tunka experiment: towards 1км 2 eas cherenkov array b.k.lubsandorzhiev for tunka collaboration
TRANSCRIPT
Tunka Experiment: Towards 1км2 EAS Cherenkov Array
B.K.Lubsandorzhiev for TUNKA Collaboration
TUNKA COLLABORATION
Scobeltsyn 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
“…..as far as Baikal it is Siberia’s dull prose, just from Baikal Siberian delightful poetry starts….” A.P.Chekhov (Letters from Siberia)
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)
QUASAR-370G
37 cm extended bialkalilow resistance hemisphericalphotocathode
2acceptance
YSO+BaF2 scintillator
Small 6 stages high anode current PMT
QUASAR-370G
2 ns TTS (FWHM)
70-80 % SER
IAmax ~ 200 mkA
Immunity to Earth’s magnetic field
TUNKA Wide Angle EAS Cherenkov Detector
675 m a.s.l. Seff ~ 1.6 105 m2 Eth ~ 500 TeV ~ 0.5o
The Tunka-25
„Remote detector“
25 QUASAR-370G tubes - 37 cm diameter - integrating 4 EMI D668 tubes
(AIROBICC tubes) - 20 cm diameter - fiber read-out, - FADC
prototype
Cherenkov light lateral distribution
Q(R) = Qkn·exp((Rkn-R)·(1+2/R)/R0)
Q(R) = Qkn·(Rkn/R)2.2
P = Q(100)/Q(200)
R0 = 102.83-0.2·P [m]
Rkn = 200 -20·P [m]
Hmax=10.62-0.12(P+2.73)2
Hmax=X0/cos - Xmax
Differential energy spectrum of CRs around the “knee”
E0[TeV] = 370(Q175) 0.96
[photoncm-2eV-1]
Eknee ~ 31015eV
1 = -2.660.01
2 = -3.100.02
Energy spectrum of CRs in wide range
Gap between direct and ground based measurements.
Approximations of their data don’t coincide!
Chemical composition of CRs around the knee
Mass composition is measured by two methods:
1. Measurements of Cherenkov light waveform at large distancesfrom a shower core (>200 m)
R ~ 300 m
2. Analysis of LDF
Hmax=1677+1006lg(FWHM)
Chemical composition around the knee
Mean mass composition
30% p, 30% He, 20%CN, 20% Fe
WHAT NEXT?
Тunka-133
133 optical detectors covering Seff ~ 1 km2 Eth ~ 1015 eV
Expected statistics for 1 year operation ( 400 hours): > 3·1015 eV ~ 3.0•105 events > 1017 eV ~ 200 events > 1018 eV ~ 1 – 3 events
Study of energy spectrum and mass composition of primary cosmic rays from “classical” knee ~3•1015 eV to maximumenergy in SNR ~1017 • Z eV
Tunka-133: position of optical detectors
Seven optical detectors form one Cluster
Optical detector
PreamplifierHV power supply
Plexi window with heating
Phototube:20 cm PMT fromAIROBICC and MACRO
Cluster’s Electronics
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
CONCLUSIONS
TUNKA experiment operates for more than 10 years.
Physics results of the experiment covers primary cosmic raysstudies in the energy range 61014 - 1017eV
The «knee» of primary energy spectrum is observed around ~3 1015eV
Primary mass composition doesn’t change significantly in therange of 1015 - 1016eV gradually rising to heavier elements athigher energies.
It is necessary to decrease energy threshold down to 1014eV to compare results with direct experiments data
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 inthe energy range of 1015- 1018 eV