Aging behavior of large area MCP–PMT

The Institute of High Energy Physics, Chinese Academy of Sciences have designed a new type of photomultiplier tube(PMT) based on microchannel plates(MCPs) with large area photocathode, known as large area microchannel plate photomultiplier tube(MCP–PMT). The aging characteristics of the large area MCP–PMTs are different from dynode PMTs and small proximity-focus MCP–PMT. In this work, a prototype large area MCP–PMT was aged by operating with nearly 1000 photoelectrons per pulse for 3 months, and aging process of the MCP–PMT was discussed based on the aging curve.

The offline data quality monitoring of the BESIII end cap TOF system

Purpose The end cap time of flight(TOF)at Beijing spectrometer was upgraded with multi-gap resistive plate chamber technology in order to improve the particle identification capability in 2015.The offline data quality monitoring is a critical aspect of the data processing chain aiming at providing data with good quality for physics analyses.Methods An offline data quality monitoring tool for upgraded end cap TOF has been developed to provide feedback about the functioning and performance of detector hardware and data processing chain.Results Detector information and reconstructed time-of-flight characteristics of charged tracks are filled into plots using full Bhabha events reconstruction results,and then,these plots are used to assess the operational conditions of the detector and the quality of the data by the experts.Conclusion This paper is describing the design and the content of performance of the offline data quality monitoring of end cap TOF and the data quality performance achieved during last 2 years’physical data taking.

Characterization of 3-inch photomultiplier tubes for the JUNO central detector

Background Jiangmen Underground Neutrino Observation(JUNO)is one of the largest experimental facilities for neutrino detecting.As its main structure,the central detector contains 20 kiloton liquid scintillator filled in an acrylic shell,and there are 18,00020-inch photomultiplier tubes(PMTs)and 25,0003-inch PMTs covering the shell.Purpose As an independent photon detection system,3-inch PMTs have been required to have excellent resolution for the single photoelectron detection,high quantum efficiency,small transit time spread and low dark noise rate.Methods Two kinds of 3-inch PMTs from HZC Photonics and Hamamatsu have been investigated as candidates.A dedicated test system for 3-inch PMTs has been designed,and various characterization parameters have been studied.Conclusion The preliminary results show these PMTs can meet the requirements of JUNO.

Research on thermoforming process of JUNO large acrylic spherical panel

Introduction Jiangmen Underground Neutrino Observation(JUNO)focuses on determining neutrino mass hierarchy and other physical purposes.The central detector is one of the keys to the JUNO.The main structure of the central detector is an acrylic spherical container with a diameter of 35.4 m,which will be the largest acrylic spherical vessel in the world.Its construction will inevitably face many great challenges and difficulties.Method The thermoforming process of large acrylic spherical panel is introduced,which is a very important step in panel production.The effect of temperature on the curvature of panel during thermoforming is discussed.The thermal deformation of panel in thermoforming process is analyzed by finite element method.The bending experiment and curvature measurement are carried out,and the influence of deformation of the panel under gravity on the curvature of the panel is analyzed.Results The current thermoforming process makes the curvature of panel smaller than that of mold.The measurement results show that the curvatures are different due to the influence of gravity when the panel is placed on the mold or vertically.Some suggestions for improving the shape of spherical panels are put forward.In the thermoforming process,the temperature of the concave-convex surfaces of the panel should be controlled at the same level as far as possible.Another feasible method is to increase the radius of the forming mold to obtain a spherical panel with designed radius.

The offline data quality monitoring of the BESIII end-cap TOF system

Background The end-cap time-of-flight(TOF)at Beijing Spectrometer was upgraded with multi-gap resistive plate chamber technology in order to improve the particle identification capability in 2015.The offline data quality monitoring(ODQM)is a critical aspect of the data processing chain aiming at providing data with good quality for physics analyses.Method An ODQM tool for upgraded end-cap TOF has been developed to provide feedback about the functioning and performance of detector hardware and data processing chain.Detector information and reconstructed time-of-flight characteristics of charged tracks are filled into plots using full Bhabha events’reconstruction results,and then,these plots are used to assess the operational conditions of the detector and the quality of the data by the experts.Result This paper describes the design and the content of performance of the ODQM of end-cap TOF and the data quality performance achieved during the last 2-year physical data taking.

The study of time calibration for upgraded end cap TOF of BESIII

Purpose The end cap time of flight at Beijing Spectrometer is upgraded with multi-gap resistive plate chamber technology in order to improve the charged particle identification capability.The time-over-threshold is used for the time slewing correction instead of the signal amplitude.Methods The correlation of the multi-peak time-over-threshold and the hit position along the strip of the charged particle is investigated.Implementation of the off-line data calibration method is discussed in detail.Results and conclusion The overall time resolution for pions with momentum around 0.8 GeV/c is about 65 ps.

Correction to:The offline data quality monitoring of the BESIII end-cap TOF system

Correction to:Radiation Detection Technology and Methods(2019)3:58 https://doi.org/10.1007/s41605-019-0132-0;(2021)5:207–212 https://doi.org/10.1007/s41605-021-00251-y The articles https://doi.org/10.1007/s41605-019-0132-0,https://doi.org/10.1007/s41605-021-00251-y have been inadvertently got published twice and were included in Volume 3 Issue 4(2019),Volume 5 issue 2(2021)Both articles are similar and the Publisher apologizes to the authors and readers for the inconvenience caused by this error.