Positron annihilation spectroscopy (PAS) provides us with an unique opportunity to obtain unique and
detailed information regarding both the electron density and the electron momenta in the
region from which the positron annihilates.
When positrons are trapped in open volume defects, the positron lifetime increases due to locally reduced electron density. The strength of this component is directly related to the defect concentration.
The positron lifetime is measured by detecting the time difference between the birth &gamma -quanta (E&gamma = 1.27 MeV) of the &beta(+) -decay in the source and one of the annihilation &gamma -quanta of with energy of 511 keV.
The detectors used are fast scintillators with a short rise time and the typical timing resolution is of the order of 180 - 280 ps.
A PAS setup has been configured using BAF2 detectors and the conventional fast-fast coincidence setup. The timing resolution of the system currently is around 300 ps, which is being improved.
|Dr Chandana Rath||Banaras Hindu University|
|Dr Asimita SenGupta||Visva Bharati University|
|Dr Sanjay Kumar||Jadavpur University|
|Dr Swati Neogy||I.I.T Kharagpur|
|Dr Rajesh Kumar||Indraprastha University|