TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022

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

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

Scintillation Light Transport In The Large Reactor Antineutrino Detector JUNO

In low-energy neutrino physics, liquid scintillator (LS) detectors play a major role. The Jiangmen Underground Neutrino Observatory (JUNO) will be a multipurpose neutrino experiment and is currently under construction in South China. JUNO's main goal is the determination of the neutrino mass ordering at a 3-4σ significance within an operation time of six years. With a target mass of 20 kt, JUNO will be the largest LS detector constructed so far. A crucial requirement is to reach an energy resolution of at least 3% @ 1 MeV. Besides other aspects, this demands a sufficiently high transparency of the liquid scintillator. This transparency is expressed in terms of the attenuation length L and scattering length Ls. In order to fulfill the demands on the energy resolution, JUNO strives for values of L=20 m and Ls =27 m, respectively. To ensure that the detector performance meets these requirements for the whole operation period and does not degrade over time, the target's transparency will be continuously monitored. This is the purpose of the laser calibration system AURORA (A Unit for Researching On-line the LS tRAnsparency), which is installed in the water volume surrounding the JUNO central detector. The first part of this thesis is about the design, construction, and performance tests of AURORA. A specially selected diode provides laser light at a wavelength of λ=430 nm, which corresponds to the spectral region of the scintillator light emission. The light is distributed into an array of 100 m long fibers by an automated fiber switch. The laser light is decoupled from GRIN lenses that permit to collimate the beam underwater. Full aperture angles of less than 0.25° can be achieved. To avoid any damage to the PMTs, piezoelectric actuators have been introduced to ensure that the beams can be remotely tilted by around 1°. Thus, even if the geometry shifted due to the detector filling, it would be possible to compensate for misalignment. Any interference with the electronic readout of the PMTs has to be avoided. The generated magnetic field of these electro-mechanical devices has been tested and found to be acceptably small. The second part of this thesis focuses on the investigation of AURORA's potential to determine the attenuation length L and the scattering length Ls of the LS studying statistical and systematical uncertainties. To evaluate the feasibility and sensitivity of the developed analysis approach, detailed studies with JUNO's official simulation framework offline have been conducted. It is found that a 50 s run provides sufficient statistics to reduce the relative uncertainty to the 0.1% level. Moreover, several sources of systematic uncertainties were studied. For an absolute measurement of the attenuation and scattering length, systematic uncertainties of ΔL=±13 cm and ΔLs=±23 cm can be achieved. For a relative measurement that compares the development of the LS transparency over time, several systematic contributions do not have to be included. In this case, the systematic uncertainties are reduced to ΔL=±7 cm and ΔLs=±11 cm, respectively.xvi, 227 Seiten, Illustrationen, Diagramme, Kart

A Liquid Scintillator Transparency monitoring Laser System for JUNO

One of the future neutrino detectors is the Jiangmen Underground Neutrino Observatory (JUNO) with its primary goal to determine the neutrino mass hierarchy from the oscillations of reactor antineutrinos. For this purpose, an energy resolution of 3% @ 1 MeV is required. Therefore, the transparency of the LS has to be sufficiently high and stable during the whole operation time (attenuation length ≥ 20 m @ 430 nm). One device for monitoring of the optical LS quality is a laser system inside the central detector of JUNO, detecting degradation effects in the liquid and a possible gradient in its refractive index. The latter can be caused by a temperature gradient leading to curved light propagation, which would need to be taken into account during the event reconstruction. This poster presents the conceptual design, the working principle and the current status of the laser system. The development is funded by the DFG Research Unit “JUNO” and the Mainz Cluster of Excellence “PRISMA”.</p

Potential for a precision measurement of solar pppp neutrinos in the Serappis Experiment

The Serappis (SEarch for RAre PP-neutrinos In Scintillator) project aims at a precision measurement of the flux of solar $pp$ neutrinos on the few-percent level. Such a measurement will be a relevant contribution to the study of solar neutrino oscillation parameters and a sensitive test of the solar luminosity constraint. The concept of Serappis relies on a small organic liquid scintillator detector ($\sim$20 m$^3$) with excellent energy resolution ($\sim$2.5 % at 1 MeV), low internal background and sufficient shielding from surrounding radioactivity. This can be achieved by a minor upgrade of the OSIRIS facility at the site of the JUNO neutrino experiment in southern China. To go substantially beyond current accuracy levels for the $pp$ flux, an organic scintillator with ultra-low $^{14}$C levels (below $10^{-18}$) is required. The existing OSIRIS detector and JUNO infrastructure will be instrumental in identifying suitable scintillator materials, offering a unique chance for a low-budget high-precision measurement of a fundamental property of our Sun that will be otherwise hard to access

Potential for a precision measurement of solar pppp neutrinos in the Serappis Experiment

The Serappis (SEarch for RAre PP-neutrinos In Scintillator) project aims at a precision measurement of the flux of solar $pp$ neutrinos on the few-percent level. Such a measurement will be a relevant contribution to the study of solar neutrino oscillation parameters and a sensitive test of the solar luminosity constraint. The concept of Serappis relies on a small organic liquid scintillator detector ($\sim$20 m$^3$) with excellent energy resolution ($\sim$2.5 % at 1 MeV), low internal background and sufficient shielding from surrounding radioactivity. This can be achieved by a minor upgrade of the OSIRIS facility at the site of the JUNO neutrino experiment in southern China. To go substantially beyond current accuracy levels for the $pp$ flux, an organic scintillator with ultra-low $^{14}$C levels (below $10^{-18}$) is required. The existing OSIRIS detector and JUNO infrastructure will be instrumental in identifying suitable scintillator materials, offering a unique chance for a low-budget high-precision measurement of a fundamental property of our Sun that will be otherwise hard to access

Potential for a precision measurement of solar pp neutrinos in the Serappis experiment

The Serappis (SEarch for RAre PP-neutrinos In Scintillator) project aims at a precision measurement of the flux of solar pp neutrinos on the few-percent level. Such a measurement will be a relevant contribution to the study of solar neutrino oscillation parameters and a sensitive test of the equilibrium between solar energy output in neutrinos and electromagnetic radiation (solar luminosity constraint). The concept of Serappis relies on a small organic liquid scintillator detector (∼20 m$^3$) with excellent energy resolution (∼2.5% at 1 MeV), low internal background and sufficient shielding from surrounding radioactivity. This can be achieved by a minor upgrade of the OSIRIS facility at the site of the JUNO neutrino experiment in southern China. To go substantially beyond current accuracy levels for the pp flux, an organic scintillator with ultra-low $^{14}$C levels (below 10$^{−18}$) is required. The existing OSIRIS detector andJUNO infrastructure will be instrumental in identifying suitable scintillator materials, offering a unique chance for a low-budget high-precision measurement of a fundamental property of our Sun that will be otherwise hard to access

TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution

The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A ton-level liquid scintillator detector will be placed at about 30 m from a core of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be measured with sub-percent energy resolution, to provide a reference spectrum for future reactor neutrino experiments, and to provide a benchmark measurement to test nuclear databases. A spherical acrylic vessel containing 2.8 ton gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon Photomultipliers (SiPMs) of &gt;50% photon detection efficiency with almost full coverage. The photoelectron yield is about 4500 per MeV, an order higher than any existing large-scale liquid scintillator detectors. The detector operates at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The detector will measure about 2000 reactor antineutrinos per day, and is designed to be well shielded from cosmogenic backgrounds and ambient radioactivities to have about 10% background-to-signal ratio. The experiment is expected to start operation in 2022