Foto från CRP mötet "The Formation and Properties of Molecules in Edge Plasmas" i Wien

For a long time, physicists have been dreaming about using fusion processes to produce energy on earth. ITER is a giant fusion tokamak being built in France as a large collaboration of several nations. The idea for a joint fusion project was launched in 1985 and the construction has been underway since 2010. In the tokamak superconducting magnets will confine the plasma in a toroidal magnetic field under very high temperature (~175 million K) and sufficient density.

In the fusion process, deuterium and tritium will form helium and release 14 MeV neutrons. The conditions of the plasma are not homogeneous and near material boundaries such (plasma edge region) the plasma temperature might be a as low as a few eV. Here molecules are formed. The molecules will interact with the plasma. To understand the dynamics of the plasma, it is important to include scattering processes including the molecules in the modeling of fusion plasmas.

The International Atomic Energy Agency (IAEA) organizes Coordinated Research Projects (CRP) were experts on fusion plasma modeling as well molecular physicists working on theoretical calculations of molecular scattering processes are invited. December 6-9, 2023, I was invited to the first CRP meeting at IAEA in Vienna. The title of this CRP is “The Formation and Properties of Molecules in Edge Plasmas“ and it will run for five years. I have previously, been involved in CRPs, where I have studied scattering processes involving different isotopes of the BeH reaction complex. For long, the plan was to have beryllium on the walls of ITER and if so, the beryllium atoms and ions will enter the plasma and form molecules such as BeH and BeH+. Beryllium is toxic and experiments on scattering processes on molecules involving beryllium are limited. Therefore, there was a need for theoretical calculations. I studied processes such as dissociative recombination, where the BeH+ molecular ion captures an electron, becomes neutral and dissociates into atoms.

Now recently, the ITER community consider not using beryllium on the walls. Instead. there are plans that walls of Tungsten (W) will be boronized (covered by a layer of boron). Therefore, molecules such as BH and BH+ will be formed. The plan is that I will in this coming CRP study processes involving BH and BH+. There are no measurements on these processes. We have just started to perform quantum chemistry calculations to determine potential energy curves, non-adiabatic coupling and autoionization widths of electronic states of BH relevant for the quantum studies of the scattering processes. I will compute cross sections and determine what fragments are formed in the scattering processes. These results will then be used in plasma simulation codes to investigate the role of the molecules formed in the plasma. The modeling is compared with measurements using molecular spectroscopy of the edge plasma.  Hopefully I will be able to contribute with a small piece of the puzzle to this complex project. 

/Professor Åsa Larson

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Professor Åsa Larson

The Formation and Properties of Molecules in Edge Plasmas

ITER

IAEA