We have built a new positron annihilation spectroscopy (PAS) system
using a BaF₂ and plastic scintillator detectors which are connected to a
DRS4 evaluation board. The DRS4 chip has millivolt resolution of the
signal which is sampled at a rate of 5Ghz. Using post processing and
ltering of the data we can get double coincidences of a ²²Na 1274 keV
gamma ray and positron annihilation 511 keV gamma ray. This new
method of PAS using a digitizer board enables us to build a cheap and
portable table top system with the same resolution as the standard analog
counterpart. Currently we are using in the process of improving resolution
using ⁶⁰Co double coincidences.