Design Of The Electronics System Of A Neutron Dose Equivalent Meter By Measuring Neutron Spectra

With the rapid of development and wide application of neutron technology,the neutron dose monitoring has become increasingly important.However,the most of the developed neutron monitors that have a single moderator with a single counter,are applied to measure the neutron from thermal neutron to 20MeV.When applied in neutron radiation fields within large range energies,most of them are not a satisfaction to energy response.In addition,it is very imprecise that commercial neutron monitors are applied in high energy field.In order to solve these problems,the neutron dose equivalent monitor with measuring neutron spectra analysis is designed.The detector consists of a spherical polyethylene moderator,a 3He proportional counter(SP9)and six cylindrical BF3 proportional counters(7.6EB70/13M),a spherical lead layer to enhance energy response for high energy neutron.The detector has a satisfactory energy response in the energy range from thermal neutron to lOGeV through the experiment test.The dimension of this detector is similar to the current commercial portable neutron dosimeter,so the detector has a high commercial value for development.In this paper,the electronics system is developed to satisfy the requirement of the signal processing of this detector and the low power consumption.According to the relevant requirements of field measurement and the structural characteristics of neutron dose equivalent meter by measuring neutron spectra,the electronic system is designed.This electronic system is composed of the amplifier circuit,the seven-channel pulse counters based on complex programmable logic device(CPLD),the instrument control circuit based on the microprocessor MSP430F5438 and the power management circuit.This detector uses a 3He proportional counter and a BF3 proportional counter to detect slow neutron.According to the characteristics of these two kinds of proportional counter,the low power amplifier circuit is designed.This amplifier circuit is composed of the charge-sensitive pre-amplifiers(automatic offset cancellation and time-constant reduction),main amplifiers,amplitude discriminator.The signal of a neutron detector is amplified by the amplifier circuit,the noise and other interfering signal is wiped off by the amplitude discriminator and the square signal of the neutron detector is obtained.In order to get the signal of the seven groups of neutron detectors,the seven-channel pulse counters based on complex programmable logic device(CPLD)is designed.For the purpose of portability,low power consumption and site measurement,the low power consumption microprocessor MSP430F5438 is used for the core of the design of control circuit,the peripheral circuit of MSP430F5438 is composed of the memory circuit(24LC128),the clock circuit(DS1302),the key and the liquid crystal circuit(QB 12864).The microprocessor MSP430F5438 is responsible for the control of the peripheral circuit,signal acquisition and data processing.According to the functional requirement of the whole system,a set of software supported for msp430f5438 is also developed.The battery is usually used for power supply of the field measuring instrument,so the power management circuit is used for converting the battery voltage to the voltage of power supply of various modules.The printed circuit board and the relevant software are developed in this work.The relevant properties of this system have been verified in the T(d,n)4He accelerator reference neutron radiation field.The results suggest that this system is the low power consumption,stable,and satisfy the functional requirement of the portable high-energy neutron dosimeter.