8
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8
FIGURE 5.2
Cockcroft–Walton generator.
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FIGURE 5.3
Van der Graaf accelerator.
5.1.1 Electrostatic accelerators
In an inspirational push in favor of accelerator development,
Rutherford spoke at The Royal Society in 1928, lamenting,
“I have long hoped for a source of positive particles more
energetic than those emitted from natural radioactive substances.”
The first accelerator developed was the Cockcroft–Walton
generator which is based on a system of multiple rectifiers
(Fig.5.2). In this generator, voltage generated by the cascade
circuit
2πI 2
1
1
U tot = 2Un −
3
n +
2
n + n
(5.1)
ωC 3
4
12
depends on the number of cells n, as well as genera ted current I , capacity C and frequency ω.
The Cockcroft–Walton accelerator helped to make Rutherford’s dream a reality. In the first-ever transmutation experiment, the accelerated 700 keV protons were sent onto a
lithium target, resulting in the production of helium.
Practical reasons (i.e., size of the device, performance of
capacitors and diodes) limited the generated voltages and
corresponding energies of the accelerated particles up to
about ∼4 MV . Cockcroft–Walton accelerators can typically
generate beam currents of several hundred mA with CW or
pulsed particle beams of few μs pulse lengths.
Another example of an electrostatic accelerators is the
“Van der Graaf” (see Fig.5.3), where a metal brush deposits
charges onto a rubber belt, carrying the charges into a metal
sphere where they are later collected by another brush. The
exchange of charges is performed with help from a discharge
between the sharp tips of the needles of the brushes and the
belt.
The ion source in the “Van der Graaf” accelerator is located inside of the metal sphere, and is charged to a high
voltage. An electrical generator (mechanically connected to
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FIGURE 5.4
Tandem electrostatic accelerator.
76 unifying physics of accelerators, lasers and plasma
& 8
&
& 8
&
&
&
a
8
FIGURE 5.2
Cockcroft–Walton generator.
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0HWDOVSKHUH
EUXVK
5XEEHU
EHOW
0HWDO
EUXVK
FIGURE 5.3
Van der Graaf accelerator.
5.1.1 Electrostatic accelerators
In an inspirational push in favor of accelerator development,
Rutherford spoke at The Royal Society in 1928, lamenting,
“I have long hoped for a source of positive particles more
energetic than those emitted from natural radioactive substances.”
The first accelerator developed was the Cockcroft–Walton
generator which is based on a system of multiple rectifiers
(Fig.5.2). In this generator, voltage generated by the cascade
circuit
2πI 2
1
1
U tot = 2Un −
3
n +
2
n + n
(5.1)
ωC 3
4
12
depends on the number of cells n, as well as genera ted current I , capacity C and frequency ω.
The Cockcroft–Walton accelerator helped to make Rutherford’s dream a reality. In the first-ever transmutation experiment, the accelerated 700 keV protons were sent onto a
lithium target, resulting in the production of helium.
Practical reasons (i.e., size of the device, performance of
capacitors and diodes) limited the generated voltages and
corresponding energies of the accelerated particles up to
about ∼4 MV . Cockcroft–Walton accelerators can typically
generate beam currents of several hundred mA with CW or
pulsed particle beams of few μs pulse lengths.
Another example of an electrostatic accelerators is the
“Van der Graaf” (see Fig.5.3), where a metal brush deposits
charges onto a rubber belt, carrying the charges into a metal
sphere where they are later collected by another brush. The
exchange of charges is performed with help from a discharge
between the sharp tips of the needles of the brushes and the
belt.
The ion source in the “Van der Graaf” accelerator is located inside of the metal sphere, and is charged to a high
voltage. An electrical generator (mechanically connected to
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1HJDWLYHLRQVRXUFH
$FFHOHUDWLQJWXEH
&KDUJHGEHOW
6WHHULQJPDJQHW
*UDGLHQWULQJV
6WHHOSUHVVXUHWDQN
+LJKYROWDJH
FIGURE 5.4
Tandem electrostatic accelerator.
76 unifying physics of accelerators, lasers and plasma