Future SK Program for e Physics Atsuko Kibayashi For the Super-Kamiokande Collaboration Okayama...
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Transcript of Future SK Program for e Physics Atsuko Kibayashi For the Super-Kamiokande Collaboration Okayama...
Future SK Program for ne Physics
Atsuko KibayashiFor the Super-Kamiokande Collaboration
Okayama UniversityJune 14, 2013
1RENO 502013/6/14
MOTIVATIONS
2013/6/14 RENO 50 2
8 MeVΔT~20μsVertices within 50cm
γ
p
n
Gde+
ne
Capt
ures
on
Gd
Gd in Water
0.0001% 0.001% 0.01% 0.1% 1%
100%
80%
60%
40%
20%
0%
2013/6/14 3RENO 50
Neutron Capture by Gadolinium
• Large cross section of Gd for neutron capture– ~49,000 barns (0.3 barns on free
proton)• Coincident signal detection to suppress
background
• Beacom and Vagins, Phys. Rev. Lett., 93:171101, 2004]
• 0.1% Gd gives 90% neutron capture eff.
• ~100 ton of Gd2(SO4)3
in SK
Physics of neby GADZOOKS!Gadolinium Antineutrino Detector Zealously Outperforming Old Kamiokande, Super!
• Observation of Supernova Relic Neutrino (SRN)– SRN has not yet been observed
• Supernova Burst Neutrinos – Better direction determination by enhancement of
electron scattering events• Reactor Neutrinos
– Precise measurements of oscillation parameters by high statistics
2013/6/14 RENO 50 4
SRN Spectrum
2013/6/14 RENO 50 5
Expected SRN Spectrum(ne fluxes)
SRN flux calculations Horiuchi st al. PRD, 79, 083013 (2009)
Expected no. of SRN events1.3-6.7 events/year/22.5kton (10-30MeV)
Need: - Large target mass- Background removability
Expected SRN Signal and BackgroundAssume :
• 90 % neutron capture efficiency,
• 74% Gd gamma detection efficiency,
• invisible muon B.G. is 35% of the SK-IV invisible muon B.G.
Expect:
• 10-45 SRN events in 10-years data taking (Evis = 10-30 MeV)
2013/6/14 6RENO 50
SN at 10kpc
ne+p
ne+p
ne+p ne+p
n+e n+e
n+en+e
Supernova Burst Directionw/o Neutron Tagging
Neutrino flux and spectrum from Livermore simulation2013/6/14 7RENO 50
SN at 10kpc
ne+p ne+p
ne+p ne+p
n+e n+e
n+e
n+e
Supernova Burst Directionw/ Neutron Tagging
Removing tagged events
Neutrino flux and spectrum from Livermore simulation2013/6/14 8RENO 50
SN Direction Determination Precision
2x better precision with neutron tagging.
Direction Determination Precision (1000 MC events)
tag eff. = 1.0
tag eff. = 0.8
tag eff. = 0.0
Num
ber o
f sup
erno
vae 振動なし
振動あり(正階層性)振動あり(逆階層性)
Direction Determination Precision
No Osc.Oscillated (normal hierarchy)Oscillated (inverted hierarchy)
2013/6/14 9RENO 50
H. Ishino
Questions
Gd in SK?
• Water transparency?• How to purify Gd water?• How to introduce/remove Gd?• Effect on SK material?• Effect on solar neutrino analysis?• In a water Cherenkov detector?2013/6/14 RENO 50 10
EGADS
EGADSR&D
2013/6/14 RENO 50 11
SK water purification system
50m
Super-Kamiokande
To Atotsu entrance
EGADS hall
Parking place
Underground site map2013/6/14 12RENO 50
EGADSEvaluating Gadolinium’s Action on Detector Systems
Gd-water filtration
Gd purification(resin to remove U keeping Gd)
200 m3 SUS tank Transparency measuring device
13
EGADS Lab. in Kamioka Mine
2013/6/14 RENO 50
15 m3 plastic tank(for dissolving Gd)
Gd Removing Resin
Feb.16, 2011
Water Monovalent Multivalent Viruses Bacteria Suspended Ions Ions Solids
Water Monovalent Multivalent Viruses Bacteria Suspended Ions Ions Solids
Water Monovalent Multivalent Viruses Bacteria Suspended Ions Ions Solids
Water Monovalent Multivalent Viruses Bacteria Suspended Ions Ions Solids
Microfiltration1,000 – 100,000 angstroms membrane pore size
Ultrafiltration 100 – 1,000 angstroms membrane pore size
Nanofiltration 10 – 100 angstroms membrane pore size
Reverse Osmosis 5 – 15 angstroms membrane pore size
size
Membrane filter technology
small large
Gd2(SO4)3
M. Vagins
200 ton EGADS
Main Tank
EGADS Selective Filtration System
Intake Pump
(>4 ton/hr)
5 m 1st Stage
Filter
Concentrated Gd NF Reject Lines
UV#1
Mem
bran
eD
egas
0.2 m 2nd Stage Filter
0.5 ton Collection
Buffer Tank
RepressurizationPump
(>0.6 MPa, >4 ton/hr)
RepressurizationPump
(>0.6 MPa, >3 ton/hr)
Nanofilter #2
Nanofilter #1
Ultrafilter #1
Repressur-izationPump
(>0.9 MPa, >2 ton/hr)
TOC
5 m Filter
0.5 ton Buffer Tank
RO #1
Ultrafilter #1
Ultr
afilte
r #2
Repressurization Pump
(>0.9 MPa, >1.5 ton/hr)
DI#2
5 m Filter
RO #2
RO Permeate Lines
Conveying Pump
(~0.35 MPa, >4 ton/hr)
Recycles RO Reject Lines
Chiller
UF#1 Reject Line
UF#2 Reject
UV#2
DI#1
To Drain
Nanofilter #1
Nanofilter #1
Nanofilter #1
Nanofilter #2Nanofilter #2
Ultr
afilte
r #2
2013/6/14 15RENO 50
M. Vagins
EGADS (Step 1)200 m3 tank
Gd-water filtration system w/o PMT
Circulation of pure water in 200 m3 tank, to evaluate basic performance of the filtration system
March – June, 2011
15m3 tank
w/o PMT
Circulation of 0.2% Gd2(SO4)3 dissolved water in15m3 tank through the filtration system
Measurement of Gd-dissolved water transparency August, 2011 – December, 2012
EGADS (Step 2)200 m3 tank
Gd-water filtration system
15m3 tank
w/o PMT
EGADS (Step 3)200 m3 tank
Gd-water filtration system
15m3 tank
Circulation of 0.2% Gd2(SO4)3 dissolved water in 200m3 tank through the filtration system.
Study of effects on SUS tank (accelerated studies have shown no problems)
December, 2012 – June, 2013
Water Transparency MeasurementMethod
2013/6/14 RENO 50 19
T. Yano
SK-III and SK-IV Ultrapure Water = 74.7% - 82.1% @ 15 m
30 k
g o
f G
d2(S
O4) 3
*8H
2O
3
5% n
cap
ture
on
Gd
60 k
g o
f G
d2(S
O4) 3
*8H
2O
5
2% n
cap
ture
on
Gd
89.4
kg
of
Gd
2(S
O4) 3
*8H
2O
6
2% o
n G
d
149
.4 k
g o
f G
d2(S
O4) 3
*8H
2O
7
3% o
n G
d
274
kg
of
Gd
2(S
O4) 3
*8H
2O
8
3% o
n G
d
400
kg
of
Gd
2(S
O4) 3
*8H
2O
8
8% o
n G
d70 % => 85% of pure water
2013/6/14 20RENO 50
M. VaginsLight Remaining at 15 m in 200 ton tank
240 PMT mounting July - August, 2013
EGADS (Step 4)200 m3 tank
Gd-water filtration system
15m3 tank
Circulation of pure water, then 0.2% Gd2(SO4)3 dissolved water
Integrated test Starting September, 2013
Mini-SK (w/ same SK material)
EGADS (last Step)200 m3 tank
Gd-water filtration system
15m3 tank
GADZOOKS!for
2013/6/14 RENO 50 23
Effect on Solar Neutrino Analysis?
• To achieve 3.5 MeV(Kin.) solar neutrino analysis in 0.2% Gd+H2O SK, the following radioactivity levels would be needed.
< 2.8 x 10-11 g(238U)/g(Gd)< 8.6 x 10-11 g(232Th)/g(Gd)< 9.6 x 10-18 g(226Ra)/g(Gd)
=> Corresponds to < 0.35 mBq/kg(Gd)
2013/6/14 RENO 50 24
M. Smy
Radioactivity of Gd2(SO4)3
Radioactivity in Gd2(SO4)3 batches measured in Canfranc [mBq/Kg, limits are @ 95% c.l.] Chain Longest lived
parent in sub-chain
Product 1 Product 2 Product 3 Product 4 Product 5
238U 238U 51 ± 21 < 33 292± 67
74 ± 28 242± 60
226Ra 8 ± 1 2,8 ± 0,6 74± 2 13± 1 13 ± 2232Th 228Ra 11 ± 2 270 ±
16(*)1099± 12 205 ± 6 21 ± 3
228Th 29 ± 3 86 ± 5 504± 6 127 ± 3 374 ± 6235U 235U < 32 < 32 < 112 < 25 < 25
227Ac/227Th 214 ± 10 1700 ± 20 2956 ± 30 1423 ± 21 1750 ± 42 Others 40K 29 ± 5 12 ± 3 (*) 101 ± 10 60 ± 7 18 ± 8
138La 8 ± 1 < 683 ± 15 3 ± 1 42 ± 3176Lu 80 ± 8 21 ± 2 566 ± 6 12 ± 1 8 ± 2
prel
imin
ary
Still
too
high
252013/6/14 RENO 50
L. Labarga
=> To reduce Radium, one solution is to use commercial selective resins available.
Answers
Gd in SK?• Water transparency? • How to purify Gd water? • How to introduce/remove Gd?
• Effect on SK material? • Effect on solar neutrino analysis?
• In a water Cherenkov detector?
2013/6/14 RENO 50 26
85% of pure water
Method being established
Mass removal still under study, commercial resin available
Gd2(SO4)3 proven to be safe
Radioactivity still too high (esp. Ra). Commercial resin will be tested.
Demonstration of Cherenkov detection of Gd(n, gamma) Gd (H.Watanabe et al. Astropart. Phys., 31, 320-328 (2009)
R&D Schedule
2013/6/14 RENO 50 27
M. Nakahata
Conclusion• For SRN detection
– A large target volume is needed => SK is the only one w/ that kind of volume– Addition of Gd unable us to detect SRN
• For SN detection– Direction accuracy can be improved by tagging ne events
2013/6/14 RENO 50 28
Gd in water Cherenkov detector R&D project (EGADS) is in progress.Gd in SK looks more and more promising.
We hope to start GADZOOKS! in a few years.
As soon as EGADS successfully demonstrates the feasibility for GADZOOKS!, schedule for GADZOOKS! will be discussed among the SK collaboration.
BACKUPS
2013/6/14 RENO 50 29
EGADS Members• ICRR, University of Tokyo
– Y. Kishimoto , M. Nakahata, H. Sekiya• Kavli, IPMU
– L. Marti, M. Vagins• Kobe University
– Y. Takeuchi• Okayama University
– H. Ishino, A. Kibayashi, Y. Koshio, T. Mori, M. Sakuda, Y. Yamada, T. Yano,• University Autonoma Madrid
– L. Labarga, P. Fernadez• University of California, Irvine
– G. Carminati, J. Griskevich, B. Kropp, A. Renshaw, M. Smy, P. Weather
2013/6/14 RENO 50 30
Ultrafilter Nanofilter
RO
RO reject(processed in another loop)
pure water (RO pass)and Gd2(SO4)3 Return to tank
Water withGd2(SO4)3 from the tank
Gd2(SO4)3 (NF reject)
Concept of the water circulation system
Gd2(SO4)3 and UF passed water (UF pass)
Small size contaminants(NF pass)
Reject large size contaminants(UF reject)
31
Reactor Neutrino at GADZSOOKS!
w/o oscillation
w/ oscillation
MeV
With / without oscillation
10 years’ sensitivity
sin2(2θ)
Δm
2 (10
-4 e
V)
Number of events at SK per year(~3000 /year)
Current solar+KamLAND error size
Sensitivity of parameter measurement( 10 years)
very preliminary 95%CL
400 kg 88%
274 kg 83%
149.4 kg 73%
89.4 kg 62%
60 kg 52%
30 kg of Gd2(SO4)3 8H2O
in 200 tons 35% captureon gadolinium
Cap
ture
s on
Gd
Gd in Water
0.0001% 0.001% 0.01% 0.1% 1%
100%
80%
60%
40%
20%
0%
Thermal neutron capture cross
section (barns)
Gd = 49700
S = 0.53
H = 0.33
O = 0.0002
2013/6/14 33RENO 50
M. Vagins
[Yano-san]2013/6/14 34RENO 50
[Yano-san]2013/6/14 35RENO 50
[Yano-san]2013/6/14 36RENO 50
Gd Recovery SystemR&D at UCI
2013/6/14 RENO 50 37
Y. Takeuchi, ICRR
M.Smy, “Low Energy Requirements for the GADZOOKS! Project”,SK meeting, Dec.3, 2006
382013/6/14 RENO 50
Epoxy Testpaint on welded part of the SUS tank
BIO-SEAL 197 BIO-DUR 560
39
M20 bolts in a flange apply epoxy w/o welding.
Epoxy paints on the base of bolt.2013/6/14 RENO 50
Epoxy TestPressure vessel
The test flanges are put on both sides and give pressure to the vessel.
Pressure test (0 5kg/cm2) was done on Oct.19, 2011.No leak and no pressure drop.
Pressure cycle (0 5kg/cm2) test was done on Oct.20-27.No leak and no pressure drop.
Long term stability test is running from Oct.28 for 3 months and no problem was found.
Successful
402013/6/14 RENO 50
Possibility of Acrylic Vesseladditional layer of protection
Basic idea: extend the frame above the PMTs and put thin acrylic plates.
Outer detector
Inner detector
Acrylic vessel
Gd-loaded water
412013/6/14 RENO 50
This apparatus deployed in the SK tank.
BGO
13 cm
18 cm 1
8 cm
5 c
m
BGO
0.2 % GdCl3Solution
Am/Be
GdCl3 test vesselTest Cherenkov emission of Gd(n,g)Gd
α + 9Be → 12C* + n 12C* → 12C + g(4.4 MeV) n + p → …… → n + Gd → Gd + g (totally 8 MeV)
BGO signal (prompt signal (large and long time pulse))
Look for Cherenkov signal (delayed signal)
Cherenkov signal of Gd gamma rays
0
Time from prompt
100ms
Vertex position92% within 2m
dR [cm]
Energy spectrum
Measured time, vertex and energy distributions are as expected from the MC simulation.
Astropart. Phys. 31, 320-328 (2009)arXiv:0811.0735