Non-contact imaging with enhanced spatial resolution by secondary electron detection

The Neutron Activation Analysis is a very sensitive method for determination of element content and composition. However, conventional methods do not provide information regarding the spatial distribution of the elements in the sample. To fulfill this need, we developed an electron imaging device with electron optics which provides element spatial distribution information based on beta-gamma coincidence. The investigated element is identified by the characteristic gamma radiation while the spatial information is obtained by the position sensitive detection of β-decay electrons. Unlike common and often invasive approaches our non-destructive method provides imaging and analysis simultaneously. This system makes use of tailor-made electron optics to select and focus coincidence electrons providing higher spatial resolution and better contrast images. For this purpose the semiconductor pixel detector Timepix is used for electron detection and is triggered by a gamma detector. In this contribution we investigate the possibility to use also the secondary electrons which are emitted from the sample surface by the primary ionizing particle crossing the surface in order to achieve higher efficiency of the device. These surface produced low-energy electrons are extracted and accelerated by a high voltage static field to be consequently detected by the Timepix detector. The low initial energy of the ejected electrons causes that the secondary electrons onto the Timepix sensor are monoenergetic with energy given by high voltage field.