Pf. Hinrichsen et al., 2-DIMENSIONAL IMPURITY DISTRIBUTIONS IN WATER TREES OCCURRING IN FIELD AGED HV CABLES, Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms, 77(1-4), 1993, pp. 517-523
Two-dimensional micro-PIXE scans of sections through large (1 to 2 mm)
vented ''water trees'', found at the inner semicon-XLPE (cross-linked
polyethylene) interface in underground HV cables, were made at 50 mum
spacing with a proton energy of 1.0 MeV. The visual appearance of one
tree is reproduced by the spatial distributions of the elements Na, C
l, K and Ca, while Si and S show only minor variation except for the c
hange at the semicon-XLPE interface. A second sample with three adjace
nt trees shows little or no correlation between the visual trees and t
he impurity distributions, although a high spatial correlation between
Na and Cl suggests the presence of NaCl in one of these three trees.