Study Anti-correlation between Neutron Detection Efficiency of the Electron-Neutron Detector Array (ENDA) and Soil Moisture

Discussion timeslot （ZOOM-Meeting）：16. July 2021- 18:00
ZOOM-Meeting URL：https : //icrc2021.desy.depf_access_abstracts
Corresponding Session：https : //icrc2021-venue.desy.de/channel /PresenterForum- 1-AllCategories /48
Abstract:
The measurement of thermal neutrons generated by cosmic ray extensive air showers (EAS) on the Earth’s surface provides a new method for studying the composition and energy of cosmic rays with energy in the so-called “knee” region. A new type of thermal neutron detector prototype array was installed in LHAASO, Haizishan, Daocheng, Sichuan, China. The array consists of 16 electron-neutron detectors (EN-detectors), so called ENDA-16-HZS, which utilize a new type scintillator based on a compound alloy of ZnS(Ag) and B2O3 with natural boron.
According to our previous paper about the performance of EN-detectors in Yangbajing, Tibet, during the period from August 2019 to January 2020, the number of neutrons in periods of rain season is significantly  (~10%) lower than that in periods of dry season. In order to quantify the anti-correlation between neutron detection efficiency and soil moisture, we adopts WKTSH1920-4G version of soil moisture meter. It works in frequency domain reflection (FDR) principle. With 4G network interface, the collected data can be uploaded to the TLINK cloud in real time, and users can obtain temperature and humidity data. Five soil moisture meters have been successfully installed at different depths inside ENDA-16-HZS in August 2020. By analyzing the data in September 2020, it is demonstrated that neutron detection efficiency of EN-detector is negatively correlated with soil moisture. The obtained anti-correlation parameters are beneficial for correction of neutrons detected in EAS events and then reduction of systematic uncertainties in the final energy spectrum recovering of different primary cosmic ray components.

Authors：Bing-Bing Li | Shu-Wang Cui | Tian-Lu Chen | Danzengluobu | D.A.Kuleshov | K.R.Levochkin, | Mao-Yuan Liu | Ye Liu | Xin-Hua Ma | Cong Shi | O.B.Shchegolev | Yu.V. Stenkin | Di-Xuan Xiao | Fan Yang | Liang-Wei Zhang 

Collaboration：Lhaaso

Indico -ID：339
Proceeding URL：https://pos.sissa.it/395/200