Evaluation of the LANL hand held multiplicity register and Canberra JSR-15

Passive Neutron Coincidence Counting (PNCC) and Passive Neutron Multiplicity Counting (PNMC) techniques are important non destructive assay methods used in the quantification of plutonium and other spontaneously fissile materials across the fuel cycle. They are based on Multiplicity Shift Register (MSR) pulse train correlation analyzers such as the Canberra Multiplicity Shift Register (MSR) JSR-14. The JSR-14, although quite successful, is somewhat limited by a 4 MHz SR and has no front panel display. Los Alamos National Laboratory (LANL) has recently developed a hand-held multiplicity register (HHMR) that possesses a 50 MHz SR as well as an interactive front panel display with user settable parameters. Under CRADA (cooperative research and development agreement) guidelines, Canberra Industries will commercialize the product. The display and user interface allows for parameter entry and provides the user with feedback of the current operating parameters as well as the MSR results, e.g., multiplicity histograms. The higher MSR clock speed will provide functionality not previously possible under extreme counting conditions, e.g., waste assay with relatively high-gram quantities of heat source material. A prototype HHMR unit was obtained from LANL and has been tested. In this paper, we present the test results of the reliability of the unit, the user interface functionality, support for existing software, and the performance of the 50 MHz MSR. The reliability tests involved the integrity of the battery and voltage supplies, signal triggering performance, and the robustness of the PC USB/virtual COM port interface. The software compatibility tests were conducted using the latest available versions of the LANL INCC and Canberra NDA 2000 software packages. A 20 MHz de-randomizer board was installed into a Canberra neutron coincidence counter to examine the performance of the 50 MHz JSR-15 MSR as compared to the 4 MHz JSR-14 MSR The functionality of JSR-14 and HHMR at low instantaneous counting rates as well as high rates was tested using a random pulser, Am-Be and
²⁵²
Cf sources. In this paper we report on the results for the tests conducted during the evaluation period.