Research Of Filtering And Shaping Techniques In Digital Nuclear Energy Spectrum Measurement System

Nuclear energy spectrum measurement technology is an important means ofacquiring information in nuclear physics research, heavy-ion physics, high-energyphysics and nuclear technology and application in the relevant fields. It has highaccuracy, high sensitivity, and its detection information obtained by other means cannotprovide. With the computer, the rapid development of electronic technology, theresearch in nuclear energy spectrum measurement technology is constantly beingupdated. At the same time, the new method of key technology of nuclear energyspectrum measurement technology, become the important content in the research in thefield of nuclear technology. Therefore, the nuclear spectrum measurement technique inthe field of nuclear technology as a research focus has been international concern.To the late20th century, nuclear energy spectrum measurement technologypresented the new trend of the development of digital, in recent years has become to themost active research direction in nuclear signal processing field. Filtering and shapingis the key technology in nuclear energy spectrum measurement technology of digital,using a digital method filtering and shaping not only can replace analog circuits,simplified the hardware circuit, but also improves the system’s ener gy resolution,stability and adaptability.The research of filtering and shaping to digital nuclear energy spectrum ofmeasurement system started earlier broad. In comparison, the domestic research in thisarea is relatively backward, mostly for computer simulation study, and digital filteringnuclear instruments developed successfully reports.The author had analyzed the components principle and structure to the analog anddigital nuclear energy spectrum measurement system, and on this basis to discuss thepros and cons between the two compared. For analog nuclear energy spectrummeasurement system, pointed out the four influence factors in the system performance simulated nuclear energy spectrum: baseline recovery, ballistic losses, pulseaccumulation, and amplitude extraction etc. Based on this cognition, putted forward theresearch method of using pulse digital to weaken the effect factors. To the digitalnuclear energy spectrum measurement system, studied the impact to system after pulsedigitization, and high-performance ADC chip was used to reduce the impact.The main algorithms of digital filter and shaping have been studied in currentnuclear energy systems. Through comparative analysis, Kalman filtering algorithmbase on sage-husa was used to process baseline recovery and the function convolutionto realize pulse trapezoidal shaping.The research suggested using double-forgotten model to establish the kalmanfiltering model, and realize the pulse baseline recovery, and good results were obtained.Due to filtering effect of the classic kalman filter, existing simplified sage-husa andimprovement sage-husa algorithm model cannot reach the expected, and therefore theimproved optimization has been implement based on existing algorithm. Usingdouble-forgotten method, a new adaptive kalman filter algorithm model based onsage-husa was established, and gets a better filtering effect, to avoid the problem offilter divergence and slow convergence of baseline.The using of function convolution realized trapezoidal (triangle) pulse shaping,make the energy resolution greatly improved in nuclear energy spectrum of themeasurement system; there has not been a domestic related introduction. In the currentliterature material, pulse trapezoidal shaping method is used mostly Z transformmethod. But, algorithm of this method is more complex, which has so far been confinedto software simulation, difficult to use in hardware system. The pulse trapezoidalshaping algorithm model using function convolution method, can in time domainwritten in the form of recursion, easy for the realization of hardware.Single-pulse function convolution was proposed. On the basis of research inexisting convolution function, putted forward the method of single and continuoussignal shaping to realize trapezoid (triangle) forming. Through the system test,compared the continuous signal shaping, the single signal shaping can avoidaccumulative error better, and improved the system resolution more.Established the two algorithm model, and realized Matlab7.0simulation, theauthor built the filtering and shaping software platform of digital nuclear energyspectrum measurement system. Actual measurement data testing proved the feasibilityof the design scheme.The nuclear energy spectrum measurement system hardware platform was designed. A new digital nuclear energy spectrum measurement system was devisedusing FPGA. The system can complete nuclear signal pulse data collection, baselinerecovery, pulse shaping, data storage and communication functions. Compared withtraditional simulation system, the performance has a more significant improvement.The digital nuclear energy spectrum measurement system has three observationwindows; we can revise relevant parameters of pulse shaping real-time, according tosignal characteristics of output pulse width and rising edge. So, the system cancooperate withdifferent detector inthe explorationof the different occasion’s work, soas to improve the whole system detecting ability and adaptability.Finally, the actual test shows that this filtering and shaping algorithm is good;Compared with traditional simulation system, the digital nuclear energy spectrummeasurement system, in the match with different detector, the energy resolution havesignificantly improved.