166 research outputs found
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,
efficiency is about 98 and the noise rate of strip is lower than
1() 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
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