  We describe a matter-wave Sagnac interferometer using Bose condensed atoms
confined in a time-orbiting potential trap. Compared to our previous
implementation [Moan et al., Phys. Rev. Lett. 124, 120403 (2020)], our new
apparatus provides better thermal stability, improved optical access, and
reduced trap anharmonicity. The trapping field can be adjusted to compensate
for small tilts of the apparatus in gravity. These features enable operation
with an effective Sagnac area of 4 mm^2 per orbit, and we observe interference
with 25% visibility after two orbits at a total interrogation time of 0.6 s.
Long-term measurements indicate a phase stability of 0.2 rad or better.
