Clearing the 'traffic jam' in nuclear detection: fast FPGA algorithm enhances neutron-gamma discrimination

Navigating the "Traffic Jam" of Nuclear Signals
In nuclear physics experiments, detectors frequently encounter "pile-up" events when operating under high-intensity radiation. Much like a traffic jam during rush hour, this occurs when two or more radiation signals overlap because they arrive almost simultaneously. This "tail-gating" effect causes energy spectrum distortion and inaccurate neutron counting, potentially leading to critical errors in data interpretation.

Bipolar Cusp-Like Shaping: Narrower, Faster, and Real-Time
A research team led by Jia-Xin Li, Hui-Liang Hou, and Zhi-Min Dai has proposed a solution utilizing a bipolar cusp-like pulse-shaping algorithm based on the "unfolding synthesis technique." By generating an ultra-narrow pulse width—compared to traditional trapezoidal or triangular shaping—the algorithm effectively "slices" through overlapping signals to drastically reduce pile-up events. Its dual-polarity design further eliminates baseline drift at high count rates, ensuring that signal amplitudes are recovered with high precision. Moreover, the algorithm’s architectural simplicity, comprised primarily of adders and multipliers, makes it ideal for implementation on Field Programmable Gate Arrays (FPGAs) This enables the real-time processing of millions of signals per second.

Data-Driven Parameter Optimization
To ensure peak performance across diverse experimental setups, the team employed a multi-objective evolutionary algorithm for parameter tuning. Rather than relying on manual trial-and-error, this data-driven approach automatically identifies the ideal decay time constants. This process achieves an optimal balance between energy resolution and the ability to distinguish between different types of radiation, rendering the system highly adaptable to various experimental conditions.

Experimental Success: A Clear "Fingerprint" for Radiation
The researchers validated their algorithm using a NaIL (Lithium-doped Sodium Iodide) scintillator, a detector highly valued for its dual sensitivity to neutrons and gamma rays. In experiments using a ²⁴¹Am-Be neutron source, the algorithm achieved a Figure of Merit (FoM) of 2.11. This result demonstrates that even in intense radiation fields, the system can clearly separate neutron "fingerprints" from background gamma rays and update energy spectra instantaneously as each signal arrives.

Broad Impact and Future Applications
"By converting complex signal processing into efficient hardware-executable algorithms, this research enhances our ability to quantify radiation in high-flux environments," the research team noted. This technology holds significant real-world implications, ranging from improving nuclear security at borders to enhancing the accuracy of real-time safety monitoring in nuclear power plants and advanced medical imaging systems."