Irradiation of astrophysical ices – IGLIAS

Several parameters are important for this project. First of all, we really need an ultra high vaccum to prevent any problem of water ice redeposition during experiments. This equipement will be installed on the beam lines of GANIL. It has to be compatible in terms of geometry and envirronement to work on this big accelerator. The evolution of changes induced during irradiation will be studied by infrared spectroscopy using a Vertex V70 spectrometer operating under vaccum.

The infrared spectrometer as been installed and all the setup is now ready. The pressure in the collision chamber is lower than 10-10 mbar. This device has been installed on the IRRSUD beam line of GANIL at the beginning of October 2016. We have performend a first experiment on a N2:CH4 sample at 10 K irradiated with Mev/u Xenon ions for the thesis of Basil Augé. The quality of the recorded spectra is exceptionnal and we do not observe any effect of pollution coming residual gaz.

The phase 2 corresponds to the research phase on irradiation of ice present in the space is started. We will have a group meeting at the beginning of the next year to choose the next samples and to think about the way to inform the scientific community that IGLIAS is now ready and open for users on the GANIL beam lines. We also want to study the irradiation of interface of carbonaceous subtrates covered with water ice.

1. Astronomy and astrophysics 576, A125(2015)
DOI : 10.1051/0004-6361/201425415
2. Interdisciplinary investigations of ion beam interactions with matter: From fundamental aspects to nanotechnology and hadronbiology (oral, Caen Mai 2015)
3. SHIM (oral, Darmstadt, Mai 2015)
4. ICACS (oral invité, Lanzhou, Juillet 2016)
5. ISWA (oral invité, Campinas, Juillet 2016)
6. HCI (oral invié, Kielce, Septembre 2016).
7. A venir ECLA Madrid 2016.

This project, a collaboration of two French laboratories (CIMAP and IAS), two Brazilian universities and a Spanish institute, relates to the effects induced by heavy ions in ices which are present in intermediate to very low temperatures encountered in space environments, from dense molecular clouds in interstellar space to comets in the solar system. The basic initial constituents of the ices are simple molecules such as H2O, CO, CO2, NH3 etc. The main objective is to simulate in the laboratory the effects of irradiation of such ices by multiply charged heavy ions of the solar wind, the giant planet’s magnetospheres and of galactic cosmic rays. The evolution of the composition of the ices will be simultaneously monitored by FTIR (Fourier Transform Infrared Absorption Spectroscopy) in the 500-5000 cm-1 region and by mass spectrometry. Our preliminary studies have shown that heavy cosmic ray ions could yield a dominant contribution to desorption of molecules by electronic sputtering, and also to destruction and fragmentation of molecules (radiolysis).In spite of their lower abundances, heavy nuclei play a significant role in the energy deposition by cosmic rays. A further result is that it is mandatory to work in ultrahigh vacuum conditions to ensure a controlled preparation of the targets and a clean monitoring of its evolution under irradiation, in particular for mass spectrometry. In addition, contamination by water may influence cross section and sputter yield measurements. The first objective of this project is to design and build an ultrahigh vacuum chamber equipped with a cold head for sample preparation interfaced to the GANIL beamlines. The irradiations will then be performed using different beam lines of the heavy ions available in the GANIL accelerator. The scientific part is divided into two objectives.
The first one is to study the evolution of “simple” ices under irradiation in a wide energy range from keV to GeV (thus covering both the physico-chemistry induced by solar wind ions, magnetosphere ions and fast cosmic rays). The high energy domain is poorly explored so far. At low energy, experiments with highly charged ions equivalent to those present in Solar wind are scare: the role of the projectile’s potential energy is an open topic. The destruction cross sections for the initial molecules, the formation cross sections for new molecules and sputtering (desorption) yields can be determined by FTIR spectroscopy.
The second scientific objective is to study more “complex” ices made of mixtures of several molecules and/or of ices containing organic molecules (formaldehyde, alcools, …) or even larger molecules with the aim to verify if more complex, pre-biotic molecules such as amino acids and others can be formed by heavy ion irradiation. Once operational and fully tested, the setup will be opened to the external community, allowing the experiments to be continued for several years at the GANIL-CIMAP-CIRIL user’s facility.