Luis Walter Alvarez
Luis Walter Alvarez (1911-88) was a US physicist best known for his contribution in particle physics. He was awarded Nobel Prize for Physics in 1968. He was the first person to measure neutron's magnetic moment, and credited for developing the bubble chamber.
He, along with his son, identified iridium in 1980 in sediment from the Cretaceous-Tertiary boundary, which he claimed, was resulted from a catastrophic meteorite impact.