Thesis outline

Introduction

• Magnetized electron beam
• Applications of the magnetized electron beam
  • Magnetized electron cooling
• Jefferson Lab magnetized electron source for the JLEIC cooler

Generation of the magnetized electron beam

• Experimental setup (DC HV gun, photocathode, cathode solenoid, RF laser, focusing solenoids, etc.)
• Beam diagnostics

Beam dynamics

• Beam matrix
• Phase space
• Emittance (thermal, phase space, geometric)
• Effective(drift) emittance (emittance of a magnetized beam)
• Measuring/calculating the beam emittance

Space charge effect

• Space charge effect in a magnetized electron beam

Simulations on the magnetized electron beam

ASTRA

• Initial particle distribution
• Field maps (3D E field map, 2D B field map)
• Space charge calculation mechanism
• Emittance

GPT

• Initial particle distribution (Laser*QE image processing)
• Field maps (3D E field map, 2D B field map)
• Space charge calculation mechanism
• Emittance

Characterization of the magnetized electron beam

Experimental method

• Beam size vs solenoid I
• Rotation angle vs solenoid I
• Emittance vs solenoid I - three different laser sizes
• Emittance vs laser spot sizes - max solenoid current

ASTRA/GPT simulations (Simulations of all the above variations)

• Conclusions (comparisons -measurements vs simulations, mismatch oscillations, negative rotation angles, etc.)

Experimental and numerical simulation results of the space charge dominated magnetized electron beam

Experimental method

• Pulse energy vs extracted charge-for different magnetizations
• Space charge current limitation dependence on gun high voltage-for different magnetizations
• Space charge current limitation dependence on pulse width-for different magnetizations
• Space charge current limitation dependence on laser spot size-for different magnetizations

GPT simulations

• Conclusions (Comparison-measurements and simulations)

Redesigning and performance of the photogun

• Existing electrostatic design
• Modified electrostatic design
• Polishing and gun assembly
• High voltage conditioning

Summary and Conclusions

Return to Sajini Wijethunga