[seminar] (2.10.2017. 14:00) From the stars to the lab (and back): Measuring the most neutron-rich isotopes

[Mihael Makek]

Poštovane kolegice i kolege,

pozivam Vas na seminar koji će održati dr. Iris Dillman sa TRIUMFa pod
naslovom:

"From the stars to the lab (and back): Measuring the most neutron-rich
isotopes"

Mjesto: Fizički odsjek, F-201
Vrijeme: ponedjeljak 2. listopada 2017, 14:00

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Dear colleagues,

I would like to invite you to the seminar by dr. Iris Dillman (TRIUMF):

"From the stars to the lab (and back): Measuring the most
neutron-rich isotopes"

Location: Department of Physics, F-201
Time: 14:00 on Monday, October 2nd, 2017


----SEMINAR ABSTRACT--------------------------------------------------

Beta-delayed neutron emission will be the dominant decay mechanism of
neutron-rich nuclei, and about half of the known isotopes are beta-delayed
neutron emitters. The emission of a neutron after beta-decay plays an
important, two-fold role in the stellar nucleosynthesis of heavy elements
in the "rapid neutron-capture process" (r process). It leads to a detour
of the material beta-decaying back to stability and the released neutrons
increase the neutron-to-seed ratio, and are re-captured during the
freeze-out phase and thus influence the final solar r-abundance curve.
Thus the neutron branching ratio of very neutron-rich isotopes is a
crucial parameter in astrophysical simulations. In addition, beta-decay
half-lives can be deduced from the time-dependent detection of
beta-delayed neutrons's.

A large fraction of the isotopes for r-process nucleosynthesis are not yet
experimentally accessible and are located in the "Terra Incognita". With
the next generation of fragmentation and ISOL facilities presently being
built or already in operation, one of the main motivation of all projects
is the investigation of very neutron-rich isotopes at and beyond the
border of presently known nuclei. However, reaching more neutron-rich
isotopes means also that multiple neutron-emission becomes the dominant
decay mechanism.

I will talk about two recent efforts concening beta-delayed neutron
emitters. In the framework of an IAEA Coordinated Research Project the
half-lives and neutron-branching ratios of all known beta-delayed neutron
emitters were re-evaluated.

The BRIKEN project ("Beta-delayed neutron measurements at RIKEN for
nuclear structure, astrophysics, and applications") has developed the most
efficient neutron detector so far for nuclear structure studies. In
conjunction with two clover detectors and the "Advanced Implantation
Detector Array" (AIDA) the setup has been used a few months ago to measure
the most neutron-rich isotopes around $^{78}$Ni, $^{132}$Sn and the Rare
Earth Region. Some preliminary results are shown from the campaign
covering the $^{78}$Ni region where the neutron-branching ratio of
$^{78}$Ni and $\approx$ 28 more isotopes were measured for the first time,
as well as the half-lives of $\approx$20 isotopes. The BRIKEN campaign
aims to (re-)measure almost all accessible beta-delayed neutron emitters
between $^{76}$Co and $^{167}$Eu, many of them for the first time. An
extension of the campaign to lighter and higher masses is planned.
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Srdačno,
Mihael Makek