Donald W. Kerst

Born in Galena, Illinois, on November 1, 1911, Donald William Kerst quickly discovered a passion for physics, for which he earned a bachelor's degree in 1934 and a doctorate in 1937 from the University of Wisconsin. After graduating, he became an instructor, assistant professor, and then professor at the University of Illinois. He remained at the University from 1938 to 1957, with the exception of brief periods at General Electric (1937-1938, 1940), at Los Alamos, New Mexico (1943–45), and at the General Atomic Laboratory, La Jolla, California (1957–62). 

Donald Kerst, ca. 1950, wielding a soldering gun and drill. 

Before coming to Illinois, Kerst wrote to then F. L, Loomis, then the department head of Physics at Illinois, describing a "small electron accelerator which will go to very high voltages" and would "increase the flux within the robot of an electron and so induce an E.M.F. along its orbit which causes an acceleration". Loomis encouraged Kerst to work on this project at Illinois. It would become his most famous invention: the betatron. Created in 1940, the betatron was a particle accelerator that used a revolutionary method that "pushed" particles, rather than "kicking" them for the purpose of acceleration. So great was its impact, that it not only influenced every single particle accelerator that came after it, but also made significant contributions to the field of medicine for the more powerful x-rays it could produce. 

A true experimentalist, Kerst stayed committed to his project despite only having a $500 budget for it, and completed the first implementation of his invention in a little under a year, according to Loomis. However, the betatron garnered interest from the military for defense purposes, and in 1943, at the personal request of Dr. J.R. Oppenheimer, Kerst joined many other great scientists at Los Alamos to begin work on scientific advancements for the Second World War, most notably the atomic bomb. 

Despite the work he was doing, which Kerst admitted in correspondence was "very worthwhile", Kerst became ill shortly after arriving in Los Alamos and made repeated appeals to both those at Illinois and in the Military to be released from his assignment early. Oppenheimer, too, made an appeal for Kerst to be released as well. However, all appeals were rejected, Kerst recovered, and continued his work there before returning to the University at Illinois. Back at Illinois, Kerst designed bigger and more powerful versions of his invention, along with working on other key Illinois innovations, such as ILLIAC. 

Prof. Gerald P. Kruger (left), Prof. Donald W. Kerst (center), and Prof. James N. Snyder (right) examine some of the computations made by the ILLIAC, University of Illinois electronic computer, September 5th, 1957. 

Eventually, Kerst made the move back to his alma mater in 1962. This was largely a result of the efforts L.R. Ingersoll, Department of Phyics head at Wisconsin, who for years sent letters reinforcing the wish for Kerst to return to Wisconsin to teach. In one of the letters, Ingersoll goes so far as to nominate Kerst for the Nobel Prize in Physics, reminding Kerst that, should he win, to "please have some kind thoughts in your head towards us here at Wisconsin". Evidently he did, for Kerst remained at Wisconsin until his retirement to Florida with his wife, Dorothy. 

Even while retired, Kerst never forgot the research he helped develop, always making sure to call regularly and get updates. Donald W. Kerst died aged 81 on August 19th, 1993. 

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Sources:

Betatron Correspondence, 1938-1970, Record Series 11/10/11, University Archives, University of Illinois. 

Correspondance. Donald W. Kerst Papers, 1937-1959, 1983-85, 1987. Record Series 11/10/30, University Archives, University of Illinois.

Kerst to Loomis, Nov. 28, 1938, Betatron Correspondence, 1938-1970, Record Series 11/10/11, University Archives, University of Illinois.

Sessler, Andrew and Keith R. Symon. (1997) "Donald William Kerst". Biographical Memiors, v. 72. The National Academies Press: Washington D.C. 

Sprott, J.C. (1993). "Eulogy to Donald W. Kerst.". Retrieved from http://sprott.physics.wisc.edu/eulogy.htm on September 3rd, 2013. 

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Betatron

Professor Donald Kerst built the world’s first magnetic induction accelerator in 1940: the betatron weighed in at just under four tons and required about 30 kilowatts to run. Branded as the “World’s Most Powerful X-Ray Machine”, the betatron could accelerate electrons at speeds of more than 158,000 miles per second and give them an energy of more than 2.5 million electron volts. At the time, this was the highest velocity ever produced by any machine. The betatron operates by giving the electrons inside the vacuum tube a continuous “push” using a magnetic field, which allows them to attain their great speed and energy.

Professor Kerst making an adjustment on the first betatron, University of Illinois, 1940

The original Betatron was called many different names, ranging from “rheotron” and “inductron” to “Super X-ray Machine” and “cosmic ray machine”. Eventually, Professor Kerst held a departmental competition. After receiving many entries, one of the most interesting being: “Ausserordentlichhochgeschwindigkeitelektronenentwickelndenschwerarbeitsbeigollitron”, which roughly translates as “Hard working by golly machine for generating extroadinarily high-velocity electrons”. Kerst eventually decided on “betatron”.

Professor Kerst poses with the "Original Betatron", University of Illinois, 1941

From the beginning, Professor Kerst identified three major applications for later incarnations of the betatron: 1) For industry, a powerful source of X-rays of 20 to 30 million volts energy, 2) For medicine, a source of x-rays or for an electron beam for use against cancer and other malignant tissues; and 3)For scientific research, a powerful X-ray and electron source with precision control, and a laboratory source of  cosmic rays, produced at energies of 250 million volts or more. The images produced by the betatron were described by Arthur Wildhagen of Scientific American  as “knife-sharp”.

As with many devices of the day, the later incarnations of the Betatron captured the military’s interest. A portable version of the betatron, or a “baby” Betatron, was developed in secret during World War II. Developed by Professor Gerald M. Almy while Professor Kerst was away working on the atomic bomb, this Betatron could generate radiation equal to that of 3 grams of radium at one-tenth of the price.

The betatron had a lasting impact on the design of other atom smashers. Power giant General Electric later built a 100 million volt betatron for personal use, but researchers at the time believed it had little practical application beyond the field of physics. 

*Learn more about Kerst and the Betatron in this blog post from the University Archives



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Works Cited:

Department of Physics.(2013). “Physics in the 1940s: The Betatron”. Retrieved on Febuary 11th, 2013 from http://physics.illinois.edu/history/Betatron.asp

Kingery, R.A. et al. (1967). Men and Ideas in Engineering: Twelve Histories from Illinois. University of Illinois Press: Urbana.

Kerst, Donald W. “Development of the Betatron and Its Place in Science”. From Talk Given at Dedication of Betatron, United States Army Arsenal, Picatinny, New Jersey.Found in University Archives Series 11/10/12, Box 14.

Wildhagen, A.R. (May, 1943). “The Betatron”. Scientific American. Reprint found in University Archives Series 11/10/12, Box 14.

Wright, Joe. (Sun, Apr. 14, 1943). “Baby Betatron”. University of Illinois News.




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