Varian Linatron High-Energy X-ray Applications 2007

Introduction
X-rays are a type of electromagnetic energy that occupies a
particular place in the electromagnetic spectrum. What we
refer to as X-rays is a type of energy that can be understood
as both particles and waves because they have characteristics
of both. Photons are the particle aspect of X-rays, which
are mass-less and travel at the speed of light. These are
produced by Linatrons when high energy electrons are
accelerated and strike a high density metal target. This
releases photons in the X-ray frequency band as shown in
Fig. 1-1.
FIGURE 1-1. Spectrum
Nondestructive testing using high energy (greater than 1
MeV) radiographic techniques has been in use for more
than 60 years. During this period, a number of highenergy
X-ray sources have been developed for the detection
of flaws in heavy metal sections. More recently, these x-ray
sources have found important uses in cargo screening and
related security inspections applications. Please consult
other Varian documentation for information on cargo
screening applications.
The first commercial high-energy X-ray source was the 1
MeV resonant transformer, introduced by General Electric
in 1939. A few years later there appeared 2 MeV versions
of the resonant transformer, Van de Graaff generators with
energies of 1 MeV and 2 MeV, and Betatrons with electron
beam energies ranging from 15 MeV to 25 MeV.
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The maximum X-ray output of these early machines was
limited. Electron linear accelerators, which became available
commercially about 1956, offered a way to substantially
increase the X-ray output and made practical the
radiography of steel sections greater than 2 feet thick. This
met the need of modern nuclear technology which required
radiographic examination of assemblies containing relatively
thick sections of very dense material, such as uranium and
tungsten alloys. Linear accelerators proved capable of
penetrating and recording flaws or other anomalies on x-ray
film through many inches of such materials.
Varian SIP (Security and Inspection Products) first
extended its linear accelerator technology into the highenergy
radiography field in December 1959 with the
delivery to the U.S. Navy of a 10 MeV machine designed
to produce high-quality radiographs of the Polaris missile
and other solid rocket motors. In the years that followed,
Varian SIP continued to supply similar machines to
government and industrial customers.
In 1968, Varian SIP introduced the Linatron®, a line of
industrial linear accelerators with energy ranges from 1 to
15 MeV. The Linatron represented a significant advance
in reliability and ease of operation and handling. A typical
Linatron installation includes an X-ray head (Figs. 1-2 and
FIGURE 1-2. Linatron M9 X-ray head.
Varian Linatron applications