Post on 28-Jan-2021
Scintillation Detector
Minfang Yeh (BNL)
PX workshop 2012
• General introduction and physics of liquid scintillator• Metal-loaded liquid scintillator• Future liquid scintillator
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Typical Cerenkov and Scintillation Detectors
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Cerenkov (Super-K)
0ββ, geo-, reactor-, beam physics ND
proton decay, supernovae (Gd),beam physics FD
~kt Detector~>50kt Detector
~100% LS~20% LS
Scintillator (Daya Bay)
PX workshop 2012 M. Yeh
Main Neutrino Interactions in Liquid Scintillator
+ p + 12C 12B 12C + 12C 12 12C + 12C 12 * 12
PX workshop M. Yeh
J.M.A. Winter (TU Munchen)
Excellent detection medium for neutrino in MeV range; need NC background reduction in GeV range
Profound physics program for Solar-, Geo-, Reactor- &, Supernova-Neutrinos, Neutrino Oscillation, Proton Decay.
Different LS combinations to meet the need of various physics
BNL Liquid Scintillator Development Facility
PX workshop 2012 M. Yeh 4
• ability to catch ionization radiation• photon-transferring mechanisms once
excited (S/F/S)
• Collaboration between Physics and Chemistry at BNL with expertise in low-background counting, organic scintillators, and in particular metal-loaded organic scintillator
• Interest of neutrino and neutron detectors (Daya Bay, SNO+, LENS)
• Investigation of a large variety of liquid scintillators
• PC, PCH, DIN, PXE, LAB• Metal-loaded and water-based
scintillators with high light-yield, long attenuation length and low flammability.
• Capability of purifying and synthesizing materials in-house and of controlling the chemical processes.
M. Yeh, Review of Metal-loaded Liquid Scintillator for Neutrino Physics, IJMPB (in prep.).
Scintillation mechanism
Comparisons of Liquid Scintillators for Neutrino Expt’s
first identified by SNO+
PX workshop M. Yeh
Past & Present Liquid Scintillator experiments
PX workshop M. Yeh
Experiment Scintillator Mix
Palo Verde 40% PC + 60% Mineral oil
CHOOZ50% paraffinic liquid + IPB
(isopropylbiphenyl)
Borexino PC
LENS LAB (PC)
MiniBOONE MO
Daya Bay LAB
SNO+ LAB
RENO LAB
Double-CHOOZ 20%PXE + 80%dodecane
KamLAND2 20% PC + 80%dodecane
NOvA 5% PC + 95% MO
Possible Future Liquid Scintillator Experiments
PX workshop 2012 M. Yeh 7
Newly Proposed Experiments (selected)
Accelerator-based
LENA
OscSNS
IsoDAR
Reactor-based
Daya Bay-II, RENO-II
SCRAAM, Stereo, NIST
-sourcesCe-LAND
LENS-Sterile
• LS not decided; but LAB is the favor
• Gd-loaded for most reactor expt’s
Metal-loaded LS for Physics
Reactor
Solar
OthersM. Yeh, Review of Metal-loaded Liquid Scintillator for Neutrino Physics, IJMPB (in preparation).
PX workshop M. Yeh
Inverse Beta Decay Detection with Gd
Ethreshold = 1.8 MeV
‘Large’ cross section σ~10-42 cm2
Distinctive coincidence signature in a large liquid scintillator detector
Cowan & Reines, Savannah River 1956
Ev - 0.8 MeV
PX workshop M. Yeh
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Searching for 0ββ-decay to answer:• whether neutrinos are Dirac or Majorana particles• probe neutrino masses at the level of tens of meV; A mbb
limit of ~20 meV would exclude Majorana neutrinos in an inverted hierarchy.
Nd-LS
• SNO+ is the only metal-loaded liquid scintillation detector.
• Flexible and easy scale-up • Any hydrophilic DDB isotopes that cannot
be done in pure LS; NOW is possible.• Installation and production in FY13
PX workshop 2012 M. Yeh
Double-beta Decay using Nd
PX workshop M. Yeh
• 8% Indium loaded LS meets the experiment needs• micro-LENS is ongoing in Kimberton mine with mini-LENS in preparation
How to make a clean and stable metal-loaded LS?
• Synthesis procedure• Purification (radioactive & optical)• QA/QC
PX workshop M. Yeh
Ex. of Gd-LS production at Daya Bay:• Gd-LS production done in 3 months• >3-yrs R&D and >1-yr 1-t prototype
monitoring on Gd-LS stability • Optical improvement and U/Th removal• QA/QC during and after production
LS storageliquid production
Gd‐LS storage
4‐t Gd‐LS batch
Self-scavenge, PH-controlled Gd salt purification
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TMHA
Low flash point, compatible light-yield, know-how production, high compatibility
PX workshop M. Yeh
Self-scavenge Gd purification
PX workshop M. Yeh
• U/Th removed to < 0.1 ppb• Optical improvement by 2x from
300-450nm
M. Yeh et al. NIM A 618 (2010) 124–130
Complexing acid and PPO purifications
Purification is a must for optical and stability improvements.
LAB produced specially by the vendor. PPO purified by re-crystallization
after washes (can also purified by mixing in PC or LAB by direct distillation)
Gd-complexing ligand purified by thin-film vacuum distillation.
heavy potion removed from the ligand solvent by 3x in 300-500nm
PX workshop M. Yeh
Absorption Length Calculation
PX workshop M. Yeh
Gd-LS LS LAB (m) 20.9 20.4 22.8
Water has long attenuation lengths (136 – 200m) observed by Super-K, SNO, etc.; dominated by scattering
Abs. at 0.002 ~ 20m
QA/QC and AD Identification• Stability All 6 ADs:• [Gd] agrees within 0.16%• [H] agrees within 0.17% (Combustion analysis)• [Gd-LS] ave. >20m• Light-yield emission agrees within 1% (Fluorescence
Spectroscopy)
PX workshop M. Yeh
Liquid scintillator Options for future experiments
• Binary liquid scintillator• Singular liquid scintillator• Water-based liquid scintillator
PX workshop M. Yeh
Option-1: Binary scintillating liquid systemLinear Alkylbenene + dodecane or mineral oil
PX workshop M. Yeh
Pseudocumene Linear Alkylbenzene
Density Matching and Solvent Purity are the keys to the stability of binary system
PX workshop M. Yeh
For the bottle with 2 phases, the top layer is light mineral oil at 80% with 0.00529%Gd and the bottom layer is PC at 20% with 0.01149%Gd.
Others of Gd in PC and DD with and without shifters have been stable since 2005.
Option-2 singular liquid scintillator
LAB + PPO (3g/L) + bis-MSB (15 mg/L) ~ 10,000 ’s / MeV
PX workshop M. Yeh
nm
AU
Option-3: Water-based Liquid Scintillator
PX workshop M. Yeh
Cost-saving for larger detector (see talk in cost-effective detector session)
Clean Cerenkov cone with scintillation at few hundreds of photons per MeV (tunable)
Fast pulse and long attenuation length with minimum ES&H concerns
A new technology ready to use:• Excellent detection medium for proton decay; and other physics• Easy to be handled for large detector• Gd-soluable• A economic large veto solvent
WbLS(PPO) between 2 – 4 ns
10-MeV e- beam at LEAF
Time-resolved fluorescence system
PX workshop M. Yeh
WbLS Attenuation Length close to pure water after 400nm
PX workshop 2012 M. Yeh 24
• UVs of 18-MΩ water and WbLS normalized to Super-K abs. curve.
• Mean-free absorption length calculated by LBNE water attenuation simulation (developed for Compatibility test).
• Need large-scale verification
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R7081 PMT QE
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WbLS-2012Daya Bay LSSuper-K scattering + absorptionWbLS-2012 emission at 265nmPPO emission at 310nmMSB emission at 365nmR7081 PMT QE
Emission at the PMT sensible region is very clean
PX workshop 2012 M. Yeh 25
• The fluor/shifter transmission needs to be optimized.
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H2O+Carbostyril-124
WbLS-2012
WbLS Scintillation vs. Cerenkov (Cs-137)
• Cerenkov increases by ~4x using Carbostyril-124 (SNO)
• A ratio of 5:1 for scintillation vs. Cerenkov
PX workshop M. Yeh
WbLS at NSRL high-energy particle-beam in 2011
• 1-GeV proton beam• Daya Bay sees ~32:1 of Scintillation vs.
Cerenkov in pure LS.• WbLS obtains ~1/3 of LS light (10:1
compared to water-filled)• Reinvestigate with 100 – 300 MeV p-beam
this fall (LDRD funded, Hide et. al.).
Figure 2: The instantaneous intensity in Hz as a function of time in spill in ms.
preliminary
PX workshop M. Yeh
Scintillation light at 90 s/MeV
• one event No Cut
• select different timing windows for k+ and μ+
events
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Select the k+ Timing Window (0 13ns)
scintillation light only no Cerenkov ring
PX workshop M. Yeh
Select the µ+ window (13 22ns)
clean μ-rings can be identified among scintillation
PX workshop M. Yeh
Sensitivity of WbLS for PDK+
PX workshop 2012 M. Yeh 31
• Event Signal-like: Prompt• K+ scintillationDelay• + and + scintillation• scintillation• Cerenkov rings from , , , Michel electron, etc.
• Event Selection Rules • 12.8 ns between prompt and delay.• No ring in Prompt. • Energy Cut on prompt event.• Rings in delay• Energy cuts in delay with rings• etc…
• 10-yr run could reach a sensitivity of 1034 for the PDK+ mode).
• Compare to SK (170 events in 1489 days), the 3-fold coincidence cuts down to ~5/y; PSD/Michel position cut can further suppress the bkg. event to 0.25/y.
A new way of loading hydrophilic metallic ions (Li, Ca, Te, etc) in scintillator
• Double-beta decay• Reactor neutrino• Geo neutrino• Supernovae neutrino
PX workshop M. Yeh
First DBD isotope in WbLS
PX workshop 2012 M. Yeh33
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0.5% X-WbLS + PPO0.5% X-WbLS + PPO/MSBLAB + PPO
X-WbLS
• Efforts to load certain metallic-ions in pure LS (=80%)
• Quick and straight in preparation of X-WbLS(=100%)
X-LS
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Photon/MeV
Typical Cerenkov and Scintillation Detectors
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Cerenkov (Super-K)
0ββ, geo-, reactor-, beam physics ND
proton decay, supernovae (Gd),beam physics FD
~kt Detector~>50kt Detector
~100% LS~20% LS
Scintillator (Daya Bay)
PX workshop 2012 M. Yeh
Cerenkov & Scintillation WbLS
Organometallic-ion WbLS
PX workshop M. Yeh
LS reactivity (compatibility) favors LAB
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glass1
BC490_on_glass1
silica3
BC490_in_xylenes_onSilica3
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BC490_in_xylenes_onGlass3
Liquid Scintillation Veto film
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current experience with LS veto-film (a project in collaboration with LNGS) to produce -thin, Teflon-based films targeting surface /β for background reduction.
Related applications to LAr light collection.• Current PVT (polyvinyl toluene) –
based polymer deteriorates under UV-light; questionable to be used under cryogenic condition.
• Current toluene-TPB (tetraphenylbutadiene) combination is not the best match for LAr emission at 128nm.
μm-thin veto filmUnder UV
PX workshop 2012 M. Yeh
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Summary Liquid scintillator continues to play a key role for neutrino detection in
(non)accelerator, reactor, double-beta decay experiments.
There are several liquid options for the future detector; depending on the physics requirements and costs.
The technology of meal-loaded LS is well developed; and its M%, attenuation length, and photon-production are tunable as needed.
The synthesis technology, material compatibility, and cost of production & purification of scintillator have been worked out and demonstrated to be stable.
WbLS with scintillation & Cerenkov detections is an excellent medium for proton decay (and other physics) and can be used for neutron tagging (enhanced by Gd loaded) .
A cost-effective large detector as well as veto system for future experiment
PX workshop M. Yeh
PX workshop M. Yeh