Long Distance Calls, ‘Star Wars’ System Use It : Ubiquitous Klystron Gets No Respect
What’s been around for half a century, looks like a piece of plumbing, can weigh a ton or be held in the palm of your hand, and makes life a lot easier?
The klystron?
The vacuum tube that beams high-speed microwave signals and continues to revolutionize technology was an obscure invention when it was born on Aug. 19, 1937, and it still gets no respect.
It remains virtually unknown by a public that usually marvels at U.S. engineering ingenuity. Even scientists still make it the butt of jokes.
The first klystron was put together by two California brothers in a back room at Stanford University with $100 and the luck of the Irish.
Since then, everyday life just hasn’t been the same.
‘Homely, Vintage Device’
“Suffice it to say, it is unlikely you get through a single day without--probably unknowingly--making use of this homely, vintage device,” writes Joel Shurkin, the university’s science writer, who is helping the school celebrate the device’s golden anniversary.
“Modern semiconductor technology cannot match the kind of power a klystron produces,” he said. “It is a million times more powerful, and it is likely to remain so for the foreseeable future.”
This is what klystrons, which run in length from several inches to several feet, do for you:
- They are on weather, air traffic control and aircraft radar systems.
- Many long-distance telephone calls still use klystron-driven microwave relays.
- Every major UHF television station broadcasts its signal with a klystron and the tubes are used in cable television to relay signals to outback communities.
- Communicating with space satellites and stations depend on klystrons, as does NASA’s Deep Space Network, which uses them to “talk” with spacecraft soaring through the solar system and beyond.
- Particle accelerators, especially those employing electrons for high-energy physics research, generally use klystrons to kick the particles to near light speed.
- Cancer patients often are treated with radiation produced by small atomic accelerators run by a klystron.
- The tube remains one of the mainstays of America’s defense system, forming integral parts of anti-missile systems. Even the so-called “Star Wars” space-based weapons defense system will use them.
The klystron was the brainchild of Sigurd and Russell Varian, the children of Irish immigrants, who respectively were a barnstorming World War II-era pilot and a dyslexic research assistant before getting into the inventing business.
University Backed Inventors
The Varians came up with 36 inventions of “varying impracticality,” according to Edward Ginzton, who worked with them and later became chairman of their company, Varian Associates Inc. of San Carlos, Calif.
They then took their 37th invention, the klystron, to friend William Hansen, a physics professor at Stanford, who in turn got the university to back the inventors.
Using the klystron, the British improved their radar system to the point they could spot German bombers on their way to England, according to Shurkin. So valuable was the secret, the British decided not to put the klystron-radar in planes that flew over occupied Europe.
The klystron works like this: a filament is heated by electrical current, which heats a cathode, which then gives off electrons. The electrons combine into bunches and speed up as they pass through several cavities of a tube.
Microwaves interacting with the “excited” electrons are amplified and speeded up before exiting.
The Varians manufacturing company accounts for more than 40% of the $150 million worth of the vacuum-tubes sold worldwide each year. Russell died in 1959, Sigurd in 1961.
