A [[well log]] made with a mandrel type [[neutron log|neutron logging]] tool having two [[neutron]] detectors. The neutron [[porosity]] is derived from the ratio of the counting rates of the two detectors. Use of the count-rate [[ratio]] greatly minimizes borehole effects. This tool can be run in liquid-filled holes, both cased and uncased, but is not usually recommended for use in gas-filled holes. See [[dual spaced neutron log|dual-spaced neutron]].