The ‘Find out Friday’ interview

Credit Dr Chuck Crawford

What is an electron gun and how are they used?

An electron gun is a device that generates a beam of electrons. Electrons are the elementary particles which make up most of the volume of atoms. Beams of electrons (an area called electron optics) are used in a very wide variety of applications. They are the basis of numerous analytical instruments, many scientific experiments, and a number of industrial processes. Electron guns have nothing to do with weapons. Electron beams get absorbed after traveling only a couple of centimeters in air. Hence virtually all electron beams are used in vacuum.

What is Kimball Physics?

Kimball Physics is an organization composed of several physicists and dozens of support staff located in New Hampshire, USA. It makes many different kinds of electron guns and electron sources. Our devices are used in esoteric physics experiments, semiconductor manufacturing, the space program, electron microscopes, and numerous other applications worldwide. This is an interesting and prosperous scientific area.

Credit Kimball Physics Inc

Weren’t electron guns formerly used in televisions and computer displays?

Yes, but that application is dead. It is fundamentally easier to process information using conduction electrons in a solid, than with free electrons in an empty vacuum. Electron guns and electron optics require vacuum. The only reason electron guns were used in old fashioned glass television tubes, is that the appropriate solid-state devices hadn’t been invented yet.

How strong or how weak can electron beams be?
Electron beam parameters can vary over very wide ranges. Useful beam currents can range from less than one electron per second (less than a billionth of a billionth of an ampere) to thousands of amperes (a range of more than twenty-two orders of magnitude). Electron energies can go from a fraction of an electron volt to tens of billions of electron volts (a range of more than ten orders of magnitude). Beam diameters can range from below one nanometer (the size of an individual atom) to several meters (another ten orders of magnitude). This makes the physics exciting, and leads to many applications.

Credit Kimball Physics Inc

How do you make an electron gun, perhaps to experiment with electron optics?
You need a vacuum to run it in. You need a source of electrons (there are several kinds). You need some metal electrodes to accelerate and focus the electrons. You need some voltage sources to drive the electrodes (power supplies or batteries). And you need some method of detecting the electron beam you produce (again several choices). Students can do it.

Where would humankind be without electron guns?
The use of electron guns is fundamental to many areas of science and technology. The manufacture of computers, cell phones, and computer games all depend on electron optics; because the manufacture of microchips requires electron optics. Even biology and medicine are dependent on electron optics (for example electron microscopes). Interestingly enough, you can use electron beams to make high performance lasers (example: free electron lasers), and conversely, you can use lasers to make high performance electron guns (example: ultra-high pulsed electron guns). These technologies along with many other technologies all complement each other.

Credit Kimball Physics Inc