Publications by authors named "K LeChien"
Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment.
Phys Rev Lett
February 2024
Article Synopsis
- * This experiment produced 2.05 MJ of laser energy, resulting in 3.1 MJ of total fusion yield, which exceeds the Lawson criterion for ignition, demonstrating a key milestone in fusion research.
- * The report details the advancements in target design, laser technology, and experimental methods that contributed to this historic achievement, validating over five decades of research in laboratory fusion.
Article Synopsis
- * In inertially confined fusion, ignition allows the fusion process to spread into surrounding fuel, potentially leading to higher energy output.
- * Recent experiments at the National Ignition Facility achieved capsule gains of 5.8 and approached ignition, even though "scientific breakeven" has not yet been fully realized.
The very short burn time and small size of burning plasmas created at advanced laser-fusion facilities will require high-spatial-resolution imaging diagnostics with fast time resolution. These instruments will need to function in an environment of extremely large neutron fluxes that will cause conventional diagnostics to fail because of radiation damage and induced background levels. One solution to this challenge is to perform an ultrafast conversion of the x-ray signals into the optical regime before the neutrons are able to reach the detector and then to relay image the signal out of the chamber and into a shielded bunker, protected from the effects of these neutrons.
View Article and Find Full Text PDFA line VISAR (Velocity Interferometer System for Any Reflector) has been designed and commissioned at the Sandia National Laboratory's Z-machine. The instrument consists of an F/2 collection system, beam transport, and an interferometer table that contains two Mach-Zehnder type interferometers and an eight channel Gated Optical Imaging (GOI) system. The VISAR probe laser operates at the 532 nm wavelength, and the GOI bandpass is 540-600 nm.
View Article and Find Full Text PDFObjective: To identify pregnancies at increased risk for trisomy 13, trisomy 18 or triploidy attributable to low fetal fraction (FF).
Methods: A FF-based risk (FFBR) model was built using data from more than 165 000 singleton pregnancies referred for single-nucleotide polymorphism (SNP)-based non-invasive prenatal testing (NIPT). Based on maternal weight and gestational age (GA), FF distributions for normal, trisomy 13, trisomy 18 and triploid pregnancies were constructed and used to adjust prior risks for these abnormalities.