[2][3] Hansen went on to become interested in the problem of accelerating electrons for X-ray experiments, using oscillating fields, rather than large static voltages.
At the University of California, Berkeley, Ernest Lawrence and his assistant David H. Sloan, had worked on an accelerator driven by a resonant coil.
Hansen exploited some of the Varian's work to develop the klystron and during the years 1937 to 1940, along with collaborators such as John R. Woodyard, founded the field of microwave electronics.
[3] In 1941, he moved his team to the Sperry Gyroscope Company where they spent the war years employing their expertise in radar applications and in other problems.
[3] [4] [5] Returning to Stanford in 1945 as a full professor, he embarked on the construction of a series of linear accelerators based on klystron technology [6] and of GeV performance.