GAMMALAS investigated a suitable mechanism for demonstrating the production of coherent gamma photons with the current technology. The process relies on laser cooling and trapping of 135mCs nuclei: they spontaneously decay in 53 minutes emitting a chain of two gamma photons (846 keV and 787 keV) and – given their alkali structure – they are well-suited for conventional laser cooling. After the excited nuclei are brought around 100 nK, they can exhibit purely quantum properties, in particular spatial coherence (Bose-Einstein Condensate, BEC). The BEC transfers its coherence the emitted gamma photons, triggering a burst of coherent gamma rays. Detailed results are presented in the paper L. Marmugi et al., “Coherent gamma photon generation in a Bose–Einstein condensate of 135mCs”, Phys. Lett. B 777, 281-285 (2018, submitted in December 2016).
GAMMALAS also built a complete experimental facility for production and laser cooling of radioactive Cs isotopes, and for demonstrating production of coherent gamma rays. Cs nuclei are produced by proton-induced fission in U or Th (e.g. 135,135mCs), or fusion-evaporation in BaF2 (e.g. 134,134mCs), at the Accelerator Laboratory of the University of Jyväskylä (Finland, partner of the Action). The particles of interest are extracted as ions, electrostatically accelerated, mass separated, and then routed to the low-energy experimental chamber. Here, ions are neutralised (i.e. transformed in neutral atoms with the addition of an external electron with thin foil implantation), extracted in vapour phase, and cooled down to around 150 microK and trapped in a Magneto-Optical Trap. Further stages of cooling (currently under test at the UCL laboratories), will lead to the BEC and the experimental demonstration of coherent gamma photons production.
The facility has been fully tested and characterised with 133Cs and with 134Cs in a test beam time. These results will be included in a forthcoming scientific publication, currently in preparation. The facility is now ready for the 135mCs beam, tentatively scheduled for spring 2018, pending finalisation of the Accelerator Laboratory timetable.
The Fellow supervised three UCL undergraduate students and four UCL PhD students. The latter are now involved full-time in the research project.
In terms of exploitation, GAMMALAS identified, in collaboration with the University of Surrey, a concrete approach to investigate the nuclear properties, and – in particular – the nuclear shape by using the technology and the facility built during the project. Future investigations will also proceed along this path, and further suitable funding sources are being explored.
Results and information about were disseminated through a series of methods:
- Project website,
http://www.ucl.ac.uk/~ucapfre/nuclear.html(s’ouvre dans une nouvelle fenêtre).
- Social media: dedicated posts on Twitter and Facebook.
- Project advertisement for future students/PhD/CDT candidates.
- Participation to outreach activities at UCL.
- Informal meetings with researchers, potential industrial partners, potential investors.
- Participation to UCL seminars.
- Participation to workshops.
- Participation to scientific conferences.
- Publication of scientific articles (one, plus one in preparation).
