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Analysis of Secondary Emission Inside of a 1.3GHz Radio Frequency Electron Gun

Analysis of Secondary Emission Inside of a 1.3GHz Radio Frequency Electron Gun. Robert Inzinga Supervisor: Dr. Raymond Fliller A0 Photo Injector Lab. Outline. The RF Gun Secondary Electron Emission ASTRA Phase scans Data and Simulations. Waveguide. Primary Solenoid. Secondary Solenoid.

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Analysis of Secondary Emission Inside of a 1.3GHz Radio Frequency Electron Gun

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  1. Analysis of Secondary Emission Inside of a 1.3GHz Radio Frequency Electron Gun Robert Inzinga Supervisor: Dr. Raymond Fliller A0 Photo Injector Lab

  2. Outline • The RF Gun • Secondary Electron Emission • ASTRA • Phase scans • Data and Simulations

  3. Waveguide Primary Solenoid Secondary Solenoid Bucking Solenoid Half Cell Full Cell Faraday Cup Cs2Te Photocathode Laser RF Gun • 1.625 Cell Cavity • 1.3GHz • Pulsed Laser • Cs2Te Photocathode • Solenoid-produced Magnetic Field • Waveguide • Faraday cup

  4. Secondary Emission • Emission from any surface when a primary electron collides with the surface • Secondary emission yield, δ • Maximum yield, δmax • Impact energy at maximum yield, Ep,max • Different for various materials and surfaces, s

  5. Motivation • Impact of primary electrons can cause damage to photocathode • Believe that secondary emission feeds multipacting at the photocathode • Electrons repeatedly striking photocathode releasing secondary electrons which also impact the photocathode • Also a source of dark current coming from the RF gun

  6. ASTRA • Used for simulations • Adjustable parameters • Electric field strength • Solenoid configurations • Secondary emission • Photo emitted charge

  7. Phase Scans Secondary emission Post pulse Ideal phase for beam emission • Varying the phase of the RF cavity relative to incoming laser pulse that causes photoemission • Charge measured on faraday cup

  8. Data Overview • Varied gun gradient • 7.4MV/m – 35.4 MV/m • Solenoid Configurations • Round Beam (Ibuck=255A, Iprim=255A, Isec= 255A) • Flat Beam (I = 0, 170, 70A) • No Solenoids (I = 0, 0, 0A)

  9. Data and Simulations • Ecath = 15MV/m • Solenoid settings at I = 255, 255, 255A Simulations Pink (no secondary emission) Green (secondary emission) Data Blue

  10. Data and Simulations • Ecath = 35.4MV/m • Solenoid settings at I = 255, 255, 255A Simulations Pink (no secondary emission) Green (secondary emission) Data Blue Secondary Emission

  11. Data and Simulations • Ecath = 35.4MV/m • Solenoid Settings at I=0,170,70A Simulations Pink (no secondary emission) Green (secondary emission) Data Blue

  12. Data and Simulations • Ecath = 35.4MV/m • Solenoid Settings at I=0,0,0A Simulations Pink (no secondary emission) Green (secondary emission) Data Blue

  13. Summary • Performed phase scans at a variety of gun settings • Simulations make it possible to identify secondary emission at photocathode • Number of secondarily emitted electrons increases with smaller gun gradient • Pattern of secondary emission varied with different solenoid settings • Need to better characterize secondary emission parameters for photocathode in RF gun

  14. Analysis of Secondary Emission Inside of a 1.3GHz Radio Frequency Electron Gun Robert Inzinga Supervisor: Dr. Raymond Fliller A0 Photo Injector Lab

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