Research On Monitoring System In Small Model Of JUNO Central Detector

The Jiangmen Neutrino Experiment(JUNO)project will be a large-scale experiment for further study of neutrinos after the Daya Bay Neutrino Experiment.In order to complete the project,we need to design a small scale model(located in Beijing Institute of High Energy Physics)to simulate the core component of Jiangmen neutrino experiment,"detector".Through the simulation of the small model,the mechanical and temperature characteristics of the detector can be predicted.By installing the small model monitoring system,the problems and shortcomings in the monitoring system can be found and eliminated in advance,which provides a reference for the design of the detector monitoring system.Therefore,this paper proposes a small model monitoring system design to improve the monitoring accuracy and stability.The main work of this paper includes:(1)For the measurement of environmental temperature of small model,the current research mainly includes radiation,fiber Bragg grating and resistance temperature measurement methods.In view of the deficiency of resistance temperature measurement method in suppressing zero offset and long-distance transmission error,a three-resistance self-correction method is proposed.Three-resistance self-tuning method can obtain the relationship between output voltage and standard resistance and PT100 resistance in the presence of zero bias by switching between two standard resistors and one PT100 thermistor through multi-channel switch.At this time,the zero bias of standard resistance and PT100 resistance can be regarded as the same,and then the circuit can be de-amplified by simultaneous calculation.The relationship between PT100 resistance and output voltage is obtained by zero offset.The validity of the self-tuning algorithm is proved by comparison experiments.In addition,the feasibility of FBG temperature sensor is discussed and verified.A small model temperature detection module is composed of FBG temperature sensor and resistance temperature measurement method.(2)For the measurement of mechanical properties of small models,the current research mainly focuses on the radial strain and spherical deformation of the supporting rod of small models.The strain measurement methods of support rod include optical fiber and vibrating string,and the deformation measurement methods include distributed optical fiber measurement and profilometer.In view of the shortcomings of optical fiber and vibrating string in environmental adaptation and the phenomenon of bias load,a strain gauge measurement method is proposed as a stress measurement module of small model support rod.By symmetrically placing two KYOWA strain gauges across the same section of 304 stainlesssteel support rod to balance the eccentric load,the strain of the support rod is measured by stress analyzer and data processing.The monitoring error is less than 4_in the range of-60 to120 Four strain gauges can reduce the error to within 1.In addition,a deformation detection module composed of SDVG20 micro-displacement sensor and C8051F350 micro-controller is designed.The experimental verification shows that the module has a monitoring error of less than 0.01 mm in the deformation range of(+1 mm),which meets the requirements of small model experiment.Temperature monitoring module,strain monitoring module and deformation monitoring module have been built in Beijing Institute of High Energy Physics.The corresponding acquisition device and PC computer interface constitute the monitoring system of small model parameters,which achieves the target and expected purpose of temperature error(<0.2 C),strain error(<4 951;),deformation error(<0.01 mm).Through the software system,the data collection,processing and display of the monitoring system are completed.The monitoring system runs steadily in the process of lifting,filling and loading the small model.The collected data are continuously recorded in the database,which provides data support for the stability of installation and operation of the small model,and provides experimental verification for the design theory of Jiangmen central detector.