E-beam basics

As you probably remember from your science courses, atoms are composed of protons and neutrons which are located in the nucleus, as well as negatively charged electrons, which are much lighter and orbit the nucleus. Because they are light and only loosely attracted to the nucleus, electrons can be easily separated from the atom, accelerated using magnetic and electric fields, and focused into a beam of energy. This resultant beam can then be scanned by means of an electromagnet to produce a "curtain" of accelerated electrons. Electrons will lose some of their energy due to interaction with air, which is why most electron beams operate in a vacuum.

The beam's strength and the amount of energy that it can deposit onto a target are determined by the difference in voltage between the cathode, where the electrons are released, and the positively charged anode which accelerates the electrons, as well as by the current, which is defined as the number of electrons in the beam which pass through a given area per second.

Everyday applications

One application of accelerated electrons is something that most of us are likely to encounter on a daily basis - our TV sets, where the cathode ray tube operates in much the same manner. In the case of the TV set the e-beam is scanned left and right and up and down the inside surface of the screen causing the chemicals embedded in the screen to fluoresce and produce an image. The tube inside a TV set accelerates electrons to 20,000 volts, whereas modern industrial accelerators can boost electron energies up to 10,000,000 volts.

Industrial applications

These high energy electrons can pass through a thin "window" made of material like titanium, and thus, instead of being scanned across the inside of a glass TV screen, can be scanned over and through objects passing directly beneath the window.

In penetrating these objects the electrons can confer upon them valuable and beneficial chemical and structural changes. For example, accelerated electrons destroy bacteria and mold, making e-beam technology ideally suited for sterilization and bioburden reduction applications. In the case of polymers and plastics, e-beam crosslinking improves a variety of properties, including tensile and impact strength, creep resistance, durability, chemical resistance, environmental stress crack resistance, barrier properties, and others.

Environmental Considerations

Unlike gamma irradiation, which involves the use of a radioactive Cobalt or Cesium source, e-beam technology neither produces nor stores any radiation in the target materials once those materials are outside of the beam. While ionizing radiation is present when the accelerator is on, workers are separated from this potential hazard by thick concrete walls. However, when the accelerator is switched off, the ionizing radiation stops, just like in a TV set.

Economic Considerations

While the value added to products by using e-beam technology can be quite high, so are the costs of installing and operating a dedicated e-beam plant.

The cost for a typical facility, including the beam, shielding, physical plant, conveyor system, safety system, utilities and support equipment can range from $5 million to $9 million, depending on accelerator voltage. That's why most manufacturers turn to contract service companies, like E-BEAM Services, Inc., which provide reliable, high-quality, cost-effective processing on a toll basis.