Radiative Lifetime Measurement of the $a^3\Sigma^+$ Metastable State of NO$^+$ Using a Linear Electrostatic Ion Trap R. Wester$^1$, K. G. Bhushan$^2$, N. Altstein$^2$, and D. Zajfman$^2$ $^1$ Max-Planck-Institut f\"{u}r Kernphysik, D-69029, Heidelberg, Germany $^2$ Department of Particle Physics, Weizmann Institute of Science, Rehovot, 76100, Israel A new type of ion trap is used to measure the radiative lifetime of the NO$^+$($a^3\Sigma^+$) metastable state. The ion trap is designed to store ion beams with an energy of a few keV and is well suited for the study of metastable states.