Dual scattering foil design for poly-energetic electron beams.

Area of Science:

• Medical Physics
• Plasma Physics
• Particle Acceleration

Background:

• Laser wakefield acceleration (LWFA) generates electron beams with energies (6-20 MeV) suitable for radiation therapy.
• LWFA electron beams exhibit a broad energy spectrum, posing challenges for therapeutic applications.
• Existing scattering foil systems are designed for mono-energetic beams, necessitating evaluation for poly-energetic LWFA beams.

Purpose of the Study:

• To assess the suitability of scattering foil systems, designed for mono-energetic beams, for poly-energetic electron beams from LWFA.
• To determine if a significant energy spread in LWFA electron beams impacts the flatness and usability of the therapeutic beam profile.

Main Methods:

• Dual scattering foil systems were designed using analytical Gaussian multiple-Coulomb scattering theory for mono-energetic beams.
• Radial planar fluence profiles for poly-energetic beams (0.5-6.5 MeV spread) were calculated analytically and via Monte Carlo (EGS/BEAM code).
• Analytic calculations guided foil adjustments, while Monte Carlo simulations verified results and analyzed phase-space characteristics.

Main Results:

• The flatness of the scattered electron beam was found to be largely insensitive to the input energy spectrum's width.
• Analytical and Monte Carlo dose calculations showed excellent agreement in the central beam region.
• Minor discrepancies outside the usable field were observed, potentially due to small-angle approximations, but did not alter the main conclusion.

Conclusions:

• Scattering foil systems designed for mono-energetic beams are suitable for poly-energetic LWFA electron beams with the same central energy.
• LWFA electron beams can be effectively shaped for therapeutic applications using established scattering foil designs.
• Further Monte Carlo studies are recommended to investigate the dosimetric properties of LWFA-generated electron beams comprehensively.