Demonstration of TNSA proton radiography on the National Ignition Facility Advanced Radiographic Capability (NIF-ARC) laser

Proton radiography using short-pulse laser drivers is an important tool in high-energy density (HED) science for dynamically diagnosing key characteristics in plasma interactions. Here we detail the first demonstration of target-normal sheath acceleration (TNSA)-based proton radiography the NIF-ARC laser system aided by the use of compound parabolic concentrators (CPCs). The multi-kJ energies available at the NIF-ARC laser allows for a high-brightness proton source for radiography and thus enabling a wide range of applications in HED science. In this demonstration, proton radiography of a physics package was performed and this work details the spectral properties of the TNSA proton probe as well as description of the resulting radiography quality.

Amplification of 200-ps high-intensity laser pulses via frequency matching stimulated Brillouin scattering

Laser pulses of 200 ps with extremely high intensities and high energies are sufficient to satisfy the demand of shock ignition, which is an alternative path to ignition in inertial confinement fusion (ICF). This paper reports a type of Brillouin scheme to obtain high-intensity 200-ps laser pulses, where the pulse durations are a challenge for conventional pulsed laser amplification systems. In the amplification process, excited Brillouin acoustic waves fulfill the nonlinear optical effect through which the high energy of a long pump pulse is entirely transferred to a 200-ps laser pulse. This method was introduced and achieved within the SG-III prototype system in China. Compared favorably with the intensity of $2~\text{GW}/\text{cm}^{2}$ in existing ICF laser drivers, a 6.96- $\text{GW}/\text{cm}^{2}$ pulse with a width of 170 ps was obtained in our experiment. The practical scalability of the results to larger ICF laser drivers is discussed.

Measurement of large optical elements used for inertial confinement fusion with ptychography

High-power laser drivers are located in huge laser facilities built for inertial confinement fusion, and have achieved important progresses in the past decade; however, many unconventional optical elements implemented still cannot be accurately measured. To solve this problem, the ptychographic iterative engine (PIE), which is a recently developed technique that can detect both the phase and modulus of the light field simultaneously, is adopted to measure the transmission function of these optical elements and then to accurately characterize their key parameters. The distinctive advantage of PIE over other traditional metrology techniques in measuring large optical elements is demonstrated in this paper by detecting the focal length of a lens array and the surface profile of a continuous phase plate.