Bearing Capacities of the Structure and Joint of JUNO Central Detector

The Jiangmen Underground Neutrino Observatory (JUNO) central detector will be placed underground to detect neutrinos. In order to achieve the feasible scheme for JUNO, the structural scheme of an acrylic ball supported by a double-layer stainless steel latticed shell is designed and modeled using ABAQUS software. The bearing capacity of the structure under working condition is investigated and influences of external factors are analyzed. For the purpose of studying the load-bearing behavior of the joint of acrylic and stainless steel in this scheme, tests of three joint specimens are conducted and the results are compared with finite element (FE) predictions. It is concluded that the structure is safe and reliable under the effects of external factors. The bearing capacity of the joint is at least 2 times as large as the design load and the stress on the acrylic is limited within 10MPa

Dark Count of 20-inch PMTs Generated by Natural Radioactivity

The primary objective of the JUNO experiment is to determine the ordering of neutrino masses using a 20-kton liquid-scintillator detector. The 20-inch photomultiplier tube (PMT) plays a crucial role in achieving excellent energy resolution of at least 3% at 1 MeV. Understanding the characteristics and features of the PMT is vital for comprehending the detector's performance, particularly regarding the occurrence of large pulses in PMT dark counts. This research paper aims to further investigate the origin of these large pulses in the 20-inch PMT dark count rate through measurements and simulations. The findings confirm that the main sources of the large pulses are natural radioactivity and muons striking the PMT glass. By analyzing the PMT dark count rate spectrum, it becomes possible to roughly estimate the radioactivity levels in the surrounding environment.Comment: 10 pages, 8 figures, and 5 table

The cosmic ray test of MRPCs for the BESIII ETOF upgrade

In order to improve the particle identification capability of the Beijing Spectrometer III (BESIII),t is proposed to upgrade the current endcap time-of-flight (ETOF) detector with multi-gap resistive plate chamber (MRPC) technology. Aiming at extending ETOF overall time resolution better than 100ps, the whole system including MRPC detectors, new-designed Front End Electronics (FEE), CLOCK module, fast control boards and time to digital modules (TDIG), was built up and operated online 3 months under the cosmic ray. The main purposes of cosmic ray test are checking the detectors' construction quality, testing the joint operation of all instruments and guaranteeing the performance of the system. The results imply MRPC time resolution better than 100$ps$, efficiency is about 98$\%$ and the noise rate of strip is lower than 1$Hz/$($scm^{2}$) at normal threshold range, the details are discussed and analyzed specifically in this paper. The test indicates that the whole ETOF system would work well and satisfy the requirements of upgrade

Design of the PMT underwater cascade implosion protection system for JUNO

Photomultiplier tubes (PMTs) are widely used underwater in large-scale neutrino experiments. As a hollow glass spherelike structure, implosion is unavoidable during long-term operation under large water pressure. There is a possibility of cascade implosion to neighbor PMTs due to shockwave. Jiangmen Underground Neutrino Observatory designed a protection structure for each 20-inch PMT, consisting of a top cover, a bottom cover, and their connection. This paper introduces the requirement and design of the PMT protection system, including the material selection, investigation of manufacture technology, and prototyping. Optimization and validation by simulation and underwater experiments are also presented.Comment: 10 pages, 15 figure

The performance of large-pitch AC-LGAD with different N+ dose

AC-Coupled LGAD (AC-LGAD) is a new 4D detector developed based on the Low Gain Avalanche Diode (LGAD) technology, which can accurately measure the time and spatial information of particles. Institute of High Energy Physics (IHEP) designed a large-size AC-LGAD with a pitch of 2000 {\mu}m and AC pad of 1000 {\mu}m, and explored the effect of N+ layer dose on the spatial resolution and time resolution. The spatial resolution varied from 32.7 {\mu}m to 15.1 {\mu}m depending on N+ dose. The time resolution does not change significantly at different N+ doses, which is about 15-17 ps. AC-LGAD with a low N+ dose has a large attenuation factor and better spatial resolution. Large signal attenuation factor and low noise level are beneficial to improve the spatial resolution of the AC-LGAD sensor

Characterisation of Spatial and Timing Resolution of IHEP AC-LGAD Strip

AC-coupled LGAD(AC-LGAD) Strip is a new design of LGAD that allows high-precision detection of particle spatiotemporal information whereas reducing the density of readout electronics. For AC-LGAD Strips, there is limited research on the impact of different strip pitches on the spatiotemporal detection performance at the small amount of injected charge. The Institute of High Energy Physics has designed an AC-LGAD Strip prototype with pitches of 150 $\mu m$, 200 $\mu m$, and 250 $\mu m$. The spatial and timing resolutions of the prototype are studied through the laser Transient Current Technique (TCT) scan with different amounts of injected charge. The results show that both the spatial and timing resolution improves as the strip pitch decreases. Increases in both temporal and spatial resolutions as the amount of charge injected increases are observed. The spatial and timing resolution is better than 60 ps and 40 $\mu m$ at 1 Minimum Ionizing Particle (MIP), and better than 10 ps and 5 $\mu m$ at 40 MIPs. Increasing Signal-to-Noise Ratio (SNR) is the key to improving spatial and temporal resolution, whereas increasing the signal attenuation rate by reducing the gap between adjacent electrodes also helps to improve spatial resolution. The enhancements of spatial and timing resolutions by both SNR and signal attenuation rate decrease with increasing amount of MIP. This study can help design and optimize the AC-LGAD Strip detectors and readout electronics