Swedish Defence Research Agency

About: Swedish Defence Research Agency is a government organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Radar & Laser. The organization has 1413 authors who have published 2731 publications receiving 56083 citations. The organization is also known as: Totalförsvarets forskningsinstitut.

Laser beam propagation in jet engine plume environments: a review

Abstract: Laser beam propagation through adverse turbulent environments such as the region close to a jet engine exhaust need to be studied in order to predict performance degradations on airborne laser systems. The turbulent plume region may introduce severe perturbations which accumulate and cause beam degradation in terms of beam wander, intensity scintillations and beam broadening at longer ranges. Applications of interest with respect to laser beam propagation in jet engine plume environments include e.g. directed infrared countermeasures (DIRCM) and active imaging. By characterising and evaluating the perturbation effects schemes for compensation or avoiding performance degradation can be devised. The turbulence effects in the plume region occur by mixing of hot exhaust flow from the jet engine with surrounding ambient air causing spatial and temporal fluctuations in the refractive index. In comparison to atmospheric turbulence considerably shorter outer- and inner scales have been observed. Typical values of the structure constant within the plume region range from 10-10 to 10-9 m-2/3 making the turbulence several order in magnitude stronger in contrast to propagation through the atmosphere. Of importance in characterisation of the jet engine plume with respect to laser beam propagation are turbulent length scales, the extent of the turbid region, variation of the structure constant and temporal flow properties. In this paper reported experimental results and modelling approaches aimed for predicting laser beam propagation degradation in jet engine plume regions are reviewed. The results will be discussed in perspective of system performance.

SEUs Induced by Thermal to High-Energy Neutrons in SRAMs

Abstract: We report on experimental SEU studies using thermal and high-energy neutrons, conducted at the TRIUMF facility, Vancouver. Different SRAM samples were used and many samples showed to be highly susceptible to thermal neutrons. Moreover, a considerable part of the total SEU-rate, at high altitudes as well as down at sea level, may be attributed to thermal neutrons for RAM based devices.

Evidence of three-body force effects in neutron-deuteron scattering at 95 MeV

Abstract: Recently, we have reported a measurement of the neutron-deuteron elastic scattering differential cross section at 95 MeV. In the present work, the previous results are confirmed with an independent measurement performed with another setup. The new data cover the full angular distribution by combining neutron detection and deuteron detection, and have an unprecedented precision in the region of the cross-section minimum, where three-nucleon forces are expected to be significant. The effect already identified in the previous measurement is clearly seen in the present data, which agree well with theoretical descriptions including three-nucleon forces.