We report the high energy radiography of dense material using MeV all-optical-driven inverse Compton x-ray source. The properties of the inverse-Compton x-ray source are controlled by means of electron energy, electron charge, scattering beam focal spot size and pulse duration to obtain optimized x-ray energy and high flux for dense material radiography. In this experiment, the x-ray has a photon energy of 8 MeV for maximal steel penetration depth, and a flux of 1011 x-ray photons per shot. With this novel x-ray source, we are able to demonstrate radiography of a 10 cm thick “kite” object through a steel shielding with thickness up to 40 cm in a single exposure. The radiography image of the “kite” object though the 40 cm steel has signal to noise ratio of 2 and image contrast of 0.1, and the “kite” object can be clearly distinguished in the image. Combining its tunability, ultrafast pulse duration and micron meter resolution, the all-optical-driven inverse Compton x-ray source provides unique capacities for flash radiography of dense material, and is of interest for ultrafast nuclear physics study.
By employing a pair of partially overlapped supersonic gas jets, we separated injection and acceleration stages of laser wakefield acceleration to produce stable, monoenergetic, and tunable electron beams. The first jet (injector) utilized a He/N2 mixture and resulted in electrons injected into the wake via ionization-assisted injection. These electrons were then accelerated in the second jet (accelerator) using pure He. By changing length and plasma density of the accelerator jet, we were able to tune electron energy in the 50 – 300 MeV range with energy spread of 10-30% and 20 pC charge. Simulations show that the injection region is limited within the overlap of the jets.
The laser-driven Thomson scattering light source generates x-rays by the scattering of a high-energy electron beam off a high-intensity laser pulse. We have demonstrated that this source can generate collimated, narrowband x-ray beams in the energy range 0.1-12 MeV. In this work, we discuss recent results on the application of this source for radiography and photonuclear studies. The unique characteristics of the source make it possible to do this with the lowest possible dose and in a low-noise environment. We will also discuss recent experimental results that study nuclear reactions above the threshold for photodisintegration and photofission. The tunable nature of the source permits activation of specific targets while suppressing the signal from background materials.
A repetitive petawatt-class Ti:sapphire laser system operating with high spatial and temporal beam quality is demonstrated. Maximum pulse energy of 30 J is obtained via five multi-pass amplification stages. Closed-loop feedback control systems in the temporal and spatial domains are used to yield Fourier-transform-limited pulse duration (33.7 fs), and diffraction-limited focal spot sizes (with several different tight focusing optics). The laser parameters have been fully characterized at high-power, and are monitored in real-time, to ensure that they meet the experimental requirements for laser-wakefield electron acceleration and x-ray generation.