Proton activation of a natural Neodymium target for the SNO+

Proton activation of a natural Neodymium target for the SNO+

Institut für Kern- und Teilchenphysik, DPG 2013
Proton activation of a natural Neodymium
target for the SNO+ experiment
Johannes Petzoldt
Dresden, 7.3.2013
01 Content
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Motivation
Principles of activation
Experimental procedure
Results
Summary
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02 Motivation
Low background experiment (0νββ of 150 Nd)
• Production of long living isotopes via cosm. p + n
• Knowledge of background required
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03 Principles - Activation
R
Activity of Y ∝ RY ∝ σY (E) · φ(E) d E
• Neutron / proton fluxes “known”
• Nearly no experimental σ(E) for Nd
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(Lebeda et al. PhysRevC.85.014602 2012, 10 − 30 MeV)
Measurement → proton activation
• Compare and enhance theoretical databases
(e.g. TENDL, MENDL)
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03 Principles - Dangerous Isotopes for SNO+
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Q-value (150 Nd) = 3371.38 keV
Long living radioisotopes T1/ 2 > 10 d
Direct (Q > 3000 keV)
Indirect (200 keV < Q < 3000 keV)
Feeding-chains
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03 Principles - Dangerous Isotopes for SNO+
• Red: direct background
• Green: indirect/pile-up
• Light blue: Feeding-chains
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04 Activation Experiment
Proton activation → cyclotron U120M (Řež, CZ)
• Cooperation with Dr. O. Lebeda and Ing. J. Štursa
(existing exp. data)
• Ep : 5 − 10 MeV and 30 − 36 MeV
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04 Activation Experiment - Targets
Natural Nd foils (25 µm and 100 µm)
• Highly reactive with air and water
• Coated with Parylene-C (polymeric plastic)
• Thickness measurement via photon absorption with
241
Am
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04 Activation Experiment - Procedure
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2 irradiations, tirr = 1 − 2 h
Each sandwich with 4 Nd targets → 4 data points
Beam current monitored by Ti foils (via nat Ti(p,x)48 V)
Energy steps (1 − 2 MeV) via Cu foils as degraders
End of irradiation = EOB (end of bombardment)
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04 Activation Experiment - Evaluation
Gamma spectrometry with HPGe (ORTEC)
• Several measurements and different distances
• tmeas = 5 min − 27 h
• Net peak area N → AEOB → σ
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05 Results - 147 Nd
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05 Results - 139 Pr
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05 Results - 143 Pm
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05 Results - 144 Pm
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05 Results - 146 Pm
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05 Results - 148m Pm
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06 Summary
Cosmogenic activation of Nd
• Identified dangerous isotopes
• Proton activation experiment
• Cross section measurement → results
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Thanks for your attention!
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07 Backup Slides - Dangerous Isotopes
Isotope
139 Ce
141 Ce
144 Ce
147 Nd
143 Pm
144 Pm
146 Pm
147 Pm
148m Pm
144 Pr
139 Nd
139 Pr
147 Pr
147 Ce
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Type of decay
Q-value (keV)
Indirect/pile-up
β + / EC
264.6
β−
580.7
−
β
318.7
−
β
895
β + / EC
1043
β + / EC
2330
β + / EC or β −
1482 / 1542
β−
224.6
β−
2611
Direct
−
β
2997.5
Feeding
β + / EC
2881.0
β + / EC
2129.0 / 1374.8
β−
2696.9
−
β
3290.0
DPG 2013
Half-life
137.6 d
32.5 d
285 d
10.98 d
266 d
363 d
5.5 y
2.6 y
41.05 d
17.28 min
29.7 min
4.41 h
13.4 min
57.0 s
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07 Backup Slides - Evaluation
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AEOB =
λ·N
t
ηabs ·Iγ · t live ·fw ·fm ·kµ
real
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σ=
• fw
• fm
A0 ·A·Z ·e
NA ·I·ρ·d·(1−e−λtirr )
−λ·tw
=e
- decay between EOB and meas.
−λ·treal
= (1 − e
) - decay while meas.
• kµ - photon absoprtion in the foil
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