8 Accelerator Engineering and Technology: Accelerator Technology
455
some 100 femtoseconds. Spatial decoding [161] uses a short laser pulse that crosses
the crystal at an angle such that when it interferes with the beam signal, the temporal
profile of the electron bunch is encoded onto the transverse profile of the laser, i.e.
mapping time into space.
Such techniques all rely on the use of very short laser pulses and precise laser to
beam synchronization.
8.7 Injection and Extraction Related Hardware: Kickers
and Septa
M. J. Barnes · J. Borburgh · V. Mertens
This chapter describes the main hardware elements involved in single-turn
injection and fast extraction, as well as resonant slow extraction: fast pulsed systems
(kickers) and magnetic and electrostatic septa. For a description of the beam
processes involved reference is made to Sect. 6.3. For space reasons other associated
components, such as stripping foils used for multi-turn injection, injection and
extraction related protection systems, or specific beam instrumentation, are not
discussed here. For certain of these components information can be found in the
corresponding chapters of this volume.
Injection and extraction regions are particularly challenging areas in accelerators
in several respects. The space allocated for these parts, which are usually located
in straight sections, is naturally rather limited so that the space available for
bending sections (in the case of a circular machine) or accelerating structures (in
the case of a linear accelerator) can be maximized, and with it the achievable
energy for a given circumference or length of the accelerator. As a result injection
and extraction related elements are often required to be as physically short and
electrically or magnetically strong as technically feasible (yet remaining reasonable
in cost). Although magnetic kickers and septa are dipole magnets, following the
same principles as ordinary bending elements, they have very distinct features and
must often fulfil conflicting design requirements. They are typically purpose-built
single elements or only produced in a small series. Many of these elements are
installed under vacuum, with the resulting implications.
Figure 8.66 shows an example of fast single-turn injection in one plane [162,
163]. The injected beam passes through the homogeneous field region (aperture)
of the septum: circulating beam is in the field-free region. The septum deflects the
injected beam onto the closed orbit at the centre of the kicker magnet; the kicker
magnet compensates the remaining angle. The septum and kicker are either side of a
quadrupole (defocusing in the injection plane) which provides some of the required
deflection and minimizes the required strength of the kicker magnet.
Magnetic septa usually have high current densities (in the order of 100 A/mm 2 );
a short interruption in the cooling can lead to their destruction. Electrostatic septa
455
some 100 femtoseconds. Spatial decoding [161] uses a short laser pulse that crosses
the crystal at an angle such that when it interferes with the beam signal, the temporal
profile of the electron bunch is encoded onto the transverse profile of the laser, i.e.
mapping time into space.
Such techniques all rely on the use of very short laser pulses and precise laser to
beam synchronization.
8.7 Injection and Extraction Related Hardware: Kickers
and Septa
M. J. Barnes · J. Borburgh · V. Mertens
This chapter describes the main hardware elements involved in single-turn
injection and fast extraction, as well as resonant slow extraction: fast pulsed systems
(kickers) and magnetic and electrostatic septa. For a description of the beam
processes involved reference is made to Sect. 6.3. For space reasons other associated
components, such as stripping foils used for multi-turn injection, injection and
extraction related protection systems, or specific beam instrumentation, are not
discussed here. For certain of these components information can be found in the
corresponding chapters of this volume.
Injection and extraction regions are particularly challenging areas in accelerators
in several respects. The space allocated for these parts, which are usually located
in straight sections, is naturally rather limited so that the space available for
bending sections (in the case of a circular machine) or accelerating structures (in
the case of a linear accelerator) can be maximized, and with it the achievable
energy for a given circumference or length of the accelerator. As a result injection
and extraction related elements are often required to be as physically short and
electrically or magnetically strong as technically feasible (yet remaining reasonable
in cost). Although magnetic kickers and septa are dipole magnets, following the
same principles as ordinary bending elements, they have very distinct features and
must often fulfil conflicting design requirements. They are typically purpose-built
single elements or only produced in a small series. Many of these elements are
installed under vacuum, with the resulting implications.
Figure 8.66 shows an example of fast single-turn injection in one plane [162,
163]. The injected beam passes through the homogeneous field region (aperture)
of the septum: circulating beam is in the field-free region. The septum deflects the
injected beam onto the closed orbit at the centre of the kicker magnet; the kicker
magnet compensates the remaining angle. The septum and kicker are either side of a
quadrupole (defocusing in the injection plane) which provides some of the required
deflection and minimizes the required strength of the kicker magnet.
Magnetic septa usually have high current densities (in the order of 100 A/mm 2 );
a short interruption in the cooling can lead to their destruction. Electrostatic septa