72 unifying physics of accelerators, lasers and plasma
Laser pulse compressor gratings are technological marvels. In order to stay below the damage threshold of the grating material, the size of the plates has to be around a meter in
diameter for some of the highest power lasers. Taking into account that the typical space between grooves is around a micrometer, we can imagine the high levels of accuracy needed
to produce such plates.
Charged particle beam compression is based on the same
principle of the path length dependence on the particle’s energy. Dispersion is created using dipole bending magnets and
the initial beam is arranged to have an E z correlation, via
its acceleration
e.
−
off-crest of RF voltag
(
(
W
'LSROH
W
(
0DJQHWV ,
,
%HDP
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W
W
FIGURE 4.30
Bunch compressor.
Fig. 4.30 shows a bunch compressor and the phase space of
the beam before and after compression.
4.3.5 Beam cooling
Beam cooling methods are usually necessary for antiparticles,
e.g., antiprotons p ¯, as they are produced on a target very “hot”
— with large emittance and energy spread. The cooling methods are intended to decrease beam emittances.
Electron cooling, invented by G.I. Budker and realized at
Novosibirsk, consists of creating a region along the orbit of
the beam where a “cold” electron beam will co-propagate together with a “hot” antiproton beam (see Fig. 4.31) at the
same velocity. Energy exchange between the beams will eventually result in cooling of the p ¯ beam.
Another method of cooling the antiproton beams was proposed by S. van der Meer and realized at CERN. In this approach, a beam particle’s betatron oscillation is detected by a
pick-up electrode, and then the signal is amplified and sent
via a short path across the ring onto a kicker (see Fig. 4.32).
This will apply a kick to the same particle, resulting in a reduction of its oscillations. This method is called stochastic
cooling and was indispensable for ensuring the discovery of
W and Z bosons (Carlo Rubbia and Simon van der Meer, Nobel Prize in Physics, 1984).
As it should be apparent from the description of stochastic cooling, this method can clearly have drawbacks in the
FIGURE 4.31
Electron cooling.
FIGURE 4.32
Stochastic cooling.
Laser pulse compressor gratings are technological marvels. In order to stay below the damage threshold of the grating material, the size of the plates has to be around a meter in
diameter for some of the highest power lasers. Taking into account that the typical space between grooves is around a micrometer, we can imagine the high levels of accuracy needed
to produce such plates.
Charged particle beam compression is based on the same
principle of the path length dependence on the particle’s energy. Dispersion is created using dipole bending magnets and
the initial beam is arranged to have an E z correlation, via
its acceleration
e.
−
off-crest of RF voltag
(
(
W
'LSROH
W
(
0DJQHWV ,
,
%HDP
( !
W
W
FIGURE 4.30
Bunch compressor.
Fig. 4.30 shows a bunch compressor and the phase space of
the beam before and after compression.
4.3.5 Beam cooling
Beam cooling methods are usually necessary for antiparticles,
e.g., antiprotons p ¯, as they are produced on a target very “hot”
— with large emittance and energy spread. The cooling methods are intended to decrease beam emittances.
Electron cooling, invented by G.I. Budker and realized at
Novosibirsk, consists of creating a region along the orbit of
the beam where a “cold” electron beam will co-propagate together with a “hot” antiproton beam (see Fig. 4.31) at the
same velocity. Energy exchange between the beams will eventually result in cooling of the p ¯ beam.
Another method of cooling the antiproton beams was proposed by S. van der Meer and realized at CERN. In this approach, a beam particle’s betatron oscillation is detected by a
pick-up electrode, and then the signal is amplified and sent
via a short path across the ring onto a kicker (see Fig. 4.32).
This will apply a kick to the same particle, resulting in a reduction of its oscillations. This method is called stochastic
cooling and was indispensable for ensuring the discovery of
W and Z bosons (Carlo Rubbia and Simon van der Meer, Nobel Prize in Physics, 1984).
As it should be apparent from the description of stochastic cooling, this method can clearly have drawbacks in the
FIGURE 4.31
Electron cooling.
FIGURE 4.32
Stochastic cooling.