  The PTOLEMY transverse drift filter is a new concept to enable precision
analysis of the energy spectrum of electrons near the tritium beta-decay
endpoint. This paper details the implementation and optimization methods for
successful operation of the filter. We present the first demonstrator that
produces the required magnetic field properties with an iron return-flux
magnet. Two methods for the setting of filter electrode voltages are detailed.
The challenges of low-energy electron transport in cases of low field are
discussed, such as the growth of the cyclotron radius with decreasing magnetic
field, which puts a ceiling on filter performance relative to fixed filter
dimensions. Additionally, low pitch angle trajectories are dominated by motion
parallel to the magnetic field lines and introduce non-adiabatic conditions and
curvature drift. To minimize these effects and maximize electron acceptance
into the filter, we present a three-potential-well design to simultaneously
drain the parallel and transverse kinetic energies throughout the length of the
filter. These optimizations are shown, in simulation, to achieve low-energy
electron transport from a 1 T iron core (or 3 T superconducting) starting field
with initial kinetic energy of 18.6 keV drained to <10 eV (<1 eV) in about 80
cm. This result for low field operation paves the way for the first
demonstrator of the PTOLEMY spectrometer for measurement of electrons near the
tritium endpoint to be constructed at the Gran Sasso National Laboratary (LNGS)
in Italy.

Instrumentation and Detectors;Instrumentation and Methods for Astrophysics