Low energy cross sections for 11B(p, 3α)

doi:10.1016/0375-9474(79)90647-X

Nuclear Physics A

Volume 315, Issues 1–2, 19–26 February 1979, Pages 253-268

https://doi.org/10.1016/0375-9474(79)90647-X Get rights and content

Abstract

The cross section for the ¹¹B(p, 3α) reaction has been measured for lab bombarding energies from 35.4 keV to 1500 keV. The astrophysical S-factor is calculated for this range of energies and an empirical fit to S is presented. The reaction rate 〈σν〉 is calculated for temperatures up to T = 500 keV/k = 5.5 × 10⁹ K. For the resonance at 163 keV [¹²C^∗(16.11 MeV)], the resonance cross section and width were measured to be σ_R = 54 ± 6 mb and Γ_{c.m. = 5.2 ± 0.5 keV}, differing somewhat from values reported in previous studies. The measured cross sections from the present work lead to the values of 〈σν〉 which are somewhat lower than those quoted previously, offering a less optimistic prospect for ¹¹B+p as an advanced fusion fuel than previously envisioned.

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The fusion reaction ¹¹B(p,α)αα draws attention since the dawn of nuclear physics for its relevance and potential application in different fields, from nuclear fusion to astrophysics and hadron therapy. Nevertheless, the understanding and description of the physics of the reaction still have some important open points, both theoretical and experimental. Among others, the energy and angular distributions of α particles produced by the different reaction channels need to be further characterized, especially at low energies. To this aim, a novel experimental set-up was conceived by combining well-characterized boron-coated targets and a two-stage monolithic detection system. Targets were produced by Pulsed Laser Deposition, a technique that allows to finely tailor thickness, density and chemical composition of coatings. The detection system, based on a ΔE-E silicon telescope, was developed to perform an effective identification and discrimination between α particles produced by the p-¹¹B reaction and primary protons, essential for the reaction kinematic analysis at low energies. Irradiations were performed by bombarding a boron-coated foil with primary protons of energies in the range 1–2.4 MeV. Results show the effectiveness of the particle discrimination. Measured energy distributions highlight the contribution of α particles generated in the two main reaction channels. A preliminary quantitative analysis of the reaction cross section was performed for each reaction channel at the different investigated energy and compared with literature data. The experimental set-up was also simulated through the Monte Carlo code FLUKA to test the model capabilities recently implemented in the code.
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Citation Excerpt :
Additionally, the overlap in energy of α1 with α11 and α12 may hamper proper yield determination (discussed in the following). On the other hand, α0 is isolated in energy and the smaller slope at the cross-section for energies above the 163 keV resonance in comparison to α1 [31] results in a more isolated resonance, simplifying background subtraction and interpretation for more complex structures. Such an approach is convenient to analyze 11B profiles for thin films or implanted boron at a range below 1 μm but presents difficulties of interpretation for thicker films: since the significant increase of the cross-section at higher energies does not allow to distinguish the α yield contribution from the 163 keV resonance in comparison to the α yield from higher energies (at 300 keV, the cross-section is already higher than at the resonance), ambiguities in interpretation of 11B depth distribution may occur if only (E-ER)/S is considered for depth conversion.
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^☆: Supported in part by the National Science Foundation [grant PHY76-83685] and by the Electric Power Research Institute [contract TPS 77–708].

^††: Present address: Bell Laboratories, Murray Hill, NJ 07974.

^†††: Present address: Los Alamos Scientific Laboratory, Los Alamos, NM 87545.

^‡: Present address: Computer Sciences Corporation, Silver Springs, MD 20910.

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Low energy cross sections for 11B(p, 3α)☆

Abstract

Nucl. Phys.

Nucl. Phys.

Nucl. Phys.

Phys. Rev.

Lawrence Livermore Laboratory Reports UCRL-74191 and 74352

Low energy cross sections for ¹¹B(p, 3α)☆