Research Of Neutron Generator Control System With Neutron Counting Feedback

The neutron generator is a small accelerator neutron source.It has the advantages of high yield,good monochromaticity,safe,controllable,small volume and so on.At present,it has important application value in the fields of petroleum logging,explosives detection and radiation therapy and so on.As the domestic neutron tube neutron generator technology starts relatively late,the degree of automation of neutron generator is not high enough.During the operation of the equipment,it often requires the intervention of operators.Moreover,it also has the problem of low stability of neutron yield and lack of exception handling mechanism.In view of the above problems,this paper designs a new closed-loop control system of neutron generator,the control system uses a He-3 neutron detector as a monitoring device of neutron yield and adjusts the electrical parameters of neutron generator by the embedded hardware system and neutron closed-loop control algorithm,which improves the stability of the neutron yield and saves labor costs.And the control system has the fault diagnosis and the self-protection mechanism,once the equipment breaks down,the system analyzes the change of the electrical parameters,finds the cause of the fault and turns on the corresponding protection mechanism to minimize the danger and loss.The neutron generator control system is divided into two parts:hardware design and software design.In terms of hardware,the system includes the main control circuit,storage power supply,ion source power supply,accelerating pole power supply,neutron detector and industrial computer.The main control circuit is the core of the hardware system.It consists of a core control board and a driver board,core control board uses TI's high-performance DSP TMS320F2810 control chip as the core and controls the drive board.The driving board consists of DA conversion circuit,AD acquisition circuit,serial communication circuit,digital signal isolation circuit,logic gate circuit and so on,by receiving the control signal of the core control board,the control of the storage power supply,the ion source power supply and the accelerating pole power supply are realized,so as to start the neutron generator.At the same time,the driver board will feedback the sampled electrical parameter information to the core control board and the electrical parameter information is displayed on industrial computer.In order to improve the reliability of the system hardware,the circuit is equipped with a variety of protection or anti-jamming devices such as transient voltage suppression diodes,digital isolation chips,which can prevent the high-voltage discharge from damaging or interfering with the controller.The software includes the lower machine(TMS320F2810)software and upper computer LabVIEW monitoring software.AD acquisition function,DA output function,timing and communication function and so on are realized in the lower computer.Cooperating with lower computer,upper computer which is a human-computer interface displays the important parameters of the neutron generator and sends user's control instruction to the lower computer,so as to realize the regulation of the three sets of power.In order to make data transmission more reliable and stable,Modbus communication protocol is used in communication.The system has manual and automatic modes.In manual mode,it is convenient for professionals to record a variety of data and analysis them.In automatic mode,the control system automatically turns on the device and stabilizes the neutron yield by the neutron closed loop control algorithm.The experimental results show:storage power supply,ion source power supply,accelerating pole power supply's parameters and adjustment step of PC are close to linear adjustment,the regulation precision of storage current is 0.7mA,the regulation precision of ion source voltage is 1V,and regulation precision of accelerating pole voltage is 0.06KV;The overall performance of the D-D neutron generator has been greatly improved,the neutron yield can reach 1.0×10~7n/s,the life span of the neutron generator reaches 1000 hours,in closed-loop automatic mode,neutron yield stability is within±2%.The device is currently used in neutron detecting mine project of China Academy of Engineering Physics,it runs well and meets the overall project requirements.