Development Of Radiation Detection Gates Detection Systems And Software

The thesis comes from the Ministry of Science major national scientific instruments Special- "The new ionizing radiation detection equipment and key parts development and application" (item number:2013YQ090811) bulky plastic and Sichuan technology support program "for nuclear safety monitor flicker alarm body y Development "(project number:2008GZ0198).This paper discusses the research results of radiation detection gates detecting systems and software, including a large volume plastic scintillator produced scintillation light-gathering techniques, signal processing unit design and detection systems application software development. The main work:(1)、In the development of detection module, in order to solve large volume plastic scintillator generating scintillation light collection technology bottleneck. Export end face flashing light method, lowering the reception area. Own processing optimization design of the light guide, through theoretical calculations and experimental geometry data, select the appropriate volume of scintillator, light guide construct appropriate to increase the collection of light, help increase the current signal output.(2)、In hardware.① By analysising charge sensitive preamplifier traditional shows, op-amp input bias current, and photomultiplier dark current flows through the large value of the feedback resistor cause a large bias voltage, and a bias voltage is amplified may causing a large voltage output, and will occupy a large output swing. The solution adopted is one aspect of the op amp non-inverting input to increase compensation resistor, on the other hand is the use of T-type resistor network instead of the feedback resistor. Helps to reduce the DC bias voltage, the circuit output accuracy is improved. ②Using FilterPro software analysis and comparison of Sallen-Key filter, Butterworth filter, Chebyshev filter, Bessel filter frequency response characteristics, the results show a step input Sallen-Key filter response has minimized rise and fall times, and no overshoot conducive output quasi Gaussian pulse waveform. ③Researching traditional screening device discovery, screening needs separately under the threshold voltage, so that the circuit structure is more complex, and need to consider broadening the width of the pulse duration and delay. DAC chip micro controller as the upper and lower threshold screening provides the power and replace the old single-shot pulse stretching and delay circuit, the circuit structure has been greatly simplified, the threshold DAC supply making equipment more intelligent.(3)、In software. Taking into account the background count rate varies with environmental factors change, in order to ensure that the equipment does not produce false positives when the background count rate increases, the use of real-time dynamic background monitoring software designed to ensure that the alarm threshold with fluctuations in the background dynamic updates, the alarm threshold is specifically identified SIGMA statistical algorithm method. Set the sampling frequency 100ms, to allow pedestrians quickly through the shortest update every minute real-time count of the background to ensure the accuracy of monitoring results. And users can easily adjust the relationship between the detection sensitivity and false alarm probabilities by the algorithm.(4)、The PC application software has been developed by MFC. Between the signal processing unit and the PC terminal USB data communication technology, USB communication protocol is more flexible than the RS485 protocol, USB transfer rate of up to 12MB/s, and the transmission of the data format no special requirements. Use database technology to manage data for easy viewing and changes.(1) Complete with a plastic scintillator high scintillation light collection rate of probe design, increasing the detector sensitivity for weak radioactive sources.(2) The completion of high-voltage power module circuit design and actual production, dominated by high-performance pulse width modulation chip and voltage doubler circuit, the output voltage -1000V, the ripple is about 40mV, the maximum output current of 0.1mA. To meet the needs of practical application.(3) Completed the optimization design charge sensitive preamplifier, using compensation resistor reduces the op amp input bias circuit, T-type resistor network instead of the feedback resistor, effectively reducing the op amp’s DC bias voltage, reducing ago set the amplifier output signal swing.(4) Completed the S-K filter design to achieve a device with as little as possible to obtain quasi-Gaussian waveform.(5) The completion of the improved design of traditional discriminator threshold voltage supply circuit, the use of single-chip process control data-DAC adjusting supply amplitude discriminators, a lower threshold voltage, increase the adjustment accuracy threshold voltage, but also greatly increased intelligent circuits. Replace two single-shot pulse delay and stretching circuit, simplifying the circuit structure, accelerate the response speed of the circuit.(6)Completed the SIGMA algorithm of programming and USB data communications chip configuration program, help to reduce the false alarm rate.(7)The completion of the monitoring system control terminal software development, data management, data using SQL Server technology.