The aluminum ion chamber uses Boron enriched with B-10 as a neutron sensing material.  The chamber has two 69-inch sensitive volumes and three electrodes.  One of the electrodes delivers high voltage to both sensing areas.  The other two are signal electrodes, one for each sensing area, which allows a choice of monitoring modes: either independent monitoring of upper and lower signals, or connection in parallel to provide a signal proportional to the integral of the flux over the full length of the detector.

Three external coaxial cable assemblies are hermetically sealed to the bottom (or top) end of the detector by a series of metallic joints.  The first 18 feet of each assembly is mineral insulated (MI) coaxial cable with stainless steel conductors and aluminum oxide insulation, terminated at each end with a ceramic-to-metal seal.  The remaining portion of each cable assembly is organic insulated coaxial cable, which is permanently spliced to the MI cable (outside the bioshield).  The three cable assemblies merge at a point about eight inches below the bottom of the detector, to become a single integrated assembly covered by a fiberglass sleeve.  After emerging from the sleeve, for the last six inches the cables are once again three separate assemblies.  Each is terminated with an HN connector which is permanently marked with the cable’s function (“HV”, “U”, “L”).