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Dear Grad Students and Postdocs,<br>
<br>
We will have a seminar from two of our own PhD students Friday (27
Feb) 12:00-13:00 in the Auditorium. Andrea Teigelhoefer will tell
us about commissioning the ion-guide laser ion source and Aaron
Gallant the first experiment with its beam. Show some support,
learn something about your colleagues, and eat some pizza. Ensure a
slice for all by signing up on the <a
href="http://doodle.com/vskmv7mhubbh9i5y">Doodle poll</a>; order
goes in Thursday 11:00. <br>
<br>
We hope to see you there!<br>
Your SGSPD Committee<br>
<br>
<b>Speaker</b>: Andrea Teigelhoefer<br>
<b>Title</b>: Pure radioactive ion beam production<br>
<b>Abstract</b>: Radioactive isotopes at TRIUMF are produced by
bombarding the nuclei of a target material with the 500MeV proton
beam from the TRIUMF cyclotron. This causes fragmentation,
spallation and fission of the target nuclei and produces a multitude
of isotopes. In order to provide these isotopes to the experiments
located in ISAC, they must be ionized, so that they can be
manipulated by means of electric and magnetic fields. At TRIUMF
three different ion sources are available: (1) surface-, (2)
electron impact, and (3) laser resonance- ion source. Only the
resonance ionization laser ion source (T RILIS) ionizes element
specific. Since TRILIS is commonly used with a hot transfer tube
(aka. surface ion source), a considerable amount of isobaric
background from elements with low ionization potential (e.g. alkali
metals) can be present in certain mass regions, which at times
precludes experiments due to insufficient signal to noise ratios. In
order to overcome the limitations due to surface ionized background,
the hot cavity of the classical RILIS was replaced by a cold RF ion
guide. In April 2014 this ion-guide laser ion source (IG-LIS) has
been successfully tested. With this new ion source it is possible to
suppress the isobaric background up to the order of 10<sup>6</sup> and <span
style="font-size:11.5pt;line-height:115%">thus provide beams
virtually free of isobaric background contamination</span>.<br>
<br>
<b>Speaker</b>: Aaron Gallant<br>
<b>Title</b>: TITAN + IG-LIS: Testing the Isobaric Multiplet Mass
Equation A = 20, 21<br>
<b>Abstract</b>: Much of our knowledge on increasingly exotic nuclei
has been obtained through the use of rare isotope beam (RIB)
facilities. High-precision mass spectrometers have made use of RIB
to refine nucleosynthesis abundance calculations, to increase our
understanding of fundamental aspects of the strong force, and to
provide signatures of exotic phenomena, such as halo formation.
Quite often, however, a beam of interest can not be measured due to
large amounts of isobaric contamination. Here we present the first
direct mass measurements of the nuclides 20,21Mg, which were
completed with the TITAN Penning trap mass spectrometer. These
measurements were only possible by using the newly developed
ion-guide laser ion source (IG-LIS), located at TRIUMF's ISAC
facility, suppressing the unwanted sodium background by a factor of
10^6, resulting in an improvement in the signal-to-noise ratio of
more than 10^4. These Mg isotopes are interesting, as they belong to
the A = 20 and 21 isobaric multiplets, and as such, their binding
energies should follow the quadratic behaviour predicted by the
isobaric multiplet mass equation (IMME). With the rise of high
precision mass measurements, large deviations from the expected
quadratic behaviour of the IMME has been seen in several multiplets,
e.g. A = 8, 9 and 32. With our new mass values, the A = 20 and 21
multiplets now show large deviations from the expected behaviour.
Calculations using the USDA/B isospin non-conserving Hamiltonian and
interactions based on chiral effective field theory using two- and
three-nucleon forces have been conducted, and are compared to the
present measurements.
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