Emittance Preservation in a Plasma Wakefield Accelerator

Ariniello, Robert

Graduate Thesis Or Dissertation

Emittance Preservation in a Plasma Wakefield Accelerator Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/1n79h573f

Abstract

Plasma wakefield accelerators have the potential to drastically reduce the size and cost of conventional particle accelerators. In these devices, a laser or charged particle beam excites a density wave in a plasma. The strong fields created by the density wave can then be used to accelerate a trailing beam to high energy. The accelerating electric field can be three to four orders of magnitude larger than that found in a typical radio frequency accelerator. Particle accelerators, however, are tools for producing the beams required by particle colliders and light sources, and these applications place strict requirements on the quality of the beam. Here, beam quality refers to the beam emittance, a measure of the transverse momentum spread of the particles in the beam. Unfortunately, the beam emittance tends to grow considerably in plasma wakefield accelerator experiments. The primary mechanism behind emittance growth, chromatic phase spreading, increases the emittance when the divergence of the beam is not matched to the focusing force of the plasma. This process can be mitigated by using a plasma source with density ramps. The focusing force of the plasma gradually increases in the ramp, reducing the beam size adiabatically. This dissertation covers the development of a laser ionized plasma source intended to demonstrate emittance preservation. We start by developing a general, analytic theory of beam evolution in an adiabatic plasma ramp. Using this theory, in combination with particle in cell and particle tracking simulations, we enumerate the requirements a plasma source must meet in order to preserve the beam's emittance. Based on these requirements, we propose an optical technique capable of producing a suitable laser ionized plasma source. Finally, we demonstrate the optical technique experimentally.

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