This hemispherical window was designed to cover the camera ports inside Argonne Lab's 12-foot (diameter) hydrogen bubble… https://www.rawpixel.com/image/3325630/free-photo-image-black-white-aec-argonne-labFree Image from public domain licenseProton with 300 GeV energy producing 26 charged particles in the 30 inch hydrogen bubble chamber at FERMILAB, c.1973.… https://www.rawpixel.com/image/3322287/free-photo-image-cc0-creative-commonsFree Image from public domain license