Zum Kernphotoeffekt am Ar40 und Ar38

Ehhalt, D.; Kosiek, R.; Pfeiffer, R.

doi:10.1007/bf01579586

“…All of the direct production mechanisms of 39 Ar from 40 Ar also apply to the production of 37 Ar from 38 Ar in AAr. We are not aware of any experimental measurements of the cross-sections on 38 Ar except for 38 Ar(γ, n) 37 Ar [80] which is roughly the same as the 40 Ar(γ, n) 39 Ar cross-section. We have therefore estimated the production rate from reactions on 38 Ar by taking the sum of the production rates from all direct 40 Ar(x, y) 39 Ar mechanisms ((679 ± 85) atoms/(kg Ar day)) and scaling it by the abundance of 38 Ar in AAr (0.000629).…”

Section: Armentioning

confidence: 91%

“…We verified that the γ flux predicted by the model agreed with experimental measurements [79] to within 20% in the energy range of interest (10-30 MeV), which we used as our estimate of the systematic uncertainty. Experimental measurements of the 40 Ar(γ, n) 39 Ar cross-section [80][81][82] and the 40 Ar(γ, p) 39 Cl cross-section [80,82] are shown in Figure 8. Where multiple measurements exist we have used the mean and sample standard deviation of the calculated production rates as our estimates of the central value and uncertainty.…”

Section: CLmentioning

confidence: 99%

Cosmogenic production of Ar39 and Ar37 in argon

Saldanha

¹

,

Back

²

,

Tsang

³

et al. 2019

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We have experimentally determined the production rate of 39 Ar and 37 Ar due to cosmic ray neutron interactions in argon at sea level. Understanding these production rates is important for argon-based dark matter experiments that plan to utilize argon extracted from deep underground because it is imperative to know what the ingrowth of 39 Ar will be during the production, transport, and storage of the underground argon. These measurements also allow for the prediction of 39 Ar and 37 Ar concentrations in the atmosphere which can be used to determine the presence of other sources of these isotopes. Through controlled irradiation with a neutron beam that mimics the cosmic ray neutron spectrum, followed by direct counting of 39 Ar and 37 Ar decays with sensitive ultra-low background proportional counters, we determined that the production rate from cosmic ray neutrons at sea-level is expected to be (759 ± 128) atoms/(kg Ar day) for 39 Ar, and (51.0 ± 7.4) atoms/(kg Ar day) for 37 Ar. We also performed a survey of the alternate production mechanisms based on the state-of-knowledge of the associated cross-sections to obtain a total sea-level cosmic ray production rate of (1048 ± 133) atoms/(kg Ar day) for 39 Ar, (56.7 ± 7.5) atoms/(kg Ar day) for 37 Ar in underground argon, and (92 ± 13) atoms/(kg Ar day) for 37 Ar in atmospheric argon.

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“…All of the direct production mechanisms of 39 Ar from 40 Ar also apply to the production of 37 Ar from 38 Ar in AAr. We are not aware of any experimental measurements of the cross-sections on 38 Ar except for 38 Ar(γ, n) 37 Ar [80] which is roughly the same as the 40 Ar(γ, n) 39 Ar cross-section. We have therefore estimated the production rate from reactions on 38 Ar by taking the sum of the production rates from all direct 40 Ar(x, y) 39 Ar mechanisms ((679 ± 85) atoms/(kg Ar day)) and scaling it by the abundance of 38 Ar in AAr (0.000629).…”

Section: Armentioning

confidence: 91%

“…We verified that the γ flux predicted by the model agreed with experimental measurements [79] to within 20% in the energy range of interest (10-30 MeV), which we used as our estimate of the systematic uncertainty. Experimental measurements of the 40 Ar(γ, n) 39 Ar cross-section [80][81][82] and the 40 Ar(γ, p) 39 Cl cross-section [80,82] are shown in Figure 8. Where multiple measurements exist we have used the mean and sample standard deviation of the calculated production rates as our estimates of the central value and uncertainty.…”

Section: CLmentioning

confidence: 99%

Cosmogenic production of $^{39}$Ar and $^{37}$Ar in argon

Saldanha,

Back,

Tsang

et al. 2019

Preprint

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We have experimentally determined the production rate of 39 Ar and 37 Ar from cosmic ray neutron interactions in argon at sea level. Understanding these production rates is important for argon-based dark matter experiments that plan to utilize argon extracted from deep underground because it is imperative to know what the ingrowth of 39 Ar will be during the production, transport, and storage of the underground argon. These measurements also allow for the prediction of 39 Ar and 37 Ar concentrations in the atmosphere which can be used to determine the presence of other sources of these isotopes. Through controlled irradiation with a neutron beam that mimics the cosmic ray neutron spectrum, followed by direct counting of 39 Ar and 37 Ar decays with sensitive ultra-low background proportional counters, we determined that the production rate from cosmic ray neutrons at sea-level is expected to be (759 ± 128) atoms/(kg Ar day) for 39 Ar, and (51.0 ± 7.4) atoms/(kg Ar day) for 37 Ar. We also performed a survey of the alternate production mechanisms based on the state-of-knowledge of the associated cross-sections to obtain a total sea-level cosmic ray production rate of (1048 ± 133) atoms/(kg Ar day) for 39 Ar, (56.7 ± 7.5) atoms/(kg Ar day) for 37 Ar in underground argon, and (92 ± 13) atoms/(kg Ar day) for 37 Ar in atmospheric argon.

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