My initial gut reaction was that the authors were ignoring the obvious solution of simply putting the ring below ground level and setting up maintenance walkway

My initial gut reaction was that the authors were ignoring the obvious solution of simply putting the ring below ground level and setting up maintenance walkways above the ring instead of next to it. Then I realised the the Earth is spherical and that it doesn’t matter how deep you put this thing, the beam will come out somewhere, even if it needs to go through a thousand kilometres of regolith to get there. So there could be some random patch of grazing land somewhere in another country that’s dangerous to go near whenever the experiment is running. PS: I solved the funding problem! Just tell the military about this new unstoppable death ray that can kill anyone even through the planet. [Disclaimer: death will be a decade from now due to cancer. Victim must remain stationary for one year. Construction work is required to retarget beam.]