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Sökning: WFRF:(Brenning Nils) > Kungliga Tekniska Högskolan

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1.
  • Aijaz, Asim, et al. (författare)
  • A strategy for increased carbon ionization in magnetron sputtering discharges
  • 2012
  • Ingår i: Diamond and related materials. - : Elsevier BV. - 0925-9635 .- 1879-0062. ; 23, s. 1-4
  • Tidskriftsartikel (refereegranskat)abstract
    • A strategy that facilitates a substantial increase of carbon ionization in magnetron sputtering discharges is presented in this work. The strategy is based on increasing the electron temperature in a high power impulse magnetron sputtering discharge by using Ne as the sputtering gas. This allows for the generation of an energetic C+ ion population and a substantial increase in the C+ ion flux as compared to a conventional Ar-HiPIMS process. A direct consequence of the ionization enhancement is demonstrated by an increase in the mass density of the grown films up to 2.8 g/cm(3); the density values achieved are substantially higher than those obtained from conventional magnetron sputtering methods.
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4.
  • Alfvén, Hannes, et al. (författare)
  • Voyager saturnian ring measurements and the early history of the solar-system
  • 1986
  • Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 34:2, s. 145-154
  • Tidskriftsartikel (refereegranskat)abstract
    • The mass distribution in the Saturnian ring system is investigated and compared with predictions from the plasma cosmogony. According to this theory, the matter in the rings has once been in the form of a magnetized plasma, in which the gravitation is balanced partly by the centrifugal force and partly by the electromagnetic forces. As the plasma is neutralized, the electromagnetic forces disappear and the matter can be shown to fall in to of the original saturnocentric distance. This causes the so called “cosmogonic shadow effect”, which has been demonstrated earlier for the asteroidal belt and in the large scale structure of the Saturnian ring system.The relevance of the cosmogonic shadow effect is investigated for parts of the fine structures of the Saturnian ring system. It is shown that many structures of the present ring system can be understood as shadows and antishadows of cosmogonic origin. These appear in the form of double rings centered around a position a factor 0.64 (slightly less than) closer to Saturn than the causing feature. Voyager data agree with an accuracy better than 1%.
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5.
  • Antunes, V. G., et al. (författare)
  • Influence of the magnetic field on the extension of the ionization region in high power impulse magnetron sputtering discharges
  • 2023
  • Ingår i: Plasma sources science & technology. - : IOP Publishing. - 0963-0252 .- 1361-6595. ; 32:7
  • Tidskriftsartikel (refereegranskat)abstract
    • The high power impulse magnetron sputtering (HiPIMS) discharge brings about increased ionization of the sputtered atoms due to an increased electron density and efficient electron energization during the active period of the pulse. The ionization is effective mainly within the electron trapping zone, an ionization region (IR), defined by the magnet configuration. Here, the average extension and the volume of the IR are determined based on measuring the optical emission from an excited level of the argon working gas atoms. For particular HiPIMS conditions, argon species ionization and excitation processes are assumed to be proportional. Hence, the light emission from certain excited atoms is assumed to reflect the IR extension. The light emission was recorded above a 100 mm diameter titanium target through a 763 nm bandpass filter using a gated camera. The recorded images directly indicate the effect of the magnet configuration on the average IR size. It is observed that the shape of the IR matches the shape of the magnetic field lines rather well. The IR is found to expand from 10 and 17 mm from the target surface when the parallel magnetic field strength 11 mm above the racetrack is lowered from 24 to 12 mT at a constant peak discharge current.
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6.
  • Appelgren, Patrik (författare)
  • Experiments with and modelling of explosively driven mangetic flux compression generators
  • 2008
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis presents work performed on explosively driven magnetic flux compression generators. This kind of devices converts the chemically stored energy in a high explosive into electromagnetic energy in the form of a powerful current pulse. The high energy density of the high explosives makes flux compression generators attractive as compact power sources. In order to study these devices a generator was designed at FOI in the mid-90ies. Two generators remained unused and became available for this licentiate work. The thesis reports experiments with, and simulations of, the operation of the two remaining generators. The aim was to fully understand the performance of the generator design and be able to accurately simulate its behaviour. The generators were improved and fitted with various types of diagnostics to monitor the generator operation. Two experiments were performed of which the first generator was operated well below its current capability limits while the second was stressed far above its limits. Since the generator generates a rapidly increasing current, a current measurement is the most important diagnostic revealing the current amplification of the generator and its overall performance. Further it is important to measure the timing of various events in the generator. With a common time reference it is possible to combine data from different probes and extract interesting information which cannot be directly obtained with a single measurement. Two types of numerical simulations have been performed: Hydrodynamic simulations of the high explosive interaction with the armature were used to verify the measured armature dynamics. A zero-dimensional code was used to perform circuit simulations of the generator. The model takes into account the inductance reduction due to the compression of the generator as well as the change in conductivity due to heating of the conductors in the generators.
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  • Appelgren, Patrik, et al. (författare)
  • Modeling of a small helical magnetic flux compression generator
  • 2008
  • Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 36:5, s. 2662-2672
  • Tidskriftsartikel (refereegranskat)abstract
    •  In order to gain experience in explosive pulsed power and to provide experimental data as the basis for computer modeling, a small high-explosive-driven helical magnetic flux-compression generator (FCG) was designed at the Swedish Defence Research Agency. The generator, of which three have been built, has an overall length of 300 mm and a diameter of 70 mm. It could serve as the energy source in a pulse-forming network to generate high-power pulses for various loads. This paper presents a simulation model of this helical FCG. The model, which was implemented in Matlab-Simulink, uses analytical expressions for the generator inductance. The model of resistive losses takes into account the heating of the conductors and the diffusion of the magnetic field into the conductors. The simulation results are compared with experimental data from two experiments with identical generators but with different seed currents, influencing the resistive losses. The model is used to analyze the performance of the generator.
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9.
  • Appelgren, Patrik, et al. (författare)
  • Small Helical Magnetic Flux-Compression Generators : Experiments and Analysis
  • 2008
  • Ingår i: IEEE Transactions on Plasma Science. - 0093-3813 .- 1939-9375. ; 36:5, s. 2673-2683
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to gain experience in explosive pulsed power and to provide experimental data for modeling, a small high-explosive-driven helical magnetic flux-compression generator (FCG) was designed at the Swedish Defence Research Agency (FOI). The generator, of which three have been built, has an overall length of 300 mm and a diameter of 70 mm. It could serve as the energy source in a pulse-forming network to generate high power pulses for various loads. This paper presents the design of, and tests with, this helical FCG. The generator had an initial inductance of 23 mu H and was operated into a load of 0.2 mu H. The generator is charged with 0.27 kg of high explosives (PBXN-5). Various types of diagnostics were used to monitor the operation of the generator, including current probes, optical fibers, and piezo gauges. With seed currents of 5.7 and 11.2 kA, final currents of 269 and 436 kA were obtained, corresponding to current amplification factors of 47 and 39. The peak of the current was reached about 30 mu s after the time of crowbar. The two generators showed only small losses in terms of 2 pi-clocking. Using signals from optical fibers, the deflection angle of the armature could be determined to be 10 degrees in good agreement with hydrodynamic simulations of the detonation process and the detonation velocity to be 8.7 km/s in agreement with tabulated value.
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