The "Radiation Continuity Checker": an instrument for monitoring nuclear disarmament treaty compliance

We describe the design and construction of an instrument to monitor compliance with future arms-control treaties. By monitoring changes in the gamma-ray spectrum emitted by a stored nuclear weapon, our device can sense perturbations in the contents of a weapon storage container that would indicate treaty noncompliance. Our instrument, the radiation continuity checker, is designed to detect significant perturbations in fissile material gamma-ray spectra (indicative of tampering) while storing no classified information about the weapon and having a negligible "false alarm rate." In this paper, we describe two prototype instruments and the strategies we have adopted to perform signal processing in these instruments. Our first prototype uses a scintillation spectrometer and a massive tungsten alloy collimator to reject the gamma-ray background. Our second prototype makes use of an active collimation scheme employing a multiple detector Compton scatter approach to reject background radiation. The signal-processing method we employ uses linear algorithms applied pulse by pulse. This eliminates the need for storage of pulse-height spectra, which are in many cases classified.