Development in MOON -- MOON-1 prototype detector status -- NOMACHI, Masaharu , Osaka University MOON collaboration 2005/SEP/18 HAW05 US-Japan
MOON collaboration P.J.Doe, R.G.H.Robertson, D.E.Vilches, J.F.Wilkerson 、 D. I. Will. CENPA, Univ. Washington. H.Ejiri, T . I t a h a s h i , N . K u d o m i , T . S h i m a R C N P R. Hazama, K.Ichihara, S.Umehara, K.Matsuoka, H.Nakamura, M.Nomachi, T. Ogama, T. Sakiuchi, Y.Sugaya and V.H.Hai Osaka Univ S.Yoshida Tohoku Univ S.R.Elliott, LANL J.Engel. Phys.Astronomy, Univ. North Carolina. M.Finger, and K. Kuroda, Phys. Charles Univ. Prague K.Fushimi, GAS, Tokushima Univ. Tokushima M. Greenfield, ICU, Tokyo. A.Gorin, I.Manouilov, A.Rjazantsev. High Energy Physics, Protvino. A. Para FNAL A. Sissakian, V. Kekelidze, V. Voronon, G. Shirkov A. Titov, JINR V. Vatulin, V. Kutsalo, VNIIEF 2005/SEP/18 HAW05 US-Japan
MOON Project (Molybdenum Observatory Of Neutrino) • Object The effective Majorana mass 50meV with ~ton of 100 Mo. • Characteristic – Source is separated from detector. It can be used 82 Se, 150 Nd, and others as well. – 100 Mo The large Q value of 100 Mo is 3.034MeV. • 5 for 0 νββ . 100 Mo has large phase space factor proportional to Q ββ 0 νββ energy signal well above most BG(<3 MeV). • • The natural abundance is large. G 0ν Q ββ A Isotope (MeV) (10 -14 y -1 ) (%) – Plastic scintillator(PL) 48 Ca 4.276 4.46 0.187 • Purity of a PL is high. • Processing is easy to large scale. 76 Ge 2.039 0.44 7.8 82 Se 2.992 1.89 9.2 100 Mo 3.034 3.17 9.6 150 Nd 3.368 13.4 5.6 G 0n : phase space volume 2005/SEP/18 HAW05 US-Japan A: isotope abundance ratio
MOON Detector • Multi layers module 100 Mo foil 100 Mo foil & Plastic scintillator – Mo foil is interleaved with Active shield PLs. 100 Mo foil – Double layer hit Active shield To detect the double beta 100 Mo foil decay, two beta rays are detected by two PLs. β Calorimeter – Active shield 100 Mo foil The other PL is used as active β Calorimeter shield to reduce BGs. 100 Mo foil – Compact module PL works both as calorimeter Active shield and as active shield. 100 Mo foil Active shield 2005/SEP/18 HAW05 US-Japan
MOON 1.8m 1.8m 180 layer ~1.8 m 1.8m x 1.8m x 180 layer 9 module x 1.8m x 1.8m x 180 layer= 5250m 2 100 Mo 40mg/cm 2 ~2t 2005/SEP/18 HAW05 US-Japan
Requirement on energy resolutuion • Good Energy resolution • Photon Collection including the energy loss in the foil and To achieve the good energy resolution, a detector resolution. photon collection efficiency should be high. MOON-1 detector is large coverage for sides of a scintillator with many PMTs (about 80 % Counts surface of the four sides is covered.) 100 Mo Foil: 6mg/cm 2 Resolution: 7%(FWHM) T 2 ν = 0.8 × 10 19 y[1] T 0 ν > 0.8 × 10 26 y[1] 2 νββ 9 6 7 k e V C o n v e r s i o n e l e c t r o n s F r o m 2 0 7 B i c h e c k i n g s o u r c e F i g . t e s t s e t u p 0 νββ P L : 5 0 * 5 0 * 1 c m 3 3 2 P M T Good energy resolution is key to distinguish 0νββ from 2νββ . Sum energy(keV) [1] Nucl.Instrum.Meth.A536:79-122,2005 11.4%(FWHM) at 1MeV region. 2005/SEP/18 HAW05 US-Japan
MOON-1 Detector MOON prototype detector (MOON-1) was developed to study the energy resolution and BG rejection capability. Plastic scintillator (PL), 6layers, 53x53x1cm 3 • P L BC408. equivalent . 100 Mo(94.5% enrich), 142g 40mg/cm 2 , 3layers • P L M o F o i l Mo foils are interleaved with two PLs. P L M o F o i l 2νββ is expected to ~3decay/year P L in the energy window 2.7-3.2 MeV region. M o F o i l P L (7% energy resolution is assumed) P L – Aluminized Mylar films are used to F i g . C r o s s s e c t i o n v i e w o f M O O N - 1 support Mo foil. and also, to suppress the cross talk of photon between PL layers. 56 PMTs( 40 K Free 0.7Bq) are attached to PLs. • P M T HAMAMATSU, R6236-01 K-MOD – Silicon cookie is used for the optical contact. P L 5 3 * 5 3 * 1 c m 3 2005/SEP/18 HAW05 US-Japan
PMT location • A PMT is attached to the 3 plastic scintillators. • The plastic scintillator, which has energy deposit, is identified by PMT hit pattern. P M T 2005/SEP/18 HAW05 US-Japan
MOON-1 detector M O O N P l a s t i c s c i n t i l l a t o r 5 3 * 5 3 * 1 c m 3 5 6 P M T s 2005/SEP/18 HAW05 US-Japan
Oto underground Laboratory MOON-1 detector has been working at Oto underground Laboratory since April/2005. This lab was used at ELEGANT-V Osaka experiment. • Depth the lab is placed at 1,300m w.e. • BG level The BG level were measured by ELEGANT group[2]. MOON-1 – Cosmic Ray: 4x10 -7 /cm 2 /sec – Neutron Flux:4x10 -5 /cm 2 /sec – Rn:10Bq/m 3 [2] Nucl. Instr. and Meth. A459(2001)177-181 2005/SEP/18 HAW05 US-Japan
Experimental setup of MOON-1 MOON-1 is placed in active and passive shield. • NaI(Tl) detector 14 of NaI(Tl) detectors are put above and below MOON-1 detector. Those are used as gamma ray active shield • Air tight box 2 0 0 c m To keep Rn concentration low, N 2 gas was flushing. P b Rn concentration C u was 125mBq/m 3 . m c P b P b 0 N a I M O O N - 1 1 C u C u 1 P l a s t i c • Lead & Copper passive shield s c i n t i l l a t o r The outside of the air tight box is covered with C u P b 10cm Cu, 15cm Pb as passive shield. A i r t i g h t b o x 2005/SEP/18 HAW05 US-Japan
2005/SEP/18 HAW05 US-Japan
2005/SEP/18 HAW05 US-Japan
Analysis outline • Measurement The first data of 11 days (live time 276 hours). • Trigger Any hit at 2,3,4,5 layer is required for trigger. Trigger signal is made by summed signal of 8 PMT on four sides. The trigger threshold is 180 keV. 1 H i t l a y e r 2 3 4 5 • Analysis for one layer of Mo foil (51g) 6 1) Energy calibration 2) The double layer hit event selection 3) The sum energy spectrum for T r i g g e r P M T s double layer hit events. 4) The remaining events F i g . t h e s c h e m a t i c v i e w o f M O O N - 1 2005/SEP/18 HAW05 US-Japan
Energy calibration • Energy calibration 2 2 N a s o u r c e , 5 1 1 k e V , 1 . 2 7 M e V Compton edge of 1.27MeV gamma-ray S e l e c t e d l a y e r from 22 Na source single layer events are selected. NaI • Full energy peak The sum of the energy deposits on Deposit on single layer Counts plastic and NaI(Tl) may cause full 1.27MeV G a m m a 22 Na energy peak. Compton edge • MOON-1 energy resolution The energy resolution is 15%(FWHM) for 1.27MeV full energy peak. The energy resolution of NaI(Tl) is keV 9%(FWHM) at 1.27MeV. Deposit on single layer + NaI Counts 511keV Gamma Full energy peak 1.27MeV Gamma Full energy peak 1.27MeV+511keV Gamma Full energy peak 2005/SEP/18 HAW05 US-Japan keV
Event selection by PMT hit pattern • PMTs are attached to plastic scintillators. Each PMT is attaced to 3 plastic scintillators. Hit pattern of 12 PMTs are used for event selection 2005/SEP/18 HAW05 US-Japan
Event selection by PMT hit pattern • Single layer Hit events For the energy calibration, single layer hit events are selected. 2005/SEP/18 HAW05 US-Japan
Event selection by PMT hit pattern • Single layer Hit events - Threshold Level - Yellow PMT: 200keV Blue PMT: 200keV 2005/SEP/18 HAW05 US-Japan
Event selection by PMT hit pattern • Double layer Hit events Double beta decay events are the double layer hit. 2005/SEP/18 HAW05 US-Japan
Event selection by PMT hit pattern • Double layer Hit events - Threshold Level - Yellow PMT: 200keV Red PMT: 500keV Blue PMT: 200keV 2005/SEP/18 HAW05 US-Japan
Double layer hit events Sum energy spectrum – the double layer hit events after 11 days of data collection counts/50keV/year 1 1 d a y s m e a s u r e m e n t s 51g 100 Mo – D o u b l e l a y e r h i t e v e n t s – NaI detectors are used for gamma-ray veto. K 4 0 1 . 4 6 M e V γ D o u b l e c o m p t o n s c a t t e r i n g T l 2 0 8 2 . 6 M e V γ D o u b l e c o m p t o n s c a t t e r i n g • No event is observed at Q-value (3MeV) region. 0 0.5 1.0 1.5 2.0 2.5 3.0 MeV 2005/SEP/18 HAW05 US-Japan
Remaining Events 1. M.C simulation counts/50keV/year – M.C. simulation for double Data Compton scattering M.C. – The gamma rays were M.C. 40 K K 4 0 generated at PMT. M.C. 208 Tl 1 . 4 6 M e V γ – The Normalizations are selected to be fit experimental data. T l 2 0 8 2 . 6 1 M e V γ K , 1 . 4 6 M e V o r T l 2 . 6 M e V 4 0 2 0 8 PMT 0 0.5 1.0 1.5 2.0 2.5 3.0 MeV S u m - e n e r g y s p e c t r u m • The shape of the spectrum shows good agreement. 2005/SEP/18 HAW05 US-Japan
Remaining Events 2. NaI active shield counts/50keV/year Without veto With veto • The events are reduced to about 50% by the gamma-ray veto. • The amount of the reduction is 0 0.5 1.0 1.5 2.0 2.5 3.0 MeV consistent with the solid angle S u m - e n e r g y s p e c t r u m of NaI detectors looking from the MOON-1 detector. 2005/SEP/18 HAW05 US-Japan
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