Measurements of X-ray doses and spectra produced by picosecond laser-irradiated solid targets

An Active Dose Measurement Device for Ultra-short, Ultra-intense Laser Facilities

Ultra-short, ultra-intense laser facilities could produce ultra-intense pulsed radiation fields. Currently, only passive detectors are fit for dose measurement in this circumstance. Since the laser device could generate a dose up to tens of mSv outside the chamber in tens of picoseconds, resulting in a high instantaneous dose rate of ~107 Sv s-1, it is necessary to perform real-time dose measurement to ensure the safety of nearby workers. Due to fast response and excellent radiation resistance, a diamond-based dose measurement device was designed and developed, and its dose-rate response and its feasibility for such occasions were characterized. The measurement results showed that the detector had a good dose-rate linearity in the range of 3.39 mGy h-1 to 10.58 Gy h-1 for an x-ray source with energy of 39 keV to 208 keV. No saturation phenomenon was observed, and the experimental results were consistent with the results obtained from Monte Carlo simulation. The charge collection efficiency was about 80%. Experimental measurements and simulations with this dose measurement device were carried out based on the "SG-II" laser device. The experimental and simulation results preliminarily verified the feasibility of using the diamond detector to measure the dose generated by ultra-short, ultra-intense laser devices. The results provided valuable information for the follow-up real-time dose measurement work of ultra-short, ultra-intense laser devices.

Towards high-energy, high-resolution computed tomography via a laser driven micro-spot gamma-ray source

Computed Tomography (CT) is a powerful method for non-destructive testing (NDT) and metrology awakes with expanding application fields. To improve the spatial resolution of high energy CT, a micro-spot gamma-ray source based on bremsstrahlung from a laser wakefield accelerator was developed. A high energy CT using the source was performed, which shows that the resolution of reconstruction can reach 100 μm at 10% contrast. Our proof-of-principle demonstration indicates that laser driven micro-spot gamma-ray sources provide a prospective way to increase the spatial resolution and toward to high energy micro CT. Due to the advantage in spatial resolution, laser based high energy CT represents a large potential for many NDT applications.

DOSIMETRIC EVALUATION OF LASER-DRIVEN X-RAY AND NEUTRON SOURCES UTILIZING XG-III PS LASER WITH PEAK POWER OF 300 TERAWATT

Current short-pulse high-intensity lasers can accelerate electrons and proton/ions to energies of giga-electron volts. For certain advanced applications, laser-accelerated electrons and protons are optimised for high-energy X-ray and neutron generation at the XG-III picosecond (ps) laser beamline. These energetic X-ray and neutron beams can significantly affect radiation safety at the facility; therefore, proper evaluation of the radiological hazards induced by laser-driven X-ray and neutron sources is required. This study presents a dosimetric evaluation of laser-driven X-ray and neutron sources at the XG-III ps laser beamline. The 'source terms' of the laser-accelerated electrons and protons are characterised utilising the particle-in-cell method and an analytical model, respectively. The Monte Carlo code FLUKA is used to calculate prompt and residual dose yields due to all radiation field components and the number of residual activated nuclei. Our results can provide a reference for radiation hazard analysis at short-pulse high-intensity laser facilities worldwide.