Deducing the 237U(n, F) Cross-section Using the Surrogate Ratio Method
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Publisher:
Published: 2005
Total Pages: 11
ISBN-13:
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Deducing the 237U(n, F) Cross-section Using the Surrogate Ratio Method
Author: Ronald Clark
Publisher:
Published: 2005
Total Pages: 38
ISBN-13:
DOWNLOAD EBOOKThe authors have deduced the {sup 237}U(n, f) cross-section over an equivalent neutron energy range of 0 to 20 MeV using the Surrogate Ratio method. A 55 MeV {sup 4}He{sup 2+} beam from the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory was used to induce fission in the following reactions {sup 238}U({alpha}, {alpha}'f) and {sup 236}U({alpha}, {alpha}'f). The {sup 238}U reaction was a surrogate for {sup 237}U(n, f) and the {sup 236}U reaction was used as a surrogate for {sup 235}U(n, f). The energies of the scattered alpha particles were detected in a fully depleted segmented silicon telescope array (STARS) over an angle range of 35{sup o} to 60{sup o} with respect to the beam axis. The fission fragments were detected in a third independent silicon detector located at backward angles between 106{sup o} to 131{sup o}.
Pu236(n,f) , Pu237(n,f) , and Pu238(n,f) Cross Sections Deduced from (p,t) , (p,d) , and (p,p') Surrogate Reactions
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Publisher:
Published: 2014
Total Pages:
ISBN-13:
DOWNLOAD EBOOKThe Pu236(n,f), Pu237(n,f) and Pu238(n,f) cross sections have been inferred by utilizing the surrogate ratio method. Targets of Pu239 and U235 were bombarded with 28.5-MeV protons, and the light ion recoils, as well as fission fragments, were detected using the STARS detector array at the K150 Cyclotron at the Texas A&M cyclotron facility. The (p, tf) reaction on Pu239 and U235 targets was used to deduce the ? (Pu236(n,f))/?(U232(n,f)) ratio, and the Pu236(n,f) cross section was subsequently determined for En=0.5–7.5 MeV. Similarly, the (p,df) reaction on the same two targets was used to deduce the ?(Pu237(n,f))/?(U233(n,f)) ratio, and the Pu237(n,f) cross section was extracted in the energy range En=0.5–7 MeV. The Pu238(n,f) cross section was also deduced by utilizing the (p,p') reaction channel on the same targets. There is good agreement with the recent ENDF/B-VII.1 evaluated cross section data for Pu238(n,f) in the range En=0.5–10.5 MeV and for Pu237(n,f) in the range En=0.5–7 MeV; however, the Pu236(n,f) cross section deduced in the present work is higher than the evaluation between 2 and 7 MeV.
General Constraints on Cross Sections Deduced from Surrogate Reactions
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Publisher:
Published: 2003
Total Pages: 10
ISBN-13:
DOWNLOAD EBOOKCross sections that cannot be measured in the laboratory, e.g. because the target lifetime is too short, can be inferred indirectly from a different reaction forming the same compound system, but with a more accessible beam/target combination (the ''surrogate-reaction'' technique). The reactions share the same compound system and a common decay mechanism, but they involve different formation processes. Therefore, an implicit constraint is imposed on the inferred cross section deduced from the measured surrogate-reaction data, through the common decay mechanism. In this paper, the mathematical consequences of this implicit constraint are investigated. General formulas are derived from upper and lower bounds on the inferred cross section, estimated from surrogate data in a procedure which does not require any modeling of the common decay process. As an example, the formulas developed here are applied to the case of the 235U(n, f) cross section, deduced from 234U(t, pf) surrogate data. The calculated bounds are not very tight in this particular case. However, by introducing a few qualitative assumptions about the physics of the fission process, meaningful bounds on the deduced cross section are obtained. Upper and lower limits for the cross-section ratio of the (n, f) reaction on the 235U isomer at E(subscript x) = 77 eV relative to the (n, f) reaction on the ground state are also calculated. The generalization of this technique to other surrogate reactions is discussed.
Absolute and Relative Surrogate Measurements of the 236U(n, F) Cross Section as a Probe for Angular Momentum Effects
Author:
Publisher:
Published: 2007
Total Pages: 10
ISBN-13:
DOWNLOAD EBOOKUsing both the absolute and relative surrogate techniques, the 236U(n, f) cross section was deduced over an equivalent neutron energy range of 0 to 20 MeV. A 42 MeV 3He beam from the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory was used to perform a (3He, [alpha]) pickup reaction on targets of 235U (J{sup {pi}}=7/2−) and 238U (J{sup {pi}}=0) and the fission decay probabilities were determined. The 235U(3He, [alpha]f) and 238U(3He, [alpha]f) were surrogates for 233U(n, f) and 236U(n, f), respectively. The cross sections extracted using the Surrogate Method were compared to directly measured cross sections. The sensitivity of these cross sections to the J{sup {pi}}-population distributions was explored.
Peacekeeping in Africa
Author: Eric Berman
Publisher: United Nations Publications UNIDIR
Published: 2000
Total Pages: 584
ISBN-13:
DOWNLOAD EBOOKThis book analyzes both indigenous and external efforts to develop African countries' individual and collective capacities to undertake peacekeeping operations. It chronicles the participation of African countries in United Nations peacekeeping operations and non-African-led multinational forces over the past 50 years. It also discusses the role of the United Nations in peacekeeping in the region and concludes with recommendations on how to make current approaches more effective--Publisher's description.
Palgrave Advances in Global Governance
Author: J. Whitman
Publisher: Springer
Published: 2009-09-16
Total Pages: 222
ISBN-13: 0230245315
DOWNLOAD EBOOKPalgrave Advances in Global Governance is an authoritative collection devoted to clarifying established understandings of global governance as a distinct form of political activity. Ranging across the actors, arenas, means and purposes of global governance, this incisive collection brings order and clarity to a burgeoning literature.
Handbook of Space Security
Author: Kai-Uwe Schrogl
Publisher: Springer
Published: 2014-10-31
Total Pages: 0
ISBN-13: 9781461420286
DOWNLOAD EBOOKSpace Security involves the use of space (in particular communication, navigation, earth observation, and electronic intelligence satellites) for military and security purposes on earth and also the maintenance of space (in particular the earth orbits) as safe and secure areas for conducting peaceful activities. The two aspects can be summarized as "space for security on earth" and “the safeguarding of space for peaceful endeavors.” The Handbook will provide a sophisticated, cutting-edge resource on the space security policy portfolio and the associated assets, assisting fellow members of the global space community and other interested policy-making and academic audiences in keeping abreast of the current and future directions of this vital dimension of international space policy. The debate on coordinated space security measures, including relevant 'Transparency and Confidence-Building Measures,' remains at a relatively early stage of development. The book offers a comprehensive description of the various components of space security and how these challenges are being addressed today. It will also provide a number of recommendations concerning how best to advance this space policy area, given the often competing objectives of the world's major space-faring nations. The critical role to be played by the United States and Europe as an intermediary and "middle diplomat" in promoting sustainable norms of behavior for space will likewise be highlighted. In providing a global and coherent analytical approach to space security today, the Handbook focuses on four areas that together define the entire space security area: policies, technologies, applications, and programs. This structure will assure the overall view of the subject from its political to its technical aspects. Internationally recognized experts in each of the above fields contribute, with their analytical synthesis assured by the section editors.
Distant Proximities
Author: James N. Rosenau
Publisher: Princeton University Press
Published: 2003-03-30
Total Pages: 460
ISBN-13: 9780691095240
DOWNLOAD EBOOKIn "Distant Proximities" one of America's senior scholars presents a work of sweeping vision that addresses the dizzying anxieties of the post-Cold War, post-September 11th world.
Sustainable Entrepreneurship
Author: Adam Lindgreen
Publisher: Routledge
Published: 2016-04-30
Total Pages: 354
ISBN-13: 1317047850
DOWNLOAD EBOOKThe way organizations manage entrepreneurship has changed dramatically over the past decade. Today, organizations take account of economic issues, but they also adopt a broader perspective of their purpose including social and environmental issues (i.e. sustainability). Yet, despite its global spread, sustainable entrepreneurship remains an uncertain and poorly defined ambition with few absolutes. This book reaffirms the important need to improve comprehension and explore the subtleties of how individuals, groups, and organizations can discover, create, and seize opportunities for blended value generation, by designing and operating sustainable ventures. It examines, in an interdisciplinary fashion and across sectoral and geographical boundaries, how entrepreneurial activities can be developed to be generally consistent with sustainable development goals, as well as by whom, for what reasons, and with what implications. The Editors comprehensively review key dimensions of the sustainable entrepreneurship phenomenon to establish an essential definition and up-to-date picture of the field. The 19 chapters cover 4 main topics: Understanding the intentions and motivations for sustainable entrepreneurship Fostering and enacting sustainability through entrepreneurial action Leading and inspiring sustainable entrepreneurial action Finding the contextually grounded implications of and challenges to sustainable entrepreneurship and blended value generation This book is an important resource for entrepreneurs and policy makers as well as students in the fields of entrepreneurship, innovation, and sustainability.
