Experimental study of positron motion in Kapton

The drift of positrons under the action of an electric field in Kapton has been observed by using a variable-energy positron beam and the Doppler broadening technique. Even if the maximum applied field (2 MV/cm) is so high that the electrostatic work for a displacement of less than 0.15 nm is larger than the thermal energy, the experimental data can be fit by the diffusion model with a field-independent mobility. The best-fit value of the mobility (ca. 1×10-3 cm2 V-1 s-1) is extremely low in comparison with other dielectrics. The results are discussed with regards to the interaction of positrons with the molecular field. © 1992 Springer-Verlag.