LCLS Gun Commissioning Status & Plans David H LCLS Gun Commissioning Status & Plans David H. Dowell LCLS Injector Commissioning Workshop October 9, 2006 Status of gun fabrication and testing Gun test results Characterization of magnetic components Systems to be commissioned The 3-Pass Commissioning Plan Summary

Gun Fabrication and Testing Process Fabricate parts Cold test sub assemblies and clamped parts Machine and measure for resonance and field balance Braze and weld final assembly Low power RF and cathode tests Furnace bake at 500deg C Assemble and configure for high power RF test (hot test) Vacuum bake of assembly in Klystron test vault Perform hot test Vacuum qualification of gun Alignment of assembly with CMM Install at S20

Gun only pictures CAD cut away view of gun interior RF Gun Fabrication and Cold RF Testing Finished & Preparing for High-Power Tests Gun only pictures CAD cut away view of gun interior

RF Field Balance Measured Using Bead Drop Technique Data compliments J. Wang, ATR Dept., SLAC

Gun Design and Measured Specifications RF Parameters Design Measured fp (GHz) 2.855987 2.855999 Q0 13960 14062 β 2.1 2.03 Mode Sep. f (MHz) 15 15.17 Field Balance 1

LCLS RF Gun: Beam Side dual rf power feeds focusing solenoid beam port: Attach 2-km linac here

cathode flange dual rf power feed focusing solenoid LCLS RF Gun: Cathode Side

Description of gun magnet system Gun solenoid: SOL1 Bucking coil: SOL1BK X,Y dipole correctors: XC00&YC00 (inside SOL1) Normal & skewed quad correctors: CQ01&SQ01 (inside SOL1) Field maps and calibrations measured

Gun Solenoid and Dipole Corrector Magnetic Measurements

Bucking Coil Magnetic Measurements

What we’re commissioning e- to L0A Q = 1 nC f = 120 Hz G = 120 MV/m gex,y = 1 mm Dt = 10 ps I = 100 A E = 6 MeV spec. dipole UV laser e- solenoid YAG screens RF gun cathode

The Gun & Gun-to-Linac Region with the Drive Laser Launch Optics Laser tube from laser room

CAD Model of the Drive Laser Launch Optics (top view) BS Wave plate Lead block Shutter Table is fully enclosed VC Power Meter Cathode CAD model of the laser launch optics (top view)

Schematic of Drive Laser Launch Optics Laser beam from drive laser Virtual in-vacuum mirror camera Virtual cathode camera lens M2 M1 Polarizer Virtual image of in-vacuum mirror mirrors used to steer laser on cathode Wave plate BS2 BS: beam splitter BS1 Joule meter shutter (BCS), rate control To the Gun window and in-vacuum mirror

Gun and Gun-to-Linac Components SOL1 Bucking Coil SOL1BK Drive laser injection cross On-axis alignment laser Drive laser Alignment laser YAG01/FC01 BXG Spectrometer YAG02 Quads YAGG1/FCG1 BPMs IM01 Current Toroid

Injector Commissioning Philosophy Commissioning plan is organized into three passes through the injector Tasks 2.3.3: 1st pass Pre-beam and beam-based hardware & software checkout Tasks 2.3.4: 2nd pass First-order optics Tasks 2.3.5: 3rd pass Full beam characterization and optimization In each pass the beam is transported from the gun through DL1 and BC1 stopping at the beam dump, TD-11.

The Injector Commissioning Schedule and the 3-Pass Plan Jan 1 2007 March 1 Approximation of real schedule!

Pass 1 Pre-Beam Commissioning RF Processing and Water & RF Controls Characterize and test gun water system controls Water system only, no RF Control loop bandwidth Temp stability RF processing with resonance control (water & LLRF) Test of LLRF phase/amplitude controls (4-gun probes) (0.1deg s-band, 0.1%) Measure recovery time after trip Interaction between LLRF & water controls

Setting RF & Centering Laser in SOL1. Pass 1 Commissioning Setting RF & Centering Laser in SOL1. Then continue transport thru L0a, L0b ending at BXS to set the injector beam energy Use fast diode at gun to time laser in rf envelope Set launch phase within rf period SOL1 at nominal field, scan laser phase until beam observed on YAG01 Meas. base width of charge vs. laser phase (is it correct?, i.e. ~110deg) Locate zero crossing & set laser phase to 30deg Center laser beam on SOL1 Vary SOL1 current & move laser on cathode until there is no motion on YAG01 Observe beam on YAG02, vary SOL1 current & move laser until there is no motion Record settings on virtual cathode, virtual mirror, etc.

Overview of Second Pass Gun/GTL Commissioning Pass 2 Commissioning Overview of Second Pass Gun/GTL Commissioning

Calibration of charge and energy diagnostics Pass 2 Commissioning Second Pass Commissioning Details of Gun/GTL Optimization, 1st of 3 parts Calibration of charge and energy diagnostics Alignment procedure for energy measurements Measurements of gun beam energy

Schottky scan to determine QE and presence of satellite laser pulses Pass 2 Commissioning Second Pass Commissioning Details of Gun/GTL Optimization, 2nd of 5 parts Schottky scan to determine QE and presence of satellite laser pulses Charge vs. laser energy to measure QE and linearity (no space charge limit of emission) QE uniformity measurement by rastering laser beam

Thermal emittance by solenoid scan at different gun fields Pass 2 Commissioning Second Pass Commissioning Details of Gun/GTL Optimization, 3rd of 5 parts Determination of emission uniformity by imaging cathode onto YAG01 and YAG02 Thermal emittance by solenoid scan at different gun fields Divergence of beam at cathode by parallel-to-point imaging at YAG02 Confirm parallel-to-point optics by varying laser radius Repeat at different gun fields

Beam alignment and calibration checks of BXG and quads Pass 2 Commissioning Second Pass Commissioning Details of Gun/GTL Optimization, 4th of 5 parts Beam alignment and calibration checks of BXG and quads Gun beam energy and energy spread vs. laser phase Low charge, short bunch Low charge, 10ps bunch High charge, 10ps bunch

Beam-based feedback systems tested and enabled Pass 2 Commissioning Second Pass Commissioning Details of Gun/GTL Optimization, 5th of 5 parts Beam-based feedback systems tested and enabled First emittance and bunch length measurements

Third Pass Commissioning Details of Gun/GTL Optimization Integrated operation with entire injector Projected and slice emittance optimization (Gun solenoid & laser shape) Longitudinal phase space measurements

Summary of Gun Commissioning Status & Plans Gun fabrication and cold testing completed Gun meets all design goals All magnetic components calibrated and characterized Gun integrated with solenoid and waveguide assembly Installed in test vault at Klystron First bake of assembly (gun vacuum in high 10-10 Torr) High-power RF (hot) testing has begun Final vacuum qualification & alignment performed after Hot-Testing Gun on schedule for Dec’06 installation Commissioning will be done in three passes Pass 1: Pre-beam checkout and beam-based checkout First transport beam through entire injector & BC1 to TD-11 Pass 2: First-order optics Characterize components and beam throughout injector Pass 3: Full beam Characterization Optimize beam quality