plus interaction with neutrons from fission and (αααα,n...

plus interaction with neutrons from fission and (αααα,n) reactionsG.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10

interaction with cosmic muons and neutrons

• direct

• activation

cosmic rays

G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10

cosmogenic production rates in Cu at sea level

Cebrian et al., Astrop. Phys.33 (2010) 316-329

M. Laubenstein, G. Heusser, Appl. Radiat. Isot. 67

(2009) 750-754

radionuclide halflife production rate (saturation activity) [µµµµBq/kg]

cosmogenic exposed unexposed estimated*

56Co 77.31 d 230 ± 30 557

57Co 271.83 d 1800 ± 400 2147

58Co 70.86 d 1650 ± 90 3878

60Co 5.27 y 2100 ± 190 < 10 2367

54Mn 312.15 d 828 ± 82 791

59Fe 44.5 d 118 ± 32 157

46Sc 83.79 d 53 ± 18 93

48V 15.97 d 110 ± 40

primordial

226Ra (U) 1600 y < 35 < 16

228Th (Th) 1.91 y < 20 < 19

40K 1.277x109 y < 120 < 110

Cosmic ray induced isotopes in stainless steel (FeCrNiMo) measured for GERDA

Steel 457.1 activity [mBq/kg] sample cosmogenic radionuclide

T1/2 →→→→

7Be 53.3 d

54Mn 312.2 d

58Co 70.9 d

56Co 77.3 d

46Sc 83.8 d

48V 16.0 d

Production →→→→ channels

spallation 56Fe(n,p2n) (µ-,ν2n)

60Ni(n,p2n) (µ-,ν2n)

58Ni(n,p)

58Ni(n,p2n) (µ-,ν2n)

48Ti(n,p2n) (µ-,ν2n)

spallation on Fe

50Cr(n,p2n) (µ-,ν2n)

spallation on Fe

G1 ≤ 3.9 1.3±0.4 0.67±0.34 ≤ 0.32 ≤ 0.35 0.30±0.11

G2 ≤ 3.0 1.5±0.1 0.99±0.12 0.17±0.06 0.24±0.06 0.36±0.07

G3 ≤ 5.7 0.92±0.24 0.56±0.23 ≤ 0.62 ≤ 0.54 0.27±0.11

G4 9.6±2.9 2.0±0.3 0.71±0.26 ≤ 0.71 ≤ 0.67 0.31±0.13

G5 4.8±1.7 1.7±0.2 0.69±0.16 0.28±0.10 0.47±0.14 0.22±0.09

G6 13.6±2.5 1.4±0.2 0.59±0.20 ≤ 0.42 ≤ 0.31 0.40±0.12

G7 ≤ 5.9 1.6±0.3 0.54±0.27 ≤ 0.6 0.61±0.26 0.39±0.13

P.Rate sea level 4.5±0.7 2.7±0.3 0.6±0.09 0.24±0.04 0.22±0.04 0.4±0.04

[(103 sec)-1 kg-1]

irradiation time at sea level:

≈ 200 d

≈ 600 d

all other isotopesare compatiblewith saturation

exposed for 314 dG2


M. Laubenstein, G. Heusser, Appl. Radiat. Isot. 67

(2009) 750-754

ANG2 LNGS, no shield

Heidelberg Moscow

GeMPI

β+

40K137Cs

ThU60Co

60Co

207Bi

0νββ

plus continuous contribution of Ge intrinsic cosmogenics

reached at Heidelberg

difference besideshigher radiopuritydue to: insufficientveto, neutron and muon activation withlonger life time thanthe blocking time and interaction of delayed neutrons


background level at shallow depth

depth dependence of background inducing muons and neutrons


energy [kev]

[ co

unts

per

ch

anne

l an

d d

ay]

iron no veto

lead with veto

lead no veto

Fe or Pb


muonic bremsstrahlung


at 15 mwe production rate still dominated by neutrons

n-induced lines(in Ge β- and β+ decays result not in a line)

surface lab W. Preusse, PhD thesis TU Freiberg

T1/2 = 0.5 s 20.4 msec47.7 s

background of Pb/Cu and veto shielded Ge-detectors at sea level and at shallow depth

at MPI-K low level lab veto active

neutrino-induced muons


J. A. Formaggio, C. J. Martoff,

Annu. Rev. Nucl. Part. Sci. 2004.

54:361–412

muon intensity versus depth

energy [kev]

[ co

unts

per

ch

anne

l an

d m

inut

e]


plated out 222Rn and 220Rn progenies

νννν+e-→→→→ νννν+e-7Be νννν

develop methods to detect noble gas radionuclides and 226Ra (via 222Rn) at the µµµµBq level

provide nitrogen for scintillator purification at the required level

40 Bq/m3 222Rn 1.2 Bq/m3 85Kr 1 mBq/m3 39Ar

100 nBq/m3 39Ar/85Kr

70 µµµµBq/m3 222Rn

solar


222Rn protection of BOREXINO


de = (D/λRn)-2

222Rn diffusion, solubility and permeability

Material description

Diffusion

coeff. D

[10-10

cm2/s]

Solubility

coeff.

S

Permeability

P

[10-8

cm2/s]

Diffusion

length

de [mm]

Polyamid supronyl 6.1 3.4 0.2 0.1

Plexi 6.2 8.2 0.5 0.1

Kalrez 12 12.1 1.4 0.24

Teflon 14 2.3 0.3 0.3

Butyl rubber 49 4.4 2.1 0.5

Rubber soft 1000 12 120 2.2

Natural rubber 17000 9.0

PU hard 88 7.9 6.9 0.6

PU soft 408 5.6 23 1.4

PVC hard 140 5.2 7.3 0.8

PVC soft 420 10 42 1.4

Apiezon M grease 1640 1.6 26.3 2.8

Silicon grease 21200 18.4 3900 10.0

PE – Polyethylene

PU – Polyurethane PVC – Polyvinylchloride

MPI-K and Krakow

Material Sample Rn emanation

[mBq/m²]

Polyurethan 90° Shore 1 O-ring, 8.4 mm * 715 mm, 0.06 m², 150 g < 0.42

Polyurethan 70° Shore 5 flat gasket discs, 0.27 m² < 0.29

Butyl rubber 65° 5 O-rings, 8.4 mm * 715 mm, 0.3 m², 791 g 13 ± 1

Butyl rubber 65 GD 3 flat gasket discs, 0.16 m² 59 ± 3

Butyl rubber 65 GD O-ring, 4 mm * 16 cm < 30

Viton 1 O-ring, 8.4 mm * 715 mm, 0.06 m² 322 ± 8

Viton GF, Batch 97100801 10 O-rings, 3.3 mm * 38 mm, 0.014 m², 23.6 g 75 ± 4

Silicon rubber 10 O-rings, 2.7 mm * 57 mm, 0.015 m², 16g 196 ± 4

Teflon-coated silicon rubber 10 O-rings, 3..5 mm * 57 mm, 0.015 m², 16g 11 ± 2

Teflon foil Foil, 28,5 m² < 0.009

PCTFE Material for valve seat < 0.32

Kalrez O-ring 7 ± 2

Nitril 190 ± 10

Gylon 3510 1 flat gasket disc, 0.006 m², 11.8 g 207 ± 4

Busto 1 flat gasket disc 1750 ± 40

G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10MPI-K

222Rn (226 Ra) emanation data

Nitrogen plant of BOREXINO

SOL LN2-tank @ MPIK


never empty the storage tank completely

activity in nitrogen [µµµµBq/kg]

nitrogen sample 39

Ar a)

85Kr a)

222

Rn b)

regular purity 12 41 40

charcoal purified 12 31 0.4

Charcoal purified liq.extr. < 0.3

Linde Worms (7.0) 0.017 0.07 1

SOL Mantua (7.0) 0.006 0.04

Westfalen Hörstel (6.0) 0.0006 0.06

required 0.4 0.14 6

air ~1.1x104 ~1.2x10

6 ~1x10

7

a) measured by rare-gas MS; 1 ppm Ar = 1.19 µµµµBq/kg; 1 ppt Kr = 1.03µµµµBq/kg

b) measured by concentration and proportional counting

Ar and Kr from different sources


rare gas activity in the atmosphere [m-3] at 15° C and 1 bar

a) strongly variable b) BFS for northern hemisphere c) Collon P. et al. NIM B123 (1997)127d) Loosli H.H. EPSL 63(1983)51 e) Barabash A.S.: Proc Int. workshop on techniques and application of Xenon detectors, Tokyo 2001, WS 2002

radionuclide 222Rn 85Kr 81Kr 39Ar 42Ar/42K

halflife 3.82 d 10.7 y 2.3 E5 y 269 y 32.9y/12.36d

decay mode α β- ε β- β-

decay energy [MeV] 5.59 0.687 0.281 0.565 0.60/3.525

concentration ~ 15 Bqa) ~ 1 Bqb) 2 µBqc) ~ 18 mBqd) ≤ 0.5 µBqe)

main source emanation from soil

nuclear reprocessing

cosmogenic cosmogenic cosmogenic

elem. vol. air conc. [%] ~1x10-18 1.14x10-4 1.14x10-4 0.00934 0.00934

Contamination of Cu [µBq/kg]

Monte Carlo simul.

Ch. Doerr,Uni HD

2002

4 HD-M detectors in one shield

surface contamination

also 70 % of the CUROCINO background is interpreted as surface contamination G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10

≤ 19

26 ± 4

87 ± 4

84 ± 5

10 ± 3

84 ± 7

228Th (Th)

1632 ± 49100 ± 4Cryostat of ANG5

≤ 110≤ 16measured by GeMPI





40K226Ra (U)

localized contamination of HDM detectorsby Monte Carlo simulations

naked Ge-crystals deployed in liquid nitrogen

one out of several

cooling medium, insulator and shield against external radiation

conventional detector crystal gladding

reduction of contact and gladding material: about factor 7000 in mass, 200 in surface

not enough space at LNGS for full shielding by liquid N2/Ar


conclusions

further sensitivity improvements are necessary and feasible

Ge gamma spectroscopy is very essential to screen materials for rare event experiments

more studies on properties and behaviour of 210Po are required


surface contamination needs more attentiongood approach: 210Po plate out studies, as done at Krakowand Ra supported Rn emanation studies

advice

design your low background experiment with plenty safety margins, since there are always surprises and contributions from unexpected sources (double braces)

underground storage and production will become more necessary

do trust Monte Carlo simulations only as far, as verification in each allows

plus interaction with neutrons from fission and (αααα,n...

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