PhD thesis supervisor: dr. Vidmantas Tomkus (apply for recommendation)
Optical measurement methods of Ultra-High Dose Rate (UHDR) radiation
Optical UHDR (Ultra-High Dose Rate) measurement techniques offer picosecond temporal resolution, enabling real-time, single-shot diagnostics of radiation dose dynamics, unlike scintillators, radiochromic films, and calorimeters which integrate over time and lack ultrafast response. Optical methods are non-invasive, immune to saturation, and less prone to damage, making them ideal for probing transient fields and ultrashort beams in modern laser-plasma accelerator HEDP (High-Energy-Density Physics) studies of the matter under extreme conditions and field-induced dynamics of FLASH radiobiology.
In this work, few optical UHDR measurement methods like fs-ps chirped optical probes to reconstruct transient refractive index changes, cross-polarized fs probes using birefringent crystals to map the optical ellipticity, changes in the absorption coefficient induced by the nonequilibrium carriers generated in doped GAGG (Gadolinium Aluminum Gallium Garnets) will be analyzed and afterwards implemented in high-intensity laser acceleration experiments. Deconvolution of mixed radiation comprising primary particles as electrons, protons, Betatron X-rays radiation from oscillating electrons in plasma and Bremsstrahlung from electron-nucleus collisions will be carried out using combination of spectral, temporal, angular, and polarization techniques, supported by Particle-in-Cell and Monte Carlo simulations as well as Machine Learning and Artificial Intelligence methods.