Low Counting Experimental Techniques 3th lecture: Detectors for low counting experiments 1: scintillation, Cherenkov, semiconductors Fedor Danevich Institute for Nuclear Research, Kyiv, Ukraine http://lpd.kinr.kiev.ua [email protected] [email protected] 1 F.A. Danevich Univ. Tor Vergata November 24, 2015 • Brief summary of the 2nd lecture The main sources of background, natural radioactivity The main sources of background are: • Environmental radioactivity (mainly the natural radioactivity) • Cosmic rays • Neutron induced background • Cosmogenic activation • Artificial radioactivity • Noise, events pile-up The most valuable gamma quanta come from 40K and daughters of 232Th, 238U The secular equilibrium is typically broken in materials which have been subjected to physical and chemical treatment due to different physical and chemical properties of daughter elements 2 F.A. Danevich Univ. Tor Vergata November 24, 2015 • Brief summary of the 2nd lecture Main components of cosmic rays The Electromagnetic To suppress the Muons penetrate for component can be suppressed Hadronic kilometers underground by tens cm of metal (lead, component one copper, steel) need to go 5-10 m underground CdWO4 crystal scintillator 77 cm no shield GIOVE = Germanium Spectrometer with Inner and induced 5 cm lead + 10 cm copper Outer Veto (Max-Planck-Institut, muons Heidelberg) 0.5 3 F.A. Danevich Univ. Tor Vergata November 24, 2015 • Brief summary of the 2nd lecture Cosmogenic activation environmental, material of detector, in-situ Permanent production of cosmogenic radionuclides under cosmic rays irradiation (e.g. 3H, 7Be, 10Be, 14C, 36Cl) Cosmogenic activation of detector materials Cosmogenic activation of materials can be calculated with reasonable accuracy: COSMO, ACTIVIA packages Cosmogenic activation in-situ (short living radioactivity, which nevertheless cannot be vetoed by anti-coincidence counters due to increase of data acquisition dead time) 4 F.A. Danevich Univ. Tor Vergata November 24, 2015 • Brief summary of the 2nd lecture Neutron induced background recoils, production of radioactive nuclides, high energy Neutron induced recoils in the CRESST cryogenic dark matter experiment (neutron calibration data) Neutron induced quanta (neutron caption) in gammas after CdWO cryogenic scintillating bolometer (to neutron capture 4 113 search for 02 decay) on Cd Internal alphas Radioactivity can be produced by neutrons in the details of experimental set-up (e.g. radioactive 116In from 115In) Main sources of neutrons: cosmic rays, spontaneous fusion of uranium, (,n) reactions 5 F.A. Danevich Univ. Tor Vergata November 24, 2015 • Brief summary of the 2nd lecture Anthropogenic radioactivity nuclear reactor disasters, bomb tests, careless handling of radioactive sources The total activity of radioactive materials after the Chernobyl disaster is 5.2·1018 Bq (Fukushima: 0.3-0.8 ·1018 Bq, continues) Chernobyl reactor after the disaster in 1986 Activity of 137Cs in atmosphere after the nuclear bomb tests 244 Cm (?) on ZnMoO4 crystal in the EDELWEISS set-up (Modane Underground Lab, France) 6 F.A. Danevich Univ. Tor Vergata November 24, 2015 • Brief summary of the 2nd lecture Electronic noise, events pile-up PMT noise in scintillation PMT noise experiments Any detector produce noise and spectrum of 14C wrong signals spectrum of 113Cd The main ways to suppress: • Pulse-shape discrimination • Stability of signal in time 2nd event Randomly coinciding events in cryogenic 1th event detector become to be the main source of background in 02 experiments with 100Mo Randomly coinciding event in cryogenic detector 7 F.A. Danevich Univ. Tor Vergata November 24, 2015 Short baseline experiments: LSND unexplained νe appearance in a νμ beam at a short distance [1] J. Link, Short baseline experiments , talk at TAUP 2015, Torino, Sep 7-12, 2015, http://www.taup-conference.to.infn.it/2015/day4/plenary/link.pdf [2] C.Athanassopoulos et al., Results on νμ→νe Neutrino Oscillations from the LSND Experiment, PRL 81 (1998) 1774 8 F.A. Danevich Univ. Tor Vergata November 24, 2015 Short baseline experiments: MiniBooNE the LSND result was not confirmed J. Link, Short baseline experiments , talk at TAUP 2015, Torino, Sep 7-12, 2015, 9 F.A. Danevich Univ. Tor Vergata November 24, 2015 Ongoing and future of short baseline experiments J. Link, Short baseline experiments , talk at TAUP 2015, Torino, Sep 7-12, 2015, 10 F.A. Danevich Univ. Tor Vergata November 24, 2015 11 F.A. Danevich Univ. Tor Vergata November 24, 2015 Long baseline experiments: T2K, MINOS disappearance of , appearance of e T2K MINOS Reconstructed energy spectra for e CC candidate events in the Far Detector. The black points indicate the experimental data. The histogram indicates the expected background (unfilled area) together with the contribution of e signal (hatched 2 area) for the best-fit value of sin (213) = 0.041 [1] P. Adamson et al., Improved Search for Muon-Neutrino to Electron-Neutrino Oscillations in MINOS Phys. Rev. Lett. 107 (2011) 181802 12 F.A. Danevich Univ. Tor Vergata November 24, 2015 Long baseline experiments: OPERA appearance of tau-neutrino A.Palazzo Sterile neutrinos, talk at TAUP 2015, torino, Sep 7-12, 2015 http://www.taup-conference.to.infn.it/2015/day3/plenary/palazzo.pdf 13 F.A. Danevich Univ. Tor Vergata November 24, 2015 Long baseline experiments started: NOA disappearance of , appearance of e NOA Brian Rebel (Fermilab) The NOvA Experiment, talk at TAUP 2015, torino, Sep 7-12, 2015 14 F.A. Danevich Univ. Tor Vergata November 24, 2015 in this lecture: • Scintillation detectors • Cherenkov counters • Semiconductor detectors 15 F.A. Danevich Univ. Tor Vergata November 24, 2015 Characteristics of detectors NaI(Tl) scintillator 60Со • Energy resolution • Time resolution • Coordinate resolution • Dead time HPGe • Density, Zeff (detection efficiency) • Composition (presence of certain elements) • Available volume • Radiopurity • Operational stability 16 F.A. Danevich Univ. Tor Vergata November 24, 2015 Scintillation detectors principle of operation , , , … escape Scintillator Light guide Photomultiplier: principle of operation (optional) Scintillation photons * Photoelectron Photo-detector (electron hole pair) Photomultiplier: quantum efficiency 17 F.A. Danevich Univ. Tor Vergata November 24, 2015 Scintillation detectors photodetectors • Photomultiplier tubes (PMT) – most commonly used in APP experiments (quantum efficiency QE ~ 20%-35%) • Photodiodes – too small working area, but very high QE ~ 70% • Silicon photomultipliers (SiPM) – started to use 76 mm 20-inch 20.5 mm 10 mm S8664-1010 Excellent energy resolution high quantum metal package hemispherical Si Avalanche achieved with avalanche efficiency R6233- R8520-406 R1449 and R3600 photodiode photodiode (APD) 16 mm size [1] 100 [1] M. Moszynski et al., IEEE TNS 46 (1999) 880 18 F.A. Danevich Univ. Tor Vergata November 24, 2015 Silicon photomultipliers (SiPM) avalanche photodiode array Typical size of one element is 0.02 - 0.1 mm Simple read out Photomultiplier Tube Avalanche SiPM Active area Photodiode Quantum Efficiency 25% … 40% … 80% … 80% Single Photon • – • Resolution Operation Voltage 1 - 3 kV 100 - 500 V 20 - 80 V 4 9 5 7 Gain 10 - 10 30 - 300 10 - 10 Insensitivity to – • • Magnetic Field Miniaturization – • • Production Costs Medium Low Potentially Low http://www.ketek.net/ 19 Scintillation detectors scintillators • Organic crystals (anthracene, stilbene, p-terphenyl, …) Plastic Liquid • Inorganic NaI(Tl), CsI(Tl), CsI(Na), BGO, CdWO4, PbWO4, YAG(Ce), GSO(Ce), LSO(Ce), CaF2(Eu), CaWO4, ZnWO4, LaBr3(Ce), CeCl3, … • Nobble gases (Xe, Ar, …) • Gaseous • Ceramic (glasses, nano-ceramic) 20 F.A. Danevich Univ. Tor Vergata November 24, 2015 Scintillation detectors energy resolution NaI(Tl) crystal scintillator Energy resolution of scintillation detector [1]: 2 2 2 2 (E/E) = (sc) + (p) +(st) , sc intrinsic resolution of scintillator, p photoelectrons (electron-hole – pairs) statistical contribution, st photodetector noise contribution Intrinsic resolution (R) of scintillators [2]: RRR2 2 2 R2 La(Br,Cl) :Ce i np inh nu 3 2 R np non-proportional response of scintillator; 2 inhomogeneity of scintillator Rnp 2 Rnu non-uniformity of light collection [1] M. Moszynski et al., IEEE TNS 46 (1999) 880 [2] P. Dorenbos, IEEE TNS 45 (1995) 2190 21 F.A. Danevich Univ. Tor Vergata November 20, 2015 Scintillation detectors decay kinetics, pulse-shape discrimination, time resolution Decay time Rise-time CaWO4 9 s Plastic 4 s scintillator 0.3 s Scintillator eff (s) Liquid and plastic scintillators 0.005 Aii decay constants, = i eff A its intensities PbWO4 0.01 Ai i NaI(Tl) 0.2 CaWO4 8 ZnWO4 24 22 F.A. Danevich Univ. Tor Vergata November 24, 2015 Temperature dependence of scintillation properties ZnWO4 [1], PbWO4 [2] [1] H. Kraus et al., ZnWO4 scintillators for cryogenic dark matter experiments, NIMA 600 (2009) 594 [2] F.A. Danevich et al., Feasibility study of PbWO4 and PbMoO4 crystal scintillatorsforcryogenic rare eventsexperiments, NIMA A 622 (2010) 608 23 F.A. Danevich Univ. Tor Vergata November 24, 2015 Scintillation detectors quenching (/ ratio) CaWO4 [1] CdWO4 [2] / ratio = E / E [1] Yu.G. Zdesenko et al., NIMA 538 (2005) 657 [2] P.G. Bizzeti et al., NIMA 696 (2012) 144 24 F.A. Danevich Univ. Tor Vergata November 24, 2015 Application of scintillation detectors inorganic scintillators Solotvina experiment: 2 decay of 116 116 Cd ( CdWO4) Plastic active shield CdWO4 116 CdWO4 crystal ~0.5 kg Plastic light guide F.A.Danevich et al., Phys. Rev. C 68 (2003) 035501 25 F.A. Danevich Univ. Tor Vergata November 24, 2015 Scintillation detectors energy resolution NaI(Tl) crystal scintillator Energy resolution of scintillation detector [1]: 2 2 2 2 (E/E) = (sc) + (p) +(st) , sc intrinsic resolution of scintillator, p photoelectrons (electron-hole – pairs) statistical contribution, st photodetector noise contribution Intrinsic resolution (R) of scintillators [2]: RRR2 2 2 R2 La(Br,Cl) :Ce i np inh nu 3 2 R np non-proportional response of scintillator; 2 inhomogeneity of scintillator Rnp 2 Rnu non-uniformity of light collection [1] M. Moszynski et al., IEEE TNS 46 (1999) 880 [2] P. Dorenbos, IEEE TNS 45 (1995) 2190 26 F.A.