LENA. Investigation of Optical Scintillation Properties and the Detection of Supernovae Relic Neutrinos. M. Wurm. January 18, 2006 LENA. M.

Transcription

1 Spectrum Investigation of Scintillation and the Detection of Supernovae Relic Neutrinos January 18, 2006

2 Outline Spectrum Spectrum 4

3 The Spectrum

4 Spectrum about 50 kt of liquid scintillator, so: Solar Neutrinos /d Neutrino Supernovae Neutrinos Supernovae Relic Neutrinos 6/a Geoneutrinos (0.4-4) 10 3 /a Proton Decay τ p > a Indirect Dark Matter Search

5 Spectrum about 50 kt of liquid scintillator, so: Solar Neutrinos /d Neutrino Supernovae Neutrinos Supernovae Relic Neutrinos 6/a Geoneutrinos (0.4-4) 10 3 /a Proton Decay τ p > a Indirect Dark Matter Search but! high transparency needed attenuation length λ att 10m

6 Proposed Spectrum PhenylXylylEthane C 16 H 18 specific gravity: kg/l flash point: 160 C HMIS rating: 0 1 CTF2: λ att 4m Al 2 O 3 -column purification Dodecane C 12 H 26 specific gravity: kg/l flash point: 74 C HMIS rating: 0 2 attenuation length: >10m

7 Measurement of Experimental Setup Spectrum Compton backscattering provides monoenergetic e (480keV ) relative measurement of different samples

8 Measurement of Results Spectrum light yield depending on... solvent composition fluor concentration

9 Measurement of Length Experimental Setup Spectrum LED emits short light pulses at 430nm emission band of scintillation light both absorption and scattering reduce intensity total attenuation measured I(x) = I in e x/λ att x tube length λ att attenuation length I in infalling intensity I(x) measured intensity

10 Measurement of Length Results Spectrum 430±10* nm [in m] Sample purified Garching MPI-K HD PXE CTF2 1.77± ±0.21 Dixie 2.26± Nippon - 9.3±0.4 Dodecane 90%+ 3.65± % ±1.0 * exact LED emission wavelength unknown Results: Al 2 O 3 -column purification effective adding high purity Dodecane would increase λ att

11 Approximation Spectrum approximated yield of pholoelectrons (per MeV): Y pe = Y L 2 3 e R/λ att c PM ε PM Y L light yield; 2/3 geometry R detector radius c PM PM coverage ε PM quantum efficiency scintillator Y L /Y CTF 2 λ att,prop Y pe (Al 2 O 3 -purified) (±2%) [m] [MeV 1 ] PXE (6g/l PPO) ± ± 6 proportion 100: ± ± 6 of PXE to 40: ± ± 11 Dodecane 20: ± ± 11 (2g/l PPO) 0: ± ± 5 sufficient photoelectron yield in both cases! mixtures would provide a higher number of free protons for inverse beta decay: ν e + p n + e +

12 GEANT4 Simulations Spectrum attenuation combines light absorption and scattering, so I(x) = I in e x/λ abs e x/λ scat = I in e x/λ att scattered light is only partially lost to PMs λ abs, λ scat important for pe simulations λ att (m) λ abs (m) λ scat (m) Y pe (/MeV)

13 Measurement of Length Experimental Setup Spectrum

14 Measurement of Length Results Spectrum Further aims: Sample λ scat [m] PXE PXE (Al 2 O 3 -purified) Dodecane 90% improved accuracy of the measurement (higher statistics) investigation of further samples (Dodecane 99%+, mixtures...) determination of the proportions of Rayleigh- to Mie-scattering in the samples

15 Supernovae Relic Neutrinos Spectrum

16 What are Supernovae Relic Neutrinos? Spectrum Supernovae release 99% of their gravitational binding energy in νs, all flavours are generated all SN contribute to an isotropic background of νs, the energies of νs emitted by SN at z>0 are red-shifted ν e can be detected by inverse beta decay ν e + p n + e + SK limit: 1.2 ν e /cm 2 s for E ν >19.3 MeV

17 Model Calculations spectral form and flux of the depend on: Spectrum SN ν-spectra influence spectral form insufficient exp. data three SN models: Lawrence Livermore - LL Keil Raffelt & Janka - KRJ Thompson Burrows & Pinto - TBP Star Formation Rate (SFR) corresponds to SN rate UV-, H α - and FIRobservations are impeded by dust extinction

18 Spectrum Event Rates & Energy Window Spectrum

19 Spectrum Event Rates & Energy Window Events in : in 10a ( +400% 30% ) Spectrum

20 Spectrum Event Rates & Energy Window Events in : in 10a ( +400% 30% ) thresholds: inverse β-decay E ν > 1.8MeV Spectrum

21 Spectrum Event Rates & Energy Window Events in : in 10a ( +400% 30% ) thresholds: inverse β-decay E ν > 1.8MeV atmospheric ν e s E ν < 30MeV Spectrum

22 Spectrum Event Rates & Energy Window Spectrum Events in : in 10a ( +400% 30% ) thresholds: inverse β-decay E ν > 1.8MeV atmospheric ν e s E ν < 30MeV reactor ν e s E ν > 10MeV?

23 Spectrum Event Rates & Energy Window Spectrum Events in : in 10a ( +400% 30% ) thresholds: inverse β-decay E ν > 1.8MeV atmospheric ν e s E ν < 30MeV reactor ν e s E ν > 10MeV? events in 10a!

24 Spectrum Event Rates & Energy Window Spectrum Events in : in 10a ( +400% 30% ) thresholds: inverse β-decay E ν > 1.8MeV atmospheric ν e s E ν < 30MeV reactor ν e s E ν > 10MeV? events in 10a! H 2 O-Čerenkov detectors spallation products invisible muons no energy window!

25 Lower E ν Threshold Spectrum low energy threshold very important to see contribution of z>1 regions! reactor ν e flux and spectra for E ν >8MeV have to be carefully considered suitable detector location (far from nuclear power plants) and high energy resolution needed

26 Reactor ν e spectra - first approach Spectrum E<8MeV parameterised spectra of U&Pu E>8MeV neutron-rich bromine isotopes 90 Br (Q=10.3MeV) β-decay: 77% yield: 0.6% 235 U 0.2% 239 Pu 92 Br (Q=12.2MeV) β-decay: 70% yield: 0.03% 235 U 0.002% 239 Pu 94 Br (Q=13.3MeV) β-decay: 70% yield: % 235 U 0.003% 239 Pu (NNDC Brookhaven)

27 Difficulties β-decays: not always to ground state lower ν e energies Spectrum additional elements with high endpoints: 96 Rb, 97 Rb, 98 Rb (Q=12.4 MeV) only the ν e -spectrum corresponding to 235 U has actually been measured to E=12MeV 238 U may play an important role

28 Spectrum placed at different locations Spectrum Energy Window (Pyhäsalmi): 10.5 MeV < E ν < 30 MeV, corresponding to events in 10 years Reactor background: 1700 events per year

29 χ 2 -tests Spectrum MC spectra were generated for all models discrimination method: χ 2 -tests comparing MC to all model spectra Results: spectroscopy with is possible LL and TBP model could be separated after 10 years with more than 90% C.L.

30 Spectrum sufficient attenuation lengths (λ R) are possible possible scintillators are pure PXE or mixtures with high percentages of Dodecane (+30% free p) measurement of scattering length important energy window for detection in, about events in 10 years spectroscopy seems to be possible reactor background crucial for detecting z>1 contribution

31 Spectrum