The Tunka Cherenkov Array Д.В.Чернов, Е.Е.Коростелева, Л.А.Кузьмичев, В.В.Просин, И.В.Яшин НИИЯФ МГУ, Москва, Россия Н.М.Буднев, О.А.Гресс, Т.И.Гресс, Л.В.Паньков, Ю.В.Парфенов, Ю.А.Семеней НИИПФ ИГУ, Иркутск, Россия Р.В.Васильев, Б.К.Лубсандоржиев, А.И.Панфилов, П.Г.Похил ИЯИ РАН, Москва, Россия C.Spiering, R.Wischnewski, DESY Zeuthen, Zeuthen, Germany

1 TeV

The Site: Tunka Valley, 675m altitude

The Tunka-25 array in 2003 „Far detector“ 25 QUASAR-370 tubes - 37 cm diameter - integrating 4 EMI D668 tubes - 20 cm diameter - fiber read-out, - FADC

QUASAR-370 in its container

EMI D668 for pulse form analysis - PMTs - fibers - optical receivers - FADCs from DESY

Electronics for pulse shape analysis delay 50 nc FADC DL515 in start run 1 D C 8 µsec R Trigger Reset VME delay 1.6 µsec Trigger from TUNKA-25 Optical cable Discr. Controller PC

Measured waveform and parametrization Time code in units of 2 nsec

Sample of atmospheric Cherenkov light pulse EXPERIMENT: F FALL (T)=A QM ·exp(-(T-T QM )/T FALL ), for T > T QM F FRONT (T)=exp(-((T-T QM )/T FRONT ) 2 )·F FALL (T), for T≤T QM

Measured FWHM as function of Left: distance shower-axis  PMT Right: zenith angle of shower

Correlation between depth of shower maximum and pulse width at different distances R to the shower axis (Corsika)

FWHM as function of shower energy Assuming that the data describe Helium, the dashed curves are expected for protons and Iron, respectively

up to R ~ 30 m: exponential Corsika,2000 m Light intensity This part depends mainly on energy This part depends mainly on distance to shower maximum E = 2 PeV

The same dependence as measured in QUEST Control experiment at Gran Sasso (EAS Top), with the number of electrons measured by scintillation counter

up to R ~ 30 m exponential R 1 One free parameter: P Corsika and parametrization

Parameter P as function of distance to shower maximum

Relation between Q, P, and energy

Тheoretical accuracy of energy reconstruction Empty circles: protons Full circles: iron protons iron

σH max = 0.3 km mean shift: ΔH = 0.15 km for p ΔH = km for Fe H max = ·(P+2.73) 2, [km] CORSIKA: Measurement of a distance to EAS maximum with the Cherenkov light LDF steepness parameter P

CORSIKA: Measurement of relative position of EAS maximum with Cherenkov light pulse FWHM at R=250 m from shower axis (X 0 /cos(θ) – X max ) = 1659 – 1006 · log 10 (FWHM/ns), g/cm 2

Results: hours Tunka million triggers events with E 0 > 6·0 14 eV and < 25° - Fit Q(R) and determine Q 1, P,  shower maximum  energy and atomic weight

TIBET KASCADE

Mean depth of EAS maximum

- Spase/Amanda

The future m² water tank (muons at 200 m distance, PeV showers) 2. Tunka-133, with 1 km² area µ e 1-2 m 3 m

Photomultipliers – 20 cm EMI with FADC read-out 19 clusters, each with 7 huts Energy range: up to eV The Tunka-133 Project

Expected statistic from 1 year operation ( 400 hours): > 3·10 15 eV ~ events > eV ~ 200 events > eV ~ 5 events TUNKA-133