Christian Buck, MPIK Heidelberg LowNu Reims, October 2009 Liquid scintillators

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Overview  Introduction  Scintillator components  Energy transfers  Metal loaded scintillators  Summary

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Liquid scintillator past Metal loaded:  Reines  Bugey  Chooz  Palo Verde Unloaded:  KamLand  Borexino

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Challenges: Stability and purity Palo Verde: A.G.Piepke, S.W.Moser, V.M.Novikov; NIM A 342 (1999) Chooz: τ ~ 240 days Gd(NO 3 ) 3 Chooz Coll.; Eur.Phys.C27, (2003) KamLand Background:

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 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

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Liquid scintillator future  Double Chooz, Daya Bay, Reno  SNO+  LENA,…

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Liquid scintillator components  Solvent –pseudocumene, toluene, anisole –„Safe scintillators“: PXE, LAB, DIN –Admixtures: alkanes, mineral oil  Primary fluor –PPO –BPO –Butyl-PBD,…  Secondary fluor –Bis-MSB –POPOP α, β, γ * PMT

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Comparison solvents: Light yield SolventYield (6 g/l PPO) PC1.00 Anisole0.81 PXE0.88 LAB0.74 Dodecan0.40 Oil0.33 MPIK measurements M.Chen, INT Workshop 2005

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Comparison solvents: Attenuation length MPIK measurements (UV/Vis, 10 cm cell) M.Wurm (TUM), ANT 2009

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Purification methods  Column purification –Radioimpurities –Optics  N 2 purging – Radon, 85 Kr – Light yield (oxygen)  Water extraction –Radioimpurities (e.g. 40 K)  Distillation – Radioimpurities – Optics

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Purification methods  Column purification –Radioimpurities –Optics  N 2 purging – Radon, 85 Kr – Light yield (oxygen)  Water extraction –Radioimpurities  Distillation – Radioimpurities – Optics Borexino KamLand CTF LAK Solar neutrino phase

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Borexino Background PRL 101, (2008) 40 K < 3 ∙ g/g 238 U: 1.6 ± 0.1∙ g/g 232 Th: 6.8 ± 1.5∙ g/g

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 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)

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Solvent mixtures Advantage: Parameters tuneable  optimize material compatibility  change timing properties  match density  adjust light yield 6 g/l PPO Light production in alkanes  Radiation creates e -- - hole pairs  Recombination, fragmentation, radicals, reactions  excited molecules  energy transfer to fluors M.Wurm, diploma thesis, TUM(2005) Light yield [% standard] C.Aberle, diploma thesis, MPIK (2008) PXE (mass fraction)

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Comparison fluors transparent well established high quantum yield BPO (Butyl-)PBD pTP PPO high(est) light yield emission around 400 nm absorption properties limited availibility low solubility poor quantum yield fast overlap with bis-MSB high light yield poor quantum yield costs

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Energy transfer (non-radiative)

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Critical concentration Critical distance R 0 : Critical conc.: 50 % Energy transfer Photon emission, decay For PPO < 1g/l in PXE, PC,… For PPO ~ 2.1 g/l in dodecane Donor *Acceptor

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Light yield model C.Buck, F.X. Hartmann, D.Motta. S.Schönert, CPL, 435 (2007) C.Aberle, diploma thesis, MPIK Heidelberg (2008) See poster by C.Aberle!

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Timing properties C.Aberle, Diploma thesis, MPIK Heidelberg (2008) D.Motta (CEA Saclay): pulse shape to tag events in different detector regions Target Gamma Catcher candidates Events Time [ns]

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 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

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 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)

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Gadolinium (Carboxylates) Double Chooz mockup (TMHA, MPIK 2003): INR/LNGS: 2 x 1.2 t Gd-LS (0.1%) in frame of LVD Now used in Daya Bay and RENO Y.Ding et al., NIM A 584 (2008) M.Yeh et al., NIM A 578 (2007) arXiv: v1 [physics.ins-det] 11 Mar 2008

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Gadolinium (β-diketones)  Purified by sublimation  stability/compatibility tests > 4 y  att. length (1 g/l) > 50 m in ROI  100 kg produced

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Scintillator production for Double Chooz Scintillator production has started Poster by F.X.Hartmann on DC scintillator chemistry

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 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: v1 [physics.ins-det] 11 Sep 2009

Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 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.)