1. A.A. Ivanov for the Yakutsk array group The scientific goals of the Yakutsk array under modernization

2. Content  Introduction  Main results and the present status of the Yakutsk array experiment of the Yakutsk array experiment  Next step astrophysical goals  Modernization of the array  Conclusions

3. Content  Introduction  Main results and the present status of the Yakutsk array experiment of the Yakutsk array experiment  Next step astrophysical goals  Modernization of the array  Conclusions

4. N.N. Efimov and D.D. Krasilnikov In 1959 D.D. Krasilnikov formulated an idea of EAS array in Yakutsk. 5.09.1964: The project is approved by the Scientific Council of AS USSR. 1967: The beginning of construction of EAS- 13 prototype (13 stations, D.D. Krasilnikov, I.Ye. Sleptsov). 1967-1970: Engineering stage; first showers detected. 1971-1973: the 1st stage array built up, consisting of 43 stations with 2 scintillators; Cherenkov light detectors; detectors of muons (N.N. Efimov). The 2nd stage of the array was completed to 1991 (I.Ye. Sleptsov). The infill array of 18 stations, and the large area muon detector was added. Additional experiments have been fulfilled to measure neutrons initiated by EAS (1976- 1987) and to detect radio signal from showers (1.9 MHz:1972-1973, 32 MHz: 1986-1989). S.N. Vernov, S.I. Nikolsky, G.B. Khristiansen

5.  Introduction  Main results and the present status of the Yakutsk array experiment of the Yakutsk array experiment  Next step astrophysical goals  Modernization of the array  Conclusions

6. Present day arrangement of the Yakutsk array detectors. S Y =8.2 km 2. - Stations with 2 scintillators (49x2+10) - Cherenkov light detectors (32) -Detectors of muons S=20 м 2 (5) -Large area detector of muons S=180 м 2 - Pinhole detectors

7. The energy spectrum of cosmic rays below E=10 18 eV Differential spectra measured with EAS arrays Differential spectra after systematic corrections to CR intensity and energy (A.A. Ivanov, S.P. Knurenko and I.Ye. Sleptsov, NJP, 11 (2009) 065008).

8. The energy spectrum of cosmic rays above E=10 18 eV Energy spectra measured with giant arrays: AGASA, HiRes, PAO and Yakutsk. Differential spectra after systematic corrections to CR intensity and energy (A.A. Ivanov, S.P. Knurenko and I.Ye. Sleptsov, NJP, 11 (2009) 065008). RERE AGASAHiResPAOYscYch AGASA10.750.631.050.82 HiRes1.3310.851.41.08 PAO1.61.211.71.3 Ysc0.910.710.610.75 Ych1.220.930.81.331 Data: PAO HiRes Ysc Ych AGASA

9. Depth of EAS maximum: measurements and models at E>10 17 eV. S.P. Knurenko and A.V. Sabourov, ISVHECRI, Fermilab, 2010. Estimation of as a function of energy. The model EPOS is used to derive lnA from X max. S.P. Knurenko and A.V. Sabourov, ISVHECRI, Fermilab, 2010. X max and UHECR composition estimations Data: ● Yakutsk o CASA-MIA □ PAO TA Simulations: ― QGSJET II – – EPOS … SIBYLL P Fe

10. Correlation of arrival directions with EG objects 51 EAS events (E > 4×10 19 eV, θ<60 0 ) detected with the Yakutsk array (M.I. Pravdin et al., 29 ICRC, Pune, 7 (2005) 243). AGNs (z<0.024) from M.P. Veron-Cetty and P. Veron Catalog, Astron. Astrophys. 455 (2006) 773. Correlation is found in 3 0 area with AGNs but not with BL Lacs and Quasars from the same Catalog. PAO result is confirmed at P~0.006 level (~2.8σ). Correlation is significant in the redshift interval (0.001, 0.025) only, and for H2 and S2 subset objects. A.A. Ivanov et al., JETP Letters, 87 (2008) 185.

11. Constraints on the photon flux in UHECRs Upper limits on the photon flux in CRs from the Yakutsk array data (Y), AGASA (A), PAO surface detectors (PSD). Limits on the photon fraction in the integral CR flux. Data: Yakutsk (Y), AGASA (A), Yakutsk +AGASA (YA), Haverah Park (HP), PAO surface detectors (PSD), PAO fluorescent detectors (PF). A.V. Glushkov et al. PRD, 82, (2010) 041101.

12. Radio signal vs. UHECR energy (data from 1986-1989). S.P. Knurenko et al. 32 MHz radio measurements at the Yakutsk EAS array// ASTRA, 2011 (submitted). Radio pulse detected at 32 MHz from EAS with θ = 54°, E=2.6×10 18 eV, the core distance R=250 м. Radio antennas within the Yakutsk array. In 1972-1973 (1.9 MHz) and 1986-1989 (32 MHz) attempts were made to detect radio signal in coincidence with EAS events. Radio detection of EAS with the Yakutsk array

13.  Introduction  Main results and the present status of the Yakutsk array experiment of the Yakutsk array experiment  Next step astrophysical goals  Modernization of the array  Conclusions

14. EAS arrays operating in the energy range 10 14 – 10 17 eV Comparing arrays’ aperture within the energy range 10 14 – 10 17 eV Target energy ranges, eV: Tibet-III 10 14 – 10 17 Kascade-Grande 10 14 – 10 18 Tunka-133 10 15 – 10 18 IceTop 10 14 – 10 18 TALE >3×10 16 AMIGA (PAO+) >10 16 Yakutsk 10 15 – 10 19

15. Is the knee in the energy spectrum due to the maximum energy of CRs accelerated in SNR, or to CR diffusion in H? Comparison of data with CR acceleration & propagation models. Where is the transition region between galactic & EG components of CRs? Dip scenario Ankle scenario E.G. Berezhko, S.P. Knurenko and L.T. Ksenofontov, APJ, 2011 (submitted) Items to be addressed to:

16. solid curve – ankle scenario dash line – dip scenario E.G. Berezhko, S.P. Knurenko and L.T. Ksenofontov, APJ, 2011 (submitted) A clue to the transition region is the accurate measurement of CR mass composition. Our next task is to modernize the Yakutsk array in order to have a precise instrument capable of measuring the highest energy galactic CRs – their sources, energy spectrum, and mass composition. Another aim is to study a transition region between galactic and extragalactic components of CRs where some irregularities in spectrum and composition can be revealed. Items to be addressed to:

17.  Introduction  Main results and the present status of the Yakutsk array experiment of the Yakutsk array experiment  Next step astrophysical goals  Modernization of the array  Conclusions

18. The accuracy of detectors timing: 10 ns; Improving arrival directions resolution; Measuring the shower disk structure; LAN channel capacity increased to 1 Gbps; New station controllers; Improving operational reliability and scope for EAS measurements New differential detectors to measure the air Cherenkov light angular and temporal structure; Measuring longitudinal profile of the showers; Estimating the mass composition of CRs; Modernized muon detectors Estimating the mass composition of CRs. The array modernization tasks

19. Amplitude of scintillation and timing signals are measured in each detector (5 ns); Data should be transmitted to the central processor where the shower events are triggered via the signal coincidences; Optical fibers will be used to connect the array stations (due to the channel capacity, and to avoid the licensing of the wireless communication). Data acquisition system Data selection Noise Events Stationa Data transmission from stations

20. SPU response Signal processing unit, SPU, with ADC (14 bit) Data processing test-bed SPU Data processor. DAQ board Power supply Corrected Without correction LED + PMT

21. One layer (1 m 2 area, 3 cm thick) plastic scintillator manufactured in IHEP, Protvino are planned to be used as SDs of the array. New stations in a triangular grid with appropriate spacing will consist of two(?) detectors in 1 mm steel housing. Plastic scintillator detector 85 fibers to transmit the scintillation signal to PMT.

22. Pinhole camera detector An illustration of the pinhole camera with the row of PMTs behind. A snapshot of the longitudinal profile of the cascade in Cherenkov light is used to locate X max and to estimate the mass composition of CRs. G.K. Garipov et al.: The Cherenkov track detector consisting of the Yakutsk array, in: 27th ICRC, Hamburg, 3 (2001) 885.

23. Wide FoV Cherenkov telescope Wide FoV Cherenkov telescope Spherical mirror, Ø26 cm, F=11.25 cm. Position sensitive PMT PMT Hamamatsu R2486 Metal tube 16×16 crossed wire Ø5 cm anode.

24. Wide FoV Cherenkov telescope Wide FoV Cherenkov telescope Lateral distribution of light from the distant point sources on the cathode surface as a function of the slant angle. Angular and temporal profile of the Cherenkov signal in vertical EAS, E=10 15 eV, core distance 800 m. Primary particles are indicated. A.A. Ivanov et al., ASTRA, 6 (2010) 53.

25.  Introduction  Main results and the present status of the Yakutsk array experiment of the Yakutsk array experiment  Next step astrophysical goals  Modernization of the array  Conclusions

26. Conclusions  The target energy range of the Yakutsk array is (10 15, 10 19 ) eV.  Longitudinal profile of the showers will be investigated with air Cherenkov light differential detectors.  Energy spectrum and mass composition of CRs will be measured with the Yakutsk array modernized.  Sources of GCRs will be searched for.  Acceleration and propagation theories of GCRs will be verified.  A transition region between G and EG components will be elucidated.