Nuclear reactions
Nuclear reaction occurs when any radiation particle, as a “bullet,”
targets any other and we obtain another particle. Avalanche of particles with
different velocities are obtained during bombardment. Very often, the proton
or the deuterium is like “bullets” in big acceleration. Presently, we know
many thousands of nuclear reactions. Rutherford used a particle of  and
transited it through the Nitrogen gas, as the first historic nuclear reaction in
1919.The particle created was the proton. This was the nuclear reaction as
shown:
14
N7 + 4He2 →1H1 +
17
O8. He applied a Wilson chamber (over culled
steam) to see the pathway of created particles. Created particles were the
Hydrogen (proton) and Oxygen (recoil particle) of atomic mass of 17. The
first historic nuclear reaction of Rutherford, you can see in photograph
1.This long, almost vertical, pathway comes from the created proton.
Photo 1.
Principles of nuclear reaction you can see in the first, the historic,
reaction. A  particle with big energy was needed to initiate this reaction.
We have a particle, “bullet”, put into a nucleus, “target”, to initiate a nuclear
reaction. Electrons  may be used as negative and are attractive to positive
nuclei. Electrons  before entering a
nucleus, interact with the orbital
electron of the “target” and the probability are very slight that these
electrons will initiate a nuclear reaction. A neutron that has no charge was
not known at that time. After Bothe and Fleischmann, we can write down
nuclear reactions. They record a “target” particle as a “bullet,” a “recoil”
nucleus and create a particle.
X (x, y) Y
We understand that:
X – represents a target, x – represent a bullet, y – created particle and Y –
represents a recoil nucleus.
A  particle must have at least 1.2 eV energy. We didn’t have other
sources of particles different from natural decays up to 1932. Intermediate
nucleus was Fluoride, atomic mass 18, (18F9) and recoil nucleus was
Oxygen (17O8). This
O8 could decay to two  particles, but we needed a
17
little bigger kinetic energy of the  particle we have. Lifetime of
18
F9 was
very short (10-15 s).
In 1932, Cockroft and Walton accelerated the proton to Energy of
1MeV. This was a turning point in nuclear reactions. They used a special
voltage accelerator, made by themselves, up to 1MVolt. J Cockroft and E.T.
S. Walton received the Nobel Prize in 1951. Their nuclear reaction looked
as follows:
7
Li3 + 1H1 → 4He2 + 4He2
7
Li3 (1H1,) 2
or:
,Two
 particles were produced and the nucleus of Lit ( Li3) was a target
(bombarded by the proton).
Protons,  particles, or other ions may be accelerated to very high Energy
by modern accelerators. We used light elements to accelerate theirs,
ofcourse. Even two neutrons could be produced when Energy of Deuterium
is over 3 MeV (d,2n). The process of “stripping” could be observed if the
energy of the bullet is over 200Mev. In this case, one of the neutrons with ½
Energy in a target end one with ½ Energy has been “stripped.” We can
accelerate particles to very high Energy in a special cyclotron made by E.
Lawrence in 1932. Edward Lawrence got the Nobel Prize in 1939.
Fig. 11.
The cyclotron works as follows: Positive ions are injected at the centre point of a Duant. The magnetic field is perpendicular to the movement of
ions and kept these about circular motion. Injecting a positive ion is
accelerated between daunts 1 and 2 by an applied electric field so that
there is acceleration between 1 and 2 (positive and negative attract each
other). Lawrence applied about 1000 Volts. The next step of acceleration
occurs when we change a polarisation of an applied electric field (change of
polarity applied to daunts). This situation we change cyclically. Accelerated
particles later reach maximum radius, left chamber (daunt 1), by a special
deflector plate.
However, mass, as Einstein predicted, increases if a particle reaches
very high speed. The mass of the particle could be calculated from
Einstein’s formula. A particle become delayed when we change potential in
daunts.
mE =
When,
m0
1  2
mE – relativistic mass of accelerated particle.
=
vc
,
c
 – velocity particle over velocity of light (do not miss

 particle)
m0 – rest mass of an accelerated particle,
The  is equal almost to 1 after reaching energy of a few MeV. Velocity of
light is very high and equals about 3x108 m/s in a vacuum. We take the
same value in the air.
We can increase magnetic field or decrease frequency of potential
difference applying to daunts, or both, to avoid increases of the particle’s
mass. We have a phase-tron, cyclotron, or phase-cyclotron, respectively.
These apparatuses are big in diameter. For example, a phase-cyclotron at
the CERN, Geneva, consumes many Watt power and has a diameter of
about 300 m in a vacuum channel under the surfaces of three countries:
Italy, France and Switzerland. We have even bigger apparatuses. Every of
them gives us energy up to GeV (109) and flax density many hundreds of
A. You can image a vacuum channel a few km long when two streams
from different directions collide.
No single country has enough money to run such an apparatus and
cooperation is required among countries. In so big an apparatus, we can
prove the existence of other particles called Quarks. Quarks are particles
very strongly bound at the nuclei, and their existence was predicted M. GellMann. Murray Gell-Mann got the Nobel Prize in 1969. Physicists even gave
special quantum numbers for those, and different “elementary” particles,
called colours, charms and others.
We knew every anti-particle to existing particles. We knew antiproton, anti-neutron, anti-electron and others. I think we can create an antiatom. Inside a nucleus, we should have anti -neutrons and anti- protons but
anti- electrons would be in orbits. Such an anti-atom would be difficult to
discover.
Particles, mainly protons, come to (our atmosphere) from the cosmos
with very high energy. Actually, we don’t know their origins. Great
“accelerators” of particles work in the USA in Brookhaven National
Laboratory, and other countries in the world, today. By these, we
increasingly recognise the Universe that surrounds us.