This morning I’ve sent e-mail my friend and ask him – what’s up? He sent me a picture, – some kind of selfie ;)). Below the picture he wrote: “Confined plasma on the plate ;)”. Plasma on his plate is very stable, but I don’t know how long will be. He’s very fond of plasma ;)). In this case plasma is very delicious cookie. But what’s actually plasma?
Over 15 billion years ago our Universe was squeezed into an extremely small ball, that was unstable and exploded violently. This was the most gigantic explosion of all time. This description of the early Universe is known today as the ‘Big Bang” model. The matter which composed the Universe was so hot that everything was in the form of plasma. Thus, in the very beginning, plasma was the first state of matter. The fragments of this explosion became the stars of our Universe, including our own Sun. During the expansion of our Universe, the matter cooled down and thus some of the plasma changed into gas, which further cooled down and became transformed into the liquid and eventually the solid states.
At the beginning of civilization, man was familiar with earth and rocks,
water and rain. Naturally, therefore, he identified the solid and the liquid states of matter. Thus we refer today to the solid and the liquid as the first and second phases of matter. A few centuries ago scientists realized that a third state of matter existed; this state is gas. The first physical law for gases was discovered by the English physicist Robert Boyle slightly over 300 years ago. The existence of a so-called fourth state of matter— plasma—was realized only about a century ago.
How can you explain someone what’s plasma mean in physics, on “funny” way?!
Let’s try to understand the four states of matter by calling upon our imagination. We are witnessing a dance competition. The conductor and the orchestra are ready to begin. The participants are well organized in pairs in a nice symmetrical way. This first phase is our solid the competition has not yet begun and the atmosphere is cold.As the music begins and the pairs perform their first dance, a slow, we enter into our second phase—the liquid; the temperature is low as they dance to the soft music. The music picks up tempo. The dancers are doing the rock and roll and we enter the third phase—the gas; the temperature is getting warmer. Now the music blares as the pop tunes begin. The girls leave their partners and everyone is jumping and dancing by himself or herself. This is the last phase—the plasma; the temperature is very hot and everyone is jumping around all over the place. This example allows us to make an analogy in which the conductor is the physicist in the laboratory; the music is the ‘heat’ which changes the phases from solid, to liquid, to gas to plasma; and our dancers are the different particles of matter. The pair represent an atom (or molecule) which is the basic unit composing solids, liquids and gases. The girls represent electrons while their partners symbolize ions.
Adding enough energy to any material, we can eventually produce a gas of electrons and ions. This last gas of electrons and ions is called a plasma. The biggest problem in plasma physics is – how to make stabile plasma.
Setting our imagination in full gear, let’s visit a big playground with
thousands of kindergarten children at play; running around clamorously, playing with different balls and colliding with one another. Picture some of them wandering off on their own without supervision. See the small feet outrunning the bigger and slower-moving ones of their supervisors. Hear some shouting and others laughing or crying. What a tumultuous situation this is indeed. Yet, unbelievably, occasionally, under very strict supervision, this big chaos can become organized in such a way that all the children are playing the same game. They can all be lined up in an orderly manner, listening to their teachers’ instructions. But do you believe that children, in general, can listen or play the same game for a very long time? Of course this is very doubtful. The bedlam is bound to start all over again and the nice collective behavior of the children will “explode” at any moment to a chaotic motion. Does controlling several thousands of kindergarten children in a big playground, with very nice and beautiful surroundings, appear to be a great task?
But the physicist, in his laboratory, trying to contain and control millions of millions of millions of charged particles, with very strong interactions between them, inside a small vessel, is faced with a much greater task. But if he wants to achieve a hot and lasting plasma necessary to solve the energy problem, then this is what he has to cope with daily in his laboratory. Charged particles, like the electrons and the nuclei in the plasma, have difficulty in crossing the lines of force of the magnetic field. Therefore a plasma can be confined by different magnetic field configurations. These magnetic fields keep the plasma inside a “bottle” so that the electrons and the ions do not touch the walls. This is the principle of the magnetic confinement scheme and the device that confines the plasma is called a “magnetic bottle”. The term magnetic bottle was coined in the 1950s by Professor Edward Teller, one of the pioneers of thermonuclear fusion physics. The motion of the particles in a plasma exerts a pressure in a similar way to the pressure of a gas. The thermal pressure in the plasma is due to the particle motion. For higher temperatures, the motion is more vigorous, causing a higher pressure. The number of plasma particles is also a factor in determining the pressure; for larger densities one has higher pressures. Usually, the plasma pressure, like the pressure of a gas, causes the plasma to expand. The plasma can be confined and not allowed to expand into the wall by a magnetic field…..