Readout Electronics For High Resolution Muon Imaging System Based On Micromegas

Since Wilhelm Conrad Rontgen published the first X-ray imaging result in his-tory,particle imaging technology has made deep influences on all aspects of productive life.Except X-ray,electron,proton,neutron and γ-ray can also be used as probes to detect the inner structure of matters.Different particles are applied to different imaging applications,depending on their penetration capabilities.The basic principle of particle imaging is to detect the interaction between mate-rials and particles,inferring the density distribution of the imaging area by using laws of interaction.In the area of detecting nuclear shielding material,volcano,large-scale buildings and etc.not only cannot artificial rays penetrate the materials,but also can-not cover such large areas.Consequentially,it is difficult to image these objects with artificial rays.However,the following two aspects make muography a good way to solve this problem.On the one hand,due to its strong penetration ability,cosmic-ray muon could penetrate hundreds of meters rock.On the other hand,cosmic-ray muon is a natural ray and exists everywhere in our daily life.It is harmless and convenient to obtain,which makes cosmic-ray an ideal probe to detect the large structures and heavy nuclear matters.At present,a great number of research groups have launched cosmic-ray muon tomography and radiography experiments,which show the ability of muography to im-age large-scale objects and heavy nuclear matters.However,most experiments have the disadvantages of long imaging time and low imaging accuracy,which cannot meet the needs.To optimize the imaging quality and imaging time,research on muon imaging facility should be investigated more deeply.Based on the requirements of cosmic-ray muon imaging,this research carried out the performance analysis,readout electronics design and imaging experiments.At first,a simulation model is developed to reconstruct the process of muography,with GEANT4 and CRY(Cosmic-RaY shower Generator)software libraries.The in-fluence of spatial resolution on the imaging quality and material discrimination is well studied by simulation.A muography facility with better position resolution needs more readout electron-ics channels and this will make the system more complicated and costly.Due to the low flux and sparse hit of cosmic-ray muon,the encoding readout method is introduced in this research.Moreover,a new encoding scheme based on Hamilton path is developed and implemented.With this method,the needed channels of readout electronics can be reduced in an order of magnitude in cosmic-ray muography.Aiming at the complex application scenarios and large system volume of cosmic ray muon imaging,this paper carries out the research of a general and scalable muon imaging readout electronics system.The system employs a discrete architecture of front-end and back-end electronics,and uses fiber optics cables with custom protocols to achieve communication between different electronics,which can be adapted to differ-ent scales of imaging experiments.With the encoding readout boards,a single front-end electronics board can readout 2048 detector channels.The back-end electronics com-pletes to gather all the data from the front-end electronics and distributes clock and trigger to them.Besides,the slow control is realized on the back-end electronics.With exh austive testing,this readout electronics system can satisfy the needs of cosmic-ray muon imaging.Then,an 8-layer muon tomography facility and a 4-layer muon radiography facility were constructed.The imaging experiments and material discriminating experiments were implemented with the tomography facility.Results show that this facility can not only image objects with 2cm size,but also can distinguish lead,tungsten,iron or copper.By measuring muon flux from different directions,the radiography facility can distinguish the area between sky and buildings.All these test results indicate that the readout electronics system can meet the demands of both muon tomography and radiography experiments.At last,this paper proposed some research goals for cosmic-ray imaging on both technology and applications.