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Neutron Mass
Introduction
Neutrons are also known as fundamental building blocks of matter. The rest mass of the neutron is equivalent to 1.67492749×10-27 kg which is just marginally more than that of the proton but about 1839 times more than that of the electron. The neutron seems to have no electric charge. Neutrons are widespread in the universe and account for more than half of all visible matter.
Discovery of Neutron
The identification of neutrons can be dated to 1930 when German nuclear physicists Herbert Becker and Walther Bothe realized that whenever the alpha particles ejected by polonium were impacted by comparatively light materials like lithium, beryllium, and boron, a penetrating kind of radiation was formed. Electric fields did not affect this permeating radiation, therefore it was considered to be a gamma ray.
The French researchers Frederic and Irene Joliot-Curie were studying atoms in 1932 noticed that high-energy protons were emitted when this extremely penetrating radiation struck paraffin wax highly energetic protons (around 5 MeV) to be emitted. Ettore Majorana, an Italian physicist, proposed that the way radiation associated with protons in the atom's nucleus was due to the presence of a neutral particle.
Ernest Rutherford made a very similar forecast about the occurrence of neutral particles in atomic nuclei in 1920. To designate these particles with a neutral charge, he proposed the terminology "neutron”.
Sources and Productions of Neutrons
There are several sources of Neutrons. Some of the best options are the following.
Fission Reaction
For this process, only a selected, including plutonium-239, uranium-235, and uranium-233, can be used to conduct a fission chain reaction.
In this process, several nuclei may randomly split into two pieces.
This splitting of nuclei causes the emission of neutrons which can cause the fission of additional nuclei.
Mostly, we use Uranium-235 makes up 0.7 per cent of naturally occurring uranium. Uranium-235 conducts nuclear fission using thermal neutrons, yielding on average 2.4 fast neutrons and releasing about 180 MeV of energy per fission.
Spallation
In this method, if target nuclei are attacked with particles with a de-Broglie wavelength that is shorter than the radius of the nucleus, a series of these processes are known as "spallation".
A spallation source is a high-flux neutron generator.
In spallation, neutrons are produced when protons with high energy collide with heavy target materials. Above a specific particle energy threshold, often between 5 and 15 MeV, the reaction takes place.
High-flux neutron generator
The nuclear fusion of temporary plasma made of deuterium or tritium is the foundation of the dense plasma focus process.
This device uses electromagnetic compression and stimulation to produce fleeting plasma.
When this plasma is generated, it is hot and thick enough to trigger nuclear fusion and neutron emission.
Neutron Generator
In this method of production of Neutrons, we use Deuterium and tritium which fuse in an exothermic event that generates neutrons.
The neutron is created with a 14.1 MeV kinetic energy.
When Deuterium atoms hit a tritium objective produce neutron.
This method can be performed on a smaller scale in the experiment with a small 100 kV accelerator.
By using this method, it is possible to produce 1011 neutrons per second.
Detection of Neutrons
There are some methods of detecting neutrons.
Fission Chamber
first of all, we take enriched uranium-235 that is used in the coating of the inside walls of the chamber by spraying.
After that, we change neutrons into charged particles because it is impossible to ionize neutrons directly.
Further, A unit of nature will fission in response to a thermal neutron. This fission will produce two highly energetic fission that ionises the argon gas of the chamber.
This ionization of argon represents the presence of highly fragmented neutrons.
Here, we took Uranium-235 because it can be used with gamma rays and is more sensitive to the flux of neutrons.
Activation Foils
Activation foils can be used to locate neutrons. This technique is based on neutron activation.
In this method, a sample is first exposed to neutron radiation to produce particular radionuclides.
We get that radioactive decay of the elements which generated radionuclides are distinct.
In the next step, by using gamma spectroscopy, which detects gamma rays at certain energies, we identify radionuclides and calculate element concentrations
Here, we use specific materials for the process, such as niobium, iron, gold, rhodium, indium, etc because, for the radiative capture of neutrons, these elements have large cross-sections.
Thus, the neutron energy spectrum can be characterised by using numerous absorber samples.
Finally, we can figure out how many neutrons thin foils were exposed to by counting how radioactive they are.
Applications
Neutrons are very important in the modern era of technology. There are some popular applications of neutrons are the following.
We use neutrons for starting a Nuclear Reactor.
We also use neutrons in Radiography.
The devices Density Gauge and Moisture Gauge that is based on the use of neutron.
In the field of jewellery, neutrons are used for Gem colourization.
In several types of research in the field of physics and medicine.
In the calibration of sensitive devices, we also neutrons.
In the field of the military, neutrons are also used for triggering nuclear weapons.
Conclusion
The neutrons are subatomic particles that have no charge. These particles were discovered at the beginning of the 20th century. There are various sources of neutrons, although nuclear fission is the most popular and traditional source. Moreover, for the detection of neutrons, we can use the activation foil method and fission chamber method. Neutrons are very useful in the modern era of technology.
FAQs
1. What is the use of neutron therapy?
This is a very useful therapy for the curing of tumours. Mostly, this method is used when traditional methods are not working due to some serious consequences.
2. What is the half-life period of Neutron?
The half-life period of neutrons outside the nucleus is 10.4 minutes and during decay, it yields energy equal to 1.29 MeV.
3. What is the neutron energy spectrum?
It is a spectrum or presentation that shows the total distribution of energy of neutrons in a medium.
4. What is the antiparticle of neutrons?
The antiparticle of the neutron is the antineutron. Anti-particles are those particles which have the same mass but are opposite in charge.
5. What is the rest mass of the neutrons in amu unit?
1.0086649 amu is the mass of a neutron when it is at rest. One amu is equal to the $\frac{1}{12}$ of mass of a carbon atom.
