1.6. General Properties and Sources of Particles and Waves 47
always integral multiples of the nucleus of hydrogen atom. He called this basic unit
“proton”.
Protons have found many useful applications in medicine and research. For ex-
ample proton beams are used to destroy cancerous tumors. They are also extensively
used in high energy physics experiments to explore the fundamental particles and
their properties.
D.1 SourcesofProtons
The effectiveness of proton beams in several fields, such as radiography, imaging,
and fundamental physics research has led to the development of state of the art
proton production facilities around the world.
Particle Accelerators
Particle accelerators are one the most important tools of fundamental physics
research. The discoveries of different quarks making up protons and neutrons have
all been made at particle colliders where particles are first accelerated at very high
energies and then made to collide either with other particles or with some other
target material. Fermi National Accelerator Laboratory in USA has huge particle
accelerators that make up the Tevatron collider. In Tevatron protons and anti-
protons are accelerated in opposite directions in a circular ring of about 4 miles in
circumference and then made to collide with each other. The resulting shower of
millions of particles created as a result of this collision are then tracked and analyzed
by very large but extremely sensitive and delicate detection systems.
Cockroft-Walton accelerator is a commonly used device to accelerate protons up
to moderate energies (several hundredMeV). In such accelerators, hydrogen ions
are generated and pumped into a high electric field, which accelerates the ions in
a number of steps. At Fermilab, the protons start their journey from a Cockroft-
Walton accelerator and are then further accelerated by passing them through linear
and circular accelerators.
Apart from fundamental physics research, particle accelerators are also being
extensively used in cancer therapy. Although the success rate for proton therapy
is high, its use has been limited largely by the unavailability of dedicated in-house
high energy proton accelerators in most of the oncology clinics. For such clinics
the other option is to use the facilities of particle accelerators not specifically built
for radiation therapy. Many such accelerator laboratories provide beam times for
cancer treatment. However, since their uptime is never guaranteed, it becomes
difficult to schedule a travel plan for patients and clinicians to the facilities. Also
the long distances that sometimes have to be traveled by patients, who are already
fatigued by the disease, make the treatment process very uncomfortable. A number
of particle accelerators have developed their own cancer therapy stations with trained
beam technicians and clinicians. Some of the major hospitals also have small sized
accelerators that are mainly used for cancer treatment.