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LENA Scintillator Characterization. Transregio 27 SFB-Tage in Heidelberg 9/10. Juli 2009 Michael Wurm. Outline. Properties of Scintillation Signal Scattering Length Experiment Light Yield Time Resolution. LENA Scintillator Characterization – Michael Wurm, TUM 1.

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lena scintillator characterization

LENAScintillator Characterization

Transregio 27

SFB-Tage in Heidelberg

9/10. Juli 2009

Michael Wurm

outline
Outline

Properties of Scintillation Signal

Scattering Length Experiment

Light Yield

Time Resolution

LENA Scintillator Characterization – Michael Wurm, TUM 1

slide3

Liquid Scintillatorca. 50kt PXE/LAB

Inner Nylon Vesselradius: 13mBuffer Regioninactive, Dr = 2mSteel Tank, 13500 PMsr = 15m, h = 100m high demands onthe optical transparencyof the scintillatorWater Cherenkov Veto1500 PMTs, Dr > 2mEgg-Shaped Cavernabout 108 m3

Overburden: 4000 mwe

LENA

Low-EnergyNeutrinoAstrophysicsSCIENTIFIC GOALS

 Nucleondecay Supernova neutrinosDiffuse SN neutrinos  Geoneutrinos Solar neutrinosAtmosphericneutrinos Neutrino propertiesbyreactors/accelerators Indirectdark matter search

signal energy and timing
Signal Energy and Timing

n

Energy Resolution

Light Yield (/MeV): 104

Photoactive Coverage: 30%

PMT Photoefficiency: 20%

+ Light Absorption/Scattering

Photoelectrons/MeV <600

Light intensity in distance r:I0 initial intensityL attenuation length:

e

LENA Scintillator Characterization – Michael Wurm, TUM 3

signal energy and timing1
Signal Energy and Timing

Energy Resolution

Light Yield (/MeV): 104

Photoactive Coverage: 30%

PMT Photoefficiency: 20%

+ Light Absorption/Scattering

Photoelectrons/MeV <600

Timing ResolutionFluorescence constants: fast component ca. 3nsslow component(s) >20ns

Time of flight diff. O(100ns)Light ScatteringLeading edge determines timing

Trailing edge for particle ID

Light scattering has impact on both light yield and pulse shape ...

LENA Scintillator Characterization – Michael Wurm, TUM 4

microscopic processes
Microscopic Processes

orthogonalparallelto lightdirection

θ

Rayleigh Scattering

off bound electronsin the scintillator

anisotropic emission:fully polarized for

Absorption/Reemission

off organic molecules/impurities in the liquid

isotropic re-emission:depends on wavelength/production process

Mie Scattering

off small particulates (mm) in the liquid

anisotropic emission

increased forward scattering amplitude, depending on diameter

removable by filtering

LENA Scintillator Characterization – Michael Wurm, TUM 5

experimental setup
Experimental Setup

measuresscatteredintensity

l=430±5nm

x10-5

monitorsbeam intensity

measurement at several angles and for both polarizations determines contributions of Rayleigh scattering, absorption-reemission etc.

LENA Scintillator Characterization – Michael Wurm, TUM 6

exemplary measurement result
Exemplary Measurement Result

Sample: DodecaneWavelength: 415nmQ=Ns/Nb is the(corrected) ratio of PM intensities

parallelto beam

orthogonalto beam

  • main contribution: Rayleigh scattering (large polarization difference)
  • no discernible increase in forward scattering: minor Mie-contribution
  • small orthogonal component at 90°: absorption/re-emission processes

LENA Scintillator Characterization – Michael Wurm, TUM 7

scattering length results
Scattering Length Results
  • no hints for Mie-scat.
  • anisotropic scattering in good agreement with Rayleigh expectation
  • correct wavelength- dependence found
  • literature values for PC, cyclohexane correctly reproduced

Results for l=430nm

LS = 22±3 m

after purification in Al2O3-column

corrections and uncertainties
Corrections and Uncertainties
  • unevenness of sample glass surface: 4% (unc.)
  • beam reflection on glass, alignment, refractive index: 0.3% (cor.)
  • background subtraction of glass scattering: diff. (unc.)
  • scattering solid angle (PM-S field of view): 4% (unc.)
  • variation of PM-S efficiency with scattering angle: 7% (unc.)
  • relative photoefficiency of the PMs: 7% (cor.)
  • greyfilter transmission (wavelength-dependent): 3.4% (cor.)
mc simulation of light yield
MC Simulation of Light Yield
  • Input Parameters:
  • event in the center
  • 104 photons/MeV
  • LENA radius: 15m
  • optical coverage: 0.3
  • photoefficiency: 0.2
  • attenuation length(from previous experi-ments at MPIK, TUM and SNO+ R&D)
  • overall range: 200-350 photoelectrons/MeV (optimum: 600pe/MeV) corresponding energy resolution at 1MeV: 7.1% to 4.6%
  • yield could be increased by state-of-the-art photocathodes (e ->40%)

LENA Scintillator Characterization – Michael Wurm, TUM 10

impact on time resolution
Impact on Time Resolution
  • Rise time determines resolution.General trends:
  • fast fluorescence component has largest impact on both rise time ts and decay flank ts
  • no effect of refractive index
  • lower scattering length smears out signal: ts larger
  • increase in attenuation length decreases ts

LENA Scintillator Characterization – Michael Wurm, TUM 11

summary
Summary

Scattering length of all current LENA

scintillator candidates has been measured.

Impact on both light yield andtime resolution was tested.

LAB provides larger light yield, whilePXE (+C12) offers better time resolution.

LENA Scintillator Characterization – Michael Wurm, TUM 12

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