  A significant aspect of the Phase-II Upgrade of the ATLAS detector is the
replacement of the current Inner Detector with the ATLAS Inner Tracker (ITk).
The ATLAS ITk is an all-silicon detector consisting of a pixel tracker and a
strip tracker. Sensors for the ITk strip tracker have been developed to
withstand the high radiation environment in the ATLAS detector after the High
Luminosity Upgrade of the Large Hadron Collider at CERN, which will
significantly increase the rate of particle collisions and resulting particle
tracks. During their operation in the ATLAS detector, sensors for the ITk strip
tracker are expected to accumulate fluences up to 1.6 x 10^15 n_eq/cm^2
(including a safety factor of 1.5), which will significantly affect their
performance. One characteristic of interest for highly irradiated sensors is
the shape and homogeneity of the electric field inside its active area. For the
results presented here, diodes with edge structures similar to full size ATLAS
sensors were irradiated up to fluences comparable to those in the ATLAS ITk
strip tracker and their electric fields mapped using a micro-focused X-ray beam
(beam diameter 2x3 {\mu}m^2). This study shows the extension and shape of the
electric field inside highly irradiated diodes over a range of applied bias
voltages. Additionally, measurements of the outline of the depleted sensor
areas allow a comparison of the measured leakage current for different fluences
with expectations for the corresponding active areas.
