Neutron diagnostic calibration at TAMU plasma focus

Summary form only given. We have been able to perform calibrations of the neutron diagnostics at the TAMU (Texas A&M University) Plasma Focus facility to a 10% or better accuracy. The key to this calibration is the use of very well characterized neutron source. The source we are using is one that was calibrated to a stated accuracy of 3% at the Los Alamos National Laboratory over about 10 years. By placing this source at the location of the plasma focus pinch, self scattering effects of the machine and surrounding structures are automatically accounted. We use the standard four-Geiger tube Los Alamos silver counter as our primary, total yield detector. These detectors have a well-determined detector efficiency and a broad neutron energy sensitivity plateau. Thus, we are able to obtain 10% or better accuracy calibrations for the silver detectors using in-situ, equilibrium activation. Other detectors within the facility can be subsequently calibrated from the silver detector results. The prompt neutron detectors must use shielded lines of sight to avoid excessive neutron pulse broadening primarily due to scattering from objects and materials near the source. Our facility uses collimated lines of sight through a 60-cm thick, concrete shield wall to eliminate most of this scattering. With lines of flight of 8.82 m and 17.4 m, the initial gamma pulse of the reaction may easily be separated from the neutron pulse to enable reliable calibrations of these detectors as well.