Nov 4, 2021
“What I initially thought looked like the result of a computer simulation, is in fact a 1970's photograph of a test of a shuttle model in a Mach 20 helium wind tunnel, using electron beam fluorescence.” — Scott Manley, https://youtu.be/v0Z_4VyuzcA
Also relating to this tweet by Scott Manley https://twitter.com/djsnm/status/1445874000521953282
“A model of the space shuttle in the Langley 22-inch helium tunnel at Mach 20. The flow is made visible by bombardment of an electron beam.”
— https://history.nasa.gov/SP-440/ch7-4.htm
Image lifted from this Reddit post, being the largest resolution version (3000×2400 px) that I could find https://www.reddit.com/r/space/comments/57ip4z/space_shuttle_wind_tunnel_test_using_electron_beam/