Identifying, quantifying, and mitigating background with the time-resolved x-ray diffraction platform at the National Ignition Facility.

The time-resolved x-ray diffraction platform at the National Ignition Facility (NIF) fields electronic sensors closer to the exploding laser-driven target than any other NIF diagnostic in order to directly detect diffracted x rays from highly compressed materials. We document strategies to characterize and mitigate the unacceptably high background signals observed in this geometry. We specifically assess the possible effects of electromagnetic pulse, x-ray fluorescence, hot electrons, and sensor-specific non-x-ray artifacts.

Modifying x-ray streak cameras for operation on igniting fusion experiments.

The National Ignition Facility produced the first nuclear fusion experiment demonstrating net positive energy gain on December 5, 2022. The x-ray streak camera that measures the bang time and burn-width from this landmark experiment had an electronic failure and did not record data. The CCD sensor was replaced with a radiation hardened CMOS sensor that has since demonstrated successful operation on repeat ignition shots.

Time resolved x-ray diffraction using the flexible imaging diffraction diagnostic for laser experiments (FIDDLE) at the National Ignition Facility (NIF): Preliminary assessment of diffraction precision.

The Flexible Imaging Diffraction Diagnostic for Laser Experiments (FIDDLE) is a new diagnostic at the National Ignition Facility (NIF) designed to observe in situ solid-solid phase changes at high pressures using time resolved x-ray diffraction. FIDDLE currently incorporates five Icarus ultrafast x-ray imager sensors that take 2 ns snapshots and can be tuned to collect X-rays for tens of ns. The platform utilizes the laser power at NIF for both the laser drive and the generation of 10 keV X-rays for ∼10 ns using a Ge backlighter foil.

Developing time-resolved x-ray diffraction diagnostics at the National Ignition Facility (invited).

As part of a program to measure phase transition timescales in materials under dynamic compression, we have designed new x-ray imaging diagnostics to record multiple x-ray diffraction measurements during a single laser-driven experiment. Our design places several ns-gated hybrid CMOS (hCMOS) sensors within a few cm of a laser-driven target. The sensors must be protected from an extremely harsh environment, including debris, electromagnetic pulses, and unconverted laser light.

Design and characterization of the time-resolved opacity spectrometer (OpSpecTR) for the NIF iron opacity campaign.

A new time-resolved opacity spectrometer (OpSpecTR) is currently under development for the National Ignition Facility (NIF) opacity campaign. The spectrometer utilizes Icarus version 2 (IV2) hybridized complementary metal-oxide-semiconductor sensors to collect gated data at the time of the opacity transmission signal, unlocking the ability to collect higher-temperature measurements on NIF. Experimental conditions to achieve higher temperatures are feasible; however, backgrounds will dominate the data collected by the current time-integrating opacity spectrometer.