The JET 2019-2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully available, a major Neutral Beam Injection (NBI) upgrade providing record power in 2019-2020, and tested the technical & procedural preparation for safe operation with tritium. Research along three complementary axes yielded a wealth of new results. Firstly, the JET plasma programme delivered scenarios suitable for high fusion power and alpha particle physics in the coming D-T campaign (DTE2), with record sustained neutron rates, as well as plasmas for clarifying the impact of isotope mass on plasma core, edge and plasma-wall interactions, and for ITER pre-fusion power operation. The efficacy of the newly installed Shattered Pellet Injector for mitigating disruption forces and runaway electrons was demonstrated. Secondly, research on the consequences of long-term exposure to JET-ILW plasma was completed, with emphasis on wall damage and fuel retention, and with analyses of wall materials and dust particles that will help validate assumptions and codes for design & operation of ITER and DEMO. Thirdly, the nuclear technology programme aiming to deliver maximum technological return from operations in D, T and D-T benefited from the highest D-D neutron yield in years, securing results for validating radiation transport and activation codes, and nuclear data for ITER.
Alpha particles with energies on the order of megaelectronvolts will be the main source of plasma heating in future magnetic confinement fusion reactors. Instead of heating fuel ions, most of the energy of alpha particles is transferred to electrons in the plasma. Furthermore, alpha particles can also excite Alfvénic instabilities, which were previously considered to be detrimental to the performance of the fusion device. Here we report improved thermal ion confinement in the presence of megaelectronvolts ions and strong fast ion-driven Alfvénic instabilities in recent experiments on the Joint European Torus. Detailed transport analysis of these experiments reveals turbulence suppression through a complex multi-scale mechanism that generates large-scale zonal flows. This holds promise for more economical operation of fusion reactors with dominant alpha particle heating and ultimately cheaper fusion electricity.
Internet users have been attacked by widespread email viruses earlier, but now scenario has been changed. Now attackers are no more interested to just attract media attention by infecting a large number of computers on the network; in fact, their interest has been shifted to compromising and controlling the infected computers for their personal profits. This new attack trend brings the concept of botnets over the global network of computers. With the high reported infection rates, the vast range of illegal activities and powerful comebacks, botnets are one of the main threats against the cyber security. This paper provides the readers with a background on botnet life-cycle, architecture and malicious activities. It also classifies botnet detection techniques, reviews the recent research works on botnet traffic detection and finally indicates some challenges posed to future work on botnet detection.
Abstract-Network monitoring is a difficult and demanding task that is a vital part of a network administrator's job. Network administrators are constantly striving to maintain smooth operation of their networks. If a network were to be down even for a small period of time, productivity within a company would decline, and in the case of public service departments the ability to provide essential services would be compromised. There are different network security approaches. This paper provides the readers with an overview of concrete software implementations of the current network monitoring approaches. In addition, it presents a comparison between those implementations.
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