In inertial confinement fusion (ICF) experiments, the spatial distribution of deuterium-tritium (DT) neutron yield directly characterizes the symmetry of fuel areal density, serving as a key metric for evaluating implosion symmetry and DT shell integrity. Neutron activation diagnostics (NADs) represent a primary method for neutron yield measurement, offering advantages such as immunity to other radiation interference and resistance to saturation. Common activation materials used in current laser-driven ICF facilities include indium, copper, and zirconium. Among these, zirconium activation, with a reaction threshold of 12.1 MeV, effectively filters out low-energy neutrons and scattered neutron backgrounds. The 909 keV gamma ray emitted from the cascade decay of the activation product ⁸⁹Zr has a high energy and a single source, which is suitable for multi-point online measurements, making it an optimal approach for diagnosing the spatial distribution of DT neutron yield.
The National Ignition Facility (NIF) in the United States pioneered the study of zirconium activation neutron yield diagnostics. The Real-Time Neutron Activation Diagnostic (RT-NAD) system consisting of 48 lanthanum bromide (LaBr₃:Ce) detectors paired with zirconium activation samples, has now been deployed around the target chamber to measure the spatial distribution of DT neutrons. This system is designed to operate over six orders of magnitude of neutron yield, providing overall yield estimates precise to 2% [1]. However, the presence of the naturally occurring radionuclide ¹³⁸La in the lanthanum bromide crystals used at NIF introduces background interference—particularly in the form of an electronic continuum—which limits the lower detection sensitivity for DT neutron yield. In contrast, cerium bromide (CeBr₃) crystals exhibit performance similar to LaBr₃:Ce but do not contain this background component, making them more suitable for low-yield (∼10¹³ n/cm²) DT neutron measurements.
Aiming at the characteristic of low DT neutron yield in 100 kJ facility, this paper proposes a zirconium activation DT neutron yield diagnostic scheme based on CeBr₃ Detector. A CeBr₃ detector and a LaBr₃:Ce detector were developed, and comparative experiments were carried out on the 100 kJ facility. A total of four shots were performed, with DT neutron yields ranging from 0.976×10¹³ to 2.36×10¹³ n/cm². Experimental results demonstrate that, due to the elimination of the electronic continuum and Compton plateau interference introduced by ¹³⁸La, the background in the 909 keV full-energy peak region of the CeBr₃ detector is significantly lower than that of the LaBr₃:Ce detector. The peak-to-background ratio for the CeBr₃ detector reaches 1.0 (25 hours post-shot), while that of the LaBr₃:Ce detector is only 0.3. Using copper activation yield measurements as a reference, the deviation range for yield measurements with the CeBr₃ detector is -1.64% to 2.21%, with a standard deviation of 1.58%; for the LaBr₃:Ce detector, the deviation range is -1.58% to 9.39%, with a standard deviation of 5.82%. These results indicate that under low DT neutron yield conditions (∼10¹³ n/cm²), the peak-to-background ratio of the 909 keV full-energy peak for the CeBr₃ detector is 3.3 times that of the LaBr₃:Ce detector. This significantly reduces the counting statistical uncertainty of the full-energy peak, resulting in a yield measurement precision 3.68 times higher than that of the LaBr₃:Ce detector. Future work will include experiments with a wider range of neutron yields, alongside theoretical analysis, to further evaluate the accuracy of CeBr₃ detector measurements under different conditions. This will help to define their operable yield range and full potential for DT neutron yield diagnostics.

Inertial Confinement Fusion; DT Neutron Yield; Zirconium Activation; Cerium Bromide Detector