Chapter 1
Beams and Beam Physics
In this chapter we will lay the foundations of basic concepts about beam
physics, and discuss various important mechanisms of production and acceleration of beams. Because of the breadth of the material and the multitude
of existing devices for each of the mechanisms, we will focus only on key concepts, and introduce them through the eyes of their inventors by using their
original historical drawings, with only minor adjustments for uniformity of
style and technical clarity.
1.1 What Is Beam Physics?
The field of beam physics deals with motion of ensembles of particles
(usually charged) in electromagnetic fields. It is called beam physics due
to the fact that, in most cases, those particles have similar coordinates,
which is the rough definition of a beam. In many cases, the positions and
momenta of the particles are sufficient to describe their motion. In this
case, the particles are described by a state vector consisting of positions and
momenta
Z = (x, p x , y, p y , z, p z ) .
In other cases, additional coordinates may be needed; typical examples include the mass, sometimes the charge, or the spin vector and the related
magnetic moment and possibly electric moment of the particle.
An ensemble of particles with such similar coordinates is called a beam
(see Fig. 1.1), and the sub-fields concerned with the study of such beams is
called beam physics. There are other fields of physics that can be described
in very similar terms and language, some of the most notable examples being
light optics and astrodynamics. There are also other sub-fields of physics
dealing with the study of the motion of such ensembles of particles; important
examples are plasma physics and the dynamics of galaxies. These fields
are different from beam physics in that in their cases, the particles usually do
not have rather similar coordinates but occupy larger regions.
The space of state vectors
Z is often called phase space, and a coordinate
system showing
Z is often called a phase space diagram. The volume of
1
DOI: 10.1201/b12074
DOI:10.1201/b12074-1
Beams and Beam Physics
In this chapter we will lay the foundations of basic concepts about beam
physics, and discuss various important mechanisms of production and acceleration of beams. Because of the breadth of the material and the multitude
of existing devices for each of the mechanisms, we will focus only on key concepts, and introduce them through the eyes of their inventors by using their
original historical drawings, with only minor adjustments for uniformity of
style and technical clarity.
1.1 What Is Beam Physics?
The field of beam physics deals with motion of ensembles of particles
(usually charged) in electromagnetic fields. It is called beam physics due
to the fact that, in most cases, those particles have similar coordinates,
which is the rough definition of a beam. In many cases, the positions and
momenta of the particles are sufficient to describe their motion. In this
case, the particles are described by a state vector consisting of positions and
momenta
Z = (x, p x , y, p y , z, p z ) .
In other cases, additional coordinates may be needed; typical examples include the mass, sometimes the charge, or the spin vector and the related
magnetic moment and possibly electric moment of the particle.
An ensemble of particles with such similar coordinates is called a beam
(see Fig. 1.1), and the sub-fields concerned with the study of such beams is
called beam physics. There are other fields of physics that can be described
in very similar terms and language, some of the most notable examples being
light optics and astrodynamics. There are also other sub-fields of physics
dealing with the study of the motion of such ensembles of particles; important
examples are plasma physics and the dynamics of galaxies. These fields
are different from beam physics in that in their cases, the particles usually do
not have rather similar coordinates but occupy larger regions.
The space of state vectors
Z is often called phase space, and a coordinate
system showing
Z is often called a phase space diagram. The volume of
1
DOI: 10.1201/b12074
DOI:10.1201/b12074-1