I What is the effect of X-rays on dielectric solids?

[hagopbul]

TL;DR Summary

i was asking about the effect of xray on dielectric solid

Hello :

i some times use XRF device for various reasons , and start to wonder dose the xray radiation induce charges on the surface of dielectric material (solid ) , can some one mention a reference about that subject ?

( it knocks an electron from an atom creating a positive charge ) , how much time dose the charge stay at the surface of that dielectric ?

also i am thinking to do a paper on effect of xray on an electronic component just to pass some time (not sure about it yet) , if any one wants to co author it with me , i am thinking of writing it to improve my experience and in my free time , didn't decide on writing it yet



Best
H

 

[QuarkyMeson]

TL;DR Summary: i was asking about the effect of xray on dielectric solid

i some times use XRF device for various reasons , and start to wonder dose the xray radiation induce charges on the surface of dielectric material (solid ) , can some one mention a reference about that subject ?

In general you should be able to polarize a given dielectric when it is exposed to an external electric field. Griffiths chapter 4 goes into detail about dielectrics in external E-fields. This effect may or may not disappear when the field is removed depending on the material and change the surface charge on the object.

Because the source is x-rays, you probably wouldn't notice polarazation since the field generated by the E&M radiation is oscillating very fast and probably randomly distributed, (I suppose, I have no experince with XRF, at least you'd need to be purposefully looking for it) so the other effect would be photoelectric effect where you're actually creating free charge by ionizing the dielectric. I haven't studied this yet so someone else can talk more about that.

( it knocks an electron from an atom creating a positive charge ) , how much time dose the charge stay at the surface of that dielectric ?

This would be the photoelectric effect I mentioned. The time you have charge on the surface depends on a whole host of enviromental and material factors.

 

[BVirtual]

I had to research the actual physics of XRF for a project I am currently working on. I learned the XRF pulse is not only incredibly brief so as to not destroy the material surface, but also was incredibly a tight beam, striking just hundreds to thousands of atoms, a very tiny cross section on the surface. The area that is charged by such an event is going to be very hard to have a 'sensor' positioned just after the XRF pulse. The sensor would have to be in the beam itself, and positioned above the surface in order to measure the surface charge 'dissipate.' Or just off to one side, and then moved across the surface while the charge propagates away from the sight of beam impact.

Any charge on the surface of the dielectric material will 'slowly' or 'rapidly' encourage nearby uncharged atoms to assume 'part' of the charge. The localized charged cross section will expand. The slight charge amount will be spread throughout the surface of the dielectric volume. Perhaps by having a very small surface facing the beam, and very small sample volume, the charge might not be so diluted over the entire dielectric as to actually have a time window where its max value can be measured?

One might think measuring the overall charge on the dielectric object change from neutral to charged, and graphing the curve might be then extrapolated to the beam impact cross section? The dielectric object would have to be held insulated from any paths of discharge. This would be an easier way to start such an experimental apparatus. There are easy ways to measure charge on an object, very sensitive methods. Then, the extrapolation to the beam impact area would let you make a decision to modify the apparatus to measure the 'spread rate' of charge across the dielectric surface. If you got good data, then you could make another apparatus change to be very close to the impact area. If that data is good, then design some sensor to be in the actual beam and measure the charge E field from an atom's diameter from the surface.

I hope these issues can be part of your design criteria in making your experiment come true.

 

[DaveE]

i am thinking to do a paper on effect of xray on an electronic component just to pass some time

There's about a 99.99% chance the defense department has beaten you to this. EMP and such.
My very brief training from my DoD satellite days basically said that free charges are generated in your semiconductor junctions so they all conduct, probably when you didn't want them to. The design issue for us wasn't so much keep working, as it was don't break and recover well when it's over. Also memory may be erased in things like EEPROMs. Old school OTP ROMs were preferred.

The other issue I dealt with was long term exposure. Devices like MOSFETs will "collect" charges in new defects in the gate and significantly shift the bias over time (Vgs(th), etc.).

Anyway, while much is probably classified (but not all), a literature search first is in order. Many smart people with a lot of money have tread this ground.

 

[BVirtual]

For your paper the academic topic is formally called "Radiation Survivability" for how the Sun's 'radiation' increases the isotopic Van Allen Belt radiation intensity. You will find many papers on it. Around 1986, I wrote the first 3D Ray Trace software for Air Force satellites, winning an 8 million dollar bonus for my firm. The isotopic radiation will 'melt' the junction surface between N-P materials, especially when miniaturized, like in an IC chip. Tiny NP junctions are melted the same amount as larger NP junctions, it is just that larger transistors can tolerant and function longer with more melting than tiny IC transistors. Eventually, the surface is either going to short out, making the transistor transmit the full supply voltage, or is going to open, and no longer switch or amplify. It depends which NP surface melts first for open or short. By melt it is meant atoms of P migrate into the N material. And N material atoms migrate into the P material. The sharp surface separation of P from N material that makes transistors work is now blurred. And soon stops functioning with more melting.

It is why modern computer chips with 81 cores are not used in outer space, as their lifetime is minimal compared to larger transistors. There is a weight trade off. With more computer power (less weight) there is more frequent replacement of the whole satellite.

Space tug boats able to swap boards, refill retro rocket fuel tanks, and tow satellites to higher orbit are very desirable. The USA Space Force has contracts out for firms wanted to specify what is the current proposed capability for board replacement using robotic arms.

I think there may be the need to update a "summary" of radiation effects on electronics. I am not currently interested enough to find the last published one, as my current project just fries anything with a chip within 3 feet of it. Plasma is like that.