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Analysis of the Optical Properties of Organic Liquid Scintillator in LENA DPG-Tagung in Heidelberg 9.3.2007 M. Wurm, T. Marrodán Undagoitia, F. v. Feilitzsch,

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Presentation on theme: "Analysis of the Optical Properties of Organic Liquid Scintillator in LENA DPG-Tagung in Heidelberg 9.3.2007 M. Wurm, T. Marrodán Undagoitia, F. v. Feilitzsch,"— Presentation transcript:

1 Analysis of the Optical Properties of Organic Liquid Scintillator in LENA DPG-Tagung in Heidelberg M. Wurm, T. Marrodán Undagoitia, F. v. Feilitzsch, M. Göger-Neff, L. Oberauer, W. Potzel, J. Winter Technische Universität München

2 30m 100m DETECTOR PERFORMANCE photoelectron yield spacial resolution particle ID timing … SCINTILLATOR PROPERTIES light yield absorption length scattering length fluorescence times … optimisation of the scintillator  laboratory measurements are required 1/10

3 SCINTILLATOR INGREDIENTS SOLVENTSFLUORS PXE (C 16 H 18 ) density: 985g/l flamepoint: 160°C attenuation length: >10m ( after Al 2 O 3 purification) Dodecane (C 12 H 26 ) density: 749g/l flamepoint: 64°C attenuation length: >12m no purification, but lower light yield LAB (C H ) density: 863g/l flamepoint: 140°C attenuation length: >10m no purification, high light yield PPO (C 15 H 11 NO) primary fluor absorption band: nm emission band: nm high solubility pTP (C 18 H 14 ) primary fluor absorption band: nm emission band: nm low solubility, better match to bisMSB bisMSB (C 24 H 22 ) secondary fluor absorption: nm emission band: nm at emission high solvent transparency 2/10

4 current laboratory work light yield attenuation length scattering length fluorescence time 3/10

5 fluorescence time coincidence measurement motivation - a scintillation signal is steep in rise; its decay is described by several exponential decay functions - this functions are due to different excitation states of the fluor molecules and the energy transfer of the solvent to the fluor(s) - signal decay times are important parameters for the detector‘s time resolution or the analysis of fast decays e.g. p → K +  → µ + 8/10

6 fluorescence time coincidence measurement near PMT measures large signal that is used for start time information far PMT measures arrival times of single photons  time difference carries information about signal decay time scintillator sample: scintillation signal due to Compton scattering, two windows let escape the light gamma source 54 Mn, 834keV 9/10

7 fluorescence time coincidence measurement PXE 2g/l PPO PXE 6g/l PPO results so far - measurements using PXE as solvent show shorter decay times with increasing fluor concentration - at least 3 (most likely 4) time components are needed to fit the light curve - pTP is faster than PPO - adding bisMSB as a secondary fluor slows the signal decay next steps - test the influence of different solvents on decay times (LAB, Dodecane) - test of more uncommon fluors with larger Stoke‘s shift 10/10

8 scattering length scattering measurements motivation - in a large detector like LENA, the amount of scintillation light that reaches the PMs on the outer surface is strongly depending on the scintillator (solvent) transparency - the transparency of the scintillator is described by its attenuation length - attenuation combines to effects: absorption & scattering - while absorbed light is lost to the signal, scattered or re-emitted light contributes to the photoelectron yield and increases the energy resolution of the detector 4/10

9 scattering length scattering measurements focussing the beam concept - measuring the dependence of light intensity on scattering angle and polarisation - determine contributions of Rayleigh, Mie and absorption&re-emission-processes LED ~430nm collimators limiting the solid angle sample rotatable PM measures scattered light reference PM measures photons per light bunch polarisation filter 5/10

10 PXE sample (Al 2 O 3 purified) 6/10

11 scattering length scattering measurements preliminary results PXE:- scattering dominates absorption - large unpolarised component - no significant angle-dependence: absorption-reemission-process? Dodecane: - scattering length of 20m - low unpolarised component next steps - narrow-bandpass-filters for LED - comparison to attenuation length measurements 7/10


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