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

[postmaster at admin.triumf.ca]

Date/Time: Fri 2009-07-24 at 14:00

Location:  ISAC-II Conference  

Speaker:   Andrew Rogers (NSCL, Michigan State University)

Title:     Study of 69Br Ground State Proton Decay and the 68Se rp-Process Waiting Point

Abstract: A complete understanding of the origin and synthesis of the elements is one of the main outstanding questions in nuclear astrophysics.  A number of nucleosynthesis processes are known and to a reasonable extent account for much of the observed solar abundances of nuclei.  However, there are a number of elements that can only be produced via processes involving proton rich nuclei.  The rapid proton capture or rp-process, is one such mechanism which occurs along the proton drip-line whereby fast proton captures on seed nuclei followed by beta-decay allow for the production of elements possibly as heavy as Te.  Type I X-ray bursts are thought to be key sites for this process.  To realistically model the rp-process in these systems experimental data such as masses, lifetimes, and proton capture rates along the proton drip-line are required which are currently lacking for many of these nuclei.

The 68Se waiting point is of particular interest, where a long beta-decay half-life coupled with inhibited proton capture restricts the amount of material that is processed beyond mass 68 in the rp-process.  However, the reaction rate for the 2p-capture process 68Se+p->69Br+p ->70Kr depends exponentially on the Q-value, which is poorly constrained.  We have performed an experiment to measure Q-values of proton unbound states of exotic nuclei at the National Superconducting Cyclotron Laboratory (NSCL) Coupled Cyclotron Facility.  The experiment was designed to reconstruct the decays of proton unbound nuclei, specifically 69Br, by detecting the decay protons using the MSU High Resolution Array (HiRA) in coincidence with a heavy residue, e.g. 68Se, which is measured in the large acceptance S800 magnetic spectrograph.  The first direct measurement of ground state proton decay from 69Br and general implications for the rp-process will be discussed.



______________________________

Subscription information available at http://admin.triumf.ca/netdata/seminars/list