the number of output photons is small, an attempt should be made to minimize it by reviewing the optimization of the undulator design.

Undulator Gap Increase Linac Coherent Light Source Stanford Synchrotron Radiation Laboratory Stanford Linear Accelerator Center Undulator Meeting, June , 2004 Heinz-Dieter Nuhn, SLAC / LCLS End of Presentation