عناصر ما وراء اليورانيوم وانتاجها - الطاقة النووية .. الفيزياء

Transuranic elements and their production - Nuclear energy .. Physics

Transuranic elements and their production

The natural elements in the periodic table of elements occupy the sum of the boxes with numbers from one to ninety-two, which is the number of the uranium element that comes at the end. As for the remaining elements, with atomic numbers greater than 92, they are produced artificially, and are called transuranic elements, and are formed as a result of bombarding heavy elements such as uranium with fast particles, some of which hit the target element. Thirteen of these elements have been produced so far, the last of which is the element with atomic number 105. All of these elements are characterized by being radioactive, and that they have been present in the Earth's interior for millions of years, and that they have since decayed into other elements. Most of these elements are produced in small quantities, and do not have many applications, except for plutonium (atomic number 94), which is considered an essential material in the work of nuclear reactors and weapons.

(Acceleration of electrons in a linear accelerator during the succession of voltage half-cycles)
(Table of transuranium elements)

Fast particle beams are not only useful in producing transuranium elements, but they are also useful in studying the elementary particles themselves. The kinetic energy of an electrically charged particle increases and reaches a large amount if we allow this particle to accelerate in an electric field called an accelerator, including the linear accelerator in which protons and electrons move in a straight line inside a tube evacuated from air. There are different types of linear accelerator, the most important of which is the magnetron, which basically consists of a row of single-axis cylindrical wires separated by narrow gaps, and connected to each other in an alternating manner that makes them oppose the voltages emitted by a very high-frequency electrical source. Due to the alternating voltage, the type of charge in the existing wires changes. It is known that electrons injected into a tube only accelerate towards the positive paths. Therefore, once inside the tube, its speed becomes constant. Then the distance between the gaps is adjusted in a way that prevents the electrons from emerging from a certain path until after half a cycle of voltage cycles has passed and the charge it carries has changed. After that, the electrons accelerate towards the next path, which has in turn become positive. The more the speed of the electrons increases, the more necessary it becomes to increase the distance between the gaps according to this speed. The electron travels the new distance for the same time and remains in phase with the same alternating current. This process is repeated along the tube, so the energy of the electrons increases as their speed increases between gaps until they become close to the speed of light at the end of the tube, i.e. they become very high in energy.

(The shape of the cyclotron as seen from above

(top image)

And as seen in a cross-section (bottom image).

As for the ring accelerators, the particles take a circular path many times. The most important of these accelerators is the accelerator known as the cyclotron, which consists of two hollow, semicircular chambers, each of which resembles the shape of the letter D, and is emptied of air, and is located between the poles of an electromagnet. Then a particle source is placed between the two chambers, and they are connected to the poles of an alternating electric source whose mission is to accelerate positive particles such as protons towards the negative chamber. When these particles are inside the chamber, they take a constant speed, and under the influence of the magnetic field, they take a circular path whose beam length changes according to the speed of the protons themselves.

In addition, the frequency of the current and the intensity of the field (which are constant) are adjusted in a way that makes the duration of the proton crossing the opening and completing the half-circle a constant period equal to half a cycle of the current itself. Once it emerges The proton from the chamber until it accelerates towards the second, which then becomes a negative chamber and thus increases the value of its kinetic energy, and then the process is repeated: an increase in speed accompanied by an increase in the length of the circular line beam. It is worth noting that the duration of one cycle is related to the magnetic field itself and not to the speed of the protons, the increase in its value is compensated for by increasing the length of the circle itself. When the protons exit the cyclotron, their speed is great and their energy is very high. The cyclotron is one of the simplest ring accelerators, and obtaining high energies requires the use of very advanced devices.

High-energy particles are used to carry out ongoing research on elementary particles in nature and to discover their properties. We can classify them within a table similar to the periodic table of elements according to their charge and spiral descent.

This method, called unified symmetry, has given great results in predicting the existence of particles that were not possible to discover in the laboratory.