Sökning: "liquid helium"
Visar resultat 1 - 5 av 27 avhandlingar innehållade orden liquid helium.
1. High-Resolution Measurement of the 4He(g,n) Reaction in the Giant Resonance Region
Sammanfattning : A comprehensive near-threshold 4He(g,n) absolute cross section measurement has been performed at the high-resolution tagged-photon facility MAX-lab located in Lund, Sweden. The 20 < Eg < 45 MeV tagged photons (covering the Giant Dipole Resonance energy region) were directed towards a liquid 4He target, and knocked-out neutrons were detected in a pair of 60 cm x 60 cm vetoed NE213A liquid scintillator arrays. LÄS MER
2. Novel RF MEMS Switch and Packaging Concepts
Sammanfattning : Radio-frequency microelectromechanical systems (RF~MEMS) are highly miniaturized devices intended to switch, modulate, filter or tune electrical signals from DC to microwave frequencies. The micromachining techniques used to fabricate these components are based on the standard clean-room manufacturing processes for high-volume integrated semiconductor circuits. LÄS MER
3. Mössbauer studies of electron population in some iron complexes
Sammanfattning : A Mössbauer effect measuring system has been constructed. With the use of a liquid helium cryostat measurements are performed at room liquid nitrogen and liquid helium temperature. A superconducting magnet with fields up to 5 Tesla has been used in the cryostat. LÄS MER
4. The electronic structure of iron compounds studied by Mössbauer spectroscopy
Sammanfattning : This thesis describes Mossbauer measurements on iron compounds in the temperature range 4.2-550 Kelvin. The experimentally obtained isomer shifts and quadrupole splittings have given information about the electronic structure of the central iron atom. A large part of the thesis deals with iron compounds that are of catalytic interest. LÄS MER
5. Development of high-Tc SQUID magnetometers for on-scalp MEG
Sammanfattning : This thesis describes the development of high critical temperature superconducting quantum interference device (high-Tc SQUID) magnetometers based on bicrystal grain boundary and nanowire junctions for the potential use in on-scalp magnetoencephalography (MEG), which is a new generation MEG technique with reduced sensor-to-subject standoff distances.MEG is a method of mapping neural dynamics in the human brain by recording the magnetic fields produced by neural currents. LÄS MER