THE DELIVERY STATUS OF JUNO 20" PMTS AND THEIR PERFORMANCE Rong Zhao 1 (on behalf of JUNO collaboration) 1Sun Yat-Sen University zhaor25@mail2.sysu.edu.cn Abstract The Jiangmen Underground Neutrino Observatory (JUNO) [1] is a multi-purposed neutrino experiment currently under construction in South China. Due to its unprecedented requirement on the photocathode coverage rate in order to reach enough energy res- olution, totally 20k 20-inch photomultipliers (PMTs) will be de- ployed in the detector system, including 5k conventional Hama- matsu dynode PMTs(R12860) and 15k newly developed PMTs us- ing micro-channel plates (MCP-PMT) by North Night Vision Tech- nology (NNVT). The JUNO collaboration has developed a PMT mass testing system to characterize these PMTs and selected the qualified ones for the final installation. Up to now, we have re- ceived and completed the characterization of 5k Hamamatsu PMTs and 13.1k MCP-PMTs. In this poster, we will present the latest de- livery details and the performance results including the typical sin- gle photon-electron (SPE) waveform, SPE spectra of two types of PMTs, SPE resolution, photon detection efficiency(PDE) and dark count rate(DCR) etc. Introduction of JUNO Detector The JUNO central detector will be filled with liquid scintillator, about 15k 20"MCP-PMTs and 5k 20"Hamamatsu PMTs will be used to collect scintillation light and Cherenkov light; the geometry of JUNO detector and PMTs are shown in Figure 1. Figure 1:JUNO detector and geometry of Hamamatsu PMT and MCP-PMT PMT Delivery and Test Status By May 2020, 18k of the total 20k PMTs have been delivered to JUNO PMT storage site, the acceptance test of 15k PMTs have been finished and 5k MCP-PMTs have been potted, as illustrated in figure below. 13.1k delivered 10k tested 15k total 5k tested 5.3k potted HAMAMATSU DYNODE PMT NNVT MCP-PMT All of the delivered PMTs will experience a detailed visual check and electronic performance test before they are potted and finally installed into JUNO detector. PMT Testing System Two container PMT testing systems with electromagnetic shield- ing are currently used for mass acceptance tests[4]. Each of them consists of 36 individual drawers (see Figure 2). The PMT inside each drawer can be illuminated with a self-stabilized LED or a pico- second laser, both with 420 nm wavelength. Two PMT scanning stations [2][3] were built for characterization of whole PMT photo- cathode. It allows for the testing of individual PMTs in all relevant aspects by scanning the photocathode and identifying any poten- tial problems. Figure 2:The container PMT mass test system and PMT scanning station JUNO PMT Performance of tested PMTs The typical single photon electron waveform of Hamamatsu PMT and MCP-PMT is shown in Figure 3: 100 150 200 250 300 350 400 t[ns] 0 2 4 6 8 10 12 14 U[mV] 100 150 200 250 300 350 400 t[ns] 6 8 10 12 14 16 18 20 U[mV] Figure 3:typical SPE waveform and 2D waveforms of Hamamatsu and MCP-PMTs. left: wave- form of Hamamatsu PMT EA0419; right: waveform of MCP-PMT PA1707-1090 SPE charge spectrum of PMTs obtained by LED with low illumina- tion(average photon number µ ≤1 ) are shown in Figure 4: Figure 4:charge spectrum of PMTs. left: Hamatsu PMT EA0419 with gain=9.9E6 and µ = 0.16, 0.79; right: MCP-PMT PA1707-1090 with gain=1.04E7 and µ = 0.14, 0.84. Performance parameters of PMTs can be derive from the charge spectrum and other dedicated measurements. Table 1:peformance parameters of JUNO accepted PMTs PMT PDE(%) DCR(kHz) FWHM(ns) TTS(ns) resolution risetime(ns) falltime(ns) p/V Hamamatsu 28.17 15.38 11.56 1.42 0.28 6.94 10.20 3.83 MCP 27.20 48.94 8.18 6.35 0.32 4.01 17.97 4.28 MCP(HQE) 30.14 49.73 7.83 6.35 0.33 4.95 17.10 3.93 PDE and DCR Distributions The PDE and DCR(the methodology and the exact definition can be found in [4]) distributions of PMTs are shown in Figure 5, for MCP-PMT the high quantum efficiency version has higher detec- tion efficiency benefiting from the new photocathode technol