The Physics of Beams
A beam is an ensemble of particles with coordinates that move in close
proximity. The study of beams is important because beams can carry two
fundamentally important scientific concepts, namely energy and information.
Energy has to be provided through acceleration, and the significance of
this aspect reflects itself in the name accelerator physics which is frequently
used synonymously with beam physics. Information is often generated by
utilizing the beam's energy and analyzed in detectors and spectrographs;
or it is transported at high rates and is thus relevant for the practical
aspects of information science.
|Beam physics has its historical roots in the seemingly disconnected
fields of optics and celestial mechanics, in which nonlinear motion of
nearby coordinates is studied; in the former often to high precision over
short distances, and in the latter frequently in a more qualitative way
over long time scales.
The field made a major step forward with the development of the Cyclotron
by E. O. Lawrence, for which he received the Nobel prize in 1939. For the
first time it was possible to produce beams of a select kind of ions at
significant energy for nuclear study.
The original cyclotron developed by E. O. Lawrence at Berkeley
||Beams have a wide variety of applications. The field of high energy physics or particle physics utilizes both
aspects of beams, and they are so important that they even are directly
reflected in the names of the field. First, common particles are brought
to energies far higher than they usually have on earth. Then this energy
is utilized in collisions to produce particles that do not exist in our
current natural environment, and information about such new particles is
In a similar way, nuclear physics uses the energy of beams to produce
isotopes that do not exist in our natural environment, and extracts information
about their properties. It also uses beams to study the dynamics of the
interaction of nuclei. Both particle physics and nuclear physics also re-create
the state of our universe when it was much hotter, and beams are used to
artificially generate the ambient temperature at these earlier times. Two
of the currently important questions are related to the understanding of
the time periods close to the big bang as well as the understanding of
nucleosynthesis, the generation of the variety of currently existing different
||In chemistry and material science, beams provide tools to study the
details of the dynamics of chemical reactions and a variety of other questions.
In many cases, these studies are performed using intense light beams, which
are produced in conventional lasers, free electron lasers, or synchrotron
light sources. Among the various medical applications, particle beams are
used for the irradiation of tumors.
In our days, the ability to transport information is being applied in
the case of fiber optics, where short light pulses provide very high transfer
rates. And electron beams transport the information in computer displays
and the television tube, one of the most wide spread consumer products.
|The motion of beams is a prime example of nonlinear dynamics; in fact,
beams were one of the first places where chaos was observed.
Also the two historical roots of the field of beam physics continue
to enjoy great progress. Modern glass lenses for cameras are better, more
versatile, and more wide spread then ever before, and modern electron microscopes
now achieve unprecedented resolutions in the Angstrom range. Celestial
mechanics has made considerable progress in the understanding of the nonlinear
dynamics of planets and the prospects for the long term stability of our
||The development of particle accelerators continues at a vibrant pace.
The Large Hadron Collider at CERN, Switzerland will reach new energy frontiers;
and the planned Next Linear Collider will provide particularly pure new
information by colliding electrons and positrons, substantially reducing
the numbers of undesirable reaction products.
The muon collider currently being contemplated may allow similarly clean
collisions while allowing the beams to be bent due to the significantly
reduced losses due to radiation.
To embark towards these new frontiers requires education of new
beam scientists, and the sharing of the exiting goals with the wider community.