Measurement System Of Muon Zenith Angle In Surface Cosmic Rays

Cosmic rays are charged high-energy subatomic particles from outer space,and secondary particles are generated when they penetrate the atmosphere.Due to absorption by the medium in the earth,short life,decay and other reasons,90%of the secondary particles that finally reach the surface of the earth are muons.Most of them are positively charged.After entering the earth,they will shift in direction under the action of the geomagnetic field,resulting in differences in the surface cosmic ray flux in different directions.This is the east-west and north-south effect of the surface cosmic rays,which is of great significance for human research in the fields of cosmic rays,geomagnetic fields,etc.But due to the complex detection methods,fewer experimental areas,and higher experimental costs,the final measurement data results are scarce,and research and teaching in this field are also lacking.Based on the above background,this paper proposes an indirect method to measure the muon zenith angle in surface cosmic rays.This method designs two multi-wire proportional chamber detectors to form a surface cosmic ray zenith angle measurement system.The system is mainly composed of a multi-wire proportional room detector,an amplification and discrimination circuit,a multi-channel time measurement module,and a network readout module based on the TCP/IP protocol.Nuclear physics experiments can be conducted without the need for other radioactive sources.The specific research content and innovations are mainly reflected in the following aspects:1.Designed a multi-wire proportional chamber detector with an effective area of200mm x 200mm,which was read out by the delay line method.The structure of the wire chamber is:the distance between the anode plane and the cathode plane is 8mm,the anode plane is composed of 48 parallel gold-plated tungsten wires with an effective length of 200mm,a distance of 4mm,and a diameter of 20um;The reading structure of the copper strip is provided with a 0.4mm protection strip in the middle of the copper strip;the delay line uses a delay network of L=1uH and C=25pF.And designed the front-end electronics circuit to meet the needs of the system,including anode high voltage,multi-stage amplification and screening circuit and time measurement circuit.After testing,the detection efficiencies of two multi-wire proportional chamber detectors for muons in surface cosmic rays are 78.57%and 81.13%,respectively.2.Using a combination of coarse counting and fine time,a multi-channel time measurement within Ins accuracy is realized on the FPGA.The actual measured statistical error is within 400ps,which meets the time test requirements between three channels and nine channels of signals.The FPGA firmware program is mainly composed of five modules:PLL,coarse counting,fine time and encoding,data merge and conversion,data buffering and sending.3.Using W5500 chip to realize the network data readout method based on TCP/IP protocol This method can read out each valid case data measured by the experiment through the network and transmit it to the back-end for statistical processing.After testing,the system can complete the error-free transmission of data at a communication rate of 8M/s.At present,the system has completed the preliminary test work,and the data results are fitted by the Origin software in accordance with the empirical formula I(?)=I0COS??.The fitting ? parameters in the four directions of east,west,south,north and north are 1.92,1.81,2.29,1.47 The asymmetry of the muon flux in the east-west and north-south directions is calculated to be 2.65%and 8.04%,respectively,which is consistent with the theoretical value within the error range,verifying the east-south-north effect of cosmic rays.