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J M Sisterson - One of the best experts on this subject based on the ideXlab platform.
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cross section measurements for proton induced reactions in fe and ni producing relatively short lived radionuclides at ep 140 500 mev
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006Co-Authors: J M Sisterson, J VincentAbstract:Abstract Cross sections for proton-induced reactions in Fe and Ni targets that produce relatively short-lived radionuclides were measured at several proton energies between 140 and 500 MeV. There are few reported measured cross sections for these reactions in this energy range and these new measurements ‘help fill in the gap’ between the many measurements at lower proton energies and the few measurements at higher energies. Thin target techniques were used in these measurements made at two accelerator facilities. Most of these radionuclides are produced in cosmic ray interactions with extraterrestrial materials and have been measured in meteorites and Lunar Rocks. Cross sections for proton-induced reactions are essential input to the theoretical models used to interpret these cosmogenic nuclide archives to learn more about the object itself or the history of the cosmic rays that fell upon it. These new cross section measurements will improve the database used as input in these analyses.
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measurement of proton production cross sections of 10be and 26al from elements found in Lunar Rocks
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1997Co-Authors: J M Sisterson, K Kim, A Beverding, P A J Englert, Marc W Caffee, A J T Jull, D J Donahue, L R Mchargue, C M Castaneda, J VincentAbstract:Cosmic rays penetrate the Lunar surface and interact with the Lunar Rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in Lunar Rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in Lunar Rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and {similar_to}87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of Lunar Rocks. We have reported already {sup 14}C production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x){sup 10}Be from 58 160 MeV[6]. Here we present new measurements for the cross sections O(p,x){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV.
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measuring excitation functions needed to interpret cosmogenic nuclide production in Lunar Rocks
The fourteenth international conference on the application of accelerators in research and industry, 1997Co-Authors: J M Sisterson, K Kim, A Beverding, P A J Englert, Marc W Caffee, J Vincent, C Castaneda, R C ReedyAbstract:Radionuclides produced in Lunar Rocks by cosmic ray interactions are measured using Accelerator Mass Spectrometry or gamma-ray spectroscopy. From these measurements, estimates of the solar proton flux over time periods characterized by the half-life of the isotope under study can be made, if all the cross sections for all the reactions of all cosmic ray particles with all elements found in Lunar Rocks are known. Proton production cross sections are very important because ∼98% of solar cosmic rays and ∼87% of galactic cosmic rays are protons in the Lunar environment. Many of the needed cross sections have never been measured. Targets of C, Al, Si, SiO2, Mg, K, Ca, Fe and Ni have been irradiated using three accelerators to cover a proton energy range of 25–500 MeV. Excitation functions for 7Be, 10Be, 22Na, and 26Al production from Mg and Al will be reported, and the consequences of using these new cross section values to estimate solar proton fluxes discussed.
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measurement of proton production cross sections of sup 10 be and sup 26 al from elements found in Lunar Rocks
Radiocarbon, 1996Co-Authors: J M Sisterson, P A J Englert, Marc W Caffee, A J T Jull, D J Donahue, L R Mchargue, J Vincent, C Castaneda, Kyeong Ja Kim, R C ReedyAbstract:Cosmic rays penetrate the Lunar surface and interact with the Lunar Rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in Lunar Rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in Lunar Rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and {similar_to}87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of Lunar Rocks. We have reported already {sup 14}C production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x){sup 10}Be from 58 160 MeV[6]. Here we presentmore » new measurements for the cross sections O(p,x){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV.« less
Arnold I Boothroyd - One of the best experts on this subject based on the ideXlab platform.
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our sun v a bright young sun consistent with helioseismology and warm temperatures on ancient earth and mars
The Astrophysical Journal, 2003Co-Authors: Juliana I Sackmann, Arnold I BoothroydAbstract:The relatively warm temperatures required on early Earth and Mars have been difficult to account for via warming from greenhouse gases. We tested whether this problem can be resolved for both Earth and Mars by a young Sun that is brighter than predicted by the standard solar model (SSM). We computed high-precision solar evolutionary models with slightly increased initial masses of Mi = 1.01-1.07 M☉; for each mass, we considered three different mass-loss scenarios. We then tested whether these models were consistent with the current high-precision helioseismic observations. The relatively modest mass-loss rates in these models are consistent with observational limits from young stars and estimates of the past solar wind obtained from Lunar Rocks and do not significantly affect the solar lithium depletion. For appropriate initial masses, all three mass-loss scenarios are capable of yielding a solar flux 3.8 Gyr ago high enough to be consistent with water on ancient Mars. The higher flux at the planets is due partly to the fact that a more massive young Sun would be intrinsically more luminous and partly to the fact that the planets would be closer to the more massive young Sun. At birth on the main sequence, our preferred initial mass Mi = 1.07 M☉ would produce a solar flux at the planets 50% higher than that of the SSM, namely, a flux 5% higher than the present value (rather than 30% lower, which the SSM predicts). At first (for 1-2 Gyr), the solar flux would decrease; subsequently, it would behave more like the flux in the SSM, increasing until the present. We find that all of our mass-losing solar models are consistent with the helioseismic observations; in fact, our preferred mass-losing case with Mi = 1.07 M☉ is in marginally (although insignificantly) better agreement with the helioseismology than is the SSM. The early solar mass loss of a few percent does indeed leave a small fingerprint on the Sun's internal structure. However, for helioseismology to significantly constrain early solar mass loss would require higher accuracy in the observed solar parameters and input physics, namely, by a factor of ~3 for the observed solar surface composition and a factor of ~2 for the solar interior opacities, the p-p nuclear reaction rate, and the diffusion constants for gravitational settling.
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our sun v a bright young sun consistent with helioseismology and warm temperatures on ancient earth and mars
arXiv: Astrophysics, 2002Co-Authors: Juliana I Sackmann, Arnold I BoothroydAbstract:The relatively warm temperatures required on early Earth and Mars have been difficult to account for via warming from greenhouse gases. We tested whether this problem can be resolved for both Earth and Mars by a young Sun that is brighter than predicted by the standard solar model. We computed high-precision solar evolutionary models with slightly increased initial masses of M_i = 1.01 to 1.07 M_sun; for each mass, we considered three different mass loss scenarios. We then tested whether these models were consistent with the current high-precision helioseismic observations. The relatively modest mass loss rates in these models are consistent with observational limits from young stars and estimates of the past solar wind obtained from Lunar Rocks, and do not significantly affect the solar lithium depletion. For appropriate initial masses, all three mass loss scenarios are capable of yielding a solar flux 3.8 Gyr ago high enough to be consistent with water on ancient Mars. We find that all of our mass-losing solar models are consistent with the helioseismic observations. The early solar mass loss of a few percent does indeed leave a small fingerprint on the Sun's internal structure. However, for helioseismology to significantly constrain early solar mass loss would require higher accuracy in the observed solar parameters and input physics, namely, by a factor of about 3 for the observed solar surface composition, and a factor of 2 for the solar interior opacities, the pp nuclear reaction rate, and the diffusion constants for gravitational settling.
J Vincent - One of the best experts on this subject based on the ideXlab platform.
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cross section measurements for proton induced reactions in fe and ni producing relatively short lived radionuclides at ep 140 500 mev
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2006Co-Authors: J M Sisterson, J VincentAbstract:Abstract Cross sections for proton-induced reactions in Fe and Ni targets that produce relatively short-lived radionuclides were measured at several proton energies between 140 and 500 MeV. There are few reported measured cross sections for these reactions in this energy range and these new measurements ‘help fill in the gap’ between the many measurements at lower proton energies and the few measurements at higher energies. Thin target techniques were used in these measurements made at two accelerator facilities. Most of these radionuclides are produced in cosmic ray interactions with extraterrestrial materials and have been measured in meteorites and Lunar Rocks. Cross sections for proton-induced reactions are essential input to the theoretical models used to interpret these cosmogenic nuclide archives to learn more about the object itself or the history of the cosmic rays that fell upon it. These new cross section measurements will improve the database used as input in these analyses.
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measurement of proton production cross sections of 10be and 26al from elements found in Lunar Rocks
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 1997Co-Authors: J M Sisterson, K Kim, A Beverding, P A J Englert, Marc W Caffee, A J T Jull, D J Donahue, L R Mchargue, C M Castaneda, J VincentAbstract:Cosmic rays penetrate the Lunar surface and interact with the Lunar Rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in Lunar Rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in Lunar Rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and {similar_to}87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of Lunar Rocks. We have reported already {sup 14}C production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x){sup 10}Be from 58 160 MeV[6]. Here we present new measurements for the cross sections O(p,x){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV.
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measuring excitation functions needed to interpret cosmogenic nuclide production in Lunar Rocks
The fourteenth international conference on the application of accelerators in research and industry, 1997Co-Authors: J M Sisterson, K Kim, A Beverding, P A J Englert, Marc W Caffee, J Vincent, C Castaneda, R C ReedyAbstract:Radionuclides produced in Lunar Rocks by cosmic ray interactions are measured using Accelerator Mass Spectrometry or gamma-ray spectroscopy. From these measurements, estimates of the solar proton flux over time periods characterized by the half-life of the isotope under study can be made, if all the cross sections for all the reactions of all cosmic ray particles with all elements found in Lunar Rocks are known. Proton production cross sections are very important because ∼98% of solar cosmic rays and ∼87% of galactic cosmic rays are protons in the Lunar environment. Many of the needed cross sections have never been measured. Targets of C, Al, Si, SiO2, Mg, K, Ca, Fe and Ni have been irradiated using three accelerators to cover a proton energy range of 25–500 MeV. Excitation functions for 7Be, 10Be, 22Na, and 26Al production from Mg and Al will be reported, and the consequences of using these new cross section values to estimate solar proton fluxes discussed.
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measurement of proton production cross sections of sup 10 be and sup 26 al from elements found in Lunar Rocks
Radiocarbon, 1996Co-Authors: J M Sisterson, P A J Englert, Marc W Caffee, A J T Jull, D J Donahue, L R Mchargue, J Vincent, C Castaneda, Kyeong Ja Kim, R C ReedyAbstract:Cosmic rays penetrate the Lunar surface and interact with the Lunar Rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in Lunar Rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in Lunar Rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and {similar_to}87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of Lunar Rocks. We have reported already {sup 14}C production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x){sup 10}Be from 58 160 MeV[6]. Here we presentmore » new measurements for the cross sections O(p,x){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV.« less
R C Reedy - One of the best experts on this subject based on the ideXlab platform.
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measuring excitation functions needed to interpret cosmogenic nuclide production in Lunar Rocks
The fourteenth international conference on the application of accelerators in research and industry, 1997Co-Authors: J M Sisterson, K Kim, A Beverding, P A J Englert, Marc W Caffee, J Vincent, C Castaneda, R C ReedyAbstract:Radionuclides produced in Lunar Rocks by cosmic ray interactions are measured using Accelerator Mass Spectrometry or gamma-ray spectroscopy. From these measurements, estimates of the solar proton flux over time periods characterized by the half-life of the isotope under study can be made, if all the cross sections for all the reactions of all cosmic ray particles with all elements found in Lunar Rocks are known. Proton production cross sections are very important because ∼98% of solar cosmic rays and ∼87% of galactic cosmic rays are protons in the Lunar environment. Many of the needed cross sections have never been measured. Targets of C, Al, Si, SiO2, Mg, K, Ca, Fe and Ni have been irradiated using three accelerators to cover a proton energy range of 25–500 MeV. Excitation functions for 7Be, 10Be, 22Na, and 26Al production from Mg and Al will be reported, and the consequences of using these new cross section values to estimate solar proton fluxes discussed.
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measurement of proton production cross sections of sup 10 be and sup 26 al from elements found in Lunar Rocks
Radiocarbon, 1996Co-Authors: J M Sisterson, P A J Englert, Marc W Caffee, A J T Jull, D J Donahue, L R Mchargue, J Vincent, C Castaneda, Kyeong Ja Kim, R C ReedyAbstract:Cosmic rays penetrate the Lunar surface and interact with the Lunar Rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in Lunar Rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in Lunar Rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and {similar_to}87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of Lunar Rocks. We have reported already {sup 14}C production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x){sup 10}Be from 58 160 MeV[6]. Here we presentmore » new measurements for the cross sections O(p,x){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV.« less
I G Usoskin - One of the best experts on this subject based on the ideXlab platform.
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energetic particles in Lunar Rocks production of cosmogenic isotopes
2015Co-Authors: Stepan Poluianov, Gennady A Kovaltsov, Anton Artamonov, I G UsoskinAbstract:The era of direct measurements of solar energetic particle (SEP) fluxes is limited to the last few decades and largely overlaps the Modern Grand Maximum of solar activity. However, for many purposes it is important to know the fluxes of SEP on much longer time scale. This can be done only using indirect proxies. Terrestrial ones, such as the nuclides 14C and 10Be in tree trunks and ice cores, may potentially resolve strongest SEP events but cannot evaluate the average SEP flux. On the other hand, Lunar rock samples, collected during the Apollo missions and measured later at the Earth, may provide information on the average fluxes of SEP throughout thousands and millions of years in the past. This option had been explored earlier, and here we revisit the approach, using the newly calculated yield functions of cosmogenic nuclide production in Lunar Rocks and more realistic spectra of solar energetic particles and galactic cosmic rays.
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occurrence probability of large solar energetic particle events assessment from data on cosmogenic radionuclides in Lunar Rocks
Solar Physics, 2014Co-Authors: Gennady A Kovaltsov, I G UsoskinAbstract:We revisited assessments of the occurrence probability distribution of large events in solar energetic particles (SEP), based on measurements of cosmogenic radionuclides in Lunar Rocks. We present a combined cumulative occurrence probability distribution of SEP events based on three timescales: directly measured SEP fluences for the past 60 years; estimates based on the terrestrial cosmogenic radionuclides 10Be and 14C for the multi-millennial (Holocene) timescale; and cosmogenic radionuclides measured in Lunar Rocks on a timescale of up to 1 Myr. These three timescales yield a consistent distribution. The data suggest a strong roll-over of the occurrence probability, so that SEP events with a proton fluence with energy > 30 MeV greater than 1011 (protons cm−2 yr−1) are not expected on a Myr timescale.
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occurrence probability of large solar energetic particle events assessment from data on cosmogenic radionuclides in Lunar Rocks
arXiv: Solar and Stellar Astrophysics, 2013Co-Authors: Gennady A Kovaltsov, I G UsoskinAbstract:We revisited assessments of the occurrence probability distribution of large events in solar energetic particles (SEP), based on measurements of cosmogenic radionuclides in Lunar Rocks. We present a combined cumulative occurrence probability distribution of SEP events based on three time scales: directly measured SEP fluences for the last 60 years; estimates based on terrestrial cosmogenic radionuclides 10Be and 14C for the multi-millennial (Holocene) time scale; and cosmogenic radionuclides measured in Lunar Rocks on the time scale of up to 1 Myr. All the three time scales yield a consistent distribution. The data suggest a strong rollover of the occurrence probability so that SEP events with the fluence of protons with energy >30 MeV greater than 10^{11} (protons /cm2/yr) are not expected at the Myr time scale.
