Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure

OSIRIS – An online scintillator radiopurity monitor for the JUNO experiment

The Jiangmen Underground Neutrino Observatory (JUNO) currently under construction in China, will be the first multi-kton liquid scintillator detector and has a vast potential for new insights into several fields of neutrino and astroparticle physics. To reach its design sensitivity for detecting reactor and solar neutrinos, a radiopure liquid scintillator is required. For IBD measurements, a radiopurity of 10$^{−15}$ g/g is needed for both $^{238}$U and $^{232}$Th, 10$^{−16}$ g/g for solar measurements.The Online Scintillator Internal Radioactivity Investigation System (OSIRIS) allows an on-line radiopurity evaluation of the scintillator during the JUNO detector filling over several months. The design of OSIRIS is optimized for tagging $^{214}$Bi-$^{214}$Po and $^{212}$Bi-$^{212}$Po coincidence decays in the decay chains of $^{238}$U and $^{232}$Th, respectively. OSIRIS will also be able to monitor the $^{14}$C and $^{210}$Po levels in the scintillator.To achieve its goals, OSIRIS features a 20 ton liquid scintillator target monitored by 76 intelligent photomultiplier tubes (iPMTs). In this novel design, each iPMT consists of a PMT and its readout electronics mounted on its back. Each hit causing these electronics to trigger is sent to the DAQ as a digitized PMT pulse. A single computer (EventBuilder) is sufficient to combine the data stream into events for further analysis.For the timing and charge calibration of the detector, two optical systems (LED- and LASER-based) are employed. The energy and position calibration of OSIRIS is performed with height-adjustable radioactive sources within the liquid scintillator. These sources cover the crucial energy range for the detection of Bi-Po signals between 0.66 MeV to 2.5 MeV.The general design of the OSIRIS detector and its subsystems is presented in this poster

OSIRIS: The Online Scintillator Internal Radioactivity Investigation System of JUNO

The Online Scintillator Internal Radioactivity Investigation System (OSIRIS) is a 20 ton liquid scintillator (LS) detector. During the months-long filling of the 20 kton JUNO central detector, it will monitor the LS radiopurity, ensuring stringent radiopurity levels needed for the various physics goals of JUNO. This is achieved by exploiting fast Bi-Po coincidences in the $^{238}$U and $^{232}$Th decay chains. The setup is expected to reach sensitivities of 10$^{−15}$ g/g or better for both $^{238}$U and $^{232}$Th. OSIRIS will also measure the $^{14}$C and $^{210}$Po levels present in the scintillator. In this poster, the general design of OSIRIS and its different subsystems will be explained. In OSIRIS, a  water-submerged acrylic vessel holding the LS is instrumented by an array of 76 self-triggering intelligent PMTs. Their timing and charge calibration will be performed  with a Laser- and an LED-based system. The calibration of the energy and vertex reconstruction of OSIRIS utilizes height-adjustable radioactive sources within the LS

OSIRIS - The Online Scintillator Internal Radioactivity Investigation System of JUNO

The 20 kton liquid scintillator detector of the Jiangmen Neutrino Underground Observatory, currently under construction in Southern China, has a vast potential for new insights into various fields of (astro-)particle physics. Stringent limits on the liquid scintillator radiopurity are required for several physics goals of JUNO. For both $^{232}$Th and $^{238}$U, a radiopurity of 10$^{−15}$ g/g is required for reactor antineutrino measurements, 10$^{−16}$ g/g for solar neutrino measurements. An independent detector, the Online Scintillator Internal Radioactivity Investigation System (OSIRIS), will be used to ensure these limits are kept. This talk will present OSIRIS and its sensitivity to $^{232}$Th and $^{238}$U in detail.OSIRIS allows an online radiopurity evaluation of the scintillator during the months-long filling of JUNO. The design of OSIRIS is optimized for tagging fast $^{214}$Bi-$^{214}$Po and $^{212}$Bi-$^{212}$Po coincidence decays in the decay chains of $^{238}$U and $^{232}$Th, respectively. The coincident decay signatures and their rates offer a potent background rejection as well as a direct translation into $^{238}$U-/$^{232}$Th-abundances in the scintillator. OSIRIS will also be able to measure the levels of $^{14}$C in the scintillator, down to a $^{14}$C/$^{12}$C ratio of 10$^{−17}$ at 90\% C.L. Furthermore, the level of $^{210}$Po and a possible contamination by $^{85}$Kr can be determined. To achieve its goals, OSIRIS features a water-submerged 20 ton liquid scintillator target monitored by 76 intelligent PMTs (iPMTs). The novel design of the iPMTs allows a triggerless readout scheme with high signal quality. A single computer is sufficient to process the data stream into events for further analysis. The timing and charge calibration of the iPMTs will be performed with Laser- and LED-based systems. The energy and vertex reconstructions will utilise height-adjustable radioactive sources within the liquid scintillator

Radiopurity treatment of the intelligent PMTs for OSIRIS

The Jiangmen Underground Neutrino Observatory (JUNO), currently under construction in Southern China, is expected to yield new insights regarding the mass hierarchy of neutrinos. In order to reach the design sensitivity for detecting reactor and solar neutrinos, a radiopure liquid scintillator is required.The Online Scintillator Internal Radioactivity Investigation System (OSIRIS) allows an on-line quality evaluation of the scintillator during filling of the JUNO detector. It features a 20 ton liquid scintillator target monitored by 76 intelligent photomultiplier tubes (iPMTs).Because contamination with radioactive isotopes might prevent OSIRIS to reach its target sensitivity, the detector has to be cleaned prior to installation. For removing potential production residues from the iPMTs, a cleaning procedure has been developed. In this talk, the construction of the facility using ultra pure water at RWTH Aachen University will be presented

Software trigger optimization for the OSIRIS pre-detector of JUNO

JUNO is a 20 kt liquid scintillator detector under construction in Jiangmen, China, whose goal is to determine the neutrino mass hierarchy. Its data taking is expected to start in 2022. In order to meet the stringent requirements on the radiopurity of the liquid scintillator, the OSIRIS pre-detector is being designed to monitor the liquid scintillator during the several months of filling the large volume of JUNO. OSIRIS will contain 20 ton of scintillator and will be equipped with 76 20-inch PMTs. The data acquisition system will have no global hardware trigger: instead, each PMT will provide a data-stream composed of the digitized PMT pulses, each containing a time stamp. Based on the latter, dedicated software will organize these data streams into events. This talk will discuss the optimization of the event trigger conditions, for the inner liquid scintillator detector as well as outer water Cherenkov detector, considering the expected rates of different radio-active contaminations, cosmogenic muons, and the PMT dark rates