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This paper studied the radiation hardness of low gain avalanche detector (LGAD) developed by the Novel Device Laboratory (NDL) in Beijing and the Institute of High Energy Physics (IHEP) of Chinese Academy of Sciences, in the context of an upgrade project of the ATLAS detector for the high luminosity phase of LHC. NDL LGAD sensors with di↵erent layouts, epitaxial resistivity, doping profile were irradiated up to 1.02 ⇥10 15 n eq /cm 2 by 70 MeV proton at Cyclotron and Radioisotope Center (CYRIC). The timing resolution of NDL LGAD sensors reached 50 picoseconds (ps) and the collected charge reached 3-4 Femtocoulombs (fC) after irradiation.

The Circular Electron Positron Collider (CEPC), proposed as a future Higgs boson factory, will operate at a center-of-mass energy of 240 GeV and will accumulate 5.6 ab−1 of integrated luminosity in 7 years. In this study, we estimate the upper limit of BR( inv) for three independent channels, including two leptonic channels and one hadronic channel, at the CEPC. Based on the full simulation analysis, the upper limit of BR( inv) could reach 0.26% at the 95% confidence level. In the Stand Model (SM), the Higgs boson can only decay invisibly via , so any evidence of invisible Higgs decays that exceed BR( inv) of the SM will indicate a phenomenon that is beyond the SM (BSM). The invariant mass resolution of the visible hadronic decay system , inv) is simulated, and the physics requirement at the CEPC detector for reaching this is given.

To meet the high radiation challenge for detectors in future high-energy physics, a novel 3D 4H-SiC detector was investigated. Three-dimensional 4H-SiC detectors could potentially operate in a harsh radiation and room-temperature environment because of its high thermal conductivity and high atomic displacement threshold energy. Its 3D structure, which decouples the thickness and the distance between electrodes, further improves the timing performance and the radiation hardness of the detector. We developed a simulation software—RASER (RAdiation SEmiconductoR)—to simulate the time resolution of planar and 3D 4H-SiC detectors with different parameters and structures, and the reliability of the software was verified by comparing the simulated and measured time-resolution results of the same detector. The rough time resolution of the 3D 4H-SiC detector was estimated, and the simulation parameters could be used as guideline to 3D 4H-SiC detector design and optimization.

We address the determination of the time resolution for the 100 μm 4H-SiC PIN detectors fabricated by Nanjing University (NJU). The time response to β particles from a 90Sr source is investigated for the detection of the minimum ionizing particles (MIPs). We study the influence of different reverse voltages, which correspond to different carrier velocities and device sizes, and how this correlates with the detector capacitance. We determine a time resolution (94 ± 1) ps for a 100 μm 4H-SiC PIN detector. A fast simulation software, termed RASER (RAdiation SEmiconductoR), is developed and validated by comparing the waveform obtained from simulated and measured data. The simulated time resolution is (73 ± 1) ps after considering the intrinsic leading contributions of the detector to time resolution.

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