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Sauron
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Anyone Up for a DIY Particle Accelerator?
Not since Bill Murray and Ivan Reitman got together with Dan Ackroyd has science been this mad.
In connection with the mild and unassuming Analytical Machinery thread I went googling for Type 220A 150 magnetron magnets which had been referred to
in a quote by @Leu from an old article. I found the complete old article, from April 1959 The Amateur Scientist, and am now downloading the entire
website (quite large) into a pdf.
Anyway immediately following that article there was a sort of Letters to the Editor section discussing a January 1959 on building your own particle
accelerator at home. I dug up that article, and sure enough it describes how to construct an electron (or proton, your choice) accelerator of
>300-350 KeV or more than twice that built in the early 1930s by the inventors of particle accelerators.
It so happens I was just reading about the use of high energy electrons to drive a reaction between carbon tetrachloride and NO gas to give a 50%
yield of trichloronitrosomethane, an intensely blue liquid. Clearly, we are talking about a free radical process here, the generation of
trichloromethyl radicals by irradiation with charged particles.
Highly interesting.
The same radical could be generated by UV or by a radical intiator like benzoyl peroxide or AIBN but I think doing so with an electron beam is well,
cool. The device uses a van de Graf generator (with plans from yet another article to build your own) and a 2 x 36" Pyrex tube evacuated to 0.01
micron Hg for accelerator tube, an Al foil window for beam with Al plate support, etc. I will supply this article here shortly.
No it isn't quite the backpack Ghostbuster weapon but it is still neater than hell.
Attachment includes above article plsu safety discussion from later issue plus VDG Generator construction article referenced. I just updated this file
with new material from a 1955 article on electrostatic generators.
[Edited on 22-2-2007 by Sauron]
[Edited on 22-2-2007 by Sauron]
Attachment: Home Scientists Particle Accelerator 2.pdf (1.1MB)
This file has been downloaded 6989 times
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Sauron
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PS The British physicists who built a very similar accelerator in 1932 of 150 KeV were J.D.Cockcroft and E.T.S.Walton. They also employed an
electrostatic generator as power source.
Gentlemen and ladies, this is not a toy. Watson and Cockcroft transmuted Al to an unstable Be isotope that decayed to He and released energy of 17
MeV.
Of course by today's standards 150 or 350 KeV is small, but you and I are not likely to get our hands on FermiLab are we? Or even the sorts of
equipment that Lawrence had at Berkeley just a few years after Watson and Cockcroft started the ball rolling.
[Edited on 21-2-2007 by Sauron]
[Edited on 21-2-2007 by Sauron]
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YT2095
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currently (no pun intended) my CW Voltage multiplier only pulls 36Kv, but the capacitor bank will more than easily contain this charge, albeit a
little to small to do anything of significance.
I Do have plans in the pipeline for a Bigger Better device though, and have most of the parts I need also, I just need a few good summer days in the
back yard to construct the thing, and couple of strong and willing people to help move it into location and a few prayer for the correct weather to
make it work 
be sure, I WILL be Posting Pics, probably sometime in the Autumn this year
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Sauron
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The van der Graf generator they propose is supposed to be capable of 20 uA @ 500,000V which sounds like 10 VA to me.
This is connected to the anode and cathode, the cathode is a nichrome filament. The optimum temperature for the filament is determined empirically;
too hot and it will release too many electrons. A simple transformer regulates the filament.
They propose a diffusion pump to pump down the tube during operation. I am wondering why not just evacuate it once, seal it and be done? It's just a
vacuum tube albeit a big one. How often would the filament need service?
They propose an Hg diffusion pump for the high vacuum stage, I'd rather go with an oil diffusion pump to avoid having 3 lbs of Hg around the lab, but
hey, this was 1959.
I was going to invest in an Ace photochemical (UV) reactor but with the lamps and power supply and special glass it is costly and UV is hazardous. I
am already blind in one eye, and can't see out of the other. A particle beam is not without hazards but, I think these are more easily manageable.
Radical initiators are not without hazard (peroxides, energetics like AIBN). It's a matter of TANSTAAFL.
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YT2095
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that`s not the sort with the Alpha emitter and the lithium target is it?
that`s the sort I was planning several years ago, the only problem being is that in my highly evacuated apparatus that I make, I use Lithium as the
Getter.
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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Sauron
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No He nuclei, no Li target, and 6Li is RIGHT OUT.
No, this is just a circa 1932 Cockcroft & Watson electrostatic powered, heated filament source, not very tightly collimated particle beam. Under
400 KeV, which greatly simplifies construction. Good for chemistry, not so hot for physics. But not to be taken lightly. In particular I would not
recommend doing what Lawrence did when he put his head in the beam.
You can accelerate electrons, or hydrogen nuclii (protons) but that's it. See the attached article above., along with safety discussion and article on
constructing the electrostatic generator.
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roamingnome
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In a very recent Chemical & Engineering News (C&EN) a young female scientist is holding a Frisbee size neutral particle accelerator that was
looking neat, in the next model they hope to collide them….
But for real experimentation I haven’t even made a working rail gun yet… and that stump still needs a quarter stick in it.. darn it…
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Sauron
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Did you read the article?
It's too early for April Fool's.
This is neither a joke nor a toy, and definitely not a weapon.
But it could be a practicable tool for a chemist. And not costly to build.
Read the article.
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tnhrbtnhb
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| Quote: | Originally posted by Sauron
Did you read the article?
It's too early for April Fool's.
This is neither a joke nor a toy, and definitely not a weapon.
But it could be a practicable tool for a chemist. And not costly to build.
Read the article. |
Personally, I think you might be better off with a cascade, not a van de graff generator. See www.powerlabs.org. You can get cascades out of the back of monitors and TVs. Also wouldn't building a cyclotron be cooler? Maybe you could use
the magnets in a magnetron?
A Neutral particle accelerator?? How does that work? What was the article and where can I see it?
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Sauron
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Lotf things might be cooler but beyond the reach of anything less than a government or a multinational corporation.
I am not a nuclear physicist, and nuclear physics is not my goal. Nor was it the goal of the fellow in Buffalo NY who built this one in '59 for $100
or so. That was a piker's budget, even Cockcroft and Watson at Rutherford's lab at Cambridge spent $200 in 1932 dollars (or I suppose the equivalent
in sterling) on theirs.
By the way apparently the proper spelling is Van de Graaff. I know I have bounced all over with variations myself...
By the way the reference I saw to a chemical reaction using high energy electrons was in PATR 2700 and they were citing a 1960 proceedings of a
conference in Warsaw, which they called "Most interesting." I agree.
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Ozone
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All sorts of fun things can be done with high density electron flux...Like making X-rays and the like (100-150kV does this nicely, especially with a
good target, like W).
Another interesting thing that can be done is to create Lichtenberg discharges, which I like very much. In this case, a piece of lucite it bombarded
with electrons. The electrons lodge into the lattice structure and create electrostatic instability. A perturbation of the "charged" material, say, a
swift rap with a grounded nail, produces an explosion as rediculous voltage is discharged through the plastic. The result--dendritic discharge
channels.
I think these things are very cool!
Cheers,
O3
-Anyone who never made a mistake never tried anything new.
--Albert Einstein
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12AX7
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Beloit's physics department has a 500keV accelerator. Sort of. It's been in parts for a while without instructions, so on and off over the last 5
years they've been putting it back together.
It consists of a 15HP VdG, belt charged with a rectified NST (fed by variac) and charge comb. The (linear) tube appears to have concentric conical
electrodes for focus. Thermionic cathode in the end. I recall hearing something about 1mA, so it's got pretty good capacity.
I don't see what good accelerators are, chemically. It's bad enough to run 50Ah through an electrochemical cell at 5V, but at 500,000!? (Granted
incident electrons will scatter and cause multiple ionizations, but what's so special about that which lower energy bombardment or a plain mercury
discharge can't do?)
I think accelerators are illegal (i.e. need license), at least those capable of ionizing radiation. Obviously there's a danger of soft x-ray
radiation (bremstrahlung (sp)) above a few kV, turning into hard radiation in the hundreds of kV. Some thickness of metal will help that, starting
with some sheet lead in the hundreds of k.
Tim
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Sauron
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Dr.Lee, who built this one in Buffalo, tested it for radiation for a year before publishing that article. As long as no heavy-element targets are
irradiated this does not seem to be an issue. Typically, Lee was interested in irradiating organic substrates and so am I. Crowcroft and Watson
irradiated Al and Li and made He in both cases. And some energy. For safety purposes I would like to know more about just what sort of energy they
released and just where in the periodic table does light vs heavy demark? Obviously a W target, water cooled, is the classic target for X-ray
generation. To be shunned, for my purposes. But W is very much on the heavy side, what about silicon as my liquids will be in Pyrex or quartz. Or do I
have to build this vertically and irradiate through a flask mouth? Inconvenient for reacts involving a gas interaction with a liquid or another gas.
Yes this could be done with UV, but I find this more interesting.
The NRC's writ does not run where I am. The Thai Office of Atomic Energy for Peace is a lot easier to deal with, and as I am not going to be making
isotopes or X-rays or endangering the public I do not think there will be a problem. I have a friend at OAEP, a gamma spectroscopist. He's a professor
of physics at a Thai university. I will get his opinions and support.
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Sauron
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@O3, that is interesting, I take it the photo was a time exposure to catch the dendritic discharge which was a very rapid event. Lucite (acrylic) is
the only material with this proprty?
This instrument wouldn't cost much to build - I am thinking the 1959 $100 is likely $1000 now. It wouldn't be all that big and heavy although it would
be delicate. It would not consume much power (just the VdG motors and the filament heater. Not much downside.
By comparison a UV reactor with power supply and safety cabinet by the time it was shipped here from Vineland NJ would cost me $5000 on a 1 L scale
(500 ml pot charges) and consume more electricity than this midget LINAC. Electricity isn't the issue obviously, I am just thinking out loud. A 5L US
reactor would need a different lamp and power supply, and would not fit in safety cabinet so I'd have to make one here - I'd probably do that anyway
with smaller one just because it's stupid to ship a cabinet from NJ.
I expect reactions of the FR type to be faster this way than with UV. Sounds like a job for a (chemical) loop reactor.
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Sauron
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Those Lichtenberg figures are fractal in nature, and while you can manually trigger them (after irradiation) with that grounded nail, they will also
happen spontaneously if you keep irradiating to the point where dielectric breakdown occurs. Acrylic is a good dielectric (insulator) and it takes
millions of volts to break it down like this.
Does anyone sell these Lichtenberg figures commercially? They are so neat looking, like frozen lightning, I bet they would sell.
The oil diffusion pump is an easy $1000 to $1500 by itself, capable of 10x-6 torr (10x-5 required) plus a power supply to heat a nichrome element and
a cold trap. This is an auxiliary pump and still needs a high performance two stage primary pump to get down to where the diffusion pump will start to
operate. The good news is that the oil diffusion pump will work, Hg diffusion pumps wll get down to 10x-7 but obviously are unjustified, cost more,
and are hazardous (8 lbs Hg in glass.)
This, not the tube and not the VdG's will be the major expense.
Here's another Lichtenberg figure, courtesy Wilkepedia.
BTW Lichtenberg is also the fellow who discovered the principle behind xerography.
[Edited on 22-2-2007 by Sauron]
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not_important
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look here
http://205.243.100.155/frames/interesting.html
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Sauron
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Oh well. I was right...just too late.
I do like the the photo of the actual dielectric breakdown.
Loud bang, bright flash.
[Edited on 22-2-2007 by Sauron]
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Sauron
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The anode end of this LINAC tube is sealed with only a 0,001" thick Al foil supported by 1/4" thick Al disc that has been drilled with a pattern of
closely spaced 3/16" holes in staggered rows, so that about 50% of the disc in beam path is absent.
Is that foil really supposed to not rupture with the tube evacuated to 0.01 micron (0.00001 torr)? I guess the key is the small diameter of the holes
in the support plate.
I am going to investigate the vacuum holding capacity of the unions for process pipe, because if they will hold a high vacuum (0.01 micron) then this
will allow for interchangeable cathodes and anodes which will greatly simplify maintanence and make the tube more versatile. I was unimpressed by the
construction details of the cathode end of the Lee design. I'm sure it worked, but it seemed a wee but quick and dirty.
If not process pipe then flat ground flanged joints maybe with an O-ring groove in one face. Those are stock glassblower items from Ace and ChemGlass
etc.
[Edited on 22-2-2007 by Sauron]
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not_important
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What's the force (pressure differential) at 100 mm vac? At 10, and at 1 mm? Then how much additional force is applied in going from 1 mm to 0.01
micron?
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Sauron
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I know a socratic question when I see one but I don't want to do the math. I'm too old for pedagogy. 
But thanks for asking.
I have appended the compilation of Amateur Scientist articles dealing with the LINAC and VDG generator power supply for it, with an additional article
from 1955 referenced in the 1957 article.
I have replaced the compilation in the first post of this thread, and those of you who haven't yet downloaded it can get the latest one there.
For those of you who already have the main file here's the latest addition.
[Edited on 22-2-2007 by Sauron]
[Edited on 22-2-2007 by Sauron]
Attachment: http___vacuum.ramapo.edu_physics_physics-doc_amsci_AmSci01_1955_04_1955-04-fs.pdf (397kB)
This file has been downloaded 1446 times
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Sauron
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At first I assumed quite incorrectly that this 2 ft long LINAC tube is mounted horizontally, however, Franklin R. Lee built this one vertically. He
has the collector if the VdG generator touching the collector of the anode end of the LINAC and he has a microammeter (of sorts) built into the
collector dome. This leaves only a small space for a sample to be interposed for irradiation.
This would still allow me to plumb a loop through that space. I was figuring on a CSLR setup anyway (continuously stirred loop reactor) as most of the
free-radical reactions I am interested in using this for involve a gas and a liquid. Chlorine and acetic acid, chlorine and methyl formate, CCl4 and
NO, etc. A peristaltic pump with a PTFE head and tubing would be chemically inert and thin enough. (The thickness issue is only critical in beam
path). I have a good number of Microflex LE peristaltic pumps on hand, no PTFE drive head but I do have a PTFE diaphragm head that will work.
What tubing material to put in beam path? Lee gives some rough numbers for what a 250KeV electron beam will penetrate, this machine is about half
again as powerful. For example he says 0.25 mm Al (about 0.01 in) vs 3 mm of PE or several meters of air. And he uses a 0.001 in Al foil to close the
tube window. He describes the relationship between beam penetration and density of target and also target molecular weight.
I think a thin glass or quartz tube in beam path may be best. The beam effect on plastics may be harder to predict. Lee discusses PE crosslinking
briefly; a good effect.
Obviously metal tubing is out, the lighter metals lack inertness and the inert ones like tantalum are heavy enough to produce hard X-rays when struck
by an electron beam.
I guess I will be reading up on electron beam effects on materials.
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Sauron
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The design theory of a VdG is interesting.
The theoretical potential of the machine is determined by the smallest radius of curvature of the spherical collector. Multiply that by 70,000 and you
have the theoretical voltage - if the collector were a perfect sphere.
However, as the collector generally has a hole in its bottom for the belt system to enter, the best real world performance is on the order of 84-85%
of theory. That assumes a few things about proper machine design were obeyed.
The current is determined by the surface area of the belt rubbing the fixed upper bearing per second. The rule of thumb is: 100 sq in per second = 1
microampere. The partical limit to belt speed is 100 ft per second so a 1" wide belt gives 12 microamps, a 2" wide belt 24 microamps
I am evaluating a commercial VdG that is 10" diameter collector, 30" high and they claim 400,000 volts. This is a $600 unit.
Well, from Dr.Lee's numbers we can quickly see the theoretical maximum is 350,000 V and the likely real potential is 300,000. The seller does not
enlighten about how many microamps. Anyway the seller's claims are looking a trifle high. Of course it is not necessary to reply on rules of thumb as
an electrometer will tell the tale.
It is certainly true that anyone feeling deprived by the odd 100,000 extra V or two can replace the collector with a larger one without a tgreat deal
of effort. As long as you don't exceed half a million volts your LINAC tube design problems remain simple. You wrap 4 turns of copper wire asoubd the
tube every 2 inches or so and twist the ends into a corona point. Above 500,000 V this is done with fixed resistors. Anyway 300-400 K is enough for
me.
The belts are rubber and the thinner the better. So you can see why rpms can't be pushed beyond a certain limit and why spare belts are a Really Good
Idea. Like, there you are doing your E.O.Lawrence impression and the experiment halts because you have to change what is after all just a big rubber
band. Really! It's like having your Bently stop because the hamsters in the engine need a break.
Fear not, latex sheet is easy to come by, one does not have to pay ripoff spare parts prices from the OEM.
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Sauron
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Upon reflection, I don't need flanged ground joints to achieve modularity, rge ebds of this 2 to 3 ft Pyrex tube (not process pipe) 2" diameter will
just have 45/50 standard taper joints and these can be sealed with high vacuum grease and clamped quite conventionally. The screw-together clamps
probably better than Keck plastic clamps. A great variety of adapters to choose from for the cathose thermionic source (filament and leads) and the
vacuum takeoff. Probably Ace threads and their fittings.
Same at the other end, allowing for change of the anode, window etc.
I found a second large commercial VdG, this one has a 12" collector rather than 10" and is about 10% cheaper ($550 vs $605).
I found a smaller VDG locally for $300 but it seems like maybe 150,000 volts (6 or 8 jnch collector) so not very attractive. Still it is unclear
whether or not I can get 220V AC versions from the US so I may snag this one just to get the motor. I also might take it, plu a larger collector on
it, increase the height of the insulator and length of the belt, and be happy. That sort of depends on whether the belt diameter is adequate
(>1.5") which is what determins the surface area of friction and therefore the current.
I found an article with construction details of a 500 KeV 200 uA VDG circa 1938 with a 24 x 12" flattened toroidal collector and obviously a very wide
belt. The only advantage of the toroidal collector compared to a 12" sphere was extra capacitance (fatter sparks) not extra voltage but that 10X
increase in amperage is impressive. To do that with a sphere you'd have a diameter for insulator of 20 inches so a sphere of 1 to 1.5 meters and a
voltage of 1.5 to 2 MeV less yhat pesky 15%. Still a real beast, it would need to be 5-6 meters high.
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Sauron
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Many more commercial VDGs have turned up, the top end of anything affordable being 400-500KV. Which is fine. Resonance Research makes museum grade
machines up to 3 Megavolts but I doubt any of us could handle the cost. Or have anyplace to put it.
One commercial machine claims to be 750KV with a 17" collector, while their 14" collectors are 400K. I think the 17" models are interesting but won't
exceed 500K (what does an extra 1.5 inches of radius get you at 70,000 per inch?)
A word of caution to those who like me are inclined to throw $$$ at problems.
The VDG required to build an electron accelerating LINAC needs to be positively charged at the collector. Duh! Well, most sellers do not even tell you
whether their VDGs are built to be + at collector or - at collector. And it seems that many of them are minus, because such machines charge faster and
give longer sparks. One company makes them both ways and specifies this in description. Their units are 400KV, 14" SS collectors and c.$600, and they
offer both 110V and 220V models. These folks get full marks from me.
They even put the manual on the web, something I wish all sellers would do.
Here it is as attachment.
[Edited on 23-2-2007 by Sauron]
Attachment: 10085[1].pdf (762kB)
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Sauron
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say, isn't that Hillary hiding behind the VdG?
[Edited on 23-2-2007 by Sauron]
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