Pulsed power system for the HAPLS Diode Pumped Laser System

Industrial and Scientific High Energy Laser Systems with output energies in the Joule to Megajoule range typically rely on flash lamps to energize the gain media. Especially in rep rated laser systems the advantage of low capital cost per lamp is outweighed by many disadvantages, such as low pump efficiency, heating of the gain medium, frequent maintenance requirement, significant capital cost for its pulsed power system, and laser performance stability. Diode Pumped Solid State Laser (DPSSL) systems represent a viable alternative. In this paper we will present an efficient, integrated power conditioning system developed for the High-Repetition-Rate Advanced Petawatt Laser System (HAPLS) that is being developed by LLNL for deployment in the international user facility Extreme Light Infrastructure Beamlines (ELI-Beamlines) in Czech Republic [1]. The High Energy Pump Laser of HAPLS is energized by 4 High Peak Power Laser Diode Arrays with total peak power of 3.2 MW that were developed by Lasertel and LLNL. The diode arrays deliver ~1kJ at repetition rate 10Hz. Each diode array is comprised of 40 individual diode tiles where every tile generates >20 kilowatts of peak power. Each tile is driven by a single pulser that contains its own energy storage, control and high current drive circuitry. As part of the HAPLS laser the pulsers are operated at approximately 520A, a pulse width of 300μs at 10Hz. In another LLNL laser system basically identical pulsers are operated at 315A, 300us at 120Hz. The pulsers were designed to be operated in a support frame called a pulser crate. Each crate is designed to hold up to 45 pulsers in a volume similar to a desktop computer. Communication with the pulsers is by means of a one-way digital optical link which greatly simplifies the internal wiring. Each crate contains a “Brain Box” which in turn contains the front end processor (FEP), machine safety system (MSS) and energy storage dump subsystems. Providing flexibility and system balancing capability each pulser can be tailored to the diode tile: it has an internal Arbitrary Waveform Generator (AWG) on board that controls the shape of the diode current pulse. The AWG can vary the pulse shape in any combination of programmable increments with resolutions 1A and 1μs up to maximums of 1kA and 350μs. Under command of the crate controller each pulser can create its own distinct waveform and deliver that waveform when triggered.