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![Fig. 1. Schematic view of the JUNO detector [12]](publication/372488222/figure/fig1/AS:11431281175848156@1689909925524/Schematic-view-of-the-JUNO-detector-12_Q320.jpg)
The Jiangmen Underground Observatory (JUNO) is a 20-kton liquid scintillator detector that employs 20,000 20-inch photomultiplier tubes (PMTs) as photon sensors, with 5,000 dynode-PMTs from HAMAMATSU Photonics K.K. (HPK), and 15,000 MCP-PMTs from North Night Vision Technology (NNVT) installed in pure water. JUNO aims to provide long-lasting and the...
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... a list of PMT performance criteria has been required for all the selected PMTs [14,23]. For this purpose, JUNO has selected two types of 20-inch PMTs: the traditional dynode-PMT and the innovative micro-channel plate (MCP) PMT, as depicted in Figure 2. In addition to the performances, the system lifetime is also required for the planned running period, and the voltage divider cannot be disassembled once the PMT waterproof is completed. ...
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... BX2 scheme was another early option for the JUNO design. In the BX2 scheme, as shown in Fig. 19, the HV divider and the decoupling capacitor circuit (Splitter) of the PMT, as well as the high voltage and Front End Unit (FEU), are integrated. The final design of the HV divider with the BX2 scheme is shown in Fig. 20, where it is only integrated with the decoupling capacitor and the amplitude limitation diode has been removed.With the BX scheme, there are many interfaces, such as the interface between the electronics and PMT waterproof potting, cables, etc. In addition, the power of each channel with the BX2 scheme is 17.5 W, and there are A ...
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... final design of the HV divider with the BX2 scheme is shown in Fig. 20, where it is only integrated with the decoupling capacitor and the amplitude limitation diode has been removed.With the BX scheme, there are many interfaces, such as the interface between the electronics and PMT waterproof potting, cables, etc. In addition, the power of each channel with the BX2 scheme is 17.5 W, and there are A special version of the PMT HV divider of the BX2 schema (only the HV divider as in Fig.20) with a decoupling capacitor of 10 nF is required to support the acceptance testing of the bare PMTs, which is designed as a plug-gable version to test the bare PMTs [14]. ...
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... system has been proposed, named 1F3 (one electronics box for three PMT channels) [12]. In the 1F3 scheme, the HV divider of the PMT is separated from the splitter, FEC, and ADC, as compared to the BX scheme. The challenge of this design is the impedance matching between the PMT and the electronics [46]. The circuit for the 1F3 scheme is shown in Fig. ...
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... wave- form will show some ringing, reflection, and a larger overshoot. According to the study of the MCP-PMT, R12 will affect the ringing. When the R12 value is smaller, the ringing is larger, the SPE amplitude is larger, and the fall time is faster. R12=5 Ω is recommended, and the ringing of the waveform of MCP-PMT is very small, as shown in Fig. 23. For JUNO, the 1F3 scheme was adopted to match the final electronics, and it was used as the final design of the HV dividers for the 20-inch PMT, as shown in Fig. 22. The SPE waveforms of dynode-PMT and MCP-PMT are shown in Fig. ...
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... the ringing is larger, the SPE amplitude is larger, and the fall time is faster. R12=5 Ω is recommended, and the ringing of the waveform of MCP-PMT is very small, as shown in Fig. 23. For JUNO, the 1F3 scheme was adopted to match the final electronics, and it was used as the final design of the HV dividers for the 20-inch PMT, as shown in Fig. 22. The SPE waveforms of dynode-PMT and MCP-PMT are shown in Fig. ...
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... fall time is faster. R12=5 Ω is recommended, and the ringing of the waveform of MCP-PMT is very small, as shown in Fig. 23. For JUNO, the 1F3 scheme was adopted to match the final electronics, and it was used as the final design of the HV dividers for the 20-inch PMT, as shown in Fig. 22. The SPE waveforms of dynode-PMT and MCP-PMT are shown in Fig. ...
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... the JUNO, the PCB design of the HV divider with good reliability is also one of the key factors. Table 7 shows the design requirements for the PCB. Fig. 25 shows the PCB design for the JUNO PMT HV divider, where the resistors and capacitors on the PCB have been selected from Vishay's wirewound components for reliability. The capacitors were se- ...
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... the HV divider is required to have a lifetime of over 20 years. With the selected components, a reliability expectation has been forecasted for the lifetime and possible failure rate of the HV dividers [47]. This has been done with different component standards and temperatures, and the results with commercial components at 20 • C are shown in Fig. 26. The capacitors contribute the maximum according to the model, even though the workload of each component in power and voltage is designed to be less than 1/2 of their nominal value. The final failure rate of each HV divider is less than 50 FIT with commercial components, which already meets the requirements of JUNO. ...
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... order to meet the requirements on the PMT flasher, special testing on the flasher of the HV divider has been conducted [48]. Smooth soldering and special cleanliness are required for the flasher, and the soldering quality is further checked with a special procedure and pre-samples, as shown in Fig. 27. The soldering, production, and following burning test of PCBs of HV dividers for 20,000 20-inch PMTs have been entrusted to Tianjin Centre Advanced Tech, CO, LTD [49]. This ensures a high level of quality control and reliability for the production of the HV dividers. The soldering quality, temperature underworking, and maximum voltage ...
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... 20,000 20-inch PMTs have been entrusted to Tianjin Centre Advanced Tech, CO, LTD [49]. This ensures a high level of quality control and reliability for the production of the HV dividers. The soldering quality, temperature underworking, and maximum voltage of 6000 V were applied to four random samples, and all of them passed the test, as shown in Fig. 27. This indicates that the production process for the HV dividers is reliable and meets the design requirements. ...
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... soldering and cleaning the PCBs, a burning test is carried out for each HV divider piece for 12 days × 24 hours at a high voltage workload of 3000,V and a temperature of 75 • C to reach 90% strength, as shown in Fig. 28. In total, 21,000 PCBs of HV dividers are subjected to aging experiments, and their aging performances are monitored by the current of the voltage divider. During the test, only four 362 kΩ resistors of dynode-PMT were found to be broken, and the failure ratio was approximately 0.000067. The burning test effectively screens out ...
