plus interaction with neutrons from fission and (αααα,n...
Transcript of 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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
background level at shallow depth
depth dependence of background inducing muons and neutrons
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
energy [kev]
[ co
unts
per
ch
anne
l an
d d
ay]
iron no veto
lead with veto
lead no veto
Fe or Pb
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
muonic bremsstrahlung
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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]
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
222Rn protection of BOREXINO
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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
199 ± 4115 ± 3Cryostat of ANG4
927 ± 46105 ± 5Cryostat of ANG3
78 ± 2291 ± 4Cryostat of ANG2
236 ± 61168 ± 8Cryostat of ANG1
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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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
G.H., Int. student workshop on ν-less ββ-decay, LNGS, 11.11.10
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