Digital discrimination method for alpha/beta ray

Abstract

The invention discloses a digital discrimination method for alpha / beta ray. The method comprises the following steps of: after the alpha / beta ray is detected by a detector, outputting a current pulsesignal by a photomultiplier tube, converting the signal by an RC feedback type charge sensitive amplifier to form a double-exponential voltage signal; digitizing the double-exponential voltage signalby a ADC to form a digital pulse signal into a FPGA for processing; eliminating a long exponential decay signal formed by the RC feedback type charge sensitive amplifier by using a current waveform recovery device; setting the width of filters according to the decay time of a ZnS (Ag) and a plastic scintillator by constructing two parallel digital square filters, and processing an output signal ofthe current waveform recovery device; automatically tracking and outputting the peak values for the square filters by peak keepers; acquiring a ratio of the two peak keepers by using a ratio comparator, counting an alpha counter exceeding a set threshold and a beta counter below the threshold, and generating a self-increasing enable signal of the alpha and beta counters after the alpha / beta ray is discriminated; and completing the counting task after the self-increasing enable signal is received.

Description

technical field [0001] The invention belongs to the technical field of radiation measurement, and in particular relates to a method for screening alpha / beta rays. Background technique [0002] The α / β surface pollution meter and the low background α / β measuring instrument can use a composite scintillator composed of ZnS(Ag) and plastic scintillator and a photomultiplier tube to form a probe to simultaneously detect α / β rays. ZnS(Ag) has a high detection efficiency for α-rays, but is insensitive to β-rays. β-rays can penetrate the ZnS(Ag) coating and reach the plastic scintillator to be absorbed. The photons emitted by the composite scintillator are converted into current pulse signals by the photomultiplier tube, and the current signals can be processed by the subsequent signal processing chain. The current pulse signal sequence has both α and β signals. Only by real-time screening of pulse signals can the pulses be counted separately to achieve the purpose of simultaneous ...

AI Technical Summary

Problems solved by technology

For the amplitude method, since the α and β signals have a relatively large overlap in amplitude, there will be mutual crosstalk for the rays in the overlapping area, and since the judging standard is the amplitude, the gain stability of the entire system is very important for the particle screening. Great effect

For the pulse width method, the pulse amplitude and baseline noise have a greater impact on the determination of the start and end positions of the pulse, resulting in inaccurate measurement of the pulse width and affecting the particle screening effect

For the above two methods, there are common defects. The key screening parameters are controlled by analog devices. In the amplitude method, the amplitude of the pulse is greatly affected by the photomultiplier tube and the amplifier circuit, and the threshold is affected by the stability of the reference voltage; In the pulse width method, the pulse width is affected by the peripheral components of the photomultiplier tube

When the environment changes and the device ages, these key parameters will change, and the stability of the entire screening effect will be affected

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