FAQ - X-ray radiation!!

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George Dowell
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

RadPro Calculator- Fooling around with dose at 10 cm from a 30 kVp 10 Ma
X-Ray source, shielded by iron or lead.

Dose at 10 cm with 2mm Iron shielding (fusor chamber? = 5 R/H

Dose at 10 cm with 2mm Pb shielding = 1 10E-21

It takes little effort to shield 30 kV rays.

George Dowell
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Richard Hull
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Re: FAQ - X-ray radiation!!

Post by Richard Hull »

The assumption here in these calcs is that you are operating a formal, tungsten target "x-ray tube". All the energy is in a focused beam blasting "naked" into air. The fusor is never this kind of device, of course, so all the unshielded values given by this program are super wrong to start with, when referencing a fusor, as the levels will be 2-3 orders of magnitude lower due to the isotropic emission and SS lower Z target-shell shield.

A better test is to let the x-ray tube filter and target be 2mm of iron which is closer to the natural fusor. Unfortunately, we aren't allowed to choose the target, but can choose Cu for our filter. The program, though, forces a minimum of 85kv for that filter and will not accept lower KV numbers. Thus, it is valueless, on many levels, for use with a fusor.

We have actually, physically measured at the SS shell of a fusor working around 35kv @10ma. We record about 100 mr/hr at the shell ~3 - 5cm distant and at 1 meter, less than one mr/hr. This is not worth consideration as a rad hazard if your operating station is over a meter distant from such a fusor and operated for infrequent, short periods.

For the paranoid, hyper-ventilator's, a millimeter or two of lead will leave you in, hopefully, a "feel good" operational environment.

For me, 50-60 kv applied is when I might put up a thin Pb shield, assuming I am 1.5 meters from the fusor.... as it is in my case.

Richard Hull
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Fusion is the energy of the future....and it always will be
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

Richard, may I ask what you measured the 100 mR/H with? A low energy intergrating ion chamber I assume? George Dowell
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

By the way a tungsten target does not turn on until above 59 keV (tungsten K edge) . A real X-Ray tube designed to work at lower HV would have an MO or copper target. Or in the case of a fusor, a very large iron target. A peak of about 6 keV would result, with a background of Bremsstrahlung from 0-35 keV (average of around 1/3 that).

Geo
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Re: FAQ - X-ray radiation!!

Post by Chris Bradley »

George Dowell wrote:
> By the way a tungsten target does not turn on until above 59 keV (tungsten K edge) .
There is an X-ray continuum too, related directly to the electrons' energies. It is not just the atomic signature from which one gets X-rays.
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

Correct Chris, that's caused by electron Bremsstrahlung.

It is not exactly an X-Ray by definition, it is Bremsstrahlung radiation, but ionizing photon radiation nonetheless. Photon's are often called by the manner of their origin, i.e. X-Rays, Gamma Rays, Annihilation Radiation,Bremsstrahlung etc.

At the receiving end, they are all the same thing and indistiguishable from one another.

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Re: FAQ - X-ray radiation!!

Post by Carl Willis »

Hi George,

Richard has mentioned at least three times toward the top of the thread that an ion chamber is preferred for dosimetric measurement of x-rays. The model I've seen him use is a Victoreen 471, and he has photos of it here: viewtopic.php?f=13&t=5972#p34416

I'd argue that the commonly-understood meaning of "x-ray" implicitly includes bremsstrahlung. There does not appear to be any confusion about what physical mechanism produces radiation in the amateur fusion environment, and no need for affecting a hyper-distinction in the nomenclature.

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Re: FAQ - X-ray radiation!!

Post by JohnCuthbert »

I'm fairly sure that most of what Dr Roentgen named X rays were what would later be classified as bremstralung, but that didn't stop them being X rays any more than light isn't light if it didn't come from the sun.
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Re: FAQ - X-ray radiation!!

Post by Richard Hull »

Yes, I use a large chambered victoreen ion chamber. Two other similar ion chamber instruments brought by others over the years have agreed to within 20%. 200mr pen dosimeters placed at varying ranges have also agreed to within a similar error range.

I have used as many as 20 pens in a single test before. My pocket dosimeter has never registered a readable amount in all the various runs where I have worn one.

The fusor, as such, is a pretty low emission x-ray device up to about 35kv due to the SS shell shielding. I rely heavily on distance and the inverse square law to operate with zero shielding up to about 40kv. at 1.5 meters there is no reading seen on the 3mr/hr lowest range with two Victoreens and one Eberline ion chamber detectors that I have.

Also about 1 run session of max output for a total of 30 minutes every three months or so (average) keeps the time averaged absorbed exposure to effectively nothing.

In short, no significant x-radiation from naked fusor IV operating between 20kv and 40kv, provided you are positioned a meter or more from it over much of its full power, operational time.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: FAQ - X-ray radiation!!

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John Cuthbert wrote:
> I'm fairly sure that most of what Dr Roentgen named X rays were what would later be classified as bremstralung, but that didn't stop them being X rays any more than light isn't light if it didn't come from the sun.

Yes actually it does John if we are to be anything like scientifically correct. We use terms like Radio, Laser Light, Arc Light, Lime Light, X-Rays etc for a reason even though they are all electromagnetic radiation.
For example in the case of a fusor or *any* vacuum chamber with two electrodes, electron flow and HV, there will be a number of sources of ionizing photon radiation. If the "target" i.e. anode is iron, the peak radiation will be at 6 keV, from the characteristic XRF of iron. Each anode element would have it's own energy of characteristic X-Ray emission, but the electron beam must be of sufficient energy to excite this emission. That's why X-Ray tubes have different target material for different usage. Ironically those very low energy X-Rays are specifically filtered in radiology because they don't penetrate tissue,rather absorbed, therefore don't add to an image, but cause the burns.

Understanding this allows the observer to select the correct instrument to monitor the dose. For example, many if not most instruments are blind to 6 keV due to self shielding.

The ion chamber I use for that is a Victoreen 440 RF/D which has a very thin magnesium window, specifically designed to allow low energy X-Rays in.

PS, to put it in perspective, my experiments with X-Rays use sources of 20 to 30 kV at up to 100 MICROAMPS only. Yes these are isotropic sources. A normal all metal fusor is a diffuse source. No one can say what Bell Jar fusors are.

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Re: FAQ - X-ray radiation!!

Post by Carl Willis »

There's no misunderstanding, George.

The argument over terminology is unnecessary. For what it's worth, the current Oxford English Dictionary discussion of the term "x-ray" includes the following:

X-rays are produced by the deceleration of charged particles, esp. electrons, or by electron transitions in atoms [...]

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Re: FAQ - X-ray radiation!!

Post by Rich Feldman »

> For what it's worth, the current Oxford English Dictionary discussion of the term "x-ray" includes the following:
> X-rays are produced by the deceleration of charged particles, esp. electrons, or by electron transitions in atoms [...]

Interpreted broadly, that includes synchrotron radiation -- the brightest practical source of continuous x-rays?

My non-professional understanding is that gamma rays are distinguished from x-rays by their source (nuclear processes) rather than by their energy.

As usual, talking comes easier than looking something up on the Internet.

-Rich
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

Yes there are still texts that try to distinguish X-Rays from Gamma rays by their position on the spectrum chart, not by their origin. If you talk to Dr. Gordon Gilmore, you better call say annihilation radiation by its real name not X-Rays!

In the case of X-Ray generators, in my humble opinion, the difference between Bremsstrahung continuum and Characteristic X-Rays peaks are quite important and relevant to the discussion.

Then again I'm no expert, just a hobbyist.

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Re: FAQ - X-ray radiation!!

Post by Carl Willis »

The x-ray/gamma ray terminology predates scientific understanding that came with the "modern physics" revolution. When Roentgen gave "X-strahlen" their name, the word simply meant the penetrating radiation emitted from a cathode-ray tube--which we now know is photons produced via two entirely-different processes. When Rutherford named "gamma rays", all he knew what that their origin was in radioactive decay and that they were more penetrating than x-rays using the sources he had. The terms remain in use today, having undergone no formal refinement or redefinition even as the underlying processes have come to be understood in detail. Their domains of common meaning have not really changed. When someone talks about x-rays, the assumption is that they are talking about penetrating radiation emitted from a cathode ray tube.

Synchrotron radiation was identified and understood later, after the modern physics revolution. Calling it x-radiation wouldn't be decisively wrong, but it would be odd.

The current Pope's Latinist, Reginald Foster, often has to translate concepts postdating the fall of Rome and its language into Latin (he's borrowed "breviloqui" from Cicero, repurposing it to mean "to Tweet"). Although it's brief speech, there's no doubt a lot is lost in the translation, such as the whole essence of Twitter being a massively-networked electronic communication medium. Cicero would be clueless. The first synchrotron radiation observed and understood correctly was in fact visible light. Roentgen would be confounded if he found his old term being used to describe it. However, he would be right at home with the penetrating radiation coming out of fusors, and could adeptly make a nice photo of his hand bones with it.

-Carl
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

So the Deuterium ions are the canal rays?

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Re: FAQ - X-ray radiation!!

Post by Rich Feldman »

George wrote:
>So the Deuterium ions are the canal rays?

I like it!

Carl, thanks for your historical perspective. I like to use words in their most general sense, especially since English so often has separate words for specific subcategories.

It's always been a delight to learn things about the history of science. People working with synchrotrons seem to generally use "x-ray" for the photon spectrum of higher energy than ultraviolet. Here's a nice historical summary, found on the Lawrence Berkeley website: http://xdb.lbl.gov/Section2/Sec_2-2.html

Which leads us to the classification (as x- or γ-ray) of 511-keV annihilation radiation.
It seems to traditionally be called gamma, although neither atomic nuclei nor radioactive decay are directly involved. Sounds right to me. There are subatomic particles reacting with each other in ways other than electron binding and electromagnetic forces.

Rich
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

To quote Dr. Gordon Gilmore from another forum:

The point about nomenclature is that it does give information about origin
and mechanism of production. You could suggest that we call any
electromagnetic radiations as photons - and scrap all that nonsense about
radio waves, light etc.

Gamma-rays are photons emitted as a consequence of de-excitation of an
excited nucleus. That nucleus could be excited because it is the product of
a nuclear decay, or it could be product of a nuclear reaction or simply
excited by being clouted by some other particle.

X-rays, at least as far as gamma-spectrometry is concerned, are photons
emitted as a consequence of de-excitation of the electron shells of an
atom. That could be a consequence of photoelectric absorption or internal
conversion etc.

Incidentally, it is incorrect - repeat incorrect - to refer to the 511
photon emitted during annihilation as the 511 gamma-ray. IT IS NOT A GAMMA
RAY. (sorry to shout!) It is not generated by de-excitation of a nucleus.
It is a photon or annihilation radiation. You can refer to the peak in a
spectrum as the 511 peak though. That's what it is.
When John Hemingway and I received the proofs of the first edition of 'The
Book' we found we had fallen into the trap ourselves and had to go through
the proofs very carefully to correct all the '511 gamma-rays'.

I could go on...
Precision in nomenclature helps understanding. Sloppy use of nomenclature
may well cause confusion and misunderstanding.

You could also ask if beta particles are simple electrons, why don't we
call them that? Because the nomenclature helps.
Beta- particles are electrons emitted during a nuclear decay.
Beta+ particles are positrons emitted during a nuclear decay.
That reminds us that those particles do not have a defined energy - any
individual will have an energy between zero and the decay energy.

In gamma spectrometry we refer to internal conversion electrons and Auger
electrons as such because they have defined energies determined by the
electron shell energy they have been expelled from.

I mentioned in an earlier post about nomenclature confusing matters in
relation to the term Branching Ratio. I won't go on again.

And of course there is isotope and nuclide. They are all *nuclides* unless
you are discussing nuclides of the same element - then you can discuss
isotopes. To say 'the isotopes Co-60 and Co-57' is correct use of the word
'isotope'. To say 'the isotopes Co-60 and Cs-137' IS NOT correct.
When you see the word isotope used incorrectly it says 'non-professional'.
Even the nuclear equipment manufacturers are getting it right these days -
not so journalists and broadcasters.

Regards,
Gordon Gilmore
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Re: FAQ - X-ray radiation!!

Post by Carl Willis »

Yes, deuterium ions in a fusor would fit the definition of canal rays.

It's common in didactic materials to find a distinction between x- and gamma rays based solely on energy, but this just reflects the historical origin of those names and is not a general guide. The common radioactive sources at the dawn of the 20th century were uranium and thorium and their daughters, which emit rather high-energy photons. The x-ray tubes of the period operated from <100 kV Ruhmkorff coils, producing mean energies in the tens of keV. It's not common to hear of 6-MeV radiotherapy photons called "gamma rays" or of americium's 59-keV photons called "x-rays", and people would indeed complain that such usages are out of line with the precedent.

Electron annihilation radiation is probably commonly labelled as gamma rays because of its close association with radioactive decay (namely, positron emission, and other decays that produce energetic gamma rays leading to pair production and thus have annihilation radiation in the downscattered spectra).

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Re: FAQ - X-ray radiation!!

Post by Daniel Firth »

I noticed a lot of replies to this FAQ in the last couple days, and wondered if there was interest in an idea I had.

I've recently received a CD V-700 from eBay. After testing all of my ore samples, I did an air plasma fusor run. It seemed to be pretty quiet up until about 17kV. 18kV started to make some good counts, 19kV was roughly middle of the X100 scale, and 20kV maxed out the instrument.

I noticed that this roughly corresponds to my neutron counts. That is, no detectable fusion under 18kV (with my instruments, anyway), very low between 18-19kV, and a sharp increase over 19 to 20kV (my power supply's max output).

Anyway, if there is interest I will do a simultaneous neutron/x-ray run, and get a bunch of photos & measurements.

The point being, it could be a simple test to see if someone's fusor is "in the ballpark" for fusion capability, without having deuterium or neutron detection equipment.

I could also get some photos & readings of the X-ray cone emission pattern from a viewport, and show how the stainless steel blocks x-rays. I would probably do this around Feb. 16th.
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Re: FAQ - X-ray radiation!!

Post by George Dowell »

While interesting, such a test is not really quantitative, because you are experiencing the low energy cut off of the GM tube walls. In other words, does the X-Ray flux really increase, or does the raised energy just allow more to get inside the tube?

This is the big stumbling block when working with XRF- some the energies are so low, most probes can't detect them no matter how much flux there is.

20 keV seems to be near the limit for metal enclosed probes of any kind. To get below 10 we need beryllium windows, then they still cut off at 4 or 5. The thin mica windowed pancake probe is one of the best *DETECTORS* at really low energies, but
what you want to *MEASURE* X-Rays.

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Re: FAQ - X-ray radiation!!

Post by Chris Bradley »

This has all been a very poor distraction from the purpose of the FAQ.

I think all of this recent stuff should be purged.

The thread discussion is the management of X-rays for personal safety. One does not stop to discuss the finer points of vehicular classifications if you are trying to warn someone they are about to get run over.

"Get out of the way of that car!!!" ... "Excuse me, we call it an 'auto' here, and the name arose because ..." SPLAAAAT.
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Re: FAQ - X-ray radiation!!

Post by Richard Hull »

Chris is correct and I was about to speak out, but will not erase the above discussion only because it is a teachable moment spread over the last 15 or so postings.

Nit-picking at specifics can teach a newb that EM radiation goes by many names for many people and it often depends on one's backgorund, education and slant as to what they call different forms of EM radiation.

For the purpose of the fusor, all dangerous, wholebody, photonic radiations are x-rays save for the hyper-rare D+D= (4He + gamma) reaction for which there is effectively zero emission.

I suggest that unless someone has some more information related to x-ray issues with the fusor, they should start a new thread in this forum.

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