POSTECH PAL Development of S-band RF gun and advanced diagnostics in PAL 박용운 (Yong Woon Park, Ph.D.) 포항 가속기 연구소 (Pohang Accelerator Laboratory, PAL) 포항공과대학교 물리학과 (Physics department) (Pohang University of Science and Technology, POSTECH) March 16, 2010 SLAC National Accelerator Laboratory

POSTECH PAL 2/57 Contents 1.Facilities in PAL 2.S-band RF gun development in PAL 3.A study of electron beam measurement by using electro-optic crystal 4.Transverse size measurement of electron beam by using interferometer March 16, 2010 SLAC National Accelerator Laboratory

POSTECH PAL Pohang Accelerator Laboratory (PAL), Korea Fs-THz beam line Test facility of injector for XFEL Gun Test facility for XFEL 160-m long 2.5-GeV S-band PLS Linac 2.5-GeV 3rd generation Pohang Light Source (PLS) 3/57 SLAC National Accelerator Laboratory March 16, 2010

POSTECH PAL Contents 1.Facilities in PAL 2.S-band RF gun development in PAL 3.A study of electron beam measurement by using electro-optic crystal 4.Transverse size measurement of electron beam by using interferometer March 16, 2010 SLAC National Accelerator Laboratory 4/57

POSTECH PAL 1 st - RF gun in PAL, 2005 March 16, 2010 SLAC National Accelerator Laboratory 5/57

POSTECH PAL Emittance Evolution measurement JJAP. Vol. 46, p.1751 (2007) March 16, 2010 SLAC National Accelerator Laboratory 6/57

POSTECH PAL 1 st RF gun in PAL, 2005 March 16, 2010 SLAC National Accelerator Laboratory 7/53

POSTECH PAL OTR FIR Undulator Radiation (future option)  Beam energy : 60 MeV max.  Beam Charge : 0.1 – 0.5 nC  Beam Emittance: < 5 mm-mrad  Beam Pulse Repetition rate: 30 Hz max.  Bunch Length Before chicane: ps After chicane: fs Beam Charge Bunch Length after RF-gun Bunch Length after Chicane nC0.3 ps< 50 fs 0.5 nC1 – 2 ps< 150 fs fs-THz Linac Layout 8/57

POSTECH PAL 1 st RF gun in PAL, /57

POSTECH PAL 2 nd RF gun in PAL March 16, rd ILC Asian R&D Seminar, SAMEER, MUMBAI 10/57

POSTECH PAL 3 rd ILC Asian R&D Seminar, SAMEER, MUMBAI March 9-10, 2010 Cavity and Cathode 11/57

POSTECH PAL Cavity surface – after machining 12/57 30 nm RMS~4nm

POSTECH PAL Cavity surface 13/ nm 40 nm, after cleaning RMS~7nm RMS~12nm

POSTECH PAL Cavity surface 14/ nm 40 nm RMS~10nm

POSTECH PAL before brazing after brazing Cathode E-gun after brazing 2 nd - RF gun in PAL, /57

POSTECH PAL RF property of 2 nd Gun without tuning pin in wave guide modes π-mode0-mode Resonant frequency Couplingβ = (Over )β = (Under ) Q0Q QLQL π-mode 0-mode 16/57

POSTECH PAL RF property of 2 nd Gun with tuning pin in wave guide modes π-mode0-mode Resonant frequency Couplingβ = (Over )β = (Under ) Q0Q QLQL /57

POSTECH PAL Gun Test Facility in PAL /57

POSTECH PAL Experiment in February 2009 Measured energy spread (squares). The electron beam energy is measured as 2.5 MeV. Solid line is Gaussian fit. Axis on the top is the expression of energy spread in terms of the wavelength from Å. The Laser radius at the cathode is 400um. The electron charge is 1pC. The longitudinal shape of laser is Gaussian. The pulse length of laser is 3ps (FWHM). The laser injection phase is 32.5 o. March 16, 2010 SLAC National Accelerator Laboratory 19/57

POSTECH PAL Low energy case with FED condition (a) Measured energy (filled dot) vs injection phase. (b) Measured energy spread (filled dot) vs injection phase. Electron beam energy is measured as 2.5 MeV. Theory (solid line), PARMELA simulation (diamond). (a)(b) 20/57

POSTECH PAL Energy spread effect on FED (a) Diffraction pattern of polycrystalline Al without the energy dispersion (a) (b) where a 0 = 4.05 Å is the lattice constant, L is the distance from the sample to the detector, λ is De Broglie wavelength of the electron, and (k, l, m) are Miller indices for the diffraction plane in the aluminum. 21/57 (b) Blurred image of the diffraction pattern with 200 keV energy dispersion. Beam energy is 2.5 MeV.

POSTECH PAL High energy cases March 16, rd ILC Asian R&D Seminar, SAMEER, MUMBAI Measured energy spread. The electron beam energy is measured as 4.8, 5.0, 5.2 MeV. The Laser radius at the cathode is 400um. The electron charge is ~100 pC. The longitudinal shape of laser is Gaussian. The pulse length of laser is 3ps (FWHM). 22/57

POSTECH PAL RF Gun development project 2008~2012 Budget: 1 M$ (0.2 M$/year) March 16, rd ILC Asian R&D Seminar, SAMEER, MUMBAI 23/57

POSTECH PAL Cavity + 1 Port CavityCavity + 2 Ports Cavity + 4 Ports Basic Concept of Four Ports method By SLAC By POSTECH 24/57

POSTECH PAL Improvement of RF gun Quadrupole mode elimination by adding two side cavities By POSTECH Emittance reduction by four ports in full cell 25/57

POSTECH PAL Test cavity design: four ports RF gun for low power test Test cavity type: BNL/SLAC/UCLA 1.6-cell photocathode RF gun with input waveguide and three symmetric vacuum ports. March 9-10, rd ILC Asian R&D Seminar, SAMEER, MUMBAI 26/57

POSTECH PAL Field measurement set up cathode x y z θ x ρ = 10 mm 27/57

POSTECH PAL Low power test result : |E z | Case 1: Cavity + 1 waveguide Case 2: Cavity + 1 waveguide + 1 vacuum port Case 3: Cavity + 1 waveguide + 3 vacuum ports θ x ρ=10 mm y Coordinates system 28/57

POSTECH PAL 3 rd RF gun for fs-THz Facility 29/57

POSTECH PAL Requirements: Vacuum : < 5x torr Emittance: < 1 mm mrad Operating frequency: GHz Field balance( * E h / ** E f )of π mode: ~1 Mode separation(f π -f 0 ): ~10 MHz Coupling factor : ~1 Pulse repetition rate: >30 Hz * E h : Maximum E-field in half cell ** E f : Maximum E-field in full cell In real gun, the tuners will be removed and the ports will be used as vacuum ports. 3rd RF Gun for fs-THz Facility at PAL 30/57

POSTECH PAL 3 rd ILC Asian R&D Seminar, SAMEER, MUMBAI March 9-10, 2010 Cavity and Cathode 31/57

POSTECH PAL Thermal analysis heat generation by the rounded port temperature distribution ℃ ~ ℃ temperature distribution ℃ ~ ℃ ΔT ~ 48 ℃ ΔT ~ 21 ℃ 32/57 March 16, 2010 SLAC National Accelerator Laboratory

POSTECH PAL Brazing of RF Gun and Wave guide brazed at February /57 Yesterday SLAC National Accelerator Laboratory March 16, 2010

POSTECH PAL Contents 1.Facilities in PAL 2.S-band RF gun development in PAL 3.A study of electron beam measurement by using electro-optic crystal 4.Transverse size measurement of electron beam by using interferometer March 16, 2010 SLAC National Accelerator Laboratory 34/57

POSTECH PAL Electro-Optic crystal March 16, 2010 SLAC National Accelerator Laboratory The refractive indices of the Electro-optic crystal are changed by the electric field from the electron beam. 35/57

POSTECH PAL Coordinates March 16, 2010 SLAC National Accelerator Laboratory 36/57

POSTECH PAL Principal refractive indices March 16, 2010 SLAC National Accelerator Laboratory 37/57

POSTECH PAL 150m in Tunnel TEO Courtesy from A. Azima Timing EO setup March 16, 2010 SLAC National Accelerator Laboratory 38/57

POSTECH PAL SNR enhancement with wave plates March 16, 2010 SLAC National Accelerator Laboratory 39/57

POSTECH PAL SNR enhancement March 16, 2010 SLAC National Accelerator Laboratory 40/57

POSTECH PAL Analysis of the electro-optic measurement at FLASH March 16, 2010 SLAC National Accelerator Laboratory 41/57

POSTECH PAL Experimental setup March 16, 2010 SLAC National Accelerator Laboratory 42/57

POSTECH PAL Change of laser delay March 16, 2010 SLAC National Accelerator Laboratory 43/57

POSTECH PAL March 16, 2010 SLAC National Accelerator Laboratory 44/57 Quantification of polarization change

POSTECH PAL Quantification of polarization change 45/57

POSTECH PAL Origin of low signal March 16, 2010 SLAC National Accelerator Laboratory 46/57

POSTECH PAL Contents 1.Facilities in PAL 2.S-band RF gun development in PAL 3.A study of electron beam measurement by using electro-optic crystal 4.Transverse size measurement of electron beam by using interferometer March 16, 2010 SLAC National Accelerator Laboratory 47/57

POSTECH PAL March 16, 2010 SLAC National Accelerator Laboratory 48/57

POSTECH PAL Simulated interferogram March 16, 2010 SLAC National Accelerator Laboratory 49/57

POSTECH PAL 1B1 diagnostics beam line in PAL March 16, 2010 SLAC National Accelerator Laboratory 50/57

POSTECH PAL Fourier transform and visibility March 16, 2010 SLAC National Accelerator Laboratory 51/57

POSTECH PAL Inverse Fourier transformation March 16, 2010 SLAC National Accelerator Laboratory 52/57

POSTECH PAL Reconstruction of transverse distribution March 16, 2010 SLAC National Accelerator Laboratory 53/57

POSTECH PAL A = 2.281, B = , C = 7.995, D = 1.817, E = Measurement result in February /57

POSTECH PAL Reconstruction of transverse distribution March 16, 2010 SLAC National Accelerator Laboratory 55/57

POSTECH PAL 56/57

POSTECH PAL Study on the visibility Eq. (8) Eq. (9) 57/57 March 16, 2010 SLAC National Accelerator Laboratory

POSTECH PAL Summary 1. RF gun development - I have many experiences on development of RF electron gun for the XFEL. To design the RF gun, I used the POISSON code and PARMELA also. For the three dimensional analysis of the field distribution in the cavity, I used CST Microwave Studio. As postdoctoral position in Pohang Accelerator Laboratory, I carried out a big Project for the development of RF gun for 4th generation light source XFEL, as you can see in the Ref. [3]. I worked with three Ph.D. candidates whom work under my supervisor. I believe that I can lead a group to carry out a project. I fully understand the emittance compensation process in the injector part of the XFEL. 2. Electron beam diagnostics - I have also many experiences on the diagnostics of electron beam using electro-optic crystal. To measure very short electron beam such as 100 fs bunch length and measuring the arrival timing for the pump and probe experiment in XFEL, this technique is very promising method. I made myself simulation code to simulate many situations of electron beam diagnostics in accelerator such as bunch charge, bunch length, beam energy, etc. I also have experience working on FLASH machine in DESY during 5 months. I made a contribution to upgrade the EO diagnostics setup with my simulation code. I found the origin of low signal in the EO setup. Many papers are published with this subject as you can see in the list of publications, as you can see in the Ref. [1, 5, 7, 8]. 3. XFEL design experience -In my Ph.D. course, I am involved also to the design of the 4th generation light source XFEL. This XFEL is called PAL-XFEL as you can see in the Ref. [13, 15] in the publication list. I can simulate the electron beam dynamics with PARMELA, ELEGANT. 4. Storage ring experience - I also have many experiences on the machine study of Pohang Accelerator Laboratory such as transverse beam size measurement with interferometer in diagnostics beam line, as you can see in the Ref. [2]. I also have many interesting on the dynamics of electron beam in the 3rd generation storage ring. March 16, 2010 SLAC National Accelerator Laboratory 58/57

POSTECH PAL Thank you for your attention March 16, 2010 SLAC National Accelerator Laboratory

POSTECH PAL 60/47 Bunching part of the electron beam March 16, 2010 SLAC National Accelerator Laboratory

POSTECH PAL 3D Refractive indices March 16, 2010 SLAC National Accelerator Laboratory 61/53

POSTECH PAL Refractive indices March 16, 2010 SLAC National Accelerator Laboratory 62/53

POSTECH PAL Analysis and simulation March 16, 2010 SLAC National Accelerator Laboratory 63/53