lena scintillator characterization transregio 27 sfb-tage in heidelberg 9/10. juli 2009 michael wurm
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LENALENAScintillator CharacterizationScintillator Characterization
Transregio 27Transregio 27SFB-Tage in HeidelbergSFB-Tage in Heidelberg
9/10. Juli 20099/10. Juli 2009
Michael WurmMichael Wurm
OutlineOutline
Properties of Scintillation Signal
Scattering Length Experiment
Light Yield
Time Resolution
LENA Scintillator Characterization – Michael Wurm, TUM 2
LENALENALow-Energy
NeutrinoAstrophysics
SCIENTIFIC GOALSSCIENTIFIC GOALS Nucleondecay Supernova neutrinosDiffuse SN neutrinos Geoneutrinos Solar neutrinosAtmosphericneutrinos Neutrino propertiesbyreactors/accelerators Indirectdark matter search
Liquid Scintillatorca. 50kt PXE/LAB
Inner Nylon Vesselradius: 13m
Buffer Regioninactive, Dr = 2m
Steel Tank, 13500 PMsr = 15m, h = 100m high demands onthe optical transparencyof the scintillator
Water Cherenkov Veto1500 PMTs, Dr > 2m
Egg-Shaped Cavernabout 108 m3
Overburden: 4000 mwe
Signal Energy and TimingSignal Energy and Timing
Energy ResolutionLight Yield (/MeV): 104
Photoactive Coverage: 30%PMT Photoefficiency: 20%+ Light Absorption/ScatteringPhotoelectrons/MeV <600
e Light intensity in distance r:
I0 initial intensityL attenuation length:
LENA Scintillator Characterization – Michael Wurm, TUM 4
Signal Energy and TimingSignal Energy and Timing
Energy ResolutionLight Yield (/MeV): 104
Photoactive Coverage: 30%PMT Photoefficiency: 20%+ Light Absorption/ScatteringPhotoelectrons/MeV <600
Timing ResolutionFluorescence constants: fast component ca. 3nsslow component(s) >20nsTime of flight diff. O(100ns)Light ScatteringLeading edge determines timingTrailing edge for particle ID
Light scattering has impact on both light yield and pulse shape ...
LENA Scintillator Characterization – Michael Wurm, TUM 5
Microscopic ProcessesMicroscopic Processes
Mie Scatteringoff small particulates (m) in the liquidanisotropic emissionincreased forward scattering amplitude, depending on diameterremovable by filtering
θθ
Rayleigh Scatteringoff bound electronsin the scintillatoranisotropic emission:
fully polarized for
orthogonalparallelto lightdirection
Absorption/Reemissionoff organic molecules/impurities in the liquidisotropic re-emission:
depends on wavelength/production process
LENA Scintillator Characterization – Michael Wurm, TUM 6
Experimental SetupExperimental Setup
measurement at several angles and for both polarizations determines contributions of Rayleigh scattering, absorption-reemission etc.
=430±5nm x10-5 monitorsbeam intensity
measuresscatteredintensity
LENA Scintillator Characterization – Michael Wurm, TUM 7
Exemplary Measurement ResultExemplary Measurement Result
parallelto beam
orthogonalto beam
Sample:Dodecane
Wavelength:415nm
Q=Ns/Nb is the(corrected) ratio of PM intensities
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 8
Scattering Length ResultsScattering 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 =430nm
LS = 22±3 mLS = 22±3 m
after purification in Al2O3-column
Corrections and UncertaintiesCorrections 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 YieldMC 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 (->40%)
LENA Scintillator Characterization – Michael Wurm, TUM 11
Impact on Time ResolutionImpact on Time ResolutionRise time determines resolution.
General trends: fast fluorescence component has largest impact on both rise time ts and decay flank s
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 12
SummarySummary
Scattering length of all current LENAscintillator candidates has been measured.
Impact on both light yield andtime resolution was tested.
LAB provides larger light yield, whilePXE (+C12) offers better time resolution.
Scattering length of all current LENAscintillator 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 13
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