Sökning: "positron lifetime measurements"

Visar resultat 1 - 5 av 7 avhandlingar innehållade orden positron lifetime measurements.

1. 1. Investigation of Nuclear Materials with Positron Measurements

   Författare :Petty Bernitt Cartemo; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; depth profiling; positron beam; nuclear materials; radiation damage; positron lifetime measurements;

   Sammanfattning : Positron Annihilation Lifetime Spectroscopy can be used to characterize radia- tion-induced material defects to subsequently optimize nuclear materials with respect to radiation damage. Nuclear Systems of the future such as Generation IV and fusion concepts demand high performance from structural materials, comprising a material's stability in highly-radiative and hot environments. LÄS MER

3. 2. Free Volume Depth Profiling at Polymer Surfaces and Interfaces

   Författare :John Algers; Centrum för analys och syntes; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; biopolymers; Polymerteknik; Polymer technology; polymer interfaces; polymer surfaces; positron lifetime; free volume;

   Sammanfattning : Pulsed low energy positron beams provide a unique and non-destructive tool to depth probe the free volume of polymers at surfaces and interfaces. Since the employment of low energy positron beams in polymer research is an emerging technique, some focus in this thesis has been on extracting methods and equations needed to interpret the experimental data. LÄS MER

4. 3. Radiation Detection Techniques for the Enhancement of Nuclear Safety

   Författare :Petty Bernitt Cartemo; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; whole body counting; depth profiling; voxel phantom; nuclear safeguards; Monte Carlo; orphan sources; radiation-induced material damage; pulsed beam; positron lifetime;

   Sammanfattning : The hazard originating from the use of nuclear materials in various areas of the society necessitates a number of experimental techniques for controlling and increasing the safety connected to radioactive substances.The following thesis is divided into two parts, representing different aspects to the detection of radiation effects. LÄS MER

5. 4. Free Volume Determination in Polymers and Polymer Blends

   Författare :Camilla Wästlund; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; positronium formation; crystallinity; polymer blends; inhibition; polymers; free volume; positron annihilation; phase separation; distribution;

   Sammanfattning : The free volume of a polymer, which corresponds to the unoccupied regions accessible to segmental motions, is an important parameter for understanding and predicting many of its characteristic properties. The concept of free volume is the basis for understanding the molecular mobility in polymers. LÄS MER

7. 5. Efficient Solid-State Power Amplifiers for RF Power Source Applications

   Författare :Renbin Tong; Dragos Dancila; Jörgen Olsson; Olof Bengtsson; Zoya Popovic; Uppsala universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; back-off efficiency; high efficiency; power source; RF energy; RF measurements; radioisotope production; solid-state power amplifiers; Engineering Science with specialization in Microwave Technology; Teknisk fysik med inriktning mot mikrovågsteknik;

   Sammanfattning : Radio Frequency (RF) power sources are extensively applied in various fields. Radioisotope production, i.e., the production of short-lived radioactive isotopes, for positron emission tomography (PET) is one of the most important applications in the medical and healthcare domains. LÄS MER