He directed the Argonaut Research Reactor facility at Argonne National Laboratory, conducting neutron measurements and developing operational procedures (1958-1959).
Using bremsstrahlung radiation from the betatron beam, he and G. S. Klaiber excited uranium nuclei and observed a prominent peak at about 20 MeV in the cross section for photons (1947), (1948), which was not anticipated by the nuclear physics community.
[2] His book "An Introduction to Nonlinear Optics" (1969) helped bridge the gap in knowledge between specialists in the field and engineers and technical managers involved with this new technology.
He launched international efforts to define and quantify issues facing the development of this advanced idea, working with many academic colleagues, including R. V. Khokhlov and V. I. Gol'danskii of the USSR and J. C. Solem of Los Alamos, opening an entirely new field of physics and making bold, creative attempts to bring the concept to fruition (1963), (1965), (1975).
Baldwin's 57-year marriage to his wife Winifred, who collaborated as copy editor and typist for many of his publications, produced three children and seven grandchildren, of these three obtained a college degree in physics.
Baldwin was an avid amateur astronomer, grinding his own lenses and building his own telescopes; fisherman; self-taught pianist, entertaining friends by playing by ear; and historical researcher.