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

X-ray diffraction at the National Ignition Facility

We report details of an experimental platform implemented at the National Ignition Facility to obtain in situ powder diffraction data from solids dynamically compressed to extreme pressures. Thin samples are sandwiched between tamper layers and ramp compressed using a gradual increase in the drive-laser irradiance. Pressure history in the sample is determined using high-precision velocimetry measurements. Up to two independently timed pulses of x rays are produced at or near the time of peak pressure by laser illumination of thin metal foils. The quasi-monochromatic x-ray pulses have a mean wavelength selectable between 0.6 Å and 1.9 Å depending on the foil material. The diffracted signal is recorded on image plates with a typical 2θ x-ray scattering angle uncertainty of about 0.2° and resolution of about 1°. Analytic expressions are reported for systematic corrections to 2θ due to finite pinhole size and sample offset. A new variant of a nonlinear background subtraction algorithm is described, which has been used to observe diffraction lines at signal-to-background ratios as low as a few percent. Variations in system response over the detector area are compensated in order to obtain accurate line intensities; this system response calculation includes a new analytic approximation for image-plate sensitivity as a function of photon energy and incident angle. This experimental platform has been used up to 2 TPa (20 Mbar) to determine the crystal structure, measure the density, and evaluate the strain-induced texturing of a variety of compressed samples spanning periods 2–7 on the periodic table

Tekenbeet: dilemma’s in de huisartsenpraktijk

Tick bites are common, and an estimated 1 in 15 individuals bitten by a tick consult their general practitioner. In 2009, there were 93,000 consultations for tick bites in the Netherlands, a threefold increase compared with 1994. About 10% of ticks in the Netherlands are infected with Borrelia burgdorferi, which causes Lyme's disease, but the prevalence of infected ticks may be higher in certain areas. The risk of Lyme's disease is small if the tick is removed within 24 hours. Erythema migrans, the classical first stage of Lyme's disease, is treated with antibiotics depending on the clinical symptoms. A skin reaction that develops within a few days, that is smaller than 5 cm, and which disappears rapidly is a hypersensitivity reaction that is not caused by Lyme's disease. Serological investigations are only necessary if skin signs are unclear but tests are only sensitive enough to prove/disprove infection after 6 weeks. Post-exposure prophylaxis is not necessary after every tick bite but can be given if the tick has been attached for longer than 24 hours. Once-only administration of antibiotics reduces the risk of Lyme's disease.</p