Search for dissertations about: "liquid helium"

Showing result 1 - 5 of 27 swedish dissertations containing the words liquid helium.

  2. 1. High-Resolution Measurement of the 4He(g,n) Reaction in the Giant Resonance Region

    Author : Björn Nilsson; Kärnfysik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; tagged photons; photonuclear reactions; liquid helium; neutron detectors; liquid scintillators; giant resonances; angular distributions; differential cross sections; total cross sections; Nuclear physics; Kärnfysik; Fysicumarkivet A:2003:Nilsson;

    Abstract : 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. READ MORE

  4. 2. Novel RF MEMS Switch and Packaging Concepts

    Author : Joachim Oberhammer; KTH; []
    Keywords : 0-level packaging; adhesive bonding; BCB; benzocyclobutene; bond strength; contact printing; film actuator; glass lid encapsulation; glass lid packaging; helium leak test; hermetic packaging; hermeticity; high isolation switch; low stress silicon nitride; low volt; TECHNOLOGY; TEKNIKVETENSKAP;

    Abstract : 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. READ MORE

  5. 3. Mössbauer studies of electron population in some iron complexes

    Author : Ulf Helgeson; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Mössbauer-effekten;

    Abstract : 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. READ MORE

  6. 4. The electronic structure of iron compounds studied by Mössbauer spectroscopy

    Author : Leif Moberg; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES;

    Abstract : 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. READ MORE

  7. 5. Development of high-Tc SQUID magnetometers for on-scalp MEG

    Author : Minshu Xie; Chalmers tekniska högskola; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; nanowire junctions; on-scalp MEG; Bicrystal grain boundary; magnetoencephalography; YBCO; magnetometers; high-Tc SQUIDs;

    Abstract : 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. READ MORE