Abstract
Beryllium is being adopted for plasma facing walls in fusion reactors. This has led to the observation of emissions from the A 2Π state of beryllium hydride. Use of these emissions to monitor Be erosion requires electron impact excitation rates. Cross sections for electron impact vibrational excitation within the X 2Σ+ state and vibrationally resolved electronic excitation to the A 2Π state are reported for BeH, BeD and BeT. Electron collisions are studied at a range of internuclear separations using the UK molecular R-matrix (UKRmol+) codes. Electronic excitation is studied both within the Franck–Condon approximation and by explicit averaging of the T-matrix elements. It is found that (a) inclusion of the effect of higher partial waves using the Born approximation leads to significant increases in the cross sections and (b) the Franck–Condon approximation underestimates the importance of collisions for which the vibrational state changes during electronic excitation.
Highlights
The current proposal for the ITER fusion reactor is that various plasma facing walls will be made of beryllium (Kupriyanov et al 2015)
It is found that (a) inclusion of the effect of higher partial waves using the Born approximation leads to significant increases in the cross sections and (b) the Franck–Condon approximation underestimates the importance of collisions for which the vibrational state changes during electronic excitation
The Joint European Torus (JET) (Gibson 1979, Schumacher 1983) is already testing an internal reactor wall called the ITER-like wall (ILW) parts of which are made of Be (Brezinsek et al 2015). Under these circumstances it is important to monitor the erosion of Be from the walls and emission spectra of beryllium hydride in various isotopic forms have already been observed in fusion plasma experiments (Darby-Lewis et al 2018, Duxbury et al 1998)
Summary
The current proposal for the ITER fusion reactor is that various plasma facing walls will be made of beryllium (Kupriyanov et al 2015). In a paper referred to as I, Darby-Lewis et al (2017) computed electron impact excitation cross sections for beryllium hydride at a single geometry corresponding to the BeH equilibrium internuclear separation These calculations used the R-matrix method (Tennyson 2010) and were the first published which used the new UKRmol+ code (Masín et al 2020). To complete the inputs for a BeH/BeD/BeT radiative collisional model it is necessary to fully consider the electron impact vibrational excitation processes in the three isotopologues This is the purpose of the current paper. In this work we develop a method based on the use of vibrational wavefunctions to vibrationally average over a grid of fixed nuclei T-matrices This procedure is significantly more computationally expensive as it requires the electron collision calculations to be performed at a grid of geometries.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
