Ready, Set, Spark

When Caltech's former Sloan Lab reopened in January 2019 as the Linde Hall of Mathematics and Physics, staff, faculty, and students encountered a structure with a transformed interior that was originally built 97 years ago. The modernized building now boasts open, flexible meeting spaces and ample blackboards for its resident mathematicians. 

Over the course of a century, it has witnessed many changes, evolving to suit the needs of the disciplines it has served: physics, mathematics, and electrical engineering. In its earliest years, the building was known by several names, including Edison High Tension Laboratory and High Voltage Research Laboratory, but was generally referred to as High Volts. It came into being out of a partnership between Caltech and the Southern California Edison (SCE) company, which contributed money to its construction in exchange for use of it for research. SCE had recently decided to change its transmission lines from 150,000 to 220,000 volts. The lines and associated equipment would need to be able to withstand a massive surge if they were struck by lightning, so SCE wanted to conduct research at a million volts, a higher voltage than could be reliably produced by any existing American laboratory. 

The design of High Volts was also a collaboration. Caltech co-founder and physicist Robert Millikan provided specifications, including a requirement that the building have ventilation to allow ozone to escape but also not let in light, so it had no windows. The interior was dominated by a single large industrial space packed with a high-voltage apparatus. A million-volt surge generator produced rapid impulses of artificial lightning. 

Royal Sorensen, professor of electrical and mechanical engineering, who invented the cascade transformer, designed a million-volt model for High Volts, composed of four 250,000 volt transformers that each weighed 22 tons. The transformer stepped up an externally-supplied 15,000 volts to a million volts of continuous current. 

Prominent architect Bertram Goodhue designed the exterior, which used a diamond pattern to provide texture in the absence of windows. Architectural sculptor Lee Lawrie provided the finishing touch with a relief sculpture above the entrance of electricity arcing between two men.

The transmission lines tested at High Volts made it possible to transmit electricity to Southern California from the Hoover Dam. Among the significant inventions of the lab was a vacuum switch designed by Sorensen and Millikan that was manufactured for aircraft and other industries.

Sorensen regularly gave a public lecture and demonstration on high voltage electricity, with the latter portion taking place in High Volts. A 1949 Engineering and Science story described one such event: “It proved to have its usual strong draw this year when, on a rainy Friday evening, almost 1000 people stormed East Bridge. Prof. Sorensen obligingly gave his lecture twice, and the lab ran off three demonstrations, while a special police detail coped with the crush.”

In a 1985 oral history, Caltech chemistry professor Jack Roberts (1918-2016) recalls visiting Caltech as a teenager for these demonstrations. "It looked like Frankenstein’s laboratory," Roberts recalled. "Great transformers topped with big mushroom rings … they’d charge up these things, and they’d start shooting off sparks, or they’d have a 'horn gap,' where a pair of wires would be close together at the top of the transformer and far apart at the top of the room. They would start an arc at the bottom and it would grow in length and rise to the ceiling. … They’d make this crackling noise as they’d go up. And then they’d charge up the condensers and shoot off big sparks. … That was really impressive!" 

High Volts was used for physics as well as electrical engineering. Charles Lauritsen in particular made it a key site for high-voltage X-ray research, building the first million-volt X-ray tube there in about 1930. This device had applications in medicine, and the Los Angeles County General Hospital began to bring cancer patients to High Volts for radiation therapy. 

In 1960, Caltech renovated High Volts into the Alfred P. Sloan Laboratory of Mathematics and Physics introducing a more conventional internal structure, with five floors of space, including new basements, rather than a single large room, and, for the first time, windows. 

—By Peter Collopy, University Archivist

Learn about early Caltech at “Becoming Caltech, 1910–1930,” a series of online presentations