advanced beam manipulation, cooling, damping and stability 217
D
E
F
W
W
FIGURE 10.42
Laser cooling steps. Absorption of a photon by an atom (a);
excited state of the atom (b); emission of a photon (c).
The laser is in resonance with the atoms only when they
are moving towards the laser, but not if they are moving sideways or away as shown in Fig. 10.43. This condition ensures
the eventual cooling of the ions.
/DVHU
WLRQ
S
$EVRU
FIGURE 10.43
Relation between laser wavelength and Doppler shifted resonance absorption of an atom moving in different directions.
10.6 Local correction
In accelerators — as well as in any other technical fields —
any unwanted disturbances are corrected either locally or
non-locally. The universality of the approaches can also be
observed with help from TRIZ, which includes relevant inventive principles (principle of preliminary anti-action).
Non-local correction is often used when it is not possible
to correct the disturbance at its origin. The general issue with
this approach lies in its non-locality — a correction needs to
propagate and be properly preserved from the point of preliminary correction to the point where it needs to act.
Local corrections, if they can be used, are often superior,
as they correct the disturbance at the origin. In this section,
we will discuss several examples of local corrections.
10.6.1 Final focus local corrections
A final focusing system (FF) of any collider is aimed to produce
a small beam size at the interaction point (IP). The final lenses
of the system (usually arranged in a final doublet — FD) are
the strongest and produce the largest chromaticity. The values of chromaticity are usually very large (if left uncorrected,
D
E
F
W
W
FIGURE 10.42
Laser cooling steps. Absorption of a photon by an atom (a);
excited state of the atom (b); emission of a photon (c).
The laser is in resonance with the atoms only when they
are moving towards the laser, but not if they are moving sideways or away as shown in Fig. 10.43. This condition ensures
the eventual cooling of the ions.
/DVHU
WLRQ
S
$EVRU
FIGURE 10.43
Relation between laser wavelength and Doppler shifted resonance absorption of an atom moving in different directions.
10.6 Local correction
In accelerators — as well as in any other technical fields —
any unwanted disturbances are corrected either locally or
non-locally. The universality of the approaches can also be
observed with help from TRIZ, which includes relevant inventive principles (principle of preliminary anti-action).
Non-local correction is often used when it is not possible
to correct the disturbance at its origin. The general issue with
this approach lies in its non-locality — a correction needs to
propagate and be properly preserved from the point of preliminary correction to the point where it needs to act.
Local corrections, if they can be used, are often superior,
as they correct the disturbance at the origin. In this section,
we will discuss several examples of local corrections.
10.6.1 Final focus local corrections
A final focusing system (FF) of any collider is aimed to produce
a small beam size at the interaction point (IP). The final lenses
of the system (usually arranged in a final doublet — FD) are
the strongest and produce the largest chromaticity. The values of chromaticity are usually very large (if left uncorrected,