1. Pia Loaiza AARM 19-20 March 2010 Background studies for EURECA EURECA The ‘submarine’ (water tank) design: background expected from stainless steel structure The ‘pool’ design: - gamma background from vessel - gamma background from copper - beta background and rejection

2. Pia Loaiza AARM 19-20 March 2010 10 -10 pb goal = no background in 150 000 kg.d Joint effort from teams from EDELWEISS, CRESST, ROSEBUD, CERN, + others… >>100 kg cryogenic experiment, multi- target Part of ILIAS/ASPERA European Roadmap Preferred site: 60 000 m 3 extension of present LSM (4  /m2/d), to be dug in 2011-2012 EURECA

3. Pia Loaiza AARM 19-20 March 2010 0 events -equivalent to ~10 3 kgd arXiv:0905.0753 accepted by PLB Gamma Rejection better than 1 in 10 5 EDELWEISS II: GAMMA REJECTION

4. Pia Loaiza AARM 19-20 March 2010 HALL B: DARK MATTER (EURECA TYPE) Hall B 12000 m 3 Approx. dimensions: 18x15x50 m Internal dimensions (2400 m 3 ): 11x6x46 m water First shielding configuration: the ‘submarine’ design

5. Pia Loaiza AARM 19-20 March 2010 STAINLESS STEEL 226 Ra 228 Th 40 K 60 CoSUM Borexino Steel for flanches Astrop. Phys. 18, 1 (2002) A (mBq/kg) 6.2  1.26.5  1.6 < 13 14  1 Single e - recoils 270000304000< 300006000001208000 Double Chooz Outkumpu P. Loaiza A (mBq/kg) 5  25.5  1.3 < 15 14  2 Single e - recoils 216000260000<340006000001114000 Edelweiss 304L C. Goldbach, G. Nollez A (mBq/kg) 4  25  214  1014  3 Single e - recoils 173000224000320006000001032000 GERDA Ugine&Alz 1.4571 - 316Ti W. Maneschg et al NIM A 593, 448 (2008) A (mBq/kg) < 0.74< 0.41< 1.1 13.8  0.7 Single e - recoils < 32000<19100< 2500593000648000 XENON Fábrica del Campo de Gibraltar, Cádiz 316Ti From L. Baudis, IDM08 A (mBq/kg) < 1.3< 0.9< 7.11.4 Single e - recoils 57000<42000< 1600060200176000 Events from 2cm thick water-tank per 100 kg Ge per year, 10 keV <E r < 50 keV ~2 ·10 5 Simulations by V. Kudryavtsev et al

6. Pia Loaiza AARM 19-20 March 2010 Gamma background from stainless steel water tank for the ‘submarine’ configuration  10 -10 pb goal = no background in 150 000 kg.d  from stainless steel water-tank: 2 ·10 5 evts/100 kg year = 8 ·10 5 evts in 150 000 kg.d  Gamma rejection factor in EDWII : 1 in 10 5 Untolerable gamma background

7. Pia Loaiza AARM 19-20 March 2010 ‘Pool’ configuration Preliminary layout, to be evolved By CEA/IRFU

8. Pia Loaiza AARM 19-20 March 2010 cryostat Cold Signals in/out Amplis Pure water Radiation level -gamma -neutron neutron gamma

9. Pia Loaiza AARM 19-20 March 2010 Attenuation of gamma-rays by water  Swimming-pool: without water, comparable e recoil event rate expected wrt ‘submarine’ design  Around factor 10 6 - 10 7 attenuation if 3 m water-shield  Different attenuation factors for different energies, hence for K, Co, U series → we expect no gamma-background events in the detectors from water tank vessel in the ‘pool’ design Plot by V. Kudryavtsev et al

10. Pia Loaiza AARM 19-20 March 2010 238 U 232 Th 40 K 60 Co A (ppb)0.01 101 mBq/kg Single e - recoils/year 1.9 ·10 5 4 ·10 5 Gamma background expected from Cu Simulations by V. Kudryavtsev et al Simulation results for e - recoils expected in 500 kg of Ge from copper parts (cryostat=2173 kg + inner parts = 692 kg), 10-50 keV: Copper 226 Ra 228 Th 40 K 60 CoSUM NOSV G. Heusser, LRT2004 A (  Bq/kg) < 20< 23< 90< 10 Single e - recoils/year ~ 2 ·10 4 ~ 4 ·10 3 ~ 2 ·10 4 Which translates to: → roughly, we need the previous Cu purity to get acceptable backg levels

11. Pia Loaiza AARM 19-20 March 2010 Beta background and rejection arXiv:0905.0753v1 EDELWEISS II: beta calibration with a 210 Pb source: Beta backgroundLevel of 210 Pb backg in ROIID rejection factor Residual background Edelweiss (fid. volume Ge)3 evts/kg.d  1 / 10 5  1 / 30 000 kg.d EURECA Ge0.3 evts/kg.d  1 / 10 5  1 / 300 000 kg.d

12. Pia Loaiza AARM 19-20 March 2010 SUMMARY  We have considered the water-tank design: Unacceptable gamma background from the stainless steel structure  Hence, we’ve chosen the ‘pool’ design: - no gammas expected in detectors from the vessel - need cryostat copper with 20  Bq/kg to get reasonable background levels - beta background should not be a problem if the level of surface contamination is improved by a factor 10 – within reach

13. Pia Loaiza AARM 19-20 March 2010 Measurements of extremely low radioactivity levels in stainless steel for GERDA Amount of costly copper to be used depends drastically on the contamination of stainless steel NIM A Vol. 593, 448 (2008), W. Maneschg et al W. Manesch, H. Simgen: Private comm. Commonly available stainless steel : 1.4571 - 316Ti has very low concentrations in primordial radionuclides (Mo content allows high corrosion resistance) Measurement campaign in collaboration with trading company Nironit Samples from different European manufacturers ElementCSiMnPSCrMoNiTi Min (%)16.52.010.5(5xC) Max (%)  0.08  1.00  2.00  0.045  0.015 18.52.513.50.7

14. Pia Loaiza AARM 19-20 March 2010 SampleG2G3G5G6 VendorIlsenburgUgine&AlzAcroniIlsenburg 228 Ra (mB/kg)< 0.86< 1 1.0  0.5 < 1.1 228 Th (mB/kg)<0.11< 0.41 1.5  0.2 <0.27 226 Ra (mB/kg)<0.24< 0.74 1.0  0.6 <0.35 234m Pa (mB/kg)<12< 45 54  16 <38 235 U (mB/kg)<0.63< 1.5 2.5  1.5 < 1.5 40 K (mB/kg)<0.93< 1.1< 0.81< 1.1 60 Co (mB/kg) 14.0  0.113.8  0.718.3  0.713  0.6 137 Cs (mB/kg)<0.16<0.36< 0.1<0.39 7 Be (mB/kg)<3<5.7 4.8  1.713  2.5 54 Mn (mB/kg) 1.5  0.10.92  0.241.7  0.21.4  0.2 58 Co (mB/kg) 0.99  0.120.56  0.230.69  0.160.59  0.2 56 Co (mB/kg) 0.17  0.06 <0.62 0.28  0.10 <0.42 46 Sc (mB/kg) 0.24  0.06 <0.54 0.47  0.14 <0.31 48 V (mB/kg) 0.36  0.070.27  0.110.22  0.090.40  0.12 U < 1 mBq/kg, Th < 1 mBq/kg, 40 K < 1 mBq/kg, 60 Co ~ 10 mBq/kg

15. Pia Loaiza AARM 19-20 March 2010 For easier comparison activities are given as U, Th and K concentrations. For the conversion of 226Ra into U and 228Th into Th secular equilibrium was assumed although this is seldom the case Concentrations in SS used in previous experiments Collab.Ref. / measureDescription 238 U (ppb) mBq/kg 232 Th (ppb) mBq/kg nat K (ppm) mBq/kg 60 Co (mBq/kg) BOREXINOAst.Phys. 18, 1, 2002 AISI304L for SSS 0.37  0.07 4.6  0.9 2.8  0.3 11.4  1.1 < 0.45 < 14 6161 Steel for flanges 0.5  0.1 6.2  1.2 1.6  0.4 6.5  1.6 < 0.42 <13 14  1 Steel for storage vessel 1.4  0.2 17  3 0.9  0.6 3.8  2.6 <0.6 <19 12  2 Steel TK3B for storage vessel 0.4  0.1 5  1 1.2  0.5 5  2 0.13  0.06 4  2 46  3 DOUBLE CHOOZ P. LoaizaOutokumpu 0.41  0.16 5  2 1.4  0.3 5.5  1.3 <0.47 <15 14  2 EDWC. Goldbag and G. Nollez 304L 0.32  0.16 4  2 1.2  0.5 5  2 0.45  0.32 14  10 14  3

16. Pia Loaiza AARM 19-20 March 2010

17. ‘Xenon stainless steel’ 316Ti steel Provider: Nironit Edelstahlhandel GmbH & Co. KG Producer: Fábrica del Campo de Gibraltar, Cádiz Grade of the material : X6CrNiMoTi17-12-2. Works Grade : ACX -280. Need to scan the samples since the 60 Co content may vary with charge number

18. Pia Loaiza AARM 19-20 March 2010 NEMO 3/SUPERNEMO PURE IRON Iron petals for NEMO 3 Will be used also for SuperNemo AK Steel, provider in France, had already get to an ‘understanding’ concerning the screening of the samples prior to the ‘command’ with LAL: Open to their needs. Material 214 Bi ( 226 Ra) (mBq/kg) 208 Tl ( 228 Th) (mBq/kg) 40 K (mBq/kg) 60 Co (mBq/kg) Pure Iron< 0.6< 0.8< 5 1.7  0.4 Pure iron does not rust Cheaper than SS Single recoils from: Electron recoils (vessel - 2 cm thick) U < 0.6 mBq/kg< 26390 Th < 0.8 mBq/kg< 37400 40 K < 5 mBq/kg< 11565 60 Co: 1.7 mBq/kg73100 Sum < 148455 < 1.5 x 10 5 Would need a rejection factor ~ 10 5 if no external shielding