Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment.

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment.

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

Survey of physician attitudes and practices related to pediatric obesity.

The purpose of this study was to survey physicians regarding their attitudes and practices related to the treatment of pediatric obesity in a primary care setting. Surveys were sent to physicians who were members of the American Academy of Pediatrics and the American Academy of Family Physicians practicing in the Southern New England area (Connecticut, Massachusetts, and Rhode Island). The 14-item survey consisted of three main areas of focus: attitudes toward obesity, treatment and referral approaches, and barriers to addressing weight concerns in children and adolescents. Physicians estimated that 27.7% of their adolescent and 23% of their child patients are overweight. The frequency with which physicians address weight issues with both child and adolescent patients appears to increase incrementally with the patient's level of overweight. When addressing obesity, one fourth of physicians think that they are not at all or only slightly competent, while 20% report feeling not at all or only slightly comfortable. These findings suggest that physicians would benefit from additional training and education regarding safe and efficacious intervention strategies for pediatric obesity, to effectively integrate the discussion of weight issues into the primary care setting.