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Liquid scintillators. Christian Buck, MPIK Heidelberg. LowNu Reims, October 2009. Overview. Introduction Scintillator components Energy transfers Metal loaded scintillators Summary. Liquid scintillator past. Metal loaded: Reines Bugey Chooz Palo Verde. Unloaded: KamLand

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overview
Overview
  • Introduction
  • Scintillator components
  • Energy transfers
  • Metal loaded scintillators
  • Summary

Reims, Neutrino Champagne 2009

liquid scintillator past
Liquid scintillator past
  • Metal loaded:
  • Reines
  • Bugey
  • Chooz
  • Palo Verde
  • Unloaded:
  • KamLand
  • Borexino

Reims, Neutrino Champagne 2009

challenges stability and purity
Challenges: Stability and purity

Palo Verde:

KamLand Background:

A.G.Piepke, S.W.Moser, V.M.Novikov; NIM A 342 (1999) 392-398

Chooz:

Gd(NO3)3

τ ~ 240 days

Chooz Coll.; Eur.Phys.C27, 331-374 (2003)

Reims, Neutrino Champagne 2009

liquid scintillator properties
Liquid scintillator properties
  • High energy resolution
  • Low energy detection threshold
  • high purity (Borexino)
  • fast signals (better understanding of timing properties)
  • moderate cost
  • Improved stability of metal loaded scintillators

Reims, Neutrino Champagne 2009

liquid scintillator future
Liquid scintillator future
  • Double Chooz, Daya Bay, Reno
  • SNO+
  • LENA,…

Reims, Neutrino Champagne 2009

liquid scintillator components
Liquid scintillator components

α, β, γ

  • Solvent
    • pseudocumene, toluene, anisole
    • „Safe scintillators“: PXE, LAB, DIN
    • Admixtures: alkanes, mineral oil
  • Primary fluor
    • PPO
    • BPO
    • Butyl-PBD,…
  • Secondary fluor
    • Bis-MSB
    • POPOP

*

PMT

Reims, Neutrino Champagne 2009

comparison solvents light yield
Comparison solvents: Light yield

MPIK measurements

M.Chen, INT Workshop 2005

Reims, Neutrino Champagne 2009

comparison solvents attenuation length
Comparison solvents: Attenuation length

MPIK measurements(UV/Vis, 10 cm cell)

M.Wurm(TUM), ANT 2009

Reims, Neutrino Champagne 2009

purification methods
Purification methods
  • Column purification
    • Radioimpurities
    • Optics
  • N2 purging
    • Radon, 85Kr
    • Light yield (oxygen)
  • Water extraction
    • Radioimpurities (e.g. 40K)
  • Distillation
    • Radioimpurities
    • Optics

Reims, Neutrino Champagne 2009

purification methods1
Purification methods

KamLand

  • Column purification
    • Radioimpurities
    • Optics
  • N2 purging
    • Radon, 85Kr
    • Light yield (oxygen)
  • Water extraction
    • Radioimpurities
  • Distillation
    • Radioimpurities
    • Optics

CTF

LAK

Borexino

Solar neutrino phase

Reims, Neutrino Champagne 2009

borexino background
Borexino Background

40K < 3 ∙10-18 g/g

238U: 1.6 ± 0.1∙10-17 g/g

232Th: 6.8 ± 1.5∙10-18 g/g

PRL 101, 091302 (2008)

Reims, Neutrino Champagne 2009

slide13
LAB
  • LAB is proposed in SNO+, Daya Bay, RENO
  • New high light yield, transparent solvent?
    • Used since decades
    • Average light yield
    • Average transparency
  • It is a high flash point, low toxicity solvent at moderate cost and reasonable optics,
  • …but:
    • Mixture
    • Biphenyls (absorption/emission!)
    • Timing properties

LAB (6 g/l PPO)

PXE (6 g/l PPO)

Reims, Neutrino Champagne 2009

solvent mixtures
Solvent mixtures

Advantage: Parameters tuneable

  • optimize material compatibility
  • change timing properties
  • match density
  • adjust light yield

6 g/l PPO

C.Aberle, diploma thesis, MPIK (2008)

  • Light production in alkanes
  • Radiation creates e-- - hole pairs
  • Recombination, fragmentation, radicals, reactions  excited molecules  energy transfer to fluors

Light yield [% standard]

PXE (mass fraction)

M.Wurm, diploma thesis, TUM(2005)

Reims, Neutrino Champagne 2009

comparison fluors
Comparison fluors

BPO

PPO

  • transparent
  • well established
  • high quantum yield
  • high(est)
  • light yield
  • emission around 400 nm
  • absorption properties
  • limited availibility

pTP

(Butyl-)PBD

  • high light yield
  • fast
  • overlap with bis-MSB
  • poor quantum yield
  • costs
  • low solubility
  • poor quantum yield

Reims, Neutrino Champagne 2009

energy transfer non radiative
Energy transfer (non-radiative)

Reims, Neutrino Champagne 2009

critical concentration
Critical concentration

Critical distance R0:

Donor *

Acceptor

50 %

50 %

Photon emission, decay

Energy transfer

Critical conc.:

For PPO < 1g/l in PXE, PC,…

For PPO ~ 2.1 g/l in dodecane

Reims, Neutrino Champagne 2009

light yield model
Light yield model

See poster by C.Aberle!

C.Buck, F.X. Hartmann, D.Motta. S.Schönert, CPL, 435 (2007) 252 - 256

C.Aberle, diploma thesis, MPIK Heidelberg (2008)

Reims, Neutrino Champagne 2009

timing properties
Timing properties

Gamma Catcher candidates

Events

Target

Time [ns]

C.Aberle, Diploma thesis, MPIK Heidelberg (2008)

D.Motta (CEA Saclay): pulse shape to tag events in different detector regions

Reims, Neutrino Champagne 2009

metal loaded scintillators
Metal loaded scintillators
  • Solar neutrinos (LENS, SIREN):
    • Metal: Ytterbium, Indium, Gadolinium
    • Challenge: High loadings
  • Reactor (Double Chooz, Daya Bay, RENO)
    • Metal: Gadolinium
    • Challenge: Stability
  • ββ-decay (SNO+)
    • Metal: Neodymium
    • Challenges: transparency; purity

Reims, Neutrino Champagne 2009

indium
Indium

Indium-loaded scintillators at LLBF > 1 year (2003/04)

  • MPIK:In(acac)3 (F.X.Hartmann et al.)
  • INR/LNGS: Carboxylic acid version

> 50 g/l Indium

D. Motta, C. Buck, F. Hartmann, T. Lasserre, S. Schönert, U.Schwan, NIM A 547 (2005) 368.

N.A. Danilov, C.Cattadori, A..di Vacri et al., Radiochemistry 47 (2005) 487-493.

Reims, Neutrino Champagne 2009

gadolinium carboxylates
Gadolinium (Carboxylates)

Double Chooz mockup (TMHA, MPIK 2003):

INR/LNGS: 2 x 1.2 t Gd-LS (0.1%) in frame of LVD

arXiv:0803.1577v1 [physics.ins-det] 11 Mar 2008

  • Now used in Daya Bay and RENO
  • Y.Ding et al., NIM A 584 (2008) 238-243.
  • M.Yeh et al., NIM A 578 (2007) 329-339.

Reims, Neutrino Champagne 2009

gadolinium diketones
Gadolinium (β-diketones)
  • Purified by sublimation
  • stability/compatibility tests > 4 y
  • att. length (1 g/l) > 50 m in ROI
  • 100 kg produced

Reims, Neutrino Champagne 2009

scintillator production for double chooz
Scintillator production for Double Chooz

Scintillator production has started

Poster by F.X.Hartmann on DC scintillator chemistry

Reims, Neutrino Champagne 2009

neodymium
Neodymium

MPIK (2003): Tests on BDK and CBX versions (F.X.Hartmann et al.)

Light yield measurements at LNGS

C.Cattadori et al., submitted to NIM A (2009)

arXiv:0909.2152v1 [physics.ins-det] 11 Sep 2009

Reims, Neutrino Champagne 2009

summary
Summary
  • Liquid scintillators key technology for upcoming large scale neutrino detectors
  • Many solvent and fluor candidates
    • Choice depends on application and detector characteristics
    • Requirement for „safe“ scintillators (PXE, LAB,…)
  • Energy transfer models allow light yield predictions
  • Several applications for metal loaded scintillators

 significant improvement in last years (stability etc.)

Reims, Neutrino Champagne 2009

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