World War II Luis Walter Alvarez

receiving collier trophy president harry truman, white house, 1946

the radar system alvarez best known , has played major role in aviation, particularly in post war berlin airlift, ground controlled approach (gca). using alvarez s dipole antenna achieve high angular resolution, gca allows ground-based radar operators watching special precision displays guide landing airplane runway transmitting verbal commands pilot. system simple, direct, , worked well, untrained pilots. successful military continued use many years after war, , still in use in countries in 1980s. alvarez awarded national aeronautic association s collier trophy in 1945 conspicuous , outstanding initiative in concept , development of ground control approach system safe landing of aircraft under weather , traffic conditions .

alvarez spent summer of 1943 in england testing gca, landing planes returning battle in bad weather, , training british in use of system. while there encountered young arthur c. clarke, raf radar technician. clarke subsequently used experiences @ radar research station basis novel glide path, contains thinly disguised version of alvarez. clarke , alvarez developed long-term friendship.

manhattan project

in fall of 1943, alvarez returned united states offer robert oppenheimer work @ los alamos on manhattan project. oppenheimer suggested first spend few months @ university of chicago working enrico fermi before coming los alamos. during these months, general leslie groves asked alvarez think of way find out if germans operating nuclear reactors, and, if so, were. alvarez suggested airplane carry system detect radioactive gases reactor produces, particularly xenon 133. equipment did fly on germany, detected no radioactive xenon because germans had not built reactor capable of chain reaction. first idea of monitoring fission products intelligence gathering. become extremely important after war.

wearing helmet , flak jacket , standing in front of great artiste, tinian 1945

as result of radar work , few months spent fermi, alvarez arrived @ los alamos in spring of 1944, later many of contemporaries. work on little boy (a uranium bomb) far along alvarez became involved in design of fat man (a plutonium bomb). technique used uranium, of forcing 2 sub-critical masses using type of gun, not work plutonium because high level of background spontaneous neutrons cause fissions 2 parts approached each other, heat , expansion force system apart before energy has been released. decided use critical sphere of plutonium , compress explosives smaller , denser core, technical challenge @ time.

to create symmetrical implosion required compress plutonium core required density, thirty 2 explosive charges simultaneously detonated around spherical core. using conventional explosive techniques blasting caps, progress towards achieving simultaneity within small fraction of microsecond discouraging. alvarez directed graduate student, lawrence h. johnston, use large capacitor deliver high voltage charge directly each explosive lens, replacing blasting caps exploding-bridgewire detonators. exploding wire detonated thirty 2 charges within few tenths of microsecond. invention critical success of implosion-type nuclear weapon. supervised rala experiments. alvarez later wrote that:

with modern weapons-grade uranium, background neutron rate low terrorists, if had such material, have chance of setting off high-yield explosion dropping 1 half of material onto other half. people seem unaware if separated u-235 @ hand, s trivial job set off nuclear explosion, whereas if plutonium available, making explode difficult technical job know.

alvarez (top right) on tinian harold agnew (top left), lawrence h. johnston (bottom left) , bernard waldman (bottom right)

again working johnston, alvarez s last task manhattan project develop set of calibrated microphone/transmitters parachuted aircraft measure strength of blast wave atomic explosion, allow scientists calculate bomb s energy. observed trinity nuclear test b-29 superfortress carried fellow project alberta members harold agnew , deak parsons.

flying in b-29 superfortress great artiste in formation enola gay, alvarez , johnston measured blast effect of little boy bomb dropped on hiroshima. few days later, again flying in great artiste, johnston used same equipment measure strength of nagasaki explosion.