  For identification and 3D-tracking of low-energy electrons a new type of
gas-based detector was designed that minimizes scattering and energy loss. The
current version of the detector is a combination of a plastic scintillator,
serving as a trigger source and energy detector, and a hexagonally structured
multi-wire drift chamber (MWDC), filled with a mixture of helium and isobutane
gas. The drift time information is used to track particles in the plane
perpendicular to the wires, while a charge division technique provides spatial
information along the wires. The gas tracker was successfully used in the
miniBETA project as a beta spectrometer for a measurement of the weak magnetism
form factor in nuclear beta decay. The precision of the three-dimensional
electron tracking, in combination with low-mass, low-Z materials and
identification of backscattering from scintillator, facilitated a reduction of
the main systematics effects. At certain conditions, a spatial resolution
better than 0.5 mm was obtained in the plane perpendicular to the wires, while
resolutions of about 6 mm were achieved along wires. Thanks to precise tracking
information, it is possible to eliminate electrons and other particles not
originating from the desired decay with high efficiency. Additionally, using
the coincidence between MWDC and scintillator, background from gamma emission
typically accompanying radioactive decays, was highly suppressed. An overview
of different event topologies is presented together with the tracker's ability
to correctly recognize them. The analysis is supported by Monte Carlo
simulations using Geant4 and Garfield++ packages. Finally, the preliminary
results from the 114In spectrum study are presented.
