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

Yu.V. Stenkin, Moscow'2011 1

The PRISMA projectThe PRISMA project

Yuri V. Stenkin

Institute for Nuclear Res. of RAS, Moscow, Russia


The Project aimsThe Project aims

Why PRISMA?PRImary Spectrum Measurement ArrayThe main goal is: TO SOLVE THE “KNEE

PROBLEM”Other aims:

– cosmic rays spectra and mass composition– cosmic ray sources– applied Geophysical measurements


History & MotivationHistory & 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.


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.


3. Phenomenological explanations3. 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.


Depth in atmosphere

No of particles

From Hayakawa manual on cosmic ray physics

EAS components equilibrium

Break of equilibrium

Break in attenuation

“knee” in Ne spectrum


When the break occurs?When the break occurs?

At E~100 TeV / nucleonFor p: ~100 TeVFor Fe: ~5 PeV (just the knee region)

For details see: Yu. Stenkin, Phys. of Atom. Nucl., 71 (2008), 99

This figures are sequences of : Lint= 90 g/cm2 in airthe Earth’s atmosphere thickness =1030 g/ cm2 (depending on altitude)


This model predicts:- the knee should occur at almost equal Ne

- first “knee” should be ~0.35 at Ne~104.8

- second “knee” should be ~0.4 at Ne~106.3

- age parameter s should decrease with Ne

- attenuation length should increase with Ne

Therefore, it predicts the position and absolute value of the knee!


ExperimentsExperiments

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)


to make a device based on new to make a device based on new principles and on novel experimentalprinciples and on novel experimental

approachesapproaches

How the problem could be solved?

On my opinion the only way is:


PRISMA could be the solutionPRISMA could be the solution

PRISMAPrism


New principlesNew 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?


New MethodsNew Methods

New method has been developed in our Lab. in 2001.

The method is based on thermal neutron “vapour” accompanying EAS


en-detector designen-detector design

6Li(n,a)3H+4.8 MeV

160,000 photons per capture

ZnS(Ag) is a unique scin-tillator for heavy particlesdetection:

Scintillator: ZnS(Ag)+6LiF

Similar to that using in neutronimaging technique

1 -PE water tank, =72 cm, h=57 cm2 -lid =30 см3 - 6’’ PMT4 - scintillator, s=0.35 м2

5 - reflecting cone


en-detector design


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


Thermal neutron time distributionsThermal neutron time distributionsMulticom Prototype, Baksan Prisma prototype, Moscow

Conclusion:Recorded neutrons can be of 2 types:

local or atmospheric


N-carpet: 400*1m2 en-detectors grid with spacing of 5 m

Central muon detector:400*1m2 plastic scinillators

Muon detector tunnels:1200*1m2 plastic scintillators

Outer trigger detectors:4*25*1m2 plastic scintillators


Main features:Main features:

•Range in primary energy: from ~10 TeV to ~30 PeV•energy resolution: ~ 10 - 20 %•angular resolution: ~ 1o

•core location: < 2.0 m•capability to measure EAS size independently in: e, n and •capability to select AS with equal E/nucleon


LOG10(Ne)= 75(67) Nmu= 612 E0/1TeV= 10015 M=7x0= -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 mapof the event:m=10*LOG10(n)


1 2 3 4 5 61E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0,01

0,1

p=2.7

CORSIKA (ver. 6.9, QGSJET, Gheisha)

N-1.9

Ne

-1.5

Ne

-1.25

n

e

Nn

1.02

dn/d

Nx

LOG10(Nx)

EAS size distribution in different components


0 5 10 15 20 2510

-3

10-2

10-1

100

101

F=0.00025+14.7*EXP(-T/0.72мс)+4.7*EXP(-T/2)+0.4*EXP(-T/11мс)

F=0.0025+15.5*(EXP(-T/1.3мс)+6.08*EXP(-T/2мс)+1.37*EXP(-Т/10.5мс)

Fe, M2 p, M2от

счет

ы /2

мс/

соб

ыти

е

T, мс

M-C simulations


A prototype of PRISMA (the ProtoPrisma array)

16 en-detectors

Location: on 4th floor inside building inMEPhi, Moscow


The ProtoPrisma schematic view


Oscillogram of a simple event (T=20 ms)


e n

Big EAS event example. Ne=(4.50.8)106, s =1.15, x = 15 m; y =23m

Nn = 106


The event oscillogram


expanded oscillogram (first 2 ms)


EAS core location distribution


Geophysical researches

1. Neutron background monitoring2. Study of the detector response to geophysical events 3. Study of the radon-due tidal waves4…..5…..

Another advantage of the en-detector is its possibility to measure thermal neutron flux of low intensity and its variations


Inter correlation coefficients are equal to from0.87 to 0.95

Neutron array

Counting rate stability


Neutron source in another building


Фурье-грамма вариаций потока тепловых нейтронов.


LocationLocation

Collaboration Institutions budget high altitude is preferable Tibet would be the best location

It depends on:

Our plans ...


1. The PRISMA project R&D1. The PRISMA project R&D

2. Expand the ProtoPrisma up to 32 en-detectors (2011)2. Expand the ProtoPrisma up to 32 en-detectors (2011)

3. Developing and construction of high-altitude prototype in 3. Developing and construction of high-altitude prototype in collaboration with Chinese physicists (2013) collaboration with Chinese physicists (2013)

4. Collaboration with LHAASO project4. Collaboration with LHAASO project

5. Geophysical researches5. Geophysical researches


Large High Altitude Air Shower Observatory

LHAASO Project: LHAASO Project: γ-γ-astronomy and origin of CRastronomy and origin of CR

Core DetectorArray

PRISMA


PRISMAYBJ prototype(2013)


Involved Institutions:Involved Institutions:

1. Institute for Nuclear Research, Moscow2. MEPhI, Moscow3. Skobeltsyn Institute, MSU, Moscow4. IHEP, Beijing, China5.

To be continued...The collaboration is open for other participants.

You are welcome!


Thank you!


I ~ E-

Nх ~ E

I ~ Nх-

=/

if has a break then has a knee

- represents a «linearity of the method»

spectrum:

Secondarycomponent

Primary


Wide range

Narrow range

CORSIKA results


M-C


1E13 1E14 1E15

1E-5

1E-4

1E-3

0,01

0,1

1

10

recorded distribution

detection efficiency

E -

arbi

trar

y un

its

primary energy, eV

P

Ethr 10 TeV / nucleon

Documents

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