Produc'on and coun'ng of uncontained sources in SNO. Simon JM Peeters

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1 Produc'on and coun'ng of uncontained sources in SNO Simon JM Peeters

2 Content The SNO experiment Calibra'on of the SNO experiment Produc'on of 222 Rn and 24 Na sources Distribu'on of uncontained radioac've sources Conclusions Registered at this conference Simon JM Peeters, LRT, August

3 Part I THE SUDBURY NEUTRINO OBSERVATORY Simon JM Peeters, LRT, August

4 Sudbury Neutrino Observatory Detector parameters Located 5890±94 mwe 1 ktonne ultra- pure D2O target inside 12 m diameter acrylic vessel 7 ktonnes ultra- pure H2O shielding Cavity with urylon liner Nitrogen blanket 9456 inward + 91 outward 10 PMTs with light concentrators (54% coverage) on 17.8 m diameter support structure Simon JM Peeters, LRT, August

5 Sudbury Neutrino Observatory CC :ν e + d p + p + e ES :ν x + e ν x + e NC :ν x + d p + n + ν x Physics signal Cherenkov light produced by electrons from ES/CC interac'ons NC interac'ons Detec'on of the neutron via: Phase I (2000/2001) Cherenkov light from Compton sca_ered electrons from gammas produced by neutron capture on D 2 O Phase II (2001/2003) Enhanced NC sensi-vity (2 tonnes NaCl) Cherenkov light from Compton sca_ered electrons from gammas produced by neutron capture on 37 Cl Phase III (2005/2006) Array of 3 He propor'onal counters Simon JM Peeters, LRT, August

6 Summary of SNO calibra'on (i) Response to signal- like events Point sources, a.o. : 16 N 6.1 MeV gamma, ~5 MeV Compton sca_ered electron AmBe, 252 Cf Analy'c and MC methods to interpolate between points Very difficult in phase III Simon JM Peeters, LRT, August

7 Summary of SNO calibra'on (ii) Response to background- like events Ex- situ techniques assay D 2 O and H 2 O β-γ gammas from 208 Tl ( 232 Th) and 214 Bi ( 238 U chain) can photo-disintegrate the deuteron In- situ techniques low energy window (4-4.5 MeV) Simon JM Peeters, LRT, August

8 Use of uncontained sources in SNO 222 Rn: : T 1/2 =3.82 d, part of 238 U chain 24 Na: T 1/2 =15 hrs, pd (2.754 MeV gamma), 232 Th-like (1β,2γ) Signal ( 24 Na) Response of the 3 He propor'onal counters making up the Neutral Current Detector array. Precise determina'on of the neutron capture of the Neutral Current Detector array Backgrounds ( 222 Rn and 24 Na) Calibrate the response of the detector electron equivalent energy and isotropy Helped with the determina'on of the detector response to light from the H 2 O Simon JM Peeters, LRT, August

9 Part II SOURCE PRODUCTION Simon JM Peeters, LRT, August

10 222 Rn Produc'on ExtracIon from mine air (D 2 O) Mine air 100 Bq/m 3 Pass to NaOH filters to remove CO 2 and a - 85 C trap to remove water vapour Cryogenic trap, counted in Lucas cells Dissolved in water Samples counted using ex- situ assay methods From 226 Ra (H 2 O) Commercial Pylon source N 2 carrier gas (no CO 2 ) Marinelli beaker for ac'vity measurement on Ge detector No Ra: checked by bubbling carrier gas through water and assay the water ~50 kbq ~100 Bq Simon JM Peeters, LRT, August

11 24 Na produc'on Th source (SNO phase II) 330 kbq Th source(2.6 MeV gamma) inside the fiducial volume SNO (D 2 O +0.2% NaCl) AcIvaIon (SNO phase III) 10% brine (from phase II) SLOWPOKE- 2 (Royal Mil. Coll, Kingston) 3.75 ml, 20 min, 5x10 11 n cm 2 s 1 Injected into 2.5 l D 2 O Pumped into vessel using calibra'on manipulator Phase III acivity measurements Sample on carefully calibrated and checked using a Ge detector Delrin can with sample in the centre of the detector compared to 252 Cf source at the same location: PMT array NCD array Simon JM Peeters, LRT, August

12 Part III MIXING SOURCES INTO SNO Simon JM Peeters, LRT, August

13 Early mixing studies SNO recircula'on systems used to distribute the radio- ac'vity Hard to predict exact water movement: Low viscosity D 2 O Movement of source Temperature difference of injected and target water Th activation data Volume weighted nr of events Simon JM Peeters, LRT, August

14 First spike: Mixing in SNO phase III Based on evidence, inject along z, most in the bo_om. Mixed after 70 hours. Second spike: inject 1-3 C warmer spike at the bo_om. Induced rota'on of the bulk, reverse circula'on. Mixed after 50 hours. 24 Na injection data Simon JM Peeters, LRT, August

15 Conclusions I have discussed the produc'on and applica'on of distributed 24 Na and 222 Rn sources in SNO These techniques have been very useful in the determina'on of the neutron detec'on efficiency and response of to natural radia'on for SNO Similar techniques could be useful for future low- background detectors Simon JM Peeters, LRT, August

16 FIN Simon JM Peeters, LRT, August

17 Simon JM Peeters, LRT, August

18 Simon JM Peeters, LRT, August

19 U/Th decays Simon JM Peeters, LRT, August

20 Event Isotropy Simon JM Peeters, LRT, August

21 Comm. D 2 O Salt (NaCl) D 2 O 3 He Counters n 2 H n captures on deuterium σ = b 6.25 MeV γ 3 H* γ 3 H n captures on chlorine n σ = 44b 8.6 MeV multiple γs 36 Cl γ γ γ 35 Cl * 36 Cl 5 cm n captures on 3 He prop. counter array σ = 5330b MeV 3 H 3 He p n n + 3 He p + 3 H Simon JM Peeters, LRT, August