A solenoidal electron spectrometer for a precision measurement of the neutron $beta$-asymmetry with ultracold neutrons

We describe an electron spectrometer designed for a precision measurement of the neutron $beta$-asymmetry with spin-polarized ultracold neutrons. The spectrometer consists of a 1.0-Tesla solenoidal field with two identical multiwire proportional chamber and plastic scintillator electron detector packages situated within 0.6-Tesla field-expansion regions. Select results from performance studies of the spectrometer with calibration sources are reported.