Application And Exploration Of Empirical Mode Decomposition Method In PRISMA-YBJ Experimental Data

Cosmic rays were discovered more than a hundred years ago by the Austrian physicist Hess.EAS(Extensive Air Shower)was first discovered 50 years ago,but the origin and acceleration mechanism of cosmic rays are still unclear.The PRISMA detector array is used to measure the thermal neutron components generated by the interaction of hadron with ground medium that from the EAS,it in order to achieve the accurate measurement of cosmic ray energy spectrum and compositions.In January 2013,four PRISMA detectors were installed in the center of the ARGO-YBJ hall.Now,the data have been accumulated more than three years.The recorded data were analyzed by the Hilbert-Huang transform empirical mode decomposition method.The feasibility and effectiveness of this method are verified.The article is divided into four parts:The first part mainly introduces the mystery of the origin of cosmic rays and its four distinct inflection points and the particles of cosmic rays.Meantime,it introduces two kind of detecting methods and thermal neutron detectors for detecting cosmic rays.An introduction to the modal decomposition method of Hilbert Huang transform used in the data acquired by the detector.In the second part,the PRISMA-YBJ experiment is introduced emphatically.The detector array are established successfully,from operation to the successful data acquisition went through more than three years,the structure and components of the thermal neutron detector are introduced.It focus on the scintillator and photo-multiplier tube,such as,the fabrication of scintillators,the scintillator efficiency testing and the testing of photo-multiplier tube.The third part is the complete introduction of the empirical modal method.For the experimental data,this method is scientific.We got the physical components of each time scale with three-year-long date from the sub-detectors by the method that it from the empirical mode decomposition to the whole empirical mode method derived from the noise processing.The fourth part,it decomposes the high-frequency aliasing signal by the empirical mode,and gets the high and low frequency signals,it indicated the method is effective for the experiment.We get the one day,half of the day,seven days and one month scale of the signal,and it is the same with the frequency analysis of the data.It likely related to the temperature of the barometric pressure and to the 27 day period of the sun.By the analysis of the PRISMA-YBJ experiment's data,we used ensemble empirical mode decomposition,to analyse the information obtained by decomposing of the cycle.We discovery the neutron signal may be affected by seasonal variations and the moon tides,and maybe there are some periodic component having a physical meaning.This information will help us understand the cosmic ray particles and further understand the cosmic ray spectrum.