Q: What is a gyroklystron?

A: A gyroklystron is a large microwave amplifier. "Gyro" comes from Latin and means "spinning" or "circle" (electrons in the device spin around in a circle). A klystron is another type of microwave amplifier.

Q: Doesn't the word "gyroklystron" sound like a Greek sandwich?

A: Yes.

Q: How does it create microwaves?

A: It converts energy from the kinetic motion of electrons into electric and magnetic fields, which resonate back and forth at a microwave frequency. The electrons are fired from an electron gun. Magnetic fields surrounding the device cause the electrons to begin to spin. The electrons travel down the length of the device and pass through a series of cavities. Here, a cavity is just an open space where electric and magnetic fields can be set up. In the first cavity, a microwave signal is sent in and interacts with the beam of electrons. This makes the beam begin to cluster together. In general, the closer the electrons cluster, the more power is created into microwaves.

As the beam continues to pass through the device, it may encounter more cavities. These cavities will help to continue the electron clustering process. Eventually the beam will reach the output cavity. This is the place where the conversion of energy occurs. The beam slows down its spinning and electric and magnetic fields are created. These fields are "let out" of the cavity through a hole at one end. From here they travel down the rest of the system where they are detected by our equipment.

Q: What is the microwave frequency range?

A: Microwave frequencies are between about 3 GHz and 300 GHz. This range is not well defined, however, and is more for convenience of definition than a well-established standard.

Q: How much conversion of energy occurs in a gyroklystron?

A: In the lab, we have converted a maximum of 32% of the electron's kinetic energy into microwaves, although programs we have run say that we may be able to get up to 42%.

Q: How do you detect the microwaves?

A: We use two methods, although a few other methods exist. The first is just putting a bunch of water at the end of the system. The microwaves will heat the water just like in a microwave oven. We measure how much the water is heated and calculate the microwave power from this. The second method uses an electronic device called a diode. When a microwave signal hits the diode, the voltage of the diode changes in proportion with the signal.

Q: How much microwave power are you trying to produce?

A: We are trying to create 100 megawatts (MW). This is equivalent to the power in 1 million light bulbs. We create this power for only 1 microsecond, which is one millionth of a second. So the total energy we produce is only equal to a light bulb kept on for 1 second.

Q: Why are you doing this?

A: Good question. First ask what a linear accelerator is and for what it is used.

Q: What is a linear accelerator and what is it used for?

A: A linear accelerator is a huge device some physicists use to try to figure out many very important questions about matter and time. For example, what happened at the beginning of the universe? What is matter composed of? The accelerator takes two beams of particles, usually electrons and positrons (which is the anti-electron) and gets them going really, really, really, really fast and rams them together in a big explosion. Some people say that this is a holdover from when they were young and would crash their "Hot Wheels" cars together.

Anyway, the electrons and positrons have to speed up in a straight line. When electrons travel in a circular path, they give up enormous amounts of energy. Another option is to bend them in a really big circle. They do this in Europe at the LEP (Large Electron Positron collider).

The way electrons and positrons are sped up for the collision is like surfing. The difference is that the particles use an electromagnetic wave, instead of a water wave. They get on the wave at a high energy point, and the wave carries them along and then pushes them faster.

There must be many waves pushing the particles along to get them going as fast as they need to get (very close to the speed of light - 186,000 miles in 1 second). But since, they are moving in a straight line, we must put many "wave creators" along that line, and in such a way so that the speed of the particles keeps increasing (you don't want the surfer to enter the wave at the wrong point - he could wipe out).

Q: How does this relate to why you are doing this?

A: We are making a "wave creator". Right now they use the devices I mentioned above: klystrons. But maybe in the future, the waves will need more power (water wave height) and higher frequency (more waves in a given time). If this is the case, the gyroklystron may be the best thing to use. We are trying to see how good it could be.

Q: Who invented the gyroklystron?

A: I DON"T KNOW BUT IT IS IN JIM'S THESIS.

Q: What else is a gyroklystron good for?

A: Anything you might need a high frequency, powerful signal for. Some things it might be good for is satellite communication, foul weather radar, EMP devices, and/or space applications like energy beaming.