1. The “Carpet-2” multipurpose air shower array of the Baksan Neutrino Observatory INR of RAS A.U. Kudzhaev
Institute for Nuclear Research, Russian Academy of Sciences, Moscow
Nalchik

2. Studying diffuse gamma-ray radiation with energies higher than
100TeV has become especially topical due to detection of astro-
physical neutrinos are a result of decays of charged pions, neu-
tral pions of the same energy should exist, and their decays
must generate considerable flux of gamma-rays with energies
above 100 TeV. In order to confirm these expectations, one
carry out new high-precision experiments in this energy range.
An experiment for measuring the flux of gamma-rays with
energy above 100 TeV is currently being prepared at the Baksan
Neutrino Observatory (the “Carpet-3” experiment). The results of
of calculations is demonstrated that by increasing the muon
detector area up to 615 m2 (the maximum possible value)
one can reach with the “Carpet-3” the world-best sensitivity to
100 TeV gamma-rays.

3. CARPET-2

4. Carpet-2 air shower array

5. Passing of muons and hadrons through the absorber of MD

6. The “Carpet-2” configuration allows to measure parameters of EAS for interval Ne= (Eo ~ 1013 – 1016 eV) with the following accuracy: core location: ΔXo=ΔY=0.35m; shower size: ΔNe/Ne ~ 0.1; arrival direction: Δψ ~ 3o; studying EAS central density structure; studying the structure of muonic component with 1GeV threshold energy; studying of hadronic component with 25 GeV threshold energy.

7. “Carpet” [196m2]

8. 2d tunnel of MD(205 detectors)

9. The “Carpet-3” shower array
planned to operate since 2018
Carpet-3:
planned to operate since 2018
Muon detector 410m2
December 2017
Additional 20 modules of
surface detectors of 9 m2
area( 18 scintillation counters of 0.5m2 area in each module)

10. Sensitivity of “Carpet-3” array to flux of diffuse cosmic photons

11. The block-scheme of “Carpet-3” shower array

12. 1st tunnel of MD(205 detectors)

14. The new liquid scintillator detector for modules of Carpet-3 array
Scheme of the new liquid scintillator detector.
Appearance of the new detector.
Comparison of the amplitude spectra on
single muons, when inner surface of the new
detector is coated with :
white paint ;
aluminium foil.
Disposition of plastic wrapping with liquid scintillator at the bottom of the detector .

15. The size of the new liquid scintillator detector : 0.66×0.74×0.31m3.
Scintillator made on the base of reactive fuel T-6.
There was measured the nonuniformity of the new detector by two
methods:
1. With the help of radioaktive gamma-source Cs137 / the energy of gamma-line is MeV/ by activity 2.2∙108 Bk. .
2. With the help of muons of cosmic rays.
The value of nonuniformity coefficient of light collection equals 0.27
and 0.21 accordingly.
The number of photoelectrons have been measured at the photocathode of PMT-49 equal to 400.

16. Current situation with “Carpet-3” construction
Two underground tunnels are filled with scintillation counters of
total continuous area of 410m2.The detectors are totally equipped
with electronics. Now is started a tune of detectors and will be
finished to end of Full scale operation of 410m2 MD is
planed to be started in the end of 2018.
At the “Carpet-2” array have been created the liquid scintillation
counter of 0.5m2 area. The counters of this type will be used for
modules in order to extend of the ground part of “Capet-3” array.
The 18 liquid scintillation counters will be placed in each module.
At present are constructed six module of 20 one, which are
placed on the surface of absorber of MD.

17. CONCLUSION
At the Baksan Neutrino Observatory INR of RAS is created the “Carpet-3” multipurpose shower array invented for investigation of diffuse gamma radiation with energy higher then 100TeV.
After final accomplished of this array it can be competitive in its class and will have a chance to get the world-best limit on the flux of gamma rays.
This will allow one to solve the problem of origin of high-energy astrophysical neutrinos detected by IceCube experiment.