Response of the PRISMA-YBJ detectors to earthquakes Yuri Stenkin on behalf of PRISMA collaboration Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 1
Outline natural neutron sources global net of en-detectors PRISMA-YBJ results PRISMA-LHAASO and geophysics Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 2
Natural neutron sources 1. Cosmic rays 2. Natural radioactivity Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 3
By measuring barometric coefficient we can estimate portion of neutrons originated from radon
The method Pulse shape digitizing En-detector n (neutrons) housing PMT scintillator FADC PC Open detector: no moderator noise ( charged ) Both types of signals are stored and analyzed charged pulses include decays of radon chain in air, mostly Bi-214 and Pb-214 while neutrons mostly come from soil, walls, roof, etc. Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 5
Geophysical researches with thermal neutrons Moon tidal waves Neutrons in thunderstorms Seasonal variations Barometric pumping effect for neutrons Earth free oscillations in neutrons, Forbush effect, etc. Earthquakes 6
Global net of the thermal neutron en-detectors Detectors are located now at five sites, 3 different geographic points: surface underground 1. N-BNO (Baksan, 1700 m a.s.l., 43E, 43N) 3 2 2. Neutron (Moscow, 170 m a.s.l., 37E, 56N) 4 (MEPhI) 1 (INR) 3. PRISMA-YBJ (Tibet, 4300m a.s.l., 90E, 30N) 4 (ARGO hall) now PRISMA-TU (Tibet University, Lhasa, 3750 m a.s.l.) 4 Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 7
Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 PRISMA PRISMA-YBJ prototype (2013-2017)
Light collecting cone PMT PRISMA-YBJ prototype PRISMA-LHAASO-64 (full scale array next year) Housing, PE water tank Scintillator: ZnS(Ag)+ 6 LiF En-detector design or ZnS(Ag)+B 2 O 3 Sensitive area 0.36 m 2 Thermal neutron recording efficiency ~20% Scintillator effective thickness 30 mg/cm 2 Some interesting results obtained with the prototype in YBJ are shown below: Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 9 9
4 th harmonic of Moon month in neutrons and charged (1 week wave) PRISMA-YBJ 4300 m a.s.l. YURI STENKIN, VICTOR ALEKSEENKO, ZEYU CAI, ZHEN CAO, CLAUDIO CATTANEO, et. al. Seasonal and Lunar Month Periods Observed in Natural Neutron Flux at High Altitude. Pure and Appl. Geophys. 174 (2017), 2763 2771 10
PRISMA-YBJ Long term variations of environmental thermal neutron flux in 2013-2017 Stenkin Yu.V., Alekseenko V.V., Cui S.W., He Ya.Yu., et al. Natural thermal neutron flux long-term variations at 4300 m a.s.l. PoS(ICRC2017)094 Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 11
Diurnal wave S1 in ARGO hall: neutrons and charged anti-correlate? S1 PRISMA-YBJ n/<n> 1.045 1.040 1.035 1.030 1.025 1.020 1.015 1.010 1.005 1.000 0.995 0.990 0.985 0.980 0.975 0.970 0.965 S1 in n S1 in charged (n norm +ch norm )/2 0 2 4 6 8 10 12 14 16 18 20 22 24 T, h Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 12
Map of Nepal earthquakes localization in April-May 2015 and in October 2016. Circles show the earthquakes, star shows Yangbajing Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 13
Himalaya geology map Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 14
Response of en-detectors to Nepal earthquakes in April-May 2015 1.12 1.10 1.08 1.06 1.04 M7.8 M6.7 Nepal EQ'April-2015 (n & ch) M7.3 n / <n> 1.02 1.00 0.98 0.96 0.94 0.92 n (8h smoothing) "charged" (8h smoothing) 0 5 10 15 20 25.04 Epicenter distance is at (580 680) km days since Ap. 21, 2015 12.05 Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 15
Specific parameter Σ=n norm +charged norm -2 was introduced to emphasize the en-detector response 0.12 EQ Nepal: n norm +ch norm EQ 0.10 0.08 n norm + charged norm - 2 0.06 0.04 0.02 0.00-0.02-0.04-0.06 0 2 4 6 8 10 12 14 16 18 20 22 25.04.15 days since Ap. 21, 2015 12.05.15 Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 16
1.5 year later: Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 17
Distributions on the Σ parameter for d1 & d4 over 3.5 years. Histograms - experimental data; smoothed curves - Gauss fits. Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 18
Diurnal waves in thermal neutrons @ EQ days Nepal EQs M4.6 M4.1 1.15 M6.7 M7.8 M7.3 M6.7 n / <n> 1.10 1.05 12.05.15 26.04.15 M6.2 11.10.16 1.00 25.04.15 0.95 0.90 n 12.10.16 0 2 4 6 8 10 12 14 16 18 20 22 24 Therefore, we saw Local effects time in diurnal T, h wave phase and not in direct current Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 19
Date Signal in d1, σ Signal in d4, σ Event Comment 2015-02-07 9.2 7.1? not understood 2015-04-26 9.6 9.4 25.04: Nepal M=7.8; 6.7 26.04: Nepal M=6.7 3 huge EQs with 0.5 and ~25 hours between them and many aftershocks 2015-05-12 6.7 6.3 Nepal M=7.3 & 6.2 2 huge EQs with ~0.5 hour between them 2016-03-29 6.2 6.7? not understood 2016-05-08 9.0 6.3 Magnetic storm, Kp=7 Powerful magnetic storm 2016-10-12 10.9 8.4 11.10: Nepal M=4.6 12.10: Nepal M=4.1 2 EQs with ~24 hours between them Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 20
Radon meter response (in ARGO hall) 3500 3000 M7.8 M6.7 M6.7 North Rn, Bq/m 3 2500 2000 1500 1000 0 1 2 3 4 5 6 7 days from 24.04.15 Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 21
Distribution of radon data peaks in 3h time series measured by a radon meter. Histograms - experimental data; smoothed curves Gauss fit. Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 22
A puzzle of possible far detector response: Baksan underground en-detector (850 m w.e.) ~4000 km from epicenter M7.8, Nepal 25.04.15 1.5 n<n> 1.0 0 2 4 6 8 10 12 14 16 18 20 22 24 Local time, h n Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018
Conclusion - We do see response of en-detectors to some Eqs - The effect depends on the region geology and probably on the EQ aftershocks appearence time - A Global net of such arrays are needed to learn more about correlations between Eqs and the en-detector response - Even far detectors are probably have some response Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018
Future plans (summary) The PRISMA-LHAASO project will include geophysical researches For this purpose are envisaged: 1. Additional outputs with large pulse integration (long charge collection) from each en-detector for ¼ of clusters 2. Special FADCs for variations study 3. Continuous monitoring of neutron background with a precise accuracy 4. The array will be included in our global net of en-detectors 5. Special attention will be paid to Solar-Earth connections phenomena (space weather) and possibility to monitor seismic activity for better understanding correlations between EQs and environmental thermal neutrons flux 6. Pure variational array of 4 en-detectors (PRISMA-TU) is deployed in 2017 at Tibet Univ. Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 25
Thank you! Yu. Stenkin, 35RCRC+25ECRS, Barnaul, 2018 26