David H. Dowell RF Gun Commissioning LCLS FAC April 16, RF Gun Commissioning Experience David H. Dowell for the LCLS Injector Team Facility Advisory Committee Meeting April 16, 2007 Description of Gun Design & Parameters Results of Gun High-Power Tests in Klystron Lab Installation at S20 and Pre-Beam Testing First Photo-Beam! Results & Observations of Initial Gun Commissioning Summary

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Z-coupling: reduces pulsed heating increases vacuum pumping Racetrack to minimize quadrupole fields Deformation tuning to eliminate field emission from tuners Iris reshaped reducing field 10% below cathode Increase 0-pi mode separation to 15MHz All 3D features included in modeling: laser port and pickup probes 3D fields used in Parmela simulation 3D RF Design of Gun RF Parameters f0 (GHz) Q β2.1 Mode Sep.  f (MHz) 15 E0:E10.999:1 Slide Compliments of Z. Li & L. Xiao C. Limborg et al., “RF Design of the LCLS Gun”, LCLS-TN-05-3 L. Xiao et al., “Dual feed rf gun design for the LCLS,” Proc Particle Acc. Conf.

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Gun-Solenoid Assembly Cut-away view of LCLS Gun Cathode weld assembly August 2005 LCLS RF Gun Mechanical Design Review Compliments E. Jongewaard

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Gun Design and Measured Specifications RF ParametersDesignMeasured f  (GHz) Q β Mode Sep.  f (MHz) Field Balance11 Measurements compliments of J. Wang and J. Lewandowski

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Conditioning Time to 120 MV/m & Dark Charge per RF Pulse High-Power Gun1 Test in Klystron Lab

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Results of Gun High-Power Tests in Klystron Lab: Only concern is the heating of the RF probes Probe external temperatures during Nov 9 conditioning to 120MV/m Upper probe temperature and calibration vs. RF power Therefore, the gun rate will be limited to 30 Hz during 2007 Commissioning. New probes for Gun 2 will have -75dB coupling and be copper plated.

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Lowering the Gun-Solenoid Assembly into the Sector 20 Injector Vault

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Gun-Solenoid Assembly is Home!

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Measurements: J. VanPelt, A. Vlieks, J. Wang, C. Rivetta Pre-Beam RF Measurements and Water System Test

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Gun Processed at Sector 20 to Nominal RF Power Thanks to R. Akre, B. Hong

David H. Dowell RF Gun Commissioning LCLS FAC April 16, First Photo-Electrons!!! It Works!!! Dark Charge Images of First Photo-Electrons April 5, 2007 Photo-Electrons: After adjusting laser-gun phase

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Early Images of Beam on Yag01 (Gun Exit) and Yag02 (Entrance to L0a) YAG01 YAG02

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Optimized Macropulse Timing in RF Waveform by Measuring Beam Energy vs. Gun Delay RF Delay (ns) Beam Momentum (GeV/c) Set Timing Here for Max Energy Used measurement to calibrate RF system (Gun RF probes)

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Schottky Scan of Gun Phase Relative to Laser Zero Crossing of RF Field Optimum Launch Phase 30deg Measurement: H. Loos, April 13, LCLS e-log

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Beam Charge vs. Drive Laser Energy & Launch Phase: Schottky Enhancement of QE Launch Phase at 30 degrees Launch Phase at 85 degrees from zero crossing

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Regen pockel cell delay = microSec Regen pockel cell delay = microSec Precise Adjustment of Regenerative Amplifier Pockel Cell Timing is Crucial measurements: B. White et al., LCLS e-log, April 11, 2007

David H. Dowell RF Gun Commissioning LCLS FAC April 16, YAGG1, Gun Spectrometer ~100keV YAG01, ~50cm from cathode YAG02, ~80cm from cathode Beam Momentum = 4.3 MeV/c measurements: H. Loos & J. Welch, LCLS e-log, April 13, 2007

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Virtual Cathode Camera YAG01 E-Beam Appears to Preserve the Laser’s Spatial Fluctuations Laser Image: S. Gilevich et al., LCLS e-log, April 2007

David H. Dowell RF Gun Commissioning LCLS FAC April 16, YAG01 YAG02 Images compliments of P. Emma & R. Iverson, LCLS e-log, April 13, 2007 YAG03 L0a Gun & Solenoid Evolution of Beam Along Injector

David H. Dowell RF Gun Commissioning LCLS FAC April 16, Summary Gun is operational at Sector 20: RF conditioning complete Water temp and LLRF control loops operating Providing beam for injector commissioning High level S/W applications being implemented Technical Issues: Gun RF probe heating limits gun operation to 115MV/m and 30 Hz. This is fixed on Gun2. Progress hindered by non-functioning, critical diagnostics!! QE is 2 to 4 times lower than expected Plan for cathode cleaning Gun-Solenoid assembly appears to be pointing down and to right