ANSI N42.41:2007 pdf download.Minimum Performance Criteria for Active Interrogation Systems Used for Homeland Security.
3.1.6 conventIonally true value (CT’s’): The commonly accepted best estimate of thc aluc of that quantity. This and the associated uncertainty will preferably be determined by a national or transfer standard, or by a reference rnstrumcnt that has been calibrated against a national or transfer standard, or by a measurement quality assurance (MQA) interaction with the National Institute of Standards and Technology N1ST). or an accredited calibration Iaboratoiy.
3.1.7 detectIon limits: The extreme of detection or identification for the substance-of-interest. The lower dejection limit is the minimum statistically qtianiitiablc system response or reading. The upper measuivmcnt limit (if any) is the maximum level at which the system responds correctly.
3.1Jl detector: A device or component designed to produce a quantifiable response to ionizing radiation normally measured clcctronically
3.1.9 false alarm: An alarm not caused by detection of a non-negligible amount of a substance-of-interest or specified simulant. Sec also: negligible amount of substance-of-Interest.
3.1.10 indication: A displayed signal from the system to the user conveying information such as detection of a suh’tancc-of-intercst, system status, system malfunction, or other cntical information.
3.1.11 interdiction: Stopping the illicit or inadvertent movement of explosives. chemical warfare agents, or nuclear materials that have been discovered as a result of actise interrogation.
31.l2 monItoring: The means prosided to indicate continuously the state or condition of a system or assembly.
31,13 precision: The degree of agreement of repeated measurements of the same parameter.
3.1.14 range: All values lying between the lower detection limit and the upper measurement limit.
3.1.15 routine test: A test that applies to a complete system to ascertain compliance with specified criteria.
3.1.16 standard desiation: The positive square root of the variance
11.17 test: A procedure whereby the system or component is evuluatesf
3.l.llt type test: A test of one or more production systems taken to be representative of the model to show that it incts defined specifications.
3.1.19 u.icertalnty: The estimated bounds of the deviation from the conventionally true alue. generally expressed as a percentage of the mean, ordinarily taken as the square root of the sum of the square of two components:
a) Type A uncertainties that are evaluated by statistical methods; and
b) Type 13 uncertainties that are evaluated by other methods.
3.2 DefinitIons of particular relevance to N42.41
3.2.1 active intcrrol.gaton : A process in which the contents of an inspection zone are irnidiated with penetrating ionizing radiation (e.g., neutrons or high-energy photons) to detennine the presence of and chemical or nuclidic composition of a hidden substance-oI-iiitercst by the analysis of stimulated secondary radiation or by analysis of nuclear resonance contrast.
3.2.2 confidence Iesel(Cl.) A measure of the reliability ot the determination of the probability of dclcction (P1)1 or the probability of a falsc alarm (PFA). Higher values of the CL indicate grcatcr reliability. Larier numbers of trial are required to establish a higher CL. The mathematical definitions in 3.2.3 and 3.2.4 arc discussed more fully along with some examples and tables in Annex B.
3.2.3 confidence Ics el (CL) for the probabilih oldetcctioii (PD): If to successes are found in a sinele set of n trials in a system obeying the binomial distribution law, then for ally chosen value of PD. designated PD . there isa corresponding number called the confidence level CL4m, it, PD r). shich is equal to tile probability that any such system with rn successes in a single set of n trials will have a true P1) value greater than or equal to that chosen value Pl)
3.2.4 confidence lead (CL) ror the probability of a false alarm (PFA): If) false-positive results are found in a single set of k trials in a system obeying the binomial distribution law, then for any chosen value of PFA. designated PFA (.there is a corresponding number called the confidence level CL(j. k. PFA ). which is equal to the probability that any such system withj success results in a single set of k trials.
3.2. 111113 compliant seitiulant: A benign substitute for a suhstancc-of-intcres. having the same elemental and nuclidic densities as the threat substance within ± I 0%.
3.2.6 ncligiblc amount of i substance-of-interest : A very small quantity of the substance that is at least ten-thousand times smaller than the detectable mass criteria of Table 4. within the smallest resolved volume element of the inspection zone. (Since both a mass and volume are seci1ied. a negligible density is also specified.)
