What do positrons do in matter?
Positrons in Matter
Positrons - the anti-particles of electron - live only a short time (some 100 pico-seconds) in "normal" matter. They find very quickly their counterpart - the electron - and annihilate themself (and the electron) – according to Albert Einstein (E = m c2) pure energy emerges.
The sensitivity of positrons corresponds to:
- changes in the electron density of matter
- defects -- characterised by their elektron density
- concentration of defects - by random walk of the positron
- size and amount of the free volume in polymers
- volume fraction and size of sub-nanometer pores (open or closed)
- volume fraction size of mesopores (2 to 50 nanometers)
Analysis of solid material or powders
– using sealed radioktive sources –
- lateral sample size: from 9x9 mm2 to 24x24 mm2
- thickness of samples: 0,300 – 2,00 mm – dependent on their density
- powder volume: min. ca. 1 cm3
- smooth surface (1200er grinding paper)
- all sources (22Na) well below the permitted limit (1MBq)
