A high energy electron spectrometer has been designed and tested using imaging plate (IP). The measurable energy range extends from $1\text{to}100\mathrm{MeV}$ or even higher. The IP response in this energy range is calibrated using electrons from L-band and S-band LINAC accelerator at energies 11.5, 30, and $100\mathrm{MeV}$ . The calibration has been extended to $0.2\mathrm{MeV}$ using an existing data and Monte Carlo simulation Electron Gamma Shower code. The calibration results cover the energy from $0.2\text{to}100\mathrm{MeV}$ and show almost a constant sensitivity for electrons over $1\mathrm{MeV}$ energy. The temperature fading of the IP shows a 40% reduction after $80\min$ of the data taken at $22.5°\mathrm{C}$ . Since the fading is not significant after this time we set the waiting time to be $80\min$ . The oblique incidence effect has been studied to show that there is a $1∕\cos \theta$ relation when the incidence angle is $\theta$ .

$K_{\alpha }$ x-ray emission, extreme ultraviolet emission, and plasma imaging techniques have been used to diagnose energy transport patterns in copper foils ranging in thickness from 5 to $75\mu \mathrm{m}$ for intensities up to $5\times {10}^{20}\mathrm{W}{\mathrm{cm}}^{-2}$. The $K_{\alpha }$ emission and shadowgrams both indicate a larger divergence angle than that reported in the literature at lower intensities [R. Stephens et al., Phys. Rev. E 69, 066414 (2004)]. Foils $5\mu \mathrm{m}$ thick show triple-humped plasma expansion patterns at the back and front surfaces. Hybrid code modeling shows that this can be attributed to an increase in the mean energy of the fast electrons emitted at large radii, which only have sufficient energy to form a plasma in such thin targets.

The results of laser-driven proton beam focusing and heating with a high energy $\left(170\mathrm{J}\right)$ short pulse are reported. Thin hemispherical aluminum shells are illuminated with the Gekko petawatt laser using $1\mu \mathrm{m}$ light at intensities of $\sim 3\times {10}^{18}\mathrm{W}∕{\mathrm{cm}}^2$ and measured heating of thin Al slabs. The heating pattern is inferred by imaging visible and extreme-ultraviolet light Planckian emission from the rear surface. When Al slabs $100\mu \mathrm{m}$ thick were placed at distances spanning the proton focus beam waist, the highest temperatures were produced at $0.94\times$ the hemisphere radius beyond the equatorial plane. Isochoric heating temperatures reached $81\mathrm{eV}$ in $15\mu \mathrm{m}$ thick foils. The heating with a three-dimensional Monte Carlo model of proton transport with self-consistent heating and proton stopping in hot plasma was modeled.

Fast electron generation in the presence of coronal plasma in front of a solid target (typically referred to as preformed plasma) in laser-matter interaction in the intensity range of 10${}^{19}$–10${}^{21}$ W/cm${}^2$ is studied in a one-dimensional slab approximation with particle-in-cell (PIC) simulations. Three different preformed plasma density scale lengths of 1, 5, and 15 μm are considered. We report an increase in both mean and maximum energy of generated fast electrons with an increase in the preformed plasma scale length (in the range 1–15 μm). The heating of plasma electrons is predominantly due to their stochastic motion in counterpropagating electromagnetic (EM) waves (incident and reflected waves) and the presence of a longitudinal electric field produced self-consistently inside the preformed plasma. The synergetic effects of this longitudinal electric field and EM waves responsible for the efficient preformed plasma electrons heating are discussed.

We report an observation of surface acceleration of fast electrons in intense laser-plasma interactions. When a preformed plasma is presented in front of a solid target with a higher laser intensity, the emission direction of fast electrons is changed to the target surface direction from the laser and specular directions. This feature could be caused by the formation of a strong static magnetic field along the target surface which traps and holds fast electrons on the surface. In our experiment, the increase in the laser intensity due to relativistic self-focusing in plasma plays an important role for the formation. The strength of the magnetic field is calculated from the bent angle of the electrons, resulting in tens of percent of laser magnetic field, which agrees well with a two-dimensional particle-in-cell calculation. The strong surface current explains the high conversion efficiency on the cone-guided fast ignitor experiments.