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

On the bridging mechanism in vibration controlled dispensing of pharmaceutical powders from a micro hopper

Accurate batch dispensing of pharmaceutical powders, on the scale of hundreds of microns, in small doses is a challenging task. A novel dispensing technique has been developed by Yang et al. using high-frequency vibration to control powder flow out of a narrow hopper. This method removes the need for mechanical valves because the powder, very quickly, forms a bridge-like structure across the passive outlet preventing outflow. Activation of the vibration has been found to destabilise the bridging structure enabling the powder to flow, when vibration stops the bridge structure quickly rebuilds and dispensing stops. In this work the Discrete Element Method (DEM) was used to simulate this novel dispensing control method in order to identify the internal mechanism that allows the flow to be controlled so precisely. A simulated conical hopper was filled with particles then oscillated vertically at high frequency (≈. 10. kHz), amplitude and frequency were scaled from the experimental system. Two orifice sizes, a variety of DEM parameters and two vibration modes were simulated. The parametric study of DEM parameters was based around a case that provided flow rates within a factor of 2 of the experimental flow rates. Dispensing after vibration was found to stop very quickly as in experiments. Visualisation of internal structures during fill, vibration and immediately after vibration revealed a central mass of slow moving particles floating above the nozzle outlet. When the vibration stops the central mass of particles drops into contact with the walls and quickly plugs the flow. © 2013 Elsevier B.V.status: publishe

Transmission of 61 C-band Channels with L-band Interferers over Record 618km of Hollow-Core-Fiber

We recirculated 61 PM-QPSK C-band channels @32GBaud, with simultaneous L-band loading, through 7.72km of hollow-core NANF with <1dB/km loss. We reached 772km for the midchannel, and 618km for all channels at average GMI 3.44 bits/symbol