Requirement for photon-detectors at directional measurement ...

Requirement for photon-detectors at directional measurement ...

Requirement
Requirement for
for photon-detectors
photon-detectors at
at directional
directional
measurement
measurement of
of anti-neutorinos
anti-neutorinos with
with KamLAND
KamLAND
Mio Nakamura
Research Center for Neutrino Science ,Tohoku University
KamLAND Kamioka Liquid Scintillator Anti-Neutrino Dete
ctor
KamLAND, constructed at 1000m underground from top of the mountain,has a balloon with a 6.5m radius, filled with 1 kton of Liquid Scintillator ( LS ).
1879 PMTs( 17or20 inch ) are set around the balloon detect scintillation to decide vertex from time difference of signal.
KamLANDs targets : reactor e , geo e , solar e

How to detect?

1000m

PMTs detect anti-neutorinos via the inverse -decay reaction in LS. ( Figure1 )
PMTs distinguish some signals of anti-neutrino from backgrounds with Coincidence.

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Li-loaded LS is proper.
Why?
Li has large neutron-capture cross section, besides generates not -ray but -ray.
-ray doesnt diffuse but stops at once. ( Figure3 )
So we can get directional data. ( Figure4 )
And we can use also coincidence, because Li-loaded LS generates prompt and
delayed signal.

Scintillation
8300photons/MeV
prompt-delayed
at 200s interval
Neutron angle depends on incoming
neutrino direction in low energy.
20 MeV MeV
10 MeV MeV
5 MeV MeV
3 MeV MeV
n<35 2 MeV We want to know which direction anti-neutrinos come from better than now. If we can get directional data of reactor-neutrino, it will be neutrino-oscillation with individual baseline. If we can get directional data of geo-neutrino, we will observe directly the interior of the earth. Vertex reconstruction using time of flight with PMT We want directional sensitive photo detectors with gain instead of PMT. Imaging ( lens + photo detector ) KamLAND LS B loaded LS (1.0%) Li loaded LS (0.15%) Li loaded LS (1.5%) prompt-delayed at 5s interval Figure2 : energy dependence The problem directional data is lost for the neutrons thermal diffusion and -ray diffusion( ~40cm ) the position resolution of PMTs is not too high ( ~10cm at object ) Now we are researching and testing organic solvent for Li. example : EDTA, crown ether Excellent! Figure4 : n event reconstructed point Test of SCITIC with LS SCITIC SCIntillation Tracking Image Camera First aim : imaging cosmic-ray with 1L LS and CCD+I.I. Procedure Plastic Scintillators ( PS ) detect going through LS. PMT detect it, and open CCDs gate. CCD records the afterglow at fluorescence plane of image intensifier ( I.I. ). CCD send the image to PC. Requirement for photo detector 1photo counting Sequent data acquisition at 1s or shorter interval small data size at one acquisition Position resolution at object 1cm or better good time resolution High gain MPPC effective 1 photon quantum positiointime resolution active area gain counting HV efficiency resolution iFWHMj PMT 430mm5~10*6 2000V22% `20cm 3.5ns MPPC 1mm~1mm 2.4~10*6 ok 100V 70% 1000 m0.25ns Position resolution etc. is good compared to PMT. But Active area of MPPC is too small Can active area of MPPC be larger? MPPC generates several hundred kHz dark noise at room temperature. I think dark noise will be reduced by 1/1000 at 200K. So I will test it soon. The output pulses from the APD pixels pile up with each other, because all APD pixels are connected to 1 readout channel. Pixel-size resolution is lost simply because of 1 readout. PSD Feature of I.I. ( courtesy of KEK ) Active area : 100mm Gain : ~106 Q.E. : 12% @ 422 nm Afterglow : a few s ( a few ns pulse incidence ) KamLAND LS + BisMSB Feature of CCD number of pixels : 310*5 type : interline readout rate : 82 frames/s CCD imaged -track ! ( Figure6 ) Figure6 : track Next, we want to observe 2-signals from Bi-Po ( Figure7 ) like anti-neutrino signal. 222 Rn Now, CCD is adapted! This CCD will be adapted for recording 2-images at dozens s intervals by HPK. ( Figure8 ) effective quantumpositioin active area efficiency resolution PSD12mm~12mm `50% Bi 214 1.5 m Feature of PSD is that it is connected to 4 readout channels to detect the center of gravity of multiple hits. It means directional data isnt lost. So data size is small. And PSD must be combined with some amplifier because PSD has no gain. 164ss CCD+I.I. Go to Test of SCITIC with LS! Po -decay delayed signal Pb Figure7 : Bi Po reaction 214 PSD+MPPC If MPPC has 4 readout channel, MPPC will be the detector getting t he center of gravity of multiple hits and with gain !? I will investigate possibility using PSD+MPPC in KamLAND. -decay prompt signal 210 CCD camera

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