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Exploring novel concepts of x-ray radiation generation

  • Author(s): Hakimi, Sahel
  • Advisor(s): Dollar, Franklin
  • et al.
Abstract

Laser Wakefield Acceleration (LWFA) is a promising technique for the development of com- pact particle accelerators. The resulting electron beams have useful characteristics such as short temporal duration and high brightness. LWFA can also generate x-ray radiation, which can be tailored by properties of the interaction such as target density profile and laser polarization.

This work will discuss the theoretical regime of x-ray driven WFA in a nanotube. In this novel regime, the acceleration gradient is predicted to be on the order of TeV/cm and this is confirmed by modeling x-ray pulses in a nanotube. In this work, we include the effects of ionic motion explicitly and investigate the possibility that the lattice force could couple with the formation of a stable wake structure. We show that wakefield formation and electron acceleration processes are not influenced by the presence of polaritons. The present work indicates the acceleration gradient on the order of TeV/cm, which agrees well with wakefield theory and is consistent with previous findings without the lattice effect. This amounts to the validation by computation of the concept of the solid state plasma wakefield in nanomaterials.

This thesis also includes experimental work designed to study the wavelength scaling of LWFA as the wavelength is decreased. An experimental platform was built in a new labo- ratory at UCI. The laser system is a commercial system with mJ scale energy and operates at kHz repetition rate. Generation of a sub-relativistic electron beam was confirmed by de- tection of bremsstrahlung radiation. This platform can be used to study electron beam and radiation generation with a near single cycle pulse as well as 2ω and 3ω of the laser pulse.

A series of LWFA experiments conducted using the HERCULES laser system are also pre- sented. The results demonstrate that wakefield temperature and dynamics can be determined by the soft x-ray spectra of the interaction. Plasma conditions, the signature of bubble for- mation and electron injection are imprinted in the xuv data. A decreased self-injection threshold was observed with a circularly polarized laser pulse revealing that self-injection is polarization dependent. A different injection mechanism for a circularly polarized laser pulse is discussed.

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