Construction, Commissioning, and Operation of Injector Test Facility (ITF) for the PAL-XFEL November 12, 2013 S. J. Park, J. H. Hong, C. K. Min, I. Y. Kim, J. H. Han, H. S. Kang, I. S. Ko (Pohang Accelerator Laboratory), and M. S. Chae (Physics Department, POSTECH) To be presented at the 17th International Conference on Accelerators and Beam Utilizations 1

ITF Location in PAL 2

Requirements for PAL XFEL Injector Energy139 MeV Charge0.2 nC Emittance< 0.5 mm mrad Energy Spread~10 -4 Rep. Rate60 Hz Bunch Length< 10 ps (FWHM) 3

3D Model of ITF 4

Overall Views of ITF Tunnel and Klystron Gallary 5

ITF Gallery view 6

Some Detail Views of Tunnel View from Gun TDS Laser System (in a dedicated clean room) 7

RF gun Brazed in house 8

ITF Beamline & ASTRA Simulations Current profile at injector end rms slice emttance at injector end Transverse normalized rms emittance and rms beam size J. H..Han 0.26 μm with flat-top laser pulse (0.34 μm with Gaussian pulse) M. S. Chae 9

ASTRA simulation Current profile at injector end rms slice emttance at injector end Transverse normalized rms emittance and rms beam size Simulation by J.-H.Han 0.26 μm with flat-top laser pulse * 0.34 μm with Gaussian 10

4-hole TypeCoaxial Type OldNew Frequency [MHz]2856 Mode Separation [MHz] β Repetition rate [Hz]60120~ 1000 Maximum Field Cathode [ MV/m] Coupling TypeDual Feed Side CouplingDual Feed side CouplingCoaxial Coupling Cathode TypeChangeable Cu CathodeFixed Cu CathodeChangeable(in vacuum) Various Material Cathode Iris ShapeCircleEllipse Cell-edge Rounding [mm]NA45 Cell-field ProbeNA2 EA in full cellNA Photocathode RF Guns for PAL XFEL 11

FPGA PC FPGA PC LLRF System Short-term RF stability measurements L0a : amplitude ~ 0.02 %, phase ~ 0.02  L0b : amplitude ~ 0.05 %, phase ~ 0.1  12

Transverse Deflecting Cavity rms bunch length ~ 1.53 ps ~ mm ~ 1.57 degS Streaked beam at downstream screen Calibration is done by measuring beam centriod offsets with varying phase shifts TDC in the ITF tunnel M. S. Chae J. H. Hong 13

Wire Scanner Tests I. Y. Kim N. S. Chung 14

Measurement of Laser-to-RF Timing Jitter C. K. Min J. H. Hong Gun phase (°) Phase jitter (°) Positive phase: Emission Negative phase: No emission Electron bunch rf-to-beam phase Charge fluctuation is the convolution of time-jitter and z-distribution of bunch charge 15

BPM Tests C. Kim S. J. Lee In-situ calibration of cavity BPMs for PAL-XFEL undulator section Cavity BPMs BEAM 16

Quad and Screen for Emittance Measurement Emittance Measurement by Quad scan what we want to measure M. S. Chae 17

Beam Image Processing original image background image Image within ROI 18

Nominal measurement condition parametervalue Beam energy139 MeV Beam charge~200 pC Laser injection phase25˚ Minimum measured emittance … measured on Mar 14 ε x ~0.71 μm (100 %) / ~0.39 μm (90 %) ε y ~0.78 μm (100 %) / ~0.43 μm (90 %) 19

Measurement result Measured on Mar 5 Laser injection phase 35˚ Measured on Mar 14 Laser injection phase 30˚ Measured on Mar 14 Laser injection phase 25˚ Measured on Mar 25 Laser injection phase 20˚ ε ~ 0.87 μm ε ~ 0.94 μm ε ~ 0.75 μm ε ~ 1.08 μm 20

gun sol. (A)L0a=0 AL0a=5 AL0a=10 A A A A A A A Measurement result Measured on Mar 27 Laser injection phase 25˚ 90% emittance gun sol. (A)L0a=0 AL0a=5 AL0a=10 A A A A A A A

Best Emittance Achieved as of October 8, 2013 (rms normalized, projected) ε x ~0.41 μm (95%) ε y ~0.48 μm (95%) ε x ~0.41 μm (95%) ε y ~0.48 μm (95%) M. S. Chae J. H. Han Emittance Measurements 22

Conclusions 1.The Injector Test Facility (ITF) for the PAL XFEL has been successfully constructed, commissioned in , and operated stably in The fast progresses was possible due to the 10-year preceding R&Ds. 2.Emittance goal has been already met with core emittance (< 90%) values far exceeding the goal. 3.Slice emittance measurements will be done in Various accelerator components including precision diagnostics are being tested with “real” low-emittance beams. 5.High-profile experiments including the “de-chirper” have been hosted with good results. 6.Focus efforts devoted to the ITF have been possible owing to the stable operation of the PLS-II. 23