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A friendly reminder for tomorrow's seminar 12h and <a
href="http://doodle.com/vskmv7mhubbh9i5y">sign up</a> for pizza. -
SGSPD Committee<br>
<br>
<div class="moz-cite-prefix">On 2/20/2015 2:16 PM, SGSPD Committee
wrote:<br>
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<blockquote cite="mid:54E7B249.50103@triumf.ca" type="cite">
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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 moz-do-not-send="true"
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. </blockquote>
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