[Triumf-seminars] TRIUMF Seminar today at 14:00

[postmaster at admin.triumf.ca]

Date/Time: Thu 2010-04-29 at 14:00

Location:  Auditorium          

Speaker:   Richard Longland (TUNL and University of North Carolina)

Title:     Investigation of the s-Process Neutron Source 22Ne+alpha

Abstract: Neutron capture processes are associated with the production of most elements heavier than iron. The s-process is one such scenario for nucleosynthesis, in which neutrons are captured at a slower rate than beta-decay occurs. An important nuclear reaction that can produce neutrons for the s-process is 22Ne + alpha. Uncertainties in the rate of this reaction directly influence nucleosynthesis in AGB stars and massive stars. Without improved nuclear physics input, constraints on heavy element synthesis in these stars cannot be reliably compared with observational evidence.  I will outline a series of experiments designed to improve our understanding of the reactions. An experiment to measure the properties of excited states in the compound 26Mg nucleus was performed, improving our understanding of the resonance properties for the 22Ne+alpha reactions. In order to further clarify the current literature data, direct measurements of both reactions should be performed in the future. In the present work, a novel method for determining a resonance strength in 22Ne+p was developed. This new strength significantly reduces 22Ne target stoichiometry uncertainty, which was one of the largest sources of uncertainty in direct 22Ne+alpha cross section measurements.  The findings of the experiments were incorporated into a re-evaluation of literature data, in which rates and their associated uncertainties were calculated with a novel Monte Carlo method. The reaction rate uncertainties were reduced by an order of magnitude.


Stimulants available 15 minutes before the talk.

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