SGSPD Seminar Fri. 27 12:00

[SGSPD Committee]

A friendly reminder for tomorrow's seminar 12h and sign up 
<http://doodle.com/vskmv7mhubbh9i5y> for pizza. - SGSPD Committee

On 2/20/2015 2:16 PM, SGSPD Committee wrote:
> Dear Grad Students and Postdocs,
>
> 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 Doodle poll 
> <http://doodle.com/vskmv7mhubbh9i5y>; order goes in Thursday 11:00.
>
> We hope to see you there!
> Your SGSPD Committee
>
> *Speaker*: Andrea Teigelhoefer
> *Title*: Pure radioactive ion beam production
> *Abstract*: 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 10^6  and thus 
> provide beams virtually free of isobaric background contamination.
>
> *Speaker*: Aaron Gallant
> *Title*: TITAN + IG-LIS: Testing the Isobaric Multiplet Mass Equation 
> A = 20, 21
> *Abstract*: 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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