RESUMO
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.
RESUMO
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.
RESUMO
OBJECTIVE: To investigate the self-reported oral health, access to dental treatment and recent use of dental services among a group of drug users attending community pharmacies and to make a comparison with a group of age and gender matched community non-drug users/patients not using services for drug users. METHOD: Review instrument completed by pharmacist interviewing drug users and other pharmacy users. SETTING: Community pharmacists SAMPLING: All known drug users attending participating pharmacies plus an equivalent number of age and gender matched non-drug using pharmacy customers. Final sample size drug users N = 125; non-drug users N = 129. KEY FINDINGS: The data show that drug users self-report considerably more difficulty in accessing dental treatment, are less likely to have visited the dentist in the last 12 months and have a significantly higher level of self-assessed oral health problems, with less use of treatment services than non drug users. CONCLUSIONS: Drug users need to be encouraged to access free dental treatment available to them on the NHS. Closer collaboration between the dental profession and others in contact with drug users, such as community pharmacists, may enhance uptake of dental services.