Wed, 08 Feb 2023
Events, Seminar Series

Dr. Greg Hackman


Explaining the anomalous abundance of 84Sr with gamma-ray and mass spectroscopy at TRIUMF-ISAC.

Wednesday, February 08, 2023
ASB10900 @ 3:30 p.m.

Host: Dr. Krzysztof Starosta



TRIUMF-ISAC was built to explain the production of the elements in stellar nucleosynthesis environments.  The TIGRESS and EMMA programs utilize gamma-ray spectroscopy and mass spectroscopy to address this and other topics in fundamental nuclear science.  Atoms and molecules of exotic isotopes are produced at the Isotope Separatior and ACcelerator facility at TRIUMF on the UBC campus.  They are ionized, extracted, mass analyzed, and accelerated to up to 10% the speed of light, high enough energy to overcome electric repulsion between atomic nuclei.  Nuclear reactions may be induced this way, resulting in, amongst other processes, the emission of photons (gamma rays) from the product nuclei themselves.  The reaction product and the photons emitted during a single reaction are measured simultaneously in the  ElectroMagnetic Mass Analyzer and the TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer respectively.  The first measurement performed with TIGRESS and EMMA together used an accelerated radioactive rubidium beam to measure the luminescence cross section 83Rb+1H®84Sr+hn.    The results indicate a lower rate for the inverse photolysis reaction than is predicted by statistical models, which in turn partially explains the anomalously high abundance of the lightest stable Sr isotope that is observed in meteorite materials originating from outside our solar system.


Presenting Author’ Biography (from TRIUMF website)

Greg Hackman received a Bachelor’s degree in Engineering Physics from the University of Alberta in 1991.  He went on to complete his Ph.D. thesis on superdeformed bands in samarium nuclei at McMaster University in 1995 and continued this work at Argonne National Laboratory.  He started work with radioactive beams as a research associate at Michigan State University and as an assistant professor at University of Kansas.

At TRIUMF, Greg is responsible for the operation and maintenance of TIGRESS (TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer).  TIGRESS allows researchers to study the structure of the nucleus and the forces that hold it together by analyzing rare nuclear reactions.  In ISAC-II, beams of exotic nuclei are accelerated to energies sufficient for them to undergo Coulomb excitation, nucleon transfer, and nuclear fusion reactions in the thin-foil target at the centre of TIGRESS.  An array of germanium crystals detects the gamma rays that result from these processes.   Greg played a major role in the building and commissioning of TIGRESS.  He was responsible for the design and operation of a dedicated detector-testing facility.  TIGRESS is now fully operational and is used in a wide range of experiments.

Greg also works on the 8pi spectrometer, studying gamma rays from the decays of neutron-rich nuclei at somewhat lower energies.  On 8pi, Greg has been responsible for electronics, data acquisition, and liquid nitrogen upgrades.  Using his expertise in gamma-ray spectroscopy, he works to further our understanding of nuclear physics.