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ArcticMyst Security by Avery

radioactive material and laser ionization threshold

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Lets imagine this,you have pulse laser with focus lense that you use to turn air or noble gases in hermeticaly sealed chamber into plasma.To ionise air with laser,the laser beam must reach certain power,it must get past the threshold required.

Now,if we place a radioactive material,lets say Uranium 238/Thorium232/Radium cube with 1cm width 1 centimeter away from the focal point of laser beam where the plasma is created,it will cause alpha,beta and x-ray/gamma radiation in the area of focal point.

My question is this,does any of the three types of radiation mentioned present in the focal point affect the minimum ionisation energy level? Will radiation allow me to lower the power of the pulse laser and still ionise air? Lets say I need minimum of 1 microjoule to cause ionization without the radioactive material cube present,will the presence of the radiation from cube allow me to lower the power to lets say 0.9 microjoule and still get plasma?

I would like to broaden this question into three sub questions,its becose the photoionisation can happen in three ways: 1. when the laser have high enough freqency,only single photon is needed ( becose higher freqency photons have higher energy ) 2. multiphoton 3. tunnel ionisation.

For example,can it be that gamma radiation present in the focal point area lowers the multiphoton energy needed but does nothing for tunnel ionisation? Or,electron ( beta radiation ) lowers ionization threshold,but not proton,remember,beta riadiation are free electrons and protons that leave radioactive atom.
 
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Reading into your question more.

Now,if we place a radioactive material,lets say Uranium 238/Thorium232/Radium cube with 1cm width 1 centimeter away from the focal point of laser beam where the plasma is created,it will cause alpha,beta and x-ray/gamma radiation in the area of focal point.

There might be a potential for x-ray creation in certain circumstances in a Vacuum perhaps. This has occurred with extremely high energy levels above 1kJ with pulses widths in the fS (femtosecond) range. Xray pulses are on the order of Attoseconds.

Alpha and Beta radiation are products of Nuclear decay only.. one cannot get these by
zapping air.

I would like to broaden this question into three sub questions,its becose the photoionisation can happen in three ways: 1. when the laser have high enough freqency,only single photon is needed ( becose higher freqency photons have higher energy ) 2. multiphoton 3. tunnel ionisation.

Laser energy density and pulse width are what is primarily responsible for air breakdown. Again, as explained above, a high power laser with a very fast pulse width is what is required to cause air breakdown.
~100KW with a nS / pS/ fS pulse width. Wavelength is immaterial.



For example,can it be that gamma radiation present in the focal point area lowers the multiphoton energy needed but does nothing for tunnel ionisation? Or,electron ( beta radiation ) lowers ionization threshold,but not proton,remember,beta riadiation are free electrons and protons that leave radioactive atom.

No, Beta particles are Electrons, not protons. Beta particles are Negatively charged.


Please check the information (i.e. do your research) and work on making coherent sentences before making posts.
This post is a frankly a convoluted mess.
Yes, my head hurts from trying to figure out what you were trying to get at.
 
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There might be a potential for x-ray creation in certain circumstances in a Vacuum perhaps. This has occurred with extremely high energy levels above 1kJ with pulses widths in the fS (femtosecond) range. Xray pulses are on the order of Attoseconds.

Alpha and Beta radiation are products of Nuclear decay only.. one cannot get these by
zapping air.

you dont understand what I meant,I didnt meant generating x-rays with laser! I mean using radioactive material to lower ionisation threshold.This entire section you written completly missed the point,maybe I should be clearer,but when I explicitly described placing radioactive material "1cm" away from focal point,I didnt thought anybody would conclude that I want to generate x rays with laser

Laser energy density and pulse width are what is primarily responsible for air breakdown. Again, as explained above, a high power laser with a very fast pulse width is what is required to cause air breakdown.
~100KW with a nS / pS/ fS pulse width. Wavelength is immaterial.



thats not true,wavelenght affects ionisation in big way,if the energy of single photon is higher that first ionisation energy then only single photon is needed for ionisation to happen,this way it can avoid the whole multiphoton/tunnel process to cause ionisation... but I get what you mean,that only applies to UV laser and those are rare,so for the most common types indeed wavelenght doesnt matter as much,its more about peak power.



Please check the information (i.e. do your research) and work on making coherent sentences before making posts.
This post is a frankly a convoluted mess.
Yes, my head hurts from trying to figure out what you were trying to get at.

ooops! you are right! I meant positron not proton.Apart from this single mistake,I dont see what you dont understand.There are tree ways to ionization to happen 1. single UV photon 2. multiphoton 3. tunnel and there are three types of radiation emited by radioactive material,Alpha,Beta and x-ray/gamma.My point was that different types of radiation might affect different types of photoionisation differently,get it?
 
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I'm going to be blunt here.
You really need to learn how to post. Full stop.


plasma is created,it will cause alpha,beta and x-ray/gamma radiation in the area of focal point.

here you talk of generating x-rays, alpha and beta from the focal point. get, it?

Your words not mine.

:can:

At high peak powers and short pulse widths air breakdown can/will occur in air regardless of wavelength. (~to a point)
in fact if you researched you'd have discovered there was a thread about exactly this.
http://laserpointerforums.com/f54/best-wavelenght-ionize-air-99614.html
 
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here you talk of generating x-rays, alpha and beta from the focal point. get, it?

Your words not mine.

You purposfully quoted only half of the sentence to really make it seem like my post was badly written.From wikipedia "Quoting out of context (sometimes referred to as contextomy or quote mining) is an informal fallacy and a type of false attribution in which a passage is removed from its surrounding matter in such a way as to distort its intended meaning"

now lets look at full sentence

"Now,if we place a radioactive material,lets say Uranium 238/Thorium232/Radium cube with 1cm width 1 centimeter away from the focal point of laser beam where the plasma is created,it will cause alpha,beta and x-ray/gamma radiation in the area of focal point."


Its clear I mean radiation from the radioactive material,not the laser pulse.Could it be written better? Yes! Perhaps I could use word introduce instead of "it will cause",but is it negative rep worthy? In my opinion not even close.
 
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diachi

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Seoul, perhaps OP isn't a native English speaker? That wasn't a negative rep worthy reply IMO - I've reversed it.

What he's asking is, if having a source of ionizing radiation such as Gamma, X-Ray, Alpha or Beta near the focal point of the beam would reduce the power required to cause breakdown of whatever gas is being used.
 
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Seoul, perhaps OP isn't a native English speaker? That wasn't a negative rep worthy reply IMO - I've reversed it.

What he's asking is, if having a source of ionizing radiation such as Gamma, X-Ray, Alpha or Beta near the focal point of the beam would reduce the power required to cause breakdown of whatever gas is being used.

Alright. I tried to understand what Fonograph wrote but got riled when he started going back to re explain what he didn't mean. Organization when writing out thinking helps all understand what it is you're getting at.
- out of all the members here I am probably the most understanding person ( and qualified) towards those people with English as a second language. I deal with ESL 24/7.. That's one of my many jobs.
My S/O is not a native English speaker either nor is my extended family.




- Sorry for the NEG rep Fono.


Back to your last post,

Laser ionization *might* be able to be assisted by Radioisotope if the source is large enough. I'd think that a strong Alpha source might in theory give enough air breakdown to accomplish this feat. A Po210, Am241 or possibly Ra226 source of 100s of mCi might do it. Good luck getting your hands on a ionization source that large without a large amount of NRC paperwork.
You can lease a 5mCi Po210 source “Nuclespot” static eliminator from NRD, Inc. but it'll cost around $150USD to do that.

There's a great article about leasing sources by Carl Willis
here.

https://carlwillis.wordpress.com/tag/po-210/



Another possibility is that using a Radioisotope might also arrest/ inhibit the formation plasma as you'd have also created a place for charge to go to ground. (the ionization in air creates a conductive path for the charge to go) similar to what the large ionization sources do on lightning arrestors.

Hope this makes sense.

So there are 2 possibilities I see in doing this. All theory.
 
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Seoul_lasers Why do you think alpha radiation is best for it? I was thinking beta radiation was best becose it "shoots" free electrons away from atoms and I reed one study where they were turning air into plasma with laser and they said the free electrons in the focal point area are very important for the ionisation to happen.
 
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Seoul_lasers Why do you think alpha radiation is best for it? I was thinking beta radiation was best becose it "shoots" free electrons away from atoms and I reed one study where they were turning air into plasma with laser and they said the free electrons in the focal point area are very important for the ionisation to happen.

Alpha radiation is the most ionizing of the 3 main kinds of ionizing radiation.
In industry, Alpha sources are used to create charged paths in air or dissipate charges (anti-static). Alpha sources can also assist spark gaps or aid in conducting charges when used in Radio Tubes and Smoke Alarms (Am241). You're right in that Alpha sources need to be in fairly close proximity to the location in which you are ionizing. Beta particles are a bit problematic as they bend easily in presence of magnetic fields (as they're electrons) and don't ionize nearly as much as Alphas, though they do have a longer range in air esp, those from Sr90 ~546KeV. A list of pure Beta emitters can be found here Pure Beta Emitters

Bottom line, you'd need a crazy large radioactive source to get any kind of useful ionization for any kind of area denial system. ( which is where I think you headed with this idea)
The source alone would be dangerous to even be near. It would be impractical and silly. We're talking on the order of 1000's mCi/Ci of activity, enough to probably cause serious radiation burns and
even possibly loss of bone marrow. So much for being non-lethal.
:p


:whistle: Read below
I had a good read on the white paper on this subject of using lasers as an air taser (non-leath directed energy device for area denial)
The Free electrons you mention for the laser air ionization experiment conducted by DARPA nearly 10 years ago were successful not because of the use of Radioactive isotopes, but because of the spectra of the laser used in the experiment. The experiment used an 10MW (that's megawatts) (ArF) Excimer laser tuned to 193nm which when pulsed in dry air causes free electrons to occur at the focal point. (193nm is UVC and is readily absorbed by atmospheric oxygen)
* 2 lasers pulsed in parallel in opposite directions were able to create a charged path in the air to allow ~ 250-300Kvdc to jump across the gap.

A heavily redacted publication can be found in the below link.
http://legolas.ece.wisc.edu/papers/Magesh_1.pdf

Hope this solves your laser air ionization quest.
 
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X-rays and gamma rays ionize and break molecular bonds, these will actually ionize your gas, making the electrons move between energy states. If you want to reduce the amount of energy required to ionize a gas you're going to need infrared and microwaves which rotate and vibrate your molecules which put energy into the electrons without moving them between energy states.
 
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X-rays and gamma rays ionize and break molecular bonds, these will actually ionize your gas, making the electrons move between energy states. If you want to reduce the amount of energy required to ionize a gas you're going to need infrared and microwaves which rotate and vibrate your molecules which put energy into the electrons without moving them between energy states.


Did you have a look at the academic paper in the link? :can:
 
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I just read through the abstract and introduction.

By the way OP why are you asking this? Sounds sketchy to me

- Well at the beginning the thread was a complete mystery as to what Fonograph was asking. It is now more apparent Fonograph wants to build an area denial system of some sort. He wants to use ionization sources to assist in laser air breakdown to do what a lower power laser can't do.
It's an impossibility as it's all about energy density. Additionally, in Fono's recent post he talks about free electrons being knocked from atoms (from Oxygen). This only occurs when you are talking about extremely short wavelengths in the hard UV spectrum..i.e. as in an Exciplex laser.

It's just not feasible or realistic with hobbyist gear. Ar and F must be injected into the laser cavity before firing. The act of energizing the Ar and F ions in the laser cavity create a differential of 6.4eV between the ground and excited states of the 2 gasses. ArF (Argon Monofluoride) occurs only while the laser cavity is energized. After a ground state is reached the Ar and F become highly repulsive/dissociate and go back to being separate gasses.
Quite a complicated laser!! Good luck on getting your hands on a tank of Fluorine!

Lesson Learned - Researcher Smells Toxic Fluorine Gas When Changing Out Gas Cylinder | Environment, Health & Safety
 




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