PhD project: Investigation of nuclear structure via high-precision mass measurements at TITAN, TRIUMF

Project description

High-precision mass measurements and spectroscopy give an insight into the variation of the nuclear structure and stability across the nuclear chart. Systematic measurements along isotopic chains and the observed shell structure of nuclei, reflected by increased binding energies at the so-called magic neutron and proton numbers, led to the development of the current shell model. From precise mass values, important differential quantities, such as the proton and neutron separation energies can be calculated, which highlight different nuclear structure effects.

Approaching the limits of nuclear binding, the structure and properties of nuclei is of great interest and attracts large attention, theoretically and experimentally. It has become evident that the nuclear shell structure can change towards the drip-line. New effects such as shell quenching, weakening or disappearance of shells around the classical magic numbers and appearance of new magic numbers have been theoretically predicted and observed in experiments. Further we are interested in applying new findings in nuclear physics to astrophysical processes – in particular the rapid neutron capture process, believed to be responsible for the creation of half of the stable isotopes beyond iron, is in need of more and high quality nuclear physics inputs.

In recent work we investigated the evolution of the N=32 neutron shell closure, that forms in neutron-rich Sc, Ca and K isotopes, but not in Cr and above. Here we performed mass measurements of neutron-rich Ti [1] and V [2] isotopes at TITAN [3,4], TRIUMF, Vancouver, Canada with a new multiple-reflection time-of-flight mass-spectrometer (MR-TOF-MS) in combination with the established TITAN Penning Trap system. 
Our direct measurements showed the transitional character of Ti, right between “no shell effects” and “strong shell effects”. The results challenge modern ab-initio theories and serve as an excellent testing ground for new shell model calculations. We plan to exploit the new experimental capabilities and push towards an investigation of the N=34 neutron shell closure, currently under discussion in Ti, and further aim to expand our studies across the mid-shell region between the proton shell closures at Z=20 and 28 in Cr, Mn and Fe isotopes along the neutron-rich side of the nuclear chart. High-priority letter-of-intend and experiment proposals have been accepted at TRIUMF.

The Phd project will be offered to a student with a strong academic background in nuclear physical, a high degree of independence and the aspiration to work within an international collaboration. You will participate during experimental campaigns at TITAN, TRIUMF, Vancouver, take on responsibility of operating of the mass spectrometers and perform data analysis. You will lead the discussions on your results within the collaboration and prepare publication in peer-reviewed journals.In addition you will work on further technical developments or ion optical simulations aiming to improve the precision, resolving power or general operation and performance of the spectrometers; hands-on and computer-based work will be required and adjusted for the incumbent's interests and operational needs. This project includes traveling to TRIUMF and, as a member of the international TITAN collaboration, offers you the opportunity to present your results at international conferences or workshops.  

Research Council scholarships cover UK/EU fees and provide tax free stipends for living costs for 42 months. The initial application deadline is 24 January 2020, however, applications reached after the deadline will continue to be considered until all the positions are filled (see how to apply and funding options).

[1] E. Leistenschneider et al., Phys. Ref. Lett. 120, 062503 (2018)
[2] M. P. Reiter et al., Phys. Rev. C 98, 024310 (2018)
[3] J. Dilling et al., NIMB 204, 492 (2003) 
[4] TITAN experiment web page - https://titan.triumf.ca/

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