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

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

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.

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.

Yu.V. Stenkin, Moscow' 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.

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

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)

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 ~ second “knee” should be  ~0.4 at N e ~ 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!

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)

Yu.V. Stenkin, Moscow' 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:

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

Yu.V. Stenkin, Moscow' 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?

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

Yu.V. Stenkin, Moscow' 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 reflecting cone

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

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

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

Yu.V. Stenkin, Moscow' 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

Yu.V. Stenkin, Moscow' Main features: Range in primary energy: from ~10 TeV to ~30 PeV energy resolution: ~ % 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

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

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

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

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

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

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

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

Yu.V. Stenkin, Moscow' The event oscillogram

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

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

Yu.V. Stenkin, Moscow' 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

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

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

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

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

Yu.V. Stenkin, Moscow' 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

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

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

Yu.V. Stenkin, Moscow' 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!

Yu.V. Stenkin, Moscow' Thank you!

Yu.V. Stenkin, Moscow' 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

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

Yu.V. Stenkin, Moscow' M-C

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