LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
Measuring the FEL gain with trajectory distortion
Z. Huang, SLACJanuary 20, 2004
Measuring the FEL gain with trajectory distortion
Z. Huang, SLACJanuary 20, 2004
LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
IntroductionIntroduction
Stop the FEL amplification in the undulator and measure the radiation properties at the end (TTF results, PRL, 2001)
LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
Single Kick Error (SKE)Single Kick Error (SKE)
Two effects of SKE (Tanaka et al., FEL2003): reduction in coupling smearing of microbunching
Critical angle to destroy FEL interaction
rad 64105.1 10
gc L
LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
Trajectory distortion in LCLSTrajectory distortion in LCLS
Offset the quad by Qx amount. If the focal length of the quad is F, then the kick angle is Q = -Qx/F
Set Q = c, since F ≈10m, Qx ≈ 60m, so that the maximum betatron amplitude xQ ≈ 2Qx
LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
GENESIS simulation resultsGENESIS simulation results
Total power still grows due to interaction with higher-order modes & spontaneous radiation (div. angle up to 100 rad) On-axis power is dominated by the FEL fundamental mode only (~1 rad) and stops growing when Qx~60 m.
LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
Z-dependenceZ-dependence
Initial stage: no microbunching to destroy, still some weak interaction + a lot of spontaneous
Exponential growth region, works reasonably well
Qx = 60 m Vary Qx
LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
SummarySummary
It worked (as in TTF,…)
Trajectory distortion can stop further growth of FEL fundamental mode, but other higher-order modes (including spontaneous) increase the background
Collimation helps to pick up on-axis signal, or can we find the hot spot by data analysis?
Measurement results should be cross-checked with other methods, if possible
LCLS undulator diagnostics and commissioning workshopLCLS undulator diagnostics and commissioning workshopJanuary 19-20, 2004 (UCLA)January 19-20, 2004 (UCLA)
Zhirong Huang, SLACZhirong Huang, [email protected]@slac.stanford.edu
Linac Coherent Light Source Stanford Synchrotron Radiation LaboratoryStanford Linear Accelerator Center
Spontaneous fundamental radiation within 3% bandwidth reaches 60 MW, FEL signal can dominate after 40m
Spontaneous v.s. FEL gainSpontaneous v.s. FEL gain
Spontaneous fundamental in 3% BW
(Z. Huang, K.-J. KimFEL2002)
