Experimental validation of a radio frequency photogun as external electron injector for a laser wakefield accelerator
- Coherence and Quantum Technology Group, Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)
A purpose-built RF-photogun as external electron injector for a laser wakefield accelerator has been thoroughly tested. Different properties of the RF-photogun have been measured such as energy, energy spread and transverse emittance. The focus of this study is the investigation of the smallest possible focus spot and focus stability at the entrance of the plasma channel. For an electron bunch with 10 pC charge and 3.7 MeV kinetic energy, the energy spread was 0.5% with a shot-to-shot stability of 0.05%. After focusing the bunch by a pulsed solenoid lens at 140 mm from the middle of the lens, the focal spot was 40 {mu}m with a shot-to-shot stability of 5 {mu}m. Higher charge leads to higher energy spread and to a larger spot size, due to space charge effects. All properties were found to be close to design values. Given the limited energy of 3.7 MeV, the properties are sufficient for this gun to serve as injector for one particular version of laser wakefield acceleration, i.e., injection ahead of the laser pulse. These measured electron bunch properties were then used as input parameters for simulations of electron bunch injection in a laser wakefield accelerator. The arrival time jitter was deduced from measurements of the energy fluctuation, in combination with earlier measurements using THz coherent transition radiation, and is around 150 fs in the present setup. The bunch length in the focus, simulated using particle tracking, depends on the accelerated charge and goes from 100 fs at 0.1 pC to 1 ps at 50 pC. When simulating the injection of the 3.7 MeV electron bunch of 10 pC in front of a 25 TW laser pulse with a waist of 30 {mu}m in a plasma with a density of 0.7 x 10{sup 24} m{sup -3}, the maximum accelerated charge was found to be 1.2 pC with a kinetic energy of {approx}900 MeV and an energy spread of {approx}5%. The experiments combined with the simulations show the feasibility of external injection and give a prediction of the output parameters that can be expected from a laser wakefield accelerator with external injection of electrons.
- OSTI ID:
- 22036671
- Journal Information:
- Journal of Applied Physics, Vol. 110, Issue 2; Other Information: (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
Similar Records
PROPOSAL FOR A PRE-BUNCHED LASER WAKEFIELD ACCELERATION EXPERIMENT AT THE BNL DUV FEL FACILITY.
Beat wave injection of electrons into plasma waves using two interfering laser pulses
Related Subjects
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ACCELERATION
BEAM BUNCHING
BEAM INJECTION
BEAM-PLASMA SYSTEMS
ELECTRON BEAMS
ELECTRON GUNS
LASER RADIATION
LASER-PRODUCED PLASMA
LIGHT TRANSMISSION
MEV RANGE
PLASMA DIAGNOSTICS
PLASMA INSTABILITY
PLASMA SIMULATION
RADIOWAVE RADIATION
SPACE CHARGE
THZ RANGE
TRANSITION RADIATION
WAKEFIELD ACCELERATORS