Neutron Fission Cross Sections for 231Th, 233Th, 235U, 237U, 239U, 241Pu, and 243Pu from 0.5 to 2.25 MeV Using (t, pf) Reactions

Cramer, J.D.; Britt, H. C.

doi:10.13182/nse70-a20705

Cited by 109 publications

(51 citation statements)

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“…Although early studies employed the (t,p) reaction as a surrogate [7,8], (p,t) has only been investigated for this purpose very recently [9,10] and only in a preliminary manner.…”

Section: Introductionmentioning

confidence: 99%

Calculations of Compound Nucleus Spin-Parity Distributions Populated via the (p,t) Reaction in Support of Surrogate Neutron Capture Measurements

Benstead¹,

Tostevin²,

Escher³

et al. 2016

EPJ Web of Conferences

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Abstract. The surrogate reaction method may be used to determine the cross section for neutron induced reactions not accessible through standard experimental techniques. This is achieved by creating the same compound nucleus as would be expected in the desired reaction, but through a different incident channel, generally a direct transfer reaction. So far, the surrogate technique has been applied with reasonable success to determine the fission cross section for a number of actinides, but has been less successful when applied to other reactions, e.g. neutron capture, due to a 'spin-parity mismatch'. This mismatch, between the spin and parity distributions of the excited levels of the compound nucleus populated in the desired and surrogate channels, leads to differing decay probabilities and hence reduces the validity of using the surrogate method to infer the cross section in the desired channel. A greater theoretical understanding of the expected distribution of levels excited in both the desired and surrogate channels is therefore required in order to attempt to address this mismatch and allow the method to be utilised with greater confidence. Two neutron transfer reactions, e.g. (p,t), which allow the technique to be utilised for isotopes further removed from the line of stability, are the subject of this study. Results are presented for the calculated distribution of compound nucleus states populated in 90 Zr, via the 92 Zr(p,t) 90 Zr reaction, and are compared against measured data at an incident proton energy of 28.56 MeV.

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“…Although early studies employed the (t,p) reaction as a surrogate [7,8], (p,t) has only been investigated for this purpose very recently [9,10] and only in a preliminary manner.…”

Section: Introductionmentioning

confidence: 99%

Calculations of Compound Nucleus Spin-Parity Distributions Populated via the (p,t) Reaction in Support of Surrogate Neutron Capture Measurements

Benstead¹,

Tostevin²,

Escher³

et al. 2016

EPJ Web of Conferences

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“…The surrogate reaction method was proposed for the first time in the 70's by Cramer and Britt [1]. It is an indirect method which aims at determining compound nucleus reaction cross sections involving short lived and/or difficult-to-produce targets.…”

Section: Introductionmentioning

confidence: 99%

First simultaneous measurement of fission and gamma probabilities of²³⁷U and²³⁹Np via surrogate reactions

Marini¹,

Ducasse²,

Jurado³

et al. 2016

EPJ Web of Conferences

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Abstract. Fission and gamma decay probabilities of 237 U and 239 Np have been measured, for the first time simultaneously in dedicated experiments, via the surrogate reactions 238 U( 3 He, 4 He) and 238 U( 3 He,d), respectively. While a good agreement between our data and neutron-induced data is found for fission probabilities, gamma decay probabilities are several times higher than the corresponding neutron-induced data for each studied nucleus. We study the role of the different spin distributions populated in the surrogate and neutron-induced reactions. The compound nucleus spin distribution populated in the surrogate reaction is extracted from the measured gamma-decay probabilities, and used as input parameter in the statistical model to predict fission probabilities to be compared to our data. A strong disagreement between our data and the prediction is obtained. Preliminary results from an additional dedicated experiment confirm the observed discrepancies, indicating the need of a better understanding of the formation and decay processes of the compound nucleus.

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“…The surrogate method [1] is an indirect measurement technique proposed in the 1970's to overcome these problems, in which a transfer reaction involving light charged particles in the entrance and exit channels is substituted for a direct neutron-induced reaction to produce the same final nuclear system. If the energies of the ingoing and outgoing charged particles are known or measured, then the excitation energy E x of the final nucleus can be deduced and can be related to the equivalent incident neutron energy E n in the following way: (1) 1 () n x n A E E S A   Indirect (n,γ) cross sections of thorium cycle nuclei using the surrogate method for a target nucleus of target mass A and neutron binding energy S n .…”

Section: Introductionmentioning

confidence: 99%

“…If the energies of the ingoing and outgoing charged particles are known or measured, then the excitation energy E x of the final nucleus can be deduced and can be related to the equivalent incident neutron energy E n in the following way: (1) 1 () n x n A E E S A   Indirect (n,γ) cross sections of thorium cycle nuclei using the surrogate method for a target nucleus of target mass A and neutron binding energy S n . The exit channel via which the final nucleus decays can then be detected with a suitable detection system.…”

Section: Introductionmentioning

confidence: 99%

Indirect (n,γ) cross sections of thorium cycle nuclei using the surrogate method

et al. 2012

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Indirect neutron capture (n,γ) cross sections have been extracted for the key thorium cycle nuclei 232 Th, 231 Pa and 230 Th using the surrogate reaction method. Final nucleus gamma decay probabilities were measured between the neutron binding energy and around 1MeV above it using the 232 Th(d,p) 233 Th, 232 Th( 3 He,t) 232 Pa and 232 Th( 3 He,α) 231 Th reactions in experiments with the Cactus gamma-detector array and Silicon Ring charged particle detectors at the Oslo Cyclotron Laboratory. Since the neutron capture cross section for 232 Th is already well known from direct measurements a comparison with these results provides a stringent test of the applicability of the surrogate method in the actinide region for indirect (n,γ) cross section measurements. In addition, a new technique for correcting measured gamma ray decay probabilities below the neutron emission energy threshold is proposed and used. We find good agreement between indirect and direct (n,γ) cross section measurements in the range 500 keV -1 MeV, but large discrepancies outside this range. Explanations for the observed differences are proposed. PACS number(s): 24.87.+y, 24.10.-i, 25.45.-z, 25.55.-e

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Neutron Fission Cross Sections for ²³¹Th, ²³³Th, ²³⁵U, ²³⁷U, ²³⁹U, ²⁴¹Pu, and ²⁴³Pu from 0.5 to 2.25 MeV Using (t, pf) Reactions

Cited by 109 publications

References 0 publications

Calculations of Compound Nucleus Spin-Parity Distributions Populated via the (p,t) Reaction in Support of Surrogate Neutron Capture Measurements

Calculations of Compound Nucleus Spin-Parity Distributions Populated via the (p,t) Reaction in Support of Surrogate Neutron Capture Measurements

First simultaneous measurement of fission and gamma probabilities of²³⁷U and²³⁹Np via surrogate reactions

Indirect (n,γ) cross sections of thorium cycle nuclei using the surrogate method

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Neutron Fission Cross Sections for 231Th, 233Th, 235U, 237U, 239U, 241Pu, and 243Pu from 0.5 to 2.25 MeV Using (t, pf) Reactions

Cited by 109 publications

References 0 publications

Calculations of Compound Nucleus Spin-Parity Distributions Populated via the (p,t) Reaction in Support of Surrogate Neutron Capture Measurements

Calculations of Compound Nucleus Spin-Parity Distributions Populated via the (p,t) Reaction in Support of Surrogate Neutron Capture Measurements

First simultaneous measurement of fission and gamma probabilities of237U and239Np via surrogate reactions

Indirect (n,γ) cross sections of thorium cycle nuclei using the surrogate method

Contact Info

Product

Resources

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Neutron Fission Cross Sections for ²³¹Th, ²³³Th, ²³⁵U, ²³⁷U, ²³⁹U, ²⁴¹Pu, and ²⁴³Pu from 0.5 to 2.25 MeV Using (t, pf) Reactions

First simultaneous measurement of fission and gamma probabilities of²³⁷U and²³⁹Np via surrogate reactions