  Silicon Drift Detectors, widely employed in high-resolution and high-rate
X-ray applications, are considered here with interest also for electron
detection. The accurate measurement of the tritium beta decay is the core of
the TRISTAN (TRitium Investigation on STerile to Active Neutrino mixing)
project. This work presents the characterization of a single-pixel SDD detector
with a mono-energetic electron beam obtained from a Scanning Electron
Microscope. The suitability of the SDD to detect electrons, in the energy range
spanning from few keV to tens of keV, is demonstrated. Experimental
measurements reveal a strong effect of the detector's entrance window structure
on the observed energy response. A detailed detector model is therefore
necessary to reconstruct the spectrum of an unknown beta-decay source.
