  For the Belle II experiment at KEK (Tsukuba, Japan) the KEKB accelerator was
upgraded to deliver a 40 times larger instantaneous luminosity than before,
which requires an increased radiation hardness of the detector components. As
the innermost part of the Belle II detector, the pixel detector (PXD), based on
DEPFET (DEpleted P-channel Field Effect Transistor) technology, is most exposed
to radiation from the accelerator. An irradiation campaign was performed to
verify that the PXD can cope with the expected amount of radiation. We present
the results of this measurement campaign in which an X-ray machine was used to
irradiate a single PXD half-ladder to a total dose of 266 kGy. The half-ladder
is from the same batch as the half-ladders used for Belle II. According to
simulations, the total accumulated dose corresponds to 7-10 years of Belle II
operation. While individual components have been irradiated before, this
campaign is the first full system irradiation. We discuss the effects on the
DEPFET sensors, as well as the performance of the front-end electronics. In
addition, we present efficiency studies of the half-ladder from beam tests
performed before and after the irradiation.
