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Tunka Experiment: Towards 1км 2 EAS Cherenkov Array

Tunka Experiment: Towards 1км 2 EAS Cherenkov Array. B.K.Lubsandorzhiev for TUNKA Collaboration.

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Tunka Experiment: Towards 1км 2 EAS Cherenkov Array

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  1. Tunka Experiment: Towards 1км2 EAS Cherenkov Array B.K.Lubsandorzhiev for TUNKA Collaboration

  2. TUNKA COLLABORATIONScobeltsyn Institute of Nuclear Physics of MSU (Moscow, Russia) Institute of Applied Physics of ISU (Irkutsk, Russia) Institute for Nuclear Research RAS (Moscow, Russia) IZMIRAN (Moscow, Russia) Universita’ Torino , Italy DESY-Zeuthen, Germany

  3. “…..as far as Baikal it is Siberia’s dull prose, just from Baikal Siberian delightful poetry starts….”A.P.Chekhov (Letters from Siberia)

  4. History of Tunka Experiment 1991-1992 experiments with QUASAR-370 tubes on the Baikal ice 1991-1993 Development of QUASAR-370 modification for EAS Cherenkov arrays - QUASAR-370G 1993 Surface Mobile EAS Cherenkov Array (SMECA) for joint work with Lake Baikal neutrino telescope NT-200 1993 - TUNKA-4 (4 QUASAR -370G) 1996 - TUNKA-13 (13 QUASAR-370G) 2000 - TUNKA-25 (25 QUASAR-370G) 200? - TUNKA-133 (1km2 Cherenkov EAS Array)

  5. QUASAR-370G 37 cm extended bialkali low resistancehemispherical photocathode 2p acceptance YSO+BaF2 scintillator Small 6 stages high anode current PMT

  6. QUASAR-370G 2 ns TTS (FWHM) 70-80 % SER IAmax ~ 200 mkA Immunity to Earth’s magnetic field

  7. TUNKA Wide Angle EAS Cherenkov Detector 675 m a.s.l. Seff ~ 1.6 105 m2 Eth ~ 500 TeV  ~ 0.5o

  8. The Tunka-25 25 QUASAR-370G tubes - 37 cm diameter - integrating 4 EMI D668 tubes (AIROBICC tubes)- 20 cm diameter - fiber read-out, - FADC „Remote detector“ prototype

  9. Cherenkov light lateral distribution P = Q(100)/Q(200) R0 = 102.83-0.2·P [m] Rkn = 200 -20·P [m] Q(R) = Qkn·exp((Rkn-R)·(1+2/R)/R0) Q(R) = Qkn·(Rkn/R)2.2 Hmax=10.62-0.12(P+2.73)2 Hmax=X0/cos - Xmax

  10. Differential energy spectrum of CRs around the “knee” E0[TeV] = 370(Q175)0.96 [photoncm-2eV-1] Eknee ~ 31015eV 1 = -2.660.01 2 = -3.100.02

  11. Energy spectrum of CRs in wide range Gap between direct and ground based measurements. Approximations of their data don’t coincide!

  12. Chemical composition of CRs around the knee Mass composition is measured by two methods: 1. Measurements of Cherenkov light waveform at large distances from a shower core (>200 m) R ~ 300 m Hmax=1677+1006lg(FWHM) 2. Analysis of LDF

  13. Chemical composition around the knee

  14. Mean mass composition 30% p, 30% He, 20%CN, 20% Fe

  15. WHAT NEXT?

  16. Тunka-133 Study of energy spectrum and mass composition of primary cosmic rays from “classical” knee ~3•1015 eV to maximum energy in SNR ~1017 • Z eV 133 optical detectors covering Seff~ 1 km2 Eth~ 1015eV Expected statistics for 1 year operation ( 400 hours): > 3·1015 eV~ 3.0•105 events > 1017 eV~ 200 events > 1018 eV~ 1 – 3 events

  17. Tunka-133: position of optical detectors Seven optical detectors form one Cluster

  18. Opticaldetector Phototube: 20 cm PMT from AIROBICC and MACRO Plexi window with heating Preamplifier HV power supply

  19. Cluster’s Electronics

  20. Reconstruction of EAS parameters Shower core location~ 6 m Primary energy measurement~ 15% Xmax measurement (LDF) ~35 – 40 g/cm2 Xmax measurement (pulse shape) ~ 25 g/cm2

  21. CONCLUSIONS TUNKA experiment operates for more than 10 years. Physics results of the experiment covers primary cosmic rays studies in the energy range 61014 - 1017eV The «knee» of primary energy spectrum is observed around ~3 1015eV Primary mass composition doesn’t change significantly in the range of 1015 - 1016eV gradually rising to heavier elements at higher energies. It is necessary to decrease energy threshold down to 1014eV to compare results with direct experiments data

  22. It is very desirable to develope new version of QUASAR phototube (~50 cm in diameter): fast (1ns TTS (fwhm)) with a few ns time response . We are planning to construct new array with 133 hemispherical phototubes (20 cm in diameter) to study primary cosmic rays in the energy range of 1015- 1018 eV

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