In 1964 Alvarez proposed what became known as the High Altitude Particle Physics Experiment (HAPPE), originally conceived as a large superconducting magnet carried to high altitude by a balloon in order to study extremely high-energy particle interactions.
În 1964, Alvarez a propus ceea ce avea să fie denumit High Altitude Particle Physics Experiment (HAPPE), conceput inițial ca un uriaș magnet supraconductor⁠(d) ridicat la o mare altitudine cu un balon⁠(d) pentru a studia interacțiuni între particule cu energii extrem de mari.