This PDF file contains the front matter associated with SPIE Proceedings Volume 11666, including the Title Page, Copyright information, and Table of Contents.

Welcome and Introduction to SPIE Photonics West LASE conference 11666: High Power Lasers for Fusion Research VI

The Laser Megajoule facility, developed by the CEA is based on 176 Nd:glass laser beams focused on a micro -target positioned inside a 10-meter diameter spherical chamber. The facility will deliver a total energy of 1.4MJ of UV light at 0.35 μm and a maximum power of 400 TW. A specific pétawatt beam, PETAL, offers a combination of a very high intensity beam, synchronized with the nanosecond beams of the LMJ. This combination allows expanding the LMJ experimental field in the High Energy Density Physics (HEDP) domain. Since October 2019, 56 beams are fully operational (7 bundle of 8 beams). The installation and the commissioning of new laser bundles and new plasma diagnostics around the target chamber are continuing, simultaneously to the realization of plasma experiments. A major project milestone has been achieved at the end of 2019, with the first experiment in the facility involving neutron production, through D-D reaction in a D2 capsule inside a gold rugby cavity. The next major milestones for LMJ will take place at the end of 2021 with the commissioning of the half LMJ (10 heating bundles of 8 beams and a specific bundle for plasma diagnostics purpose). The full presentation will describe the software environment used for the laser operation, the first results on the laser damages using our 3w optical components inspection system, the laser damages analysis software, the system of spot blocking, and the last performances obtained with the PETAL beam.

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory contains a 192-beam 4.2 MJ neodymium glass laser (around 1053 nm or 1w) that is frequency converted to 351nm light or 3w. It has been designed to support the study of Inertial Confinement Fusion (ICF) and High Energy Density Physics (HEDP). The NIF Precision Diagnostic System (PDS) was reactivated and new diagnostic packages were designed and fielded that offer a more comprehensive suite of high-resolution measurements. The current NIF laser performance will be presented as well as the preliminary results obtained with the various laser experimental campaigns using the new diagnostic tool suites.

As major milestone of commissioning phase of beam transport section for the 10 PetaWatts beamlines of Extreme Light Infrastructure Nuclear Physics (ELI-NP) located in Magurele (Romania), we have propagated the beam throughout the beam transport section and measured its energy as well as its pulse duration after compression at full energy and full aperture. 10 consecutive laser pulses have been shot at a repetition rate of 1 shot per minute with compressed pulse energy ranging between 241 and 246 Joules while pulse duration has been measured at 23 fs leading to the first ever operation above 10 PetaWatts peak power

An overview of LaserNetUS: a national network of high power lasers for groundbreaking research.

Optical parametric chirped-pulse amplification (OPCPA) using high-energy Nd:glass lasers has the potential to produce ultra-intense pulses (>10²³ W/cm²). We report on the performance of the final high-efficiency amplifier in an OPCPA system, based on large-aperture (63 x 63-mm²) partially deuterated potassium dihydrogen phosphate (DKDP) crystals. The seed beam (170 nm, 100 mJ) was provided by the preceding OPCPA stages. The maximum pump-to-signal conversion efficiency of 33% was achieved with a 52-mm-long DKDP crystal and 40-J pump energy at 527 nm due to the flattop super-Gaussian pump beam profile and flat-in-time pulse shape. The 11.8-J output signal was compressed to 20 fs.

We will present in this paper the latest development made in the frame of High repetition rate PW laser. Increasing the repetition rate in high energy laser requires to master a lot of different parameters and especially the cooling and the reliability. We have worked in this direction in the frame of two projects: ELI ALPS in hungaria and HIBEF in Germany. We will show in the talk the developments that we have accomplished to reach at the same time a high energy and a high average power: specific pump laser (50J at 10Hz), High average power cryo cooling. We will also focus on the reliability of these systems and present the results gathered during the last months.

The transverse spontaneous Raman scattering in a configuration analogous to the geometry of a large-aperture potassium dihydrogen phosphate polarization rotator plate for inertial confinement fusion-class lasers is investigated. The experimental setup enabled effectively measuring the transverse Raman scattering in 360° around the beam propagation direction for any crystal optic-axis (OA) alignment. Results reveal the angular dependence of the transverse Raman scattering signal as a function of (1) the angle between the OA and the pump-beam propagation and (2) the angle of the X-Y axis around the OA. These results enable the consideration of optimal crystal cut designs for specific applications.

We will present in this paper the latest results and ongoing developments on high rep-rate high energy glass lasers. These lasers are dedicated to applications such as Ti:Sa pumping, OPCPA pumping, Laser Shock Peening a nd also Laser Driven Dynamic Shock Compression.

As high-intensity short-pulse lasers that can operate at high-repetition-rate (HRR) (>10 Hz) come online around the world, the high-energy-density (HED) science they enable will experience a radical paradigm shift. The >10^3x increase in shot rate over today’s shot-per-hour drivers translates into dramatically faster data acquisition and more experiments, and thus the potential to significantly accelerate the advancement of HED science. We will present the vision and ongoing work to realize a HRR framework that allows for rapidly delivered optimal experiments by bringing together feedback laser control loops, high-throughput targetry and diagnostics, cognitive simulation, enhanced HED codes, and advanced data analytics.

The world’s largest and most energetic laser facility, the National Ignition Facility (NIF) is dedicated to understanding inertial confinement fusion by irradiating a mm scale fusion target using 192 precisely aligned laser beams. The optical Thompson scattering (OTS) laser is being commissioned to understand the target implosion physics, especially for under-dense plasma conditions. The OTS will enable the diagnosis of the plasma performance leading to better control of the symmetry and efficiency of target implosion. Both 3w and 5w probe beams can be selectively chosen for diagnosing various plasma densities. Just as the NIF laser, the OTS system is aligned using several closed loop controls. CCD images of the laser beams are analyzed using automatic alignment image processing algorithm to provide beam position and motorized mirrors are mobilized to steer those beams to the desired path and location. One such control loop of the OTS uses a pair of far field diffraction pattern generated by a spherical object connected to a shaft. During the control loop alignment movements, the diffraction rings may be partially missing due to obstruction by the aperture. This paper describes the systematic process of algorithm development for detection of the diffraction rings and the necessary modifications as the requirements change. It describes the template design and algorithm for position detection from such images under challenging illumination and obstructive conditions. Among other novelties of this work is the use of a single computational neuron, inspired by a bipolar binary associative memory, employed to evaluate the quality and uncertainty of the location measurement, and avoid false detection.

Application of deep learning to shaped, short-pulse laser-driven ion acceleration. Using a neural network as a universal approximator function, i.e., a surrogate model, we can map out large areas of parameter space. The neural network is informed by a large dataset of about 1,000, mid-fidelity particle-in-cell simulations modeling instances of Target-Normal Sheath Acceleration. The neural-network-based function allows us to rapidly explore regions of interest in search of optimal input parameters and features of interest.

High intensity, high-repetition rate (HRR) lasers, that is lasers that can operate on the order of 1 Hz or faster, are quickly coming on-line around the world. High intensity lasers have long been an impactful tool in high energy density (HED) science since they are capable of creating matter at extreme temperatures and pressures relevant to this field. The advent of HRR technology enhances to this capability since HRR enables these types of these experiments to be performed faster, thus leading to an acceleration in the rate of learning in fundamental HED science. However, in order to use the full potential of HRR systems, high repetition rate diagnostics in addition to real-time analysis tools must be developed to process experimental measurements and outputs at a rate that matches the laser. Towards this goal, we present an automated machine learning based analysis for a synthetic X-ray spectrometer, which is a common diagnostic in HED experiments.