1. Yu.V. Stenkin, Moscow'20111 The PRISMA project Yuri V. Stenkin Institute for Nuclear Res. of RAS, Moscow, Russia

2. Yu.V. Stenkin, Moscow'20112 The Project aims Why PRISMA? PRImary Spectrum Measurement Array The main goal is: TO SOLVE THE “KNEE PROBLEM” Other aims: –cosmic rays spectra and mass composition –cosmic ray sources –applied Geophysical measurements

3. Yu.V. Stenkin, Moscow'20113 History & Motivation Why do we need a new project? 1. The “knee problem” is a milestone of the cosmic ray physics. 2. Very few experiments have been designed specially for that. (KASCADE and Tibet AS are the best ones). 3. The problem still exists.

4. Yu.V. Stenkin, Moscow'20114 The “knee problem” The “knee problem” The problem is more than 50-years old! 1. Astrophysical explanation. In 1958 there was published a paper (G.V. Kulikov & G.B. Khristiansen) claiming the knee existence in cosmic ray energy spectrum. They observed a sharp change of slope in EAS size spectrum and proposed a model describing this effect as an evidence of existence of 2 sources of c. r.: Galactic and Metagalactic ones. 2. Nuclear-physical explanation. But, from the beginning and up to now there exist alternative explanations of this effect by dramatic change of particle interactions at these energies (S.I.Nikolsky, Kazanas & Nikolaidis, A.A.Petrukhin). Very few people know that there exist one more explanation.

5. Yu.V. Stenkin, Moscow'20115 3. Phenomenological explanations The knee in electromagnetic component can be explained by a break of equilibrium between the EAS components at energy of ~ 100 TeV / nucleon when the number of cascading hadrons is close to 0.

6. Yu.V. Stenkin, Moscow'20116 Depth in atmosphere No of particles From Hayakawa manual on cosmic ray physics EAS components equilibrium Break of equilibrium Break in attenuation “knee” in N e spectrum

7. Yu.V. Stenkin, Moscow'20117 When the break occurs? At E~100 TeV / nucleon For p: ~100 TeV For Fe: ~5 PeV (just the knee region) For details see: Yu. Stenkin, Phys. of Atom. Nucl., 71 (2008), 99 This figures are sequences of : L int = 90 g/cm 2 in air the Earth’s atmosphere thickness =1030 g/ cm 2 (depending on altitude)

8. Yu.V. Stenkin, Moscow'20118 This model predicts: - the knee should occur at almost equal N e - first “knee” should be  ~0.35 at N e ~10 4.8 - second “knee” should be  ~0.4 at N e ~10 6.3 - age parameter s should decrease with N e - attenuation length should increase with N e Therefore, it predicts the position and absolute value of the knee!

9. Yu.V. Stenkin, Moscow'20119 Experiments Experiments Tibet AS vs KASCADE Both gave many interesting results. BUT, they did not answer the question on the knee origin and thus, the knee problem is still open! Moreover, the problem became even less clear…. (see G. Schatz. Proc. 28th ICRC, Tsukuba, (2003), 97; Yu. Stenkin. Proc. 29th ICRC, Pune (2005), v.6, 621; M.Amenomori et al. Astrophys. J, (2008), v.678, 1165)

10. Yu.V. Stenkin, Moscow'201110 to make a device based on new principles and on novel experimental approaches How the problem could be solved? On my opinion the only way is:

11. Yu.V. Stenkin, Moscow'201111 PRISMA could be the solution PRISMA Prism

12. Yu.V. Stenkin, Moscow'201112 New principles The main EAS component is: hadrons Therefore, let us concentrate mostly on the hadronic component Bun, instead of huge and expensive hadron calorimeter of fixed area, let us make simple, inexpensive and of unlimited area detector. How this could be done?

13. Yu.V. Stenkin, Moscow'201113 New Methods New method has been developed in our Lab. in 2001. The method is based on thermal neutron “vapour” accompanying EAS

14. Yu.V. Stenkin, Moscow'201114 en-detector design 6 Li(n,a) 3 H+4.8 MeV 160,000 photons per capture ZnS(Ag) is a unique scin- tillator for heavy particles detection: Scintillator: ZnS(Ag)+ 6 LiF Similar to that using in neutron imaging technique 1 -PE water tank,  =72 cm, h=57 cm 2 -lid  =30 см 3 - 6’’ PMT 4 - scintillator, s=0.35 м 2 5 - reflecting cone

15. Yu.V. Stenkin, Moscow'201115 en-detector design

16. Yu.V. Stenkin, Moscow'201116 The detector is almost insensitive to single charged particles. But, it can measure the number N of charged particles if N>5.

17. Yu.V. Stenkin, Moscow'201117 Thermal neutron time distributions Multicom Prototype, BaksanPrisma prototype, Moscow Conclusion: Recorded neutrons can be of 2 types: local or atmospheric

18. Yu.V. Stenkin, Moscow'201118 N-carpet: 400*1m 2 en- detectors grid with spacing of 5 m Central muon detector: 400*1m 2 plastic scinillators Muon detector tunnels: 1200*1m 2 plastic scintillators Outer trigger detectors: 4*25*1m 2 plastic scintillators

19. Yu.V. Stenkin, Moscow'201119 Main features: Range in primary energy: from ~10 TeV to ~30 PeV energy resolution: ~ 10 - 20 % angular resolution: ~ 1 o core location:< 2.0 m capability to measure EAS size independently in: e, n and  capability to select AS with equal E/nucleon

20. Yu.V. Stenkin, Moscow'201120 LOG10(Ne)= 75(67) Nmu= 612 E0/1TeV= 10015 M=7 x0= -27.53 y0= -18.36 TETA= 21.7 FI= 79.3 Z= 11.98 Km Part_type= 14 M-C simulations. CORSIKA 6.900 + PRISMA array A map of the event: m=10*LOG10(n)

21. Yu.V. Stenkin, Moscow'201121 EAS size distribution in different components

22. Yu.V. Stenkin, Moscow'201122 M-C simulations

23. Yu.V. Stenkin, Moscow'201123 A prototype of PRISMA (the ProtoPrisma array) 16 en-detectors Location: on 4th floor inside building in MEPhi, Moscow

24. Yu.V. Stenkin, Moscow'201124 The ProtoPrisma schematic view

25. Yu.V. Stenkin, Moscow'201125 Oscillogram of a simple event (T=20 ms)

26. Yu.V. Stenkin, Moscow'201126 e n Big EAS event example. Ne=(4.5  0.8)10 6, s =1.15, x = 15 m; y =23m Nn = 106

27. Yu.V. Stenkin, Moscow'201127 The event oscillogram

28. Yu.V. Stenkin, Moscow'201128 expanded oscillogram (first 2 ms)

29. Yu.V. Stenkin, Moscow'201129 EAS core location distribution

30. Yu.V. Stenkin, Moscow'201130 Geophysical researches 1. Neutron background monitoring 2. Study of the detector response to geophysical events 3. Study of the radon-due tidal waves 4….. 5….. Another advantage of the en-detector is its possibility to measure thermal neutron flux of low intensity and its variations

31. Yu.V. Stenkin, Moscow'201131 Inter correlation coefficients are equal to from 0.87 to 0.95 Neutron array Counting rate stability

32. Yu.V. Stenkin, Moscow'201132 Neutron source in another building

33. Yu.V. Stenkin, Moscow'201133 Фурье-грамма вариаций потока тепловых нейтронов.

34. Yu.V. Stenkin, Moscow'201134 Location Collaboration Institutions budget high altitude is preferable Tibet would be the best location It depends on: Our plans...

35. Yu.V. Stenkin, Moscow'201135 1. The PRISMA project R&D 2. Expand the ProtoPrisma up to 32 en-detectors (2011) 3. Developing and construction of high-altitude prototype in collaboration with Chinese physicists (2013) 4. Collaboration with LHAASO project 5. Geophysical researches

36. Yu.V. Stenkin, Moscow'201136 Large High Altitude Air Shower Observatory LHAASO Project: γ-astronomy and origin of CR Core Detector Array PRISMA

37. Yu.V. Stenkin, Moscow'201137 PRISMA YBJ prototype (2013)

38. Yu.V. Stenkin, Moscow'201138 Involved Institutions: 1. Institute for Nuclear Research, Moscow 2. MEPhI, Moscow 3. Skobeltsyn Institute, MSU, Moscow 4. IHEP, Beijing, China 5. To be continued... The collaboration is open for other participants. You are welcome!

39. Yu.V. Stenkin, Moscow'201139 Thank you!

40. Yu.V. Stenkin, Moscow'201140 I ~ E -  N х ~ E  I ~ N х -  =/=/ if  has a break then  has a knee  - represents a «linearity of the method» spectrum: Secondary component Primary

41. Yu.V. Stenkin, Moscow'201141 Wide range Narrow range CORSIKA results

42. Yu.V. Stenkin, Moscow'201142 M-C

43. Yu.V. Stenkin, Moscow'201143 P E thr  10 TeV / nucleon