[Triumf-seminars] UBC departmental oral defense: Mathew Smith

[Barry Davids]

The UBC Departmental Doctoral Oral Examination for Mathew Smith is set  
for Friday, April 4th at 2:00 pm in Hennings 318.

Research Supervisors:
         Dr. Jens Dilling
         Dr. Kirk Madison

Committee Members:
         Dr. Stan Yen
         Dr. John Ng

Thesis Title:  A Mass Measurement of the Short-lived Halo Nucleus 11Li  
with the TITAN Penning Trap Spectrometer


ABSTRACT

New measurements of the masses of the isotopes 8,9,11Li were made using
the recently commissioned TITAN Penning trap mass spectrometer at TRI-
UMF. The measurement of halo nucleus 11Li represents a new standard in
Penning trap mass spectrometry, as it is the shortest lived, t1/2 =  
8.8 ms,
isotope ever weighed using this technique. Low energy, E = 20 keV ,  
beams
of these radioactive isotopes were produced using the ISAC facility.  
These
were subsequently cooled and bunched using a square-wave-driven Radio-
Frequency Quadrupole (RFQ) ion guide, which was filled with hydrogen
gas. The cooled ion bunches were then passed into a Penning trap where
the mass measurements were made.

A description of the RFQ in the ISAC hall is given along with some
results from the commissioning of the device. A new set of harmonic  
decel-
eration optics is presented which have been successfully used to  
inject ions
into the RFQ. Cooling of lithium ions with high DC efficiencies of 20%,  
in
helium, and 40%, in hydrogen are shown. Extraction of extremely short
ion bunches, 30 ns FWHM, is also demonstrated. Storage times for stable
lithium ions in helium and hydrogen were investigated. It was found that
lithium ions could be cooled in hydrogen for up to 30 ms without  
significant
losses whereas cooling in helium lead to exponential losses with a  
half-life of
5.7(1) ms.

The TITAN Penning trap is described and the 8,9,11Li data presented.
Final values for the mass excess ∆(8 Li) = 20945.70(38) keV , ∆(9  
Li) =
24954.80(60) keV and ∆(11 Li) = 40728.1(12) keV are obtained. The  
9,11Li
results are then used to obtain a new value for two neutron separation  
energy
of 11 Li, S2n = 369.3(1.3) keV . This agrees with the recent  
measurement from
the MISTRAL spectrometer, 376(5) keV at the two sigma level, but shows
over three standard deviations from the most recent atomic mass  
evaluation,
300(20) keV .



-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.triumf.ca/pipermail/triumf-seminars/attachments/20080403/1922d14f/attachment.html