Why Bremsstrahlung <20keV for Tungsten?

[cemtu]

TL;DR Summary

Why isn't there Bremsstrahlung Radiation for Energy less than 20 keV for Tungsten?

https://www.researchgate.net/figure...-shown-for-a-tungsten-anode-with_fig4_8365056

Fast electrons produce X-rays in the anode of an X-ray tube through two different methods. The first one is the interaction of electrons with the nuclei of the target atom. As an electron passes near a nucleus, the positive charge of the nucleus affects the negative charge of the electron, attracting it towards itself and changing its direction.

This causes the electron to undergo decelerated motion and, consequently, lose energy. The kinetic energy lost by the electron is emitted as a photon. The radiation produced in this way is called "general radiation" or "bremsstrahlung."

Bremsstruhlung Radiation's Energy Magnitude depends on,

1. the voltage of X-Ray Tube that accelerates and gives kinetic energy to electron
2. how close does an electron passes near a nucleus
3. atomic number (element type, Z) of that nucleus

So,

• why isn't there Bremsstrahlung Radiation for Energy less than 20 keV for Tungsten?
• Is it about the source of thermionic emission of the electron source, which bombards the cathode? So no start of bombardment(emission of the electron) before 20 keV from the anode to the cathode??

 

[malawi_glenn]

You would need to have log scale rather than linear scale on the vertical axis

 

[cemtu]

You would need to have log scale rather than linear scale on the vertical axis

So the graph representation is false there.

 

[malawi_glenn]

So the graph representation is false there.

False?

 

[malawi_glenn]

https://www.researchgate.net/figure...e-which-can-be-seen-in-fig2-is_fig1_347969227

this is probably how the graph would look with log-scale

 

[Lord Jestocost]

So the graph representation is false there.

The graph representation isn't false per se. A better kind of representation regarding Bremsstrahlung can you find on http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/xrayc.html

 

[malawi_glenn]

Those graphs need to be read "from right to left" if you wanna compare with the graph in the OP

 

[cemtu]

View attachment 327698
https://www.researchgate.net/figure...e-which-can-be-seen-in-fig2-is_fig1_347969227

this is probably how the graph would look with log-scale

why does it seem false without a log scale(the relative photon output number is zero in my OP until about 20 keV)?

 

[malawi_glenn]

why does it seem false without a log scale(the relative photon output number is zero in my OP until about 20 keV)?

You must be joking right?

 

[snorkack]

You are still not addressing the question. Many overviews of bremsstrahlung unfortunately do not.
This:
http://www.sprawls.org/ppmi2/XRAYPRO/
and a few others give the reason, though:

If no filtration is present where the spectrum is essentially a triangle, the amount of radiation produced is approximately proportional to the KV squared.

Apparently around 20 keV is where the absorption of tungsten increases rapidly.

 

[cemtu]

You must be joking right?

No, I am geniune.

 

[cemtu]

You are still not addressing the question. Many overviews of bremsstrahlung unfortunately do not.
This:
http://www.sprawls.org/ppmi2/XRAYPRO/
and a few others give the reason, though:

Apparently around 20 keV is where the absorption of tungsten increases rapidly.

yeah, but below 20 it seems that we have 0 relative photon output number I still don't get it.

 

[malawi_glenn]

No, I am geniune.

All graphs stould be in log scale in order to be true?

 

[cemtu]

All graphs stould be in log scale in order to be true?

what? I mean why is that?

 

[malawi_glenn]

what? I mean why is that?

How else are we gonna compare 5 to 50000? In a linear scale, 5 would look like zero :(

 

[cemtu]

How else are we gonna compare 5 to 50000? In a linear scale, 5 would look like zero :(

oh, thats it? I thought there is somehow more than that. Thank you!

 

[malawi_glenn]

oh, thats it? I thought there is somehow more than that. Thank you!

Even 100 would be within the thickness of the line representing the horizontal axis.

Why is $e^{-x} = 0$ for $x>4$? I mean, look at the graph:

 

[nightvidcole]

Soft X-rays are re-absorbed before they exit the X-ray tube. You would need a thin window of low-Z material (for example, beryllium) in order to allow the soft X-rays to come out.