3. INTRODUCTION
• It is a device which is used to accelerate
positive charge particle in presence of
cross (perpendicular to each other)
electric and magnetic field.
• In a cyclotron, charged particles
accelerate outwards from the Centre along
a spiral path. These particles are held to a
spiral trajectory by a static magnetic field
and accelerated by a rapidly varying
electric field.
4. HISTORY
• In 1928 Hungarian physicist Leo
Szilard invented and patented the linear
accelerator.
• In January 1929, Szilárd became the first
person to discuss the resonance condition
(what is now called the cyclotron frequency)
for a circular accelerating apparatus, in a
patent application in Germany. He also
invented and patented the first cyclotron
and betatron too.
5. • A couple months later, in the early summer of 1929, Ernest
Lawrence came up with the cyclotron idea and published a
paper in Science in 1930, and patented the device in 1932.
• He used large electromagnets recycled from obsolete Poulsen
arc radio transmitters. A graduate student, M. Stanley
Livingstone, did much of the work of translating the idea into
working hardware.
• At the Radiation Laboratory of the University of California,
Lawrence and his collaborators constructed a series of
cyclotrons which were the most powerful accelerators in the
world at the time; a 69 cm (27 in) 4.8 MeV machine (1932), a
94 cm (37 in) 8 MeV machine (1937), and a 152 cm (60 in)
16 MeV machine (1939). Lawrence received the 1939 Nobel
Prize in Physics for the invention and development of the
cyclotron and for results obtained with it.
Core of the first Belgian cyclotron,
built in Heverlee in 1947
A 37'' cyclotron at Lawrence Hall
of Science, Berkeley California
6. PRINCIPLE
• In Cyclotron cross electric and magnetic field are present in which
electric field is used to accelerate charge particle while magnetic
field is used to circulate the charge particle
• Lorentz’s force is basic principle of cyclotron.
Lorentz force: It is force on a charge particle in presence of cross
electric and magnetic field.
Fe + Fm
= qE +qV×B
8. CONSTRUCTION
• Three main constructional parts are:
Large sized magnet to create uniform magnetic
field in between its two face to face placed
magnetic opposite poles
Two low height hollow half cylinders made of
high conductive metals. These components of
cyclotron are called Dees.
A high frequency alternating high voltage source.
9. WORKING
• A cyclotron accelerates a charged particle beam using
a high frequency alternating voltage which is applied
between two hollow “D”-shaped sheet metal
electrodes known as the “dees” inside a vacuum
chamber.
• The Dees are placed face to face with a narrow gap
between them, creating a cylindrical space within
them for particles to move. Particles are injected into
10. • Dees are located between the poles of electromagnet which applies
a static magnetic field B perpendicular to the electrode plane.
• The magnetic field causes the path of the particle to bend in a
circle due to the Lorentz force perpendicular to their direction of
motion.
• An alternating voltage of several thousand volts are applied
between the dees. The voltage creates an oscillating electric field
in the gap between the dees that accelerates the particles.
• The frequency of the voltage is set so that particles make one
circuit during a single cycle of the voltage. To achieve this
condition, the frequency must be set to particle’s cyclotron
frequency.
11. CALCULATION
• In magnetic field magnetic force acts as centripetal
force,
qvB=
𝑚𝑣2
𝑟
r=
𝑚𝑣
𝑞𝐵
• Radius at each turn increases due to increase in velocity,
therefore it behaves like Spiral.
12. • Now from previous equation we get angular frequency as,
v=
𝑞𝑟𝐵
𝑚
rω= 𝑞𝑟𝐵/𝑚 (v=rω)
ω =
𝑞𝐵
𝑚
• as ω=2πf So the frequency is,
f=
𝑞𝐵
2π𝑚
• Now Time period (T)=1/frequency so,
T=
2π𝑚
𝑞𝐵
• Hence, Time period of Dees and the frequency of H.F. Oscillator is independent of
path of charged particle
13. TYPES of CYCLOTRON
• The cyclotron has evolved in a number of different forms
i. Classic cyclotron - The first type of cyclotron, described in previous sections,
which had uniform magnetic field and constant frequency, is mostly obsolete.
It was limited to completely non relativistic energies (the output energy small
compared to the particle's rest energy), and had focusing problems.
ii. Synchrocyclotron - an obsolete machine which extended energies into the
relativistic regime by decreasing the radio frequency of the oscillator as the
orbit of the particle got larger to keep it in synchronism with the particle.
This was the most powerful accelerator during the 1950s, before
the synchrotron. It operated in pulses, instead of continuously, so its
luminosity (beam current) was very low.
14. iii.Isochronous cyclotron (isocyclotron) - a category which
includes most current machines, extends output energy
into the relativistic regime by using shaped pole pieces to
create a non-uniform magnetic field stronger in peripheral
regions to increase centripetal force on the particle as it
gains relativistic mass, with alternating-gradient
focusing to keep the beam focused.
iv.H− cyclotron - a cyclotron that accelerates negative
hydrogen ions, which make it easy to deflect the beam out
of the machine. At the beam exit point at the periphery of
the dees, a metal foil strips the electrons from the
hydrogen ions, transforming them into positively charged
H+ ions. These are bent in the opposite direction by the
magnet, so the beam leaves the machine.
15. APPLICATIONS
• For several decades, cyclotrons were the best source of high-
energy beams for nuclear physics experiments; several cyclotrons
are still in use for this type of research. The results enable the
calculation of various properties, such as the mean spacing
between atoms and the creation of various collision products.
Subsequent chemical and particle analysis of the target material
may give insight into nuclear transmutation of the elements used
in the target.
16. • Cyclotron beams can be used to bombard
other atoms to produce short-lived
positron emitting isotopes suitable for PET
imaging.
• Cyclotron can be used in particle therapy
to treat cancer
PET
cyclotron
17. LIMITATIONS
• Neutral particles (e.g. neutron) do not interact with electric or magnetic fields.
So, cyclotrons cannot be used to accelerate them.
𝐾𝑖𝑛𝑒𝑡𝑖𝑐 𝑒𝑛𝑒𝑟𝑔𝑦 ∝
1
𝑚
So if mass decreases then due to inverse proportionality kinetic energy decreases,
KE if m
18. • It is very problematic to maintain Gap between dees as,
𝐹 = 𝑞𝐸
𝑚𝑎 = 𝑞𝐸
𝑎 =
𝑞𝐸
𝑚
𝐸 =
𝑉
𝑑
𝑎 =
𝑞𝑉
𝑚𝑑
𝑎∝
1
𝑑
So if d then a and if d then a
(d is gap between dees)
Standard gap between dees is 5mm
19. • Since electrons have very small mass, their speed increases very
rapidly and soon the resonance between the high voltage and the
particle becomes lost. Hence, a cyclotron cannot accelerate
electrons.
• Cyclotrons can accelerate particles to speeds much less than the
speed of light (in the non-relativistic regime).
20. FACTS
• To accelerate particles with relativistic speed, synchrocyclotrons
(frequency of the voltage is adjusted after each cycle), and
isochronous cyclotrons (the magnetic field is adjusted) are used.
These modifications are made to balance the increasing mass of the
accelerating particle as its speed tends to the speed of light.
• Ernest O. Lawrence invented the first-ever cyclotron at the
University of California, Berkeley in 1932. It was a 69 cm diameter
machine with a maximum energy of 4.8 MeV. He was awarded the
Nobel Prize in 1939 for this invention. He also invented a
synchrocyclotron in 1945.
21. • The largest cyclotron is at TRIUMF (Canada’s
particle accelerator center), which has a diameter
of 18 m and maximum energy of 520 MeV.
• The Superconducting Ring Cyclotron (SRC) can
produce high-intensity beams of accelerated
particles. At RIKEN, a large research institute in
Japan, there is an SRC of 19 m diameter. It has six
superconducting sectors.
TRIUMF
RIKEN
![CYCLOTRON
Group Members:
Yash [6667]
Vaibhav [6661]
Ashutosh [6665]](https://image.slidesharecdn.com/cyclotron-211019070601/85/cyclotron-1-320.jpg)
