The originally published form of our detection criterion, Eq. (3), assumed a well-characterized background and a signal that is much smaller than the prevailing background, i.e., [Formula presented]. These conditions, however, are not always met for all cases considered in the article. We now implement “Currie's equation” for the general case. While all conclusions remain unchanged, the updated detection criterion affects Fig. 1 and Algorithm 1, as well as the values for time to detection and shielding limit reported in Tables 2 and 3. These updates are detailed here. The authors would like to apologize for any inconvenience caused. DOI of original article: 10.1016/j.nima.2020.164983. The expression given by Eq. (3) (“Currie's equation”) provides the minimum detectable signal for the detection of nuclear material, where we use [Formula presented] for a detection probability of 99% and a false-alarm rate of 1% . [Formula presented] As in the original paper, Eq. (3) can be rearranged to yield the time to detection, shielding limit, or minimum detectable quantities, the latter of which is shown in Fig. 1. A well-characterized background decreases the minimum detectable quantity of special nuclear material, as compared to a background measured in finite time. An elevated background would effectively increase the minimum detectable quantity of special nuclear material since [Formula presented]. [Formula presented] The maximum shielding and detection criterion of Algorithm 1 have been updated with the corresponding critical level, [Formula presented]. If the detected counts exceed the critical level, then an anomaly is detected, though it should be noted that detecting an anomaly does not guarantee the presence of the threshold quantity. If this statistical check is not passed and the estimated shielding thickness exceeds the calculated maximum shielding, then the result is inconclusive. Otherwise, absence is confirmed if the detected counts are below the critical level without exceeding the maximum shielding. The time to detection and shielding limits in Tables 2 and 3 have also been updated in correspondence with the new detection criterion; revised values are highlighted in red. For both experimental cases, an anomaly is correctly identified. In all cases shown in the article for plutonium, an anomaly would be correctly reported by the algorithm based on the data acquired during the inspection (Steps 1–4). For the uranium case highlighted in Table 3, an anomaly is correctly identified even though the counts are below the minimum detectable amount corresponding to a detection probability of 99%. CRediT authorship contribution statement Eric Lepowsky: Conceptualization, Methodology, Software, Experiments, Writing, Validation. Jihye Jeon: Conceptualization, Computer simulations, Writing, Validation. Alexander Glaser: Conceptualization, Methodology, Writing, Supervision.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics