The plastic veto detector array (PV) was designed for the pibeta experiment to provide a means by which non-pion beta decay events could be rejected quickly via hardware. Early in-beam tests have shown that a sufficiently restrictive event trigger can be made without the PV so that data from the PV will only be used offline. The PV is still a vital component of the pion beta decay experiment because it provides a clear indication of whether particles traveling from the target to the CsI calorimeter are charged or neutral. The CsI alone cannot distiguish between a 70 MeV photon from a p 0 decay and a 70 MeV postitron from a p +-> e+ n decay.
This chapter describes the plastic veto detector array (PV) located in the interior of the pibeta detector as shown in Figure 3.7. The geometry of the PV is discussed as well as some of the properties of the components. Results from data taken with a cosmic ray tomography apparatus are also presented.