06 November 2009
Within the Manhattan Project was a sizable scientific and technical effort to determine the progress of the Nazi atomic bomb program. One of the key scientists in this effort was future Nobel Laureate Luis W. Alvarez who in 1944 was working at Los Alamos in New Mexico when he was asked by General Leslie Groves, the head of the Manhattan Project, if there were a way to detect from the air if the Germans were operating plutonium-fueled reactors. Given only a week by Groves, Alvarez proposed an airborne collection system to detect Xenon-133, a by-production of reactor fission with a five-day half life which had distinctive patterns of gamma and beta radiation making it an ideal marker for German reactor activity.
General Groves' idea was to determine the locations of potential German reactors and then disrupt their atomic bomb effort via airstrikes.
With the help of General Electric, Alvarez designed an activated charcoal-based filter system that would fit in the nose compartment of a Douglas A-26 Invader that would fly several hundred feet above the ground. In the fall of 1944, three A-26s carrying Alvarez's Xenon-133 detector scoured three possible areas where intelligence analysts thought a German reactor might be operating. Fast and agile enough to evade AAA-gunfire but large enough to carry the bulky detector, no Xenon-133 was ever found.
Source: Spying on the Bomb- American Nuclear Intelligence from Nazi Germany to Iran and North Korea by Jeffrey T. Richelson. W.W. Norton, 2007, p40-41, 49-50.