Large photocathode 20-inch PMT testing methods for the JUNO experiment

The 20kt Liquid Scintillator (LS) JUNO detector is being constructed by the International Collaboration in China, with the primary goal of addressing the question of neutrino mass ordering (hierarchy). The main challenge for JUNO is to achieve a record energy resolution, ~3% at 1MeV of energy released in the LS, which is required to perform the neutrino mass hierarchy determination. About 20 000 large 20-inch PMTs with high Photon Detection Efficiency (PDE) and good photocathode uniformity will ensure an approximately 80% surface coverage of the JUNO detector. The JUNO collaboration is preparing equipment for the mass tests of all PMTs using 4 dedicated containers. This approach allows us to test 144 PMTs in parallel. The primary measurement in the container will be the PMT response to illumination of its photocathode by a low-intensity uniform light. Each of the 20 000 PMTs will undergo the container test. Additionally, a dedicated scanning system was constructed for sampled tests of PMTs that allows us to study the variation of the PDE over the entire PMT photocathode surface. The core of the scanning station is a rotating frame with 7 LED sources of calibrated short light flashes that are placed along the photocathode surface covering zenith angles from the top of a PMT to its equator. The collection efficiency of a large PMT is known to be very sensitive to the Earth Magnetic Field (EMF), therefore, understanding the necessary level of EMF suppression is crucial for the JUNO Experiment. A dark room with Helmholtz coils compensating the EMF components is available for these tests at a JUNO facility. The Hamamatsu R12860 20-inch PMT is a candidate for the JUNO experiment. In this article the container design and mass-testing method, the scanning setup and scanning method are briefly described and preliminary results for performance test of this PMT are reported.Comment: This talk was presented on The International Conference "Instrumentation for Colliding Beam Physics" (INSTR-17

On the Applicability of HF and μ-PCD Methods for Determination of Carrier Recombination Lifetime in the Non-passivated Single-crystal Silicon Samples

Comparison of the results of measuring the carrier recombination lifetime in silicon single crystals by contactless HF and microwave μ-PCD methods was carried out. It has been shown that HF method gives a large error compared with a μ-PCD method. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3613

Some Aspects of Phosphorus Diffusion in Germanium in In0,01Ga0,99As / In0,56Ga0,44P / Ge Heterostructures

The results of experimental and theoretical researches of phosphorus distribution in the first cascade of a multi cascade solar cell based on nanoscale structures AIIIBV / Ge are presented. Secondary ion mass spectroscopy has been applied to obtain profiles of phosphorus and gallium in In0.01Ga0.99As / In0.56Ga0.44P / Ge heterostructure. In the germanium surface there is a thin layer of about 26 nm, in which the gallium concentration exceeds the concentration of phosphorus. Therefore a nanoscale p-n junction forms that does not have a significant impact on the solar cells performance at room temperature. Phosphorus diffusion is much slower in this area than in area with electronic conductivity. The main p-n junction is formed at a distance of 130-150 nm from the surface of the germanium. Diffusivity of gallium (DGa = 1,4×10 – 15 cm2/s) is markedly higher than described in a literature. Diffusivity of P increase from DP = 3×10-15 cm2/s on the boundary of the heterostructure In0, 49Ga0, 51P to DP = 5,2×10 – 14 cm2/s in n-type Ge. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3364

Microchannel avalanche photodiode with wide linearity range

Design and physical operation principles of new microchannel avalanche photodiode (MC APD) with gain up to 10^5 and linearity range improved an order of magnitude compared to known similar devices. A distinctive feature of the new device is a directly biased p-n junction under each pixel which plays role of an individual quenching resistor. This allows increasing pixel density up to 40000 per mm^2 and making entire device area sensitive.Comment: Submitted to Journal of Technical Physic

Lanthanum-Gallium Tantalate Crystals and their Electrophysical Characterization

Lanthanum-gallium tantalate single crystal (La3Ta0.5Ga5.5O14, langatate, LGT) is a perspective piezoe-lectric material as an active component of pressure sensors. An investigation of the growth conditions in-fluence (the growth atmosphere) on the electrophysical сharacterization of LGT, obtained in different at-mospheres (Ar, Ar + O2) was carried out. The frequency dependences of the relative dielectric constant (ε11/ε0) and of the admittance depend on the growth atmosphere. The langatate electrophysical сharacteri-zation in alternating electric fields were analyzed by means of the impedance spectr oscopy method. The behavior of short circuit currents in specimens of polar cuts of LGT single crystals with the same material electrodes without preliminary polarization is described. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3628

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

JUNO Conceptual Design Report

The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine the neutrino mass hierarchy using an underground liquid scintillator detector. It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants in Guangdong, China. The experimental hall, spanning more than 50 meters, is under a granite mountain of over 700 m overburden. Within six years of running, the detection of reactor antineutrinos can resolve the neutrino mass hierarchy at a confidence level of 3-4$\sigma$, and determine neutrino oscillation parameters $\sin^2\theta_{12}$, $\Delta m^2_{21}$, and $|\Delta m^2_{ee}|$ to an accuracy of better than 1%. The JUNO detector can be also used to study terrestrial and extra-terrestrial neutrinos and new physics beyond the Standard Model. The central detector contains 20,000 tons liquid scintillator with an acrylic sphere of 35 m in diameter. $\sim$17,000 508-mm diameter PMTs with high quantum efficiency provide $\sim$75% optical coverage. The current choice of the liquid scintillator is: linear alkyl benzene (LAB) as the solvent, plus PPO as the scintillation fluor and a wavelength-shifter (Bis-MSB). The number of detected photoelectrons per MeV is larger than 1,100 and the energy resolution is expected to be 3% at 1 MeV. The calibration system is designed to deploy multiple sources to cover the entire energy range of reactor antineutrinos, and to achieve a full-volume position coverage inside the detector. The veto system is used for muon detection, muon induced background study and reduction. It consists of a Water Cherenkov detector and a Top Tracker system. The readout system, the detector control system and the offline system insure efficient and stable data acquisition and processing.Comment: 328 pages, 211 figure