Liquid scintillators Christian Buck MPIK Heidelberg Low Nu
Liquid scintillators Christian Buck, MPIK Heidelberg Low. Nu Reims, October 2009
Overview Ø Introduction Ø Scintillator components Ø Energy transfers Ø Metal loaded scintillators Ø Summary Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Liquid scintillator past Metal loaded: Ø Reines Ø Bugey Ø Chooz Ø Palo Verde Unloaded: Ø Kam. Land Ø Borexino Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Challenges: Stability and purity Palo Verde: Kam. Land Background: A. G. Piepke, S. W. Moser, V. M. Novikov; NIM A 342 (1999) 392 -398 Chooz: Gd(NO 3)3 τ ~ 240 days Chooz Coll. ; Eur. Phys. C 27, 331 -374 (2003) Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Liquid scintillator properties Ø High energy resolution Ø Low energy detection threshold Ø high purity (Borexino) Ø fast signals (better understanding of timing properties) Ø moderate cost Ø Improved stability of metal loaded scintillators Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Liquid scintillator future Ø Double Chooz, Daya Bay, Reno Ø SNO+ Ø LENA, … Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Liquid scintillator components α, β, γ Ø Solvent – pseudocumene, toluene, anisole – „Safe scintillators“: PXE, LAB, DIN – Admixtures: alkanes, mineral oil Ø Primary fluor – PPO – Butyl-PBD, … Ø Secondary fluor – Bis-MSB – POPOP Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 * PMT
Comparison solvents: Light yield Solvent Yield (6 g/l PPO) PC 1. 00 Anisole 0. 81 PXE 0. 88 LAB 0. 74 Dodecan 0. 40 Oil 0. 33 MPIK measurements Christian Buck MPIK Heidelberg M. Chen, INT Workshop 2005 Reims, Neutrino Champagne 2009
Comparison solvents: Attenuation length MPIK measurements (UV/Vis, 10 cm cell) Christian Buck MPIK Heidelberg M. Wurm (TUM), ANT 2009 Reims, Neutrino Champagne 2009
Purification methods Ø Column purification – Radioimpurities – Optics Ø N 2 purging – Radon, 85 Kr – Light yield (oxygen) Ø Water extraction – Radioimpurities (e. g. 40 K) Ø Distillation – Radioimpurities – Optics Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Purification methods Ø Column purification – Radioimpurities CTF – Optics Ø N 2 purging – Radon, 85 Kr LAK – Light yield (oxygen) Ø Water extraction – Radioimpurities Ø Distillation – Radioimpurities Solar neutrino – Optics phase Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 Kam. Land Borexino
Borexino Background 40 K < 3 ∙ 10 -18 g/g 238 U: 1. 6 ± 0. 1∙ 10 -17 g/g 232 Th: 6. 8 ± 1. 5∙ 10 -18 g/g Christian Buck MPIK Heidelberg PRL 101, 091302 (2008) Reims, Neutrino Champagne 2009
LAB Ø LAB is proposed in SNO+, Daya Bay, RENO Ø New high light yield, transparent solvent? – Used since decades – Average light yield – Average transparency Ø It is a high flash point, low toxicity solvent at moderate cost and reasonable optics, LAB (6 g/l PPO) Ø …but: PXE (6 g/l PPO) – Mixture – Biphenyls (absorption/emission!) – Timing properties Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Solvent mixtures 6 g/l PPO C. Aberle, diploma thesis, MPIK (2008) Light yield [% standard] Advantage: Parameters tuneable Ø optimize material compatibility Ø change timing properties Ø match density Ø adjust light yield Light production in alkanes Ø Radiation creates e-- - hole pairs Ø Recombination, fragmentation, radicals, reactions excited molecules energy transfer to fluors PXE (mass fraction) M. Wurm, diploma thesis, TUM(2005) Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Comparison fluors PPO • transparent • well established • high quantum yield BPO • high(est) light yield • emission around 400 nm • absorption properties • limited availibility (Butyl-)PBD p. TP • high light yield • fast • overlap with bis-MSB • poor quantum yield • costs • low solubility • poor quantum yield 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: Donor * Acceptor 50 % Photon emission, decay Energy transfer Critical conc. : For PPO < 1 g/l in PXE, PC, … For PPO ~ 2. 1 g/l in dodecane Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
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) Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
![Timing properties Events Gamma Catcher candidates Target Time [ns] C. Aberle, Diploma thesis, MPIK](http://slidetodoc.com/presentation_image/381fdac6cf7d3f06bc30fcaa6cb29b65/image-19.jpg "Timing properties Events Gamma Catcher candidates Target Time [ns] C. Aberle, Diploma thesis, MPIK")
Timing properties Events Gamma Catcher candidates Target Time [ns] C. Aberle, Diploma thesis, MPIK Heidelberg (2008) D. Motta (CEA Saclay): pulse shape to tag events in different detector regions Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Metal loaded scintillators Ø Solar neutrinos (LENS, SIREN): – Metal: Ytterbium, Indium, Gadolinium – Challenge: High loadings Ø Reactor (Double Chooz, Daya Bay, RENO) – Metal: Gadolinium – Challenge: Stability Ø ββ-decay (SNO+) – Metal: Neodymium – Challenges: transparency; purity Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Indium-loaded scintillators at LLBF > 1 year (2003/04) Ø MPIK: In(acac)3 (F. X. Hartmann et al. ) > 50 g/l Indium Ø INR/LNGS: Carboxylic acid version 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. 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) 238 -243. • M. Yeh et al. , NIM A 578 (2007) 329 -339. Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009 ar. Xiv: 0803. 1577 v 1 [physics. ins-det] 11 Mar 2008
Gadolinium (β-diketones) Ø Purified by sublimation Ø stability/compatibility tests > 4 y Ø att. length (1 g/l) > 50 m in ROI Ø 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) ar. Xiv: 0909. 2152 v 1 [physics. ins-det] 11 Sep 2009 Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
Summary Ø Liquid scintillators key technology for upcoming large scale neutrino detectors Ø Many solvent and fluor candidates - Choice depends on application and detector characteristics - Requirement for „safe“ scintillators (PXE, LAB, …) Ø Energy transfer models allow light yield predictions Ø Several applications for metal loaded scintillators significant improvement in last years (stability etc. ) Christian Buck MPIK Heidelberg Reims, Neutrino Champagne 2009
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