Precision microwave measurements in atomic helium

In this paper we describe two very-high-precision microwave measurements of fine structure intervals in atomic helium. In separate experiments, the 10 (+)F(3)-to-10(+)G(4) and the 2(3)P(1)-to-2(3)P(0) intervals are measured. T he measurements provide precise tests of quantum electrodynamics in two ver y different regimes of atomic physics. The n=10 measurement, when compared to similarly precise theory for the interval, is among the most precise mea surements of any physics on the 10(-8) m distance scale. Comparing precise theory to experiment for the 2(3)P interval will yield a determination of t he line-structure constant.