Cygnus Performance on Ten Subcritical Experiments*

The Cygnus Dual Beam Radiographic Facility includes two identical radiographic sources -Cygnus 1 and Cygnus 2. Cygnus is the radiography source used in Subcritical Experiments (SCEs) at the Nevada National Security Sites (NNSS). The machine specifications are: Electric 2.25MV, 60-kA, 60-ns; Radiation 4-Rad, 1-mm, 50-ns; Operation single shot, 2-shots/day. Cygnus has operated at the NNSS since February 2004. In this period, it has participated on ten SCE projects -Armando, Bacchus, Barolo A, Barolo B, Pollux, Vega, Ediza, Nightshade A, Nightshade B, and Nightshade C. SCE projects typically require over a hundred preparatory shots culminating in a single high-fidelity or SCE shot, and typically take over a year for completion. Therefore, SCE shots are high risk and high value making reliability and reproducibility utmost priority. In this regard, major effort is focused on operational performance. A quantitative performance measurement is valuable for tracking and maintaining Cygnus preparedness. In this work, we present a new model for analysis of Cygnus performance. This model uses x-ray dose distribution as the basis for calculation of Reliability, Record, and Reproducibility. It will be applied both to long-term (historical) and short-term (readiness) periods for each of the ten SCEs.