Atlas Exp: Solving Calorimeter Challenges

[prochatz]

Considering the Atlas experiment, which are the basic theoretical decisions someone must take in order to create an effective calorimeter? In other words, which are the basic problems that someone must solve to achieve the best possible effectiveness?

For example, the high temperature problem can be solved with cryogenic methods (Liquid Argon). The geometrical orbits of particles can be fully observed if we construct our calorimeter in the shape of a barel. Are there any similar problem that physicists had to face?

 

[Vanadium 50]

I'm not sure what you mean by these "problems". What is the "high temperature problem"? Lots of people have room temperature calorimeters. If by "geometric orbits" you mean "tracks", the tracking occurs before the particle has reached the calorimeter.

 

[prochatz]

I'm not sure what you mean by these "problems".

In order to construct an effective calorimeter someone must, first of all, take into account all the parameters of the experiment that may lead to fail.

What is the "high temperature problem"? Lots of people have room temperature calorimeters.

I'm talking about the LAr Calorimeters in Atlas experiment. Not an ordinary calorimeter.

If by "geometric orbits" you mean "tracks", the tracking occurs before the particle has reached the calorimeter.

That's right, I mean tracks.

Before constructing the LAr calorimeters, in Atlas experiment, someone must know all the parameters and design these devices in order to work efficiently.

If we are talking about a "face to face" collision then we should definitely place the calorimeters in the shape of a cylinder. Otherwise, we will lose information.

If we do not use Argon (in the calorimeters) and use some other element we will fail gathering the electrons due to couplings with the element.

What other parameters had the physicists to take into account before proceding to the construction of the LAr Calorimeters?

 

[Vanadium 50]

You didn't tell me what this "high temperature problem" is. I think it would go better if you would answer my call for clarification rather than explain to me why I don't need to know it. It is absolutely not true that argon is the only possible element. Krypton works as well - and in fact, works better.

 

[prochatz]

You didn't tell me what this "high temperature problem" is.

As far as I know electronics cannot work efficiently in high temperatures. This is one of the reasons we must use methods to cool off our system.

It is absolutely not true that argon is the only possible element. Krypton works as well - and in fact, works better.

I did not mentioned that Argon is the only possible element someone could use. However, Argon is one element that works well enough. An element that could "kill" the after collission particles should be avoided.

I'll try to ask some more specific questions in order to understand each other. Maybe is something that I do not totally understand.

i)Why are we using Argon in calorimeters?
ii)Why are we using liquid Argon instead of gaseous Argon?
iii)Why does the full structure have barrel shape?

 

[humanino]

i)Why are we using Argon in calorimeters?
ii)Why are we using liquid Argon instead of gaseous Argon?
iii)Why does the full structure have barrel shape?

Have you had a chance to take a look at the technical design report ? It would help if you could find this, and point to specific questions with regards to it. I doubt your questions are not already answered there. Another possible document would be a NIM paper. From which source of information do you start ?

 

[Vanadium 50]

The electronics for the ATLAS LAr calorimeter are at room temperature.

Argon is ionized by particles, and then the ions are collected on electrodes and the signal is amplified. You can use whatever pretty much any material you want as an ionization medium, and different materials have different ion survival times, signal heights, drift speeds, etc. Liquid argon happens to be a convenient material: a big signal with a fast recovery time. But people can and do use other materials.

The beamline has cylindrical symmetry - it makes sense for the detector to match it rather than adding nonuniformities.