The Jiangmen Underground Neutrino Observatory Liangjian Wen JUNO Neutrino Astronomy & Astrophysics Workshop, Nanjing University, Apr.17-18, 2016
JUNO Experiment Jiangmen Underground Neutrino Observatory 20 kton LS detector, 3%/ 𝑭 energy resolution A multiple-purpose neutrino experiment J. Phys. G 43: 030401 (2016) (arXiv:1507.05613) Rich Physics Reactor neutrinos: q 12 osc. maximum Mass hierarchy & Precision measurement PRD 88, 013008 (2013) of mixing parameters Daya Bay NPP Supernova neutrinos Geo-neutrinos 700 m overburden Solar neutrinos 53 km Sterile neutrinos 53 km Atmospheric neutrinos Taishan NPP, 18.4 GW th Exotic searches Yangjiang NPP, 2 17.4 GW th
Supernova Neutrino Rates ~ 5k in 10s for 10kpc Atmospheric several/day Solar (10-1000)/day 700 m Cosmic muons ~ 250k/day 0.003 Hz/m 2 , 215 GeV 10% multiple-muon Geo-neutrinos 36 GW, 53 km 1-2/day reactor , ~ 60/day 4 20k ton LS
Reactor e signal and backgrounds Inverse- decay reaction: p e n e τ 200 μ s n + p d + γ (2.2 MeV) Neutrino Event: coincidence in time, space and energy Background Rate Uncertainties 30% 1% 100% 20% 50% Background Shape Uncertainties 5% negligible 20% 10% 50% 5
Sensitivity on MH JUNO MH sensitivity with 6 years' data: Ref: Y.F Li et al, (a) Use Relative Y.F Li et al PRD 88, 013008 (2013) absolute D m 2 Meas. 4 s 5 s Ideal case 3 s 4 s (b) Realistic case (a) If accelerator experiments, e.g NOvA, T2K, can measure D M 2 mm to ~1% level (b) Take into account multiple reactor cores, uncertainties from energy non-linearity, etc |D m 2 mm | Ideal Core distr. DYB & HZ Shape B/S (stat.) B/S (shape) Size 52.5 km Real Real 1% 6.3% 0.4% 1% Dc 2 +16 - 3 -1 - 1 - 0.6 - 0.1 + (4-12) MH 6
Precision Measurement Probing the unitarity of U PMNS to ~1% more precise than CKM matrix elements ! +BG +1% b2b Statistics +1% EScale +1% EnonL sin 2 θ 12 0.54% 0.67% Δ m 2 0.24% 0.59% 21 Δ m 2 0.27% 0.44% ee Probing the unitarity of U PMNS to ~1% 0.16% 0.24% 0.16% 0.27% 0.39% 0.54% E resolution Correlation among parameters 7
Precision Measurement Unitarity test of neutrino mixing matrix. (precision of s𝑗𝑜θ 12 is critical) • • Narrow down the parameter space of the effective mass |m ee | of NDBD • Discriminate models of the neutrino masses and mixing. 2 + Δ𝑛 21 2 + Δ𝑛 32 2 =1 Test if Δ𝑛 13 • 8
Requirements on Energy Resolution • 3%/ 𝑭 energy resolution stochastic term noise term Generic form constant term Impact to MH sensitivity – LS att. length: >20m@430nm 6 yrs Absorption 60 m + Rayleigh scattering 30 m – PMT parameters • QE: >30%@430nm (CE modeled in MC) • photo-coverage: >75% • charge resolution: <30% • QE non-uniformity: <20% • time resolution: <3ns JUNO Data validated Full MC (DYB&DC) • dark noise: <50kHz/PMT 9
20” MCP -PMT R&D in JUNO Evaluate both the PMT characteristics’ impacts on MH hierarchy and the cost. Finished 20 ” PMT bidding at end of 2015: -- 15000 MCP-PMT (China) -- 5000 Dynode-PMT (Japan) 10
Liquid Scintillator • LAB+PPO+bisMSB (no Gd-loading) • Increase light yield – Optimization of fluors concentration • Increase transparency – Good raw solvent LAB – Online handling/purification Distillation, Filtration, Water extraction, Nitrogen stripping, … To be tested with Daya Bay detector • Reduce radioactivity water extraction – No Gd, Less risk. Singles<~3Hz Al 2 O 3 column (>0.7MeV), with U/Th <10 -15 g/g, Linear Alky Benzene Atte. Length 40 K< 10 -16 g/g (LAB) @ 430 nm RAW (specially made) 14.2 m Vacuum distillation 19.5 m SiO 2 coloum 18.6 m Al 2 O 3 coloum 24~25 m Al 2 O 3 Test 11
JUNO-LS Pilot plant • Test the overall design of purification system at Daya Bay. Replace the target LS in one detector Al 2 O 3 column • Quantify the effectivities of subsystems – Optical : >20m A.L @430nm? – Radio-purity: 10 -15 g/g (U, Th) ? Pure LAB • Determine the choice of sub-systems – Al 2 O 3 column, distillation, gas striping, water extraction Steam stripping system Distillation system Distillation and steam stripping system (by LAB and Al 2 O 3 Italian group). mixing tank Be transported Al 2 O 3 column pilot plant installed to Daya Bay at in Daya Bay LS hall Apr/May 12
JUNO Layout 13
Electronics Calibration Filling+ overflow Top Tracker Central detector AS: ID35.4m 43.5m Acrylic sphere+ SSLS: ID40.1m 20kt Liquid Scin+ Connecting ~17000 20” PMT+ bars: ~600 ~34000 3’’ PMT Water Cherenkov ~2 000 20’’ PMT Pillar: JUNO ~100 Detector D43.5m Scheme AS: Acrylic sphere; SSLS: stainless steel latticed shell
CD Option Selection Acrylic sphere+ SS truss Balloon+ SS tank SS truss+ Acrylic sphere March, July, 2014 2015 Acrylic module+ Final decision: SS tank Acrylic sphere + SS truss Acrylic sphere+ SS tank Balloon + Acrylic support+ SS tank 15
Detector Dimension T wBuffer = 1.43 m PMT mounting on SS Struss T WP = 1.2m R LS =17.2 T acrylic = 0.12m R CD-PMT = 17.82 + T wBuffer R WP = 43.5m 16
Sensitivity vs. dimension Only consider the statistical impact on chi2 from accidental background: Divide LS into equal-mass-bin, calculate the c 2 contribution from each shell, then 17
Electronics Calibration Filling + Overflow Top Tracker Central detector AS: ID35.4m 43.5m Acrylic sphere+ SSLS: ID40.1m 20kt Liquid Scin+ ~17000 20” PMT+ ~34000 3 ’’ PMT Water Cherenkov ~2 000 20’’ PMT JUNO Detector D43.5m Scheme AS: Acrylic sphere; SSLS: stainless steel latticed shell
JUNO Central Detector H-beam Connecting bar Connecting node Supporting leg Appended Steel piece Acrylic sphere Stainless steel latticed shell acrylic • • ID:Ø35.4m ID: Ø40.1m • • Thickness:120mm OD: Ø41.1 120mm acrylic wall • • Weight: ~600t Total Weight: ~600t Connecting node H-beam • Acrylic panel ~560 • • 21 latitude circles: 400x300x12x18 • Connecting steel piece 21 layers + top chimney inserted into acrylic • + bottom flange 32 longitude circle: 500x300x12x18 • ~260 pieces • ~100 Supporting legs • ~560 connecting nodes • Connecting bar: Ø70 19
Acrylic Sphere R&D Acrylic stress is a critical issue for engineering design. The maximum stress of acrylic is concentrated at connecting nodes How to reduce the stress on acrylic node? a. Lower the load on connecting bar b. Improve the design of connecting node Worst stress case: the total vertical load is ~2600t, ~560 connecting nodes will carry it a. Lower the max load on connecting bar b. How to improve the node design • • Add the quantity of bar Add light block X Optimize the structure of node • • Improve the load distribution on bars Two kinds of node for compressive area and tensile area How to improve the load distribution on bars? Type B Type A Adjust the stiffness of some connecting bars High tensile strength High compressive strength spring 20
Acrylic Sphere R&D Forming panel size: 3m x 8m x 120mm Acrylic divided into 200+ panels Prototype of spherical panel The problems of shrinkage and shape variation were resolved. Three companies had good practices. 21
Prototypes of connecting node Another key point of acrylic sphere, ~500 nodes needed, production in acrylic company 1:1 Prototypes and strength test 1:4 Prototypes and strength test Type A Purpose: • Compare the FEA and test result Type B • Improve the structure design and bonding technology • Get the ultimate breaking capacity of connecting structure 22
Calibration System ACU Guide Tube GT CLS 23
PMT arrangement CD: 20 inch and 3inch PMTs were arranged on the steel structure 20” PMT(~17000) 3” sPMT(~34000) A rranged between 20” PMTs The supper layer method is the best one, can get the highest coverage 24 Coverage for different arrangement tries
PMT Readout Backend part- Out of water ”Dry” part Front part under-water Flash ADC of 1GHz Made the final decision last year Put most of electronics underwater and sealed with BASE, HV together. Use the single CAT5+ cable to transfer data, hit, clock, power and trigger • Needs to consider the integration and potting structure with PMT • Replacement under water is almost impossible, need high reliability of potting, electronics and HV 25
PMT Potting Potting requirement became higher • Base, High Voltage unit and the front-end electronics need to be potted • Working under 45m high-purity water; • 20 years lifetime • 0.5% failure rate for the first 6 years The conceptual design of JUNO PMT Potting Status: • Conceptual design of the overall structure is finished • Study on potting sealants, cable sealing and the thermo-conductivity is ongoing • 41 PMTs of 5 types were potted and used for JUNO Waterproof prototype. Obtained good experience sealant Adhesive or oil 26
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