Research during corona crisis — Successful experiment program of FAIR Phase 0
Very successful experiments, high-quality ion beams for research — the current experiment period on the GSI and FAIR campus has ended with a positive outcome despite the corona pandemic. At the existing accelerator facility researchers were able to conduct experiments with a wide variety of ion beams on numerous topics. This opened the way for new discoveries and excellent research opportunities in the future. Scientific operations at the modernised accelerators are part of the FAIR experimental program, the so-called "FAIR Phase 0", which already offers outstanding experimental opportunities while FAIR is still under construction.
Although the experimental program had to be restricted from March 2020 onwards due to the corona pandemic, operation could be partially continued under strict regulations according with the official requirements. Approximately two thirds of the planned experiments could be conducted. Scientists from all over the world, who usually come to the campus for the experiments, were no longer able to travel from that date. However, they supported the research program and the GSI/FAIR staff on site with advice and assistance remotely wherever possible.
In addition to the GSI facilities UNILAC (linear accelerator), SIS18 (ring accelerator), FRS (fragment separator) and ESR (experimental storage ring) as well as the existing experiment setups and the Petawatt high energy laser PHELIX, FAIR developments and detectors, measuring apparatus and other high-tech facilites specially manufactured for FAIR could already be used. Additionally, the commissioning of the first FAIR storage ring CRYRING has progressed to the point, where it is now ready for scientific experiments. Thus, the current FAIR Phase 0 scientific program already represents a major step towards future research at FAIR.
The experiments dealt with topics from a wide range of scientific disciplines, from medicine and materials research to the properties of superheavy elements and the complex structure of short-lived isotopes that play a role in element synthesis in the universe.
In a biophysics experiment, for example, it was shown for the first time that it is possible to use carbon beams to create conditions that are necessary for a so-called FLASH therapy of tumors. In FLASH therapy, a very high dose is applied in a very short time (high dose rate). Studies with proton beams have shown that this technique reduces damage to healthy tissue while maintaining the same level of effectiveness. Until now, FLASH therapy has only been applicable using electron and proton accelerators. Thanks to the improvements at the GSI accelerator facility as part of the preparations for FAIR, the necessary dose rate of five billion ions per 200 milliseconds can now also be achieved for carbon.
Another field of research that benefits from the increased intensities of the GSI accelerators is the study of isotopes that play a role in the synthesis of elements in the universe. Light nuclei up to iron are produced by fusion reactions in stars, heavy elements possibly in explosions of massive stars at the end of their evolution (supernova explosions) or in the collision of neutron stars, extremely compact objects that unite the mass of up to two suns in a radius of a few kilometers. The actual synthesis of elements takes place via nuclear reactions of a multitude of mostly unstable nuclei along specific reaction paths. In a dedicated experiment, extremely neutron-rich nuclei were studied that could not be produced in an accelerator laboratory until now. Isotopes with mass numbers around 200 near the magic neutron number N=126 play a crucial role in the synthesis of even heavier nuclei. Several isotopes in this range have been detected for the first time and their properties determined, among them possibly 200-tungsten. This would be the first time that such a heavy nucleus could be produced in the laboratory, which is directly on one of the element synthesis pathways.
Another experiment with a similar objective was conducted at the Experimental Storage Ring ESR using the entire accelerator chain of UNILAC, SIS18 and FRS. The importance of the bound beta decay of thallium in element formation processes has been emphasized in many scientific publications, and has now been measured for the first time.
The investigation of superheavy elements has been part of GSI's scientific portfolio for many years. In the nuclear reaction of 48Ca+244Pu (calcium and plutonium), among others, two flerovium isotopes are produced: 288Fl and 289Fl. Flerovium is an atomic nucleus with atomic number Z=114 and was first produced in 1999 in a research laboratory in Dubna. However, its nuclear structure is not yet fully understood, so the TASCA setup at GSI was used for the first time to measure alpha and photon emissions of flerovium isotopes in coincidence. In this experiment as many Flerovium isotopes were detected as in all experiments since the first detection of this nucleus.
While heavy nuclei are produced in stars, stellar explosions and the laboratory by nuclear reactions, on dust particles complex molecules are produced from simple organic ones by cosmic rays and are subsequently destroyed again. In an experiment of materials research, it could be shown that these destruction processes can be temperature-dependent and that higher temperatures possibly lead to a longer lifetime of complex molecules under the influence of cosmic radiation.
This is only a small excerpt of the scientific findings of the past experimental period. All in all, the "FAIR Phase 0" program allows a forward-looking combination of important tests of FAIR instrumentation on the one hand and high-quality experiments on the other. In this way, outstanding scientific results can be achieved and the FAIR community can be further developed. On the way to the commissioning of the FAIR accelerator center, further regular experimental periods at the existing and continuously modernized facilities are planned for the coming years. (BP/CP/YL)