I know anons downplay ETS tweets, but as researchers we should dig into every possibility. I've seen the ADS system discussed on here before, but haven't researched it myself. I'm not sure if a smaller portable version has been developed, and if so, who has the technology.
Anyway, just thought I'd throw it out here in case any anons want to dig deeper to find out if this is a plausible cause of Merkel's episode.
https://twitter.com/TrueEyeTheSpy/status/1141069513980620801
https://en.wikipedia.org/wiki/Active_Denial_System
2 year old article saying no portable system:
https://www.scienceabc.com/innovation/the-active-denial-system-test-what-is-it-what-does-it-do.html
Interesting article from someone who volunteered to be a target of the ADS. (Pic related)
https://www.wired.com/2012/03/pain-ray-shot/