kamland & kaska prototype (in view of safeguards)
DESCRIPTION
KamLAND & KASKA Prototype (In view of safeguards). F.Suekane Research Center for Neutrino Science Tohoku University [email protected]. Applied Antineutrino Physics Workshop @Laurence Livermore National Lab., CA, USA 2006.9.24-26. KamLAND Collaboration. PMT. Electronics. - PowerPoint PPT PresentationTRANSCRIPT
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KamLAND & KASKA Prototype(In view of safeguards)
F.SuekaneResearch Center for Neutrino Science
Tohoku University
Applied Antineutrino Physics Workshop@Laurence Livermore National Lab., CA, USA
2006.9.24-26
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KamLAND Collaboration
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KamLAND Detector
Cosmicray veto
Balloon
S.S. tank
PMT
Liquid Scintillator
buffer oil
Electronics
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Oil Purification system
Rn free N2 Gas Generator
Corridor to detector
Water Purification systemMonitor Displays
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KamLAND; Distance to Reactors
68GWth
<L>~180km =>
€
Δm2 ~ 0.01eV
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Issues for KamLAND Detector Design
Event rate ~ only 1/day/kt (or 1/3years/t)
Large overburden to shield cosmic-rays: @2700mwe, cosmic-rar rate=10-5 of surface Extremely radio-pure liquid scintillator: Purification system -> U/Th/40K <10-10ppm
Delayed coincidence
Thick Shields: at least 50cm of water + 2.5m of Buffer Oil
=> Background reduction is essential
Large Liquid Scintillator (M~1kton) Transparency and stability is essential Simple is better
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Key Detector Elements
•Liquid Scintillator: (1150m3) Dodencane(80%)+PC(20%)+PPO(1.5g/L) Light output >8,000photons/MeV, att.>10m (Gd is not used)
•Balloon: 13m diam. 135mt Nylon/EVOH multilayer film. Held by Kevlar mesh.
•Buffer Oil: (1700m3) 2.5mt. n-Dodecane+Isoparaffin
•PMT: 1325 17" aperture PMT + 554 20" aperture => 34% photo-coverage
•Purification system: Water extraction + N2 bubbling U =>3.5x10-18g/g
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Event Display: Low Energy Event
(Enomoto WIN05)
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e identification
n+p→ d+γ 2.2MeV( )
ν e +p→ n+e+
2.2MeV~200É s
1~8MeV
t
Signal Property
e+ signal n signal
e+ +e−→ 2γ
Eν −0.8MeV( )
(ep -> e+n); an ideal reaction, because
• Only e contributes (no background from other neutrino species)• Low threshold Energy (1.8MeV)• Large cross section (~100e) • p is abundant in LS• Cross section precisely known (=0.2%)• e energy can be measured (E=Evisible+0.8MeV)• Delayed Coincidence -> powerful background rejection
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Single Backgrounds
208Tl decay ~2.5/day
238U/222Rn: 3.5x10-18g/g = 2decay/day232Th: 5.2x10-17g/g =10decay/day40K: <2.7x10-16g/g <4000decay/day
Cosmic-ray=0.3Hz
Reactor analysis threshold
ep threshold
(cf: sea water contains10-9g/g of U.)
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Neutrino Event Spectrum
€
N Eν( ) = N0 Eν( ) 1− sin2 2θsin2 Δm2L4Eν
⎛
⎝ ⎜
⎞
⎠ ⎟
Very Good S/N
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Reactor neutrino oscillation does exist
Long range detection has to take intoaccount the effect of the neutrino oscillation
=> Avoid L=50km
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Reactor Power Variation
In 2003, many power reactors stopped.
€
∝ PL2∑
KamLAND is already monitoring gross reactor opeartion in Japan
€
PL2∑
observed rate
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KASKA PrototypeNeutrino Experiments at Kasniwazaki-Kariwa Nuclear Power Station
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KASKA MembersNiigata University: N.Tamura, M.Tanimoto, H.Miyata, H.Nakano T.Kawasaki, M.Katsumata, T.Iwabuchi, M.Aoki, N.Nakajima, K.SakaiTohoku University: F.Suekane, Y.Sakamoto, S.Tsuchiya, H.TabataTokyo Metropolitan University: T.Sumiyoshi, H.Minakata, O.Yasuda , K.SakumaTokyo Institute of Technology: M.Kuze, K.Nitta, H.Furuta, J.Maeda, Y.FunakiKobe University: T.HaraKEK: N.Ishihara, H.SugiyamaMiyagi University of Education: Y.Fukuda, AkiyamaHiroshima Institute of Technology: Y.NagasakaOsaka University: Nomachi
~30people
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KASKA-13
~0.4km70m
~1.6km
150m
~0.35km24.3GW(world' largest)
6ton x 2
~50m
2x6ton
L=1.6km
sin2213<0.015
Kashiwazaki-Kariwa Nuclear Power Station
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Detector & Shaft Hole
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Neutrino Detection
ν e +p→ e+ +n
Then
e+ +e−→ 2γ 2×0.511MeV( )
n+Gd→ Gd'+γ's Eγ∑ ~8MeV( )
pÉÀe
e+e-ɡ(0.511MeV)ɡ(0.511MeV)nGdɡɡɡɡ
Eγ∑ ~8MeV
30 É s prompt signal Delayed signal
8MeV30É s1~8MeVtSignal Property
=> use Gd
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KASKA Prototype
* Test of γ-catcher.* Am/Be e like signal.
e detection at research reactor.
*Magnetic shield test•MC development
•LS handling
0.9m3
in Tohoku Univ.
16 8"PMT
UV transparent Acylic sphere
Sources(Am/Be ,60Co)
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60Co signal
(1.3MeV γ +1.2MeV γ
1γ escape
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Am/Be signal
Eprompt
E del
ayed
t
Ed
Ep
Gd-γ
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Background for reactor
Window
Preliminary
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Prototype@Joyo research reactor
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Fast Reactor (Pu rich)Pth=140MWFrequent ON/OFFL~25m~150 pen reaction/day
KASKA Prototype
25m
Purpose: Not for safegard R&D, just to see reactor ON/OFF for demonstration.
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Some modification for Joyo experiment
Not to scale
0.05% Gd Liquid Scintillator (900L)
Lead Shields
Cosmic-ray anti-counters
Light shield
Paraffin Blocks
N2
* 0.05% Gd LS(10%BC521+15%PC+75%isoParaffin oil)* Lead shield, * Cosmic-ray anti counter* Paraffin Blocks* n/γ pulse shape discrimination(PSD)
Event Selections• 3.5MeV<Ep<6MeV• 6MeV<Ed<9MeV ΔT<50s• Fiducial cuts(R<45cm)• PSD cut => efficiency ~5% => S/N~1/a few x10
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n/γ PSD with prototype LS
n(=p) singal
γ (=e) signal
Qtotal
Qtail
€
R ≡QtailQtotal
60Co γ fast n
R
For 50% of γ efficiency, n rejection rate >90% => S/Nbecomes more than 5 times better
is different for γ and n
The most sever BKG on surface is fast neutron. => n/γ separation will be essential
Real data
cut
t
ADC gates
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Acrylic sphere
Cosmic-ray Anti counter
Gd-LS
Reactor is behind the wall
2006.8.30
2006.9.20
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Energy spectrum of singles (no cuts)
Reactor ON
Reactor OFF
Very Preliminary
Measured by 1PMT
Just starting data taking.
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Possible Improvements
* More PMT Coverage: => Better PSD => Less leakage from low energy BKG
* Better Shield: Thicker lead & paraffin block shields, Double acrylic sphere (buffer region) * Better Anticounter coverage: => Cosmic-ray related BKG
* Higer reactor power: Monju(fast reactor) => x5 High Power ABWR => x30
* Shorter distance: => ~ 1/L2
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Simple Summary
•KamLAND successfully measures reactor neutrinos at distance hundreds of km from reactors.
•KASKA prototype is going to take fast reactor data shortly