For experiments performed at LLNL’s National Ignition Facility (NIF), the goal is not just to measure the interaction between the target and the laser beams. Researchers also need to understand what’s happening to the material in the target and how it changes over time. This capability to see inside the target as it interacts with NIF’s 192 laser beams is especially useful in high-energy-density experiments and those exploring material strength.
A decade ago, NIF experiments relied on a technique known as long-delay backlighter (LDBL), in which lengthened optical fibers allowed selected laser beams to arrive up to a microsecond after those that are directed at the target. The delayed laser beams irradiated an x-ray backlighter behind the target, using the radiation produced to see what transpired during the experiment; the data was then recorded by diagnostic equipment. The LDBL method provided extraordinarily high-speed imaging of material interactions. As an example of the strong collaboration between Computing and NIF staff, this seemingly simple change required specialized software to redefine timing values for the lengthened fibers as well as operational expertise to provide the requested delay without introducing error. Read more...
