GEANT4 simulation of BOREXINO Solar Neutrino Detector.

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GEANT4 simulation of BOREXINO Solar Neutrino Detector.

GEANT4 simulation

of BOREXINO Solar Neutrino

Detector.

Igor Machulin (Kurchatov Instute, Moscow)

for the BOREXINO collaboration

GEANT4 workshop

Catania, Italy, 4 October


The Borexino Detector at Gran-Sasso Laboratory.

Real-time observation of low energy Solar neutrinos.

Neutrinos are detected by

electron scattering.

● Threshold - 250 keV.

● 300 tonnes scintillator

viewed by 2200

photomultipliers.

● The detector core is a

transparent spherical

vessel surrounded by

1000 tonnes of a highpurity

buffer liquid.

● 208 outward-pointing

PMT serving as a veto for

penetrating muons.


GEANT4 Code for BOREXINO simulates the Detection

of neutrons, gammas, e+, e-, α-particles &

scintillation photons.

● Special attention is devoted to the propagation and detection

of scintillation photons.

● Photon tracking takes into account the interactions of the emitted photons with

scintillator (Pseudocumene + 1.5g/l PPO), Pseudocumene (PC) buffer and nylon

vessel films. This processes include:

● ● Elastic Raleigh scattering of photons in scintillator and PC buffer.

● ● Absorption and reemission of photons on PPO molecules.

● ● Absorption of photons by DMP quencher molecules in PC buffer.

● ● Photon absorption in thin Nylon vessels.

● The cross-sections for this interactions also as time characteristics of reemission

process were experimentally measured for different light wavelengths [NIM, A440,

(2000), 360].


Photo of BOREXINO with

installed PMTs.

GEANT4 Scintillation Event

in BOREXINO


GEANT4 code structure allows to have the

exact description of BOREXINO detector

optical surfaces and the processes of light

reflection and refraction (special thanks to

Peter Gumplinger for consulting).

Reflection of light from the surfaces:

PMT photocathodes, PMT aluminium light guides, stainless

steel vessel, Tyvec diffusive reflector.

Refraction of light on the borders of scintillator, nylon vessels

and Pseudocumene buffer.

Wavelength dependence of PMT photocathode quantum

efficiency.


Radon-loaded scintillation source (4cm quarz tube)

in the centre of BOREXINO (with air).

Comparison of experiment and GEANT4 simulation

for photo-electron amplitude distributions.

222 Rn and 218 Po

α peaks

E=5.44, 6.0 MeV

Scintillator yield = 11200 Photon/MeV.

Simulation

214 Po α peak

E=7.69 MeV


Radon-loaded scintillation source in the centre of BOREXINO.

Comparison of experiment and GEANT4 simulation

for photoelectron time distributions.

MC Simulation

Photons, reflected

from Steel Vessel

and PMTs


Distant Reactor Antineutrino Detection in

~

BOREXINO (reaction ν + p → n + e +

):

tracks of e+ and neutron, simulated by GEANT4.


GEANT4 Tracking of Cherenkov Photons

in Water from Muons,

crossing Outer Veto of BOREXINO.

Vertical 100 GeV muon.

Cherenkov photons,

reflected from diffusive

Tyvec surfaces.

VETO PMT


GEAN4 simulation of inner BOREXINO

detector, filled with water

(first stage before scintillator filling).

Vertical 100 GeV muon,

crossing the Central

part

of BOREXINO

GEANT4 result:

12 Photoelectrons from all PMTs

per 1 cm of muon path

in BOREXINO detector.

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