Nuclear pulse pile-up rejection technique based on a symmetrical zero-area bald-top shaper

Digital multi-channel pulse amplitude analyzer, known for its ballistic deficit immunity, high stability, and adjustable parameters, is widely used in high-resolution energy spectrum measurements of X-rays and gamma-rays. Digital multi-channel pulse amplitude analyzers employ fast and slow dual-channel pulse shaping algorithms used for pulse pile-up discrimination and pulse amplitude extraction, respectively. Traditional fast shaping channels utilize unipolar or bipolar triangular shapers to discriminate pulse pile-up, but the short shaping time reduces their filtering effect against high-frequency noise. This study proposes a symmetric zero-area bald-top shaper that features automatic baseline restoration capability, making it more minor baseline fluctuations at high counting rates. Experimental results of the characteristic X-ray energy spectrum measurements show that the proposed pulse shaper significantly reduces spurious peaks caused by pile-up at high counting rates compared to conventional fast shaping methods.