Background: Luis Walter Alvarez was born in San Francisco on June 13, 1911, the second child and oldest son of Walter C. Alvarez, a physician, and his wife Harriet nee Smyth, and a grandson of Luis F. Alvarez, a physician who lived for a time in Spain, then Cuba, and finally the United States, who found a better method for diagnosing macular leprosy. He had an older sister, Gladys, a younger brother, Bob, and a younger sister, Bernice. His aunt, Mabel Alvarez, was a California artist specializing in oil painting. He attended Madison School in San Francisco from 1918 to 1924, and then San Francisco Polytechnic High School.
Context: Alvarez's sister, Gladys, worked for Ernest Lawrence as a part-time secretary, and mentioned Alvarez to Lawrence. Lawrence then invited Alvarez to tour the Century of Progress exhibition in Chicago with him. After he completed his oral exams in 1936, Alvarez, now engaged to be married to Geraldine Smithwick, asked his sister to see if Lawrence had any jobs available at the Radiation Laboratory. A telegram soon arrived from Gladys with a job offer from Lawrence. This started a long association with the University of California, Berkeley. Alvarez and Smithwick were married in one of the chapels at the University of Chicago and then headed for California. They had two children, Walter and Jean. They were divorced in 1957. On December 28, 1958, he married Janet L. Landis, and had two more children, Donald and Helen. At the Radiation Laboratory he worked with Lawrence's experimental team, which was supported by a group of theoretical physicists headed by Robert Oppenheimer. Alvarez devised a set of experiments to observe K-electron capture in radioactive nuclei, predicted by the beta decay theory but never observed. Using magnets to sweep aside the positrons and electrons emanating from his radioactive sources, he designed a special purpose Geiger counter to detect only the "soft" X-rays coming from K capture. He published his results in the Physical Review in 1937. When deuterium (hydrogen-2) is bombarded with deuterium, the fusion reaction yields either tritium (hydrogen-3) plus a proton or helium-3 plus a neutron (2H + 2H - 3H + p or 3He + n). This is one of the most basic fusion reactions, and the foundation of the thermonuclear weapon and the current research on controlled nuclear fusion. At that time the stability of these two reaction products was unknown, but based on existing theories Hans Bethe thought that tritium would be stable and helium-3 unstable. Alvarez proved the reverse by using his knowledge of the details of the 60-inch cyclotron operation. He tuned the machine to accelerate doubly ionized helium-3 nuclei and was able to get a beam of accelerated ions, thus using the cyclotron as a kind of super mass spectrometer. As the accelerated helium came from deep gas wells where it had been for millions of years, the helium-3 component had to be stable. Afterwards Alvarez produced the radioactive tritium using the cyclotron and the 2H + 2H reaction and measured its lifetime. In 1938, again using his knowledge of the cyclotron and inventing what are now known as time-of-flight techniques, Alvarez created a mono-energetic beam of thermal neutrons. With this he began a long series of experiments, collaborating with Felix Bloch, to measure the magnetic moment of the neutron. Their result of m0 = 1.93+-0.02 mN, published in 1940, was a major advance over earlier work. CANNOTANSWER
Question: Did he invent anything ?

Answer:

foundation of the thermonuclear weapon