Feb 042019

Today is the birthday (1883) of Reinhold Rudenberg (or Rüdenberg) a German- born electrical engineer and inventor, credited with many innovations in electric power and related fields, but best known for the invention of the electrostatic-lens electron microscope.

Reinhold Rudenberg was born in Hanover. His father Georg was a manufacturer, who operated a plant for preparing and cleaning feathers and down goods. His mother was a daughter of the chief rabbi of the county of Braunschweig. He attended the Technical University of Hanover (then Technische Hochschule), and after receiving his electrical engineering degrees (Dipl. Ing.) and doctorate (Dr. Ing.), both in 1906, he worked for Ludwig Prandtl as a teaching assistant at the Institute for Applied Physics and Mechanics at Göttingen University. There he also attended courses in physics and the celebrated Advanced Electrodynamics course by Emil Wiechert, who only ten years earlier had been one of the discoverers of the electron.

After leaving Göttingen in 1908 he started at the manufacturer of electrical machinery Siemens-Schuckertwerke (SSW), part of the Siemens group of companies, in Berlin. He entered as a machine design engineer, and quickly advanced to head this department. His work soon broadened to include transmission lines, distribution systems, and protective relays and switches. In 1923 he was appointed Director of the Scientific Department (Wissenschaftliche Abteilung) of SSW responsible for the research on and development of machinery and systems for the firm. Simultaneously he was named Chief Electrical Engineer (Chef-Elektriker) of the firm.

In 1916, Rudenberg designed the electric generator for the main power station in Cologne, then the largest known. He published much and became a prolific inventor. His books, especially on electrical transients, were widely read and used as college texts.

In 1930, just after returning home from a summer vacation on the Dutch seaside, his 2 year-old son became ill with leg paralysis. This was soon diagnosed as poliomyelitis, which at that time was a frightening disease with a death rate of 10-25% as the disease progressed to the lungs. Polio was then known to be caused by a virus, too small to be visible under an optical microscope. From that time Rudenberg was determined to find or invent a way to make such a small virus visible. He thought that electrons, because of their subatomic size, as he had learned in Göttingen from Wiechert, would be able to resolve such small particles, and he investigated ways to focus these to create their enlarged image.

Already in 1927 Hans Busch, his friend since Göttingen, had published an analysis of a magnetic coil acting as a lens. Rudenberg reasoned that an electron beam leaving a point on an object in an axially symmetric electrostatic system could be focused back to an image point if the radial electric field was proportional to the electron distance from the axis. Thus, he believed that real magnified images could be obtained under these conditions. As the date of a public lecture on electron optics was approaching Siemens applied for a patent on Rudenberg’s electrostatic-lens instrument and his general electron microscope principles on May 30th, 1931. Siemens also obtained patents in six other countries. In Germany this, or patents derived therefrom, were granted at various later times from 1938-1954. Some competitors voiced complaints against the Rudenberg patents, but ignored or did not notice the earlier year that Rudenberg began his invention (1930) nor the difference of the stimulus that initiated it, nor would they recognize the technical differences between his electrostatic electron lenses and the magnetic lenses used by others.

Rudenberg taught at Göttingen, Berlin, London, and in the U.S. at MIT and Harvard University. At Harvard he was head of the Department of Electrical Engineering at the Graduate School of Engineering from 1939-1952, when he retired. He died on Christmas Day, 1961.

Rudenberg’s mother was from Braunschweig, close to Hanover where he was born, and is well known for a number of food and drink specialties. Braunschweig had many breweries, and since the 14th century has produced a beer called Mumme, that can be made in various strengths. Two major breweries still produce Mumme in Braunschweig, the Hofbrauhaus Wolters, founded in 1627, and the former Feldschlößchen brewery, founded in 1871. Braunschweiger Mettwurst is a soft, spreadable smoked pork sausage which is nothing like Braunschweiger in the US, which is just a liver sausage (full details on the original are https://www.bookofdaystales.com/steinway/ ). Other traditional local dishes include white asparagus, Braunschweiger Lebkuchen, and Uhlen un Apen (Low German for “Owls and Guenons”, a pastry).  Then there is Braunkohl, a kale dish served with Bregenwurst (originally brain sausage, but now made with pork products).



1 lb kale, cleaned and chopped
50 gm Bauchspeck, diced
½ onion, chopped
beef stock
1 tbsp mustard
4 Bregenwurst


Bring a pot of water to a boil and blanch the kale for 1 minute, then drain.

In a frying pan, brown the Bauchspeck. Sauté the onion in the pan with the Bauchspeck and its grease and add the kale. Cook for 2 to 3 minutes and then add beef stock to cover. Simmer for 30 minutes.

Add the mustard and stir. Place the sausages on top of the kale and simmer for another 30 minutes. Add pepper to taste.

Serve hot with boiled potatoes.

  2 Responses to “Electron Microscope”

  1. Thanks, Juan, for posting this interesting article about my grandfather! My cousin shared this with all the rest of us cousins. It is a privilege to have known him, even for the few times we visited him while he was alive. I’ve posted your article on Facebook, so you may get some interest from my culinary friends.

    • My pleasure. Reinhold Rudenberg is not exactly a household name, and I do like to give credit where credit is due.

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