# How does particle accelerator work?

Hi,
so as I continue with the book I am reading right now about particle physics I will write about the basics behind particle accelerators.

There are several types of accelerators, they can be divided into groups by either the energy they can create or what kind of particles they are colliding, some accelerators even do not have this circle but they rather just hit some big target.

Inside accelerator you will surely have some great detector which is going to collect the data for you. In Large Hadron Collider (LHC) in CERN there are two main detectors: ATLAS and CMS. There are two so you can compare their results.

Those detectors are huge, ATLAS has 21 meters in diameter.
Then there is the tube in which you have got those particles running. In LHC there are protons in both direction. Those protons are taken from little bottle with hydrogen, this bottle would serve for billions of years because there are 10^27 particles inside.

When you take these particles you will speed them up. The particles in LHC those are protons are separated to groups. Between each group is seven meters of vacuum. In each of those clouds of protons are 100 billions of protons. This cloud can get thin as 1% of millimeter right before collision.

Protons are all positively charged so it is hard to keep them in the cloud. Because of their charge, you can speed them up using magnets. To get the top speed you have to use extremely strong magnets, which means electromagnets [1]. Those magnets will speed the particles to 99.999996% of speed of light, so obviously that is where theory of relativity comes to role, for example those particles are not spheres but rather pies because of their huge speeds — effects of relativity.

After you speed up those particles you are going to collide them. This happens at the detectors which are going to measure all the stuff that is flying away from the collision. You may identify particles by their direction of traveling, by this you may know their charge. Also how deep they were able to fly. Mions for example have longer life times than most other particles so they are able to fly through the accelerator, while bosons w and z or tauon have such a low life time that they wont fly very far and most of the time you are going to observe their products rather that those particles alone.

Dragallur

[1] Electromagnets are magnets powered by electricity because when you have electricity, it creates (electro)magnetic field. This gets stronger the stronger is the current. In particle accelerators it can get so strong that the magnets would melt at a moment because of friction with electrons, that is why they must be cooled to little over absolute zero, using liquid helium.

Only picture

# Taking closer look on, NOTHING!

Hi,
in this post I want to look on literal nothingness, vacuum, empty space.
And why are neutron stars so freaking dense.

When you put your hands as far away from the other one and imagine that this is the volume of atom the nucleus is going to be thinner than the diameter of human hair.. well yes, that escalated quickly. And I am not even talking about electrons which are much smaller than protons and neutrons.

This simply means that you are, and everything you know, is mostly made up of empty space.

Now for the neutron stars.
Neutron stars are collapsed massive stars. They are extremely small and dense at the same time and the gravity of all the stuff keeps this stable.
Wow, neutron star is pretty scary when you take that their diameter ranges from 10-20 kilometers and at the same time they have 1.35 to 2.1 of Solar mass. The first picture corresponds to this, so if you would compress all humanity to size of sugar cube it would be as dense as neutron star. So in neutron star there is not much of empty space.

That is all for neutron stars but let me return to the empty space and vacuum.

Vacuum is extremely important, while I don’t want to list all technology using it, let me say that for example simple straw is working because of vacuum.
While you are not making the best vacuum ever, when drinking your juice from straw, you are lowering the pressure so the juice runs up. If you would lower the pressure a lot like in space this effect would be much stronger (you would not explode).

There is actually scale on Wikipedia about the levels of vacuum. OK now lets assume that you would be able to suck out all of the air and stuff inside closed box.
Is there going to be something?

Yes, it may sound strange but there is lot of stuff, and this stuff likes to change a lot.

Lets introduce you virtual particles!
OK, they are real kind of, at least it is known that they really exist. They have to do a lot with quantum theories like quantum field theory.. I do not understand any of it but that is not really important right now.

Virtual particles are particles that are popping in and out of existence all the time. In this kind of way they should be in pairs which then both disappear in nearly NO time. I read that since they are so virtual and may not carry any energy or momentum they may even travel faster than light or travel in time (this is questionable, as you will see (source Wikipedia)). Those particles are made in pair, one of them is anti particle so they then collide and annihilate.

OK, I know that there must be something more to it since at the same time SOME virtual particles can travel faster than light as Wikipedia says, while force can not be transferred faster than the speed of light.

So there is all the stuff popping in and out of existence which is constantly annihilating. But when this happens on the edge of black hole when one particle is inside the event horizon and the other one outside, the one outside does not annihilate and it pops into existence and escapes the black holes gravity. Since conversation of mass/energy this must have taken something from the black hole. This really happens in what is called Hawking radiation, when eventually black hole can evaporate!
To watch something more about vacuum, check this video by Veritasium where he is talking about quantum fluctuations.

Dragallur

# Red shift once more

Hi,
so last time I was writing about Dopplers effect and I was using normal Dopplers effect but actually I forgot something very important and those are relativistic speeds.

Relativistic speed is the speed when Newtonian physics is no longer able to accurately predict what is going to happen. This can happen from 1 to 10% of speed of light. This border is hard to define since it is hard to define when Newtonian physics is not enough accurate.

On the left you can see graph of increasing mass when you increase speed.

That is one of many relativistic effect, this also means that when you are walking you are heavier. Also another effect is time dilation for example.

Time dilation is the problem with red shift in Universe. You can not just use equations like I used before but you need to use special relativity with time dilation, since the thing is speeding away from you and the time runs differently for you and it.
This equation is the right one, more accurate for huge speeds with which you will be in astronomy probably dealing with.

Lambdas are the wave lengths of the one you are observing and the real one of the object. V is velocity and c speed of light, z is the red shift.

So I checked with one problem which I found on the internet. It was about quasar far away which is moving in high speeds. The red shift is 0.158.

So i used this calculator to find out what is v/c which was 0.14656. With this I found out what is the speed which was 43,695 km/s. Then I put it in the equation above and the red shift was about 0.15777 (something). So I can see that I did it right and this equation is truly giving us the red shift.

Dragallur

1st picture
2nd picture is from czech wiki article about relativistic Doppler effect