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jpsmith123

Mon Aug 12 2019, 10:48PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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"so my pick is number three then - a microtron, or some other type of cyclic accelerator."

I hate to be the bearer of bad news but ANY circular accelerator comes under the "cost and complexity" category; that is to say, any circular accelerator is generally going to be way beyond the resources and capability of a typical hobbyist.

"yea, but there is a ton of new ones, which were unheard of at the time of that book."

Please provide a link proving the existence of a working microtron that is technologically so far advanced in some meaningful sense, compared with the microtrons described in the book by Kapitza, as to be reasonably described as "unheard of."

" they build microtrons on neodymium magnets these days, with iron core weight about 20 kilos only."

Who does? This sounds like somebody's research proposal, not a description of a working microtron. To the extent it's possible in the first place that's not something you're going to build.

2Spoons

Tue Aug 13 2019, 12:17AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
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I had a bit of a look into plasma wake accelerators - but I believe they require a very fast laser pulse. Might still be doable for someone really keen.

father dest

Tue Aug 13 2019, 06:05PM

Registered Member #54795 Joined: Mon Apr 06 2015, 11:55AM
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>I hate to be the bearer of bad news but ANY circular accelerator comes under the "cost and complexity" category; that is to say, any circular accelerator is generally going to be way beyond the resources and capability of a typical hobbyist.

this dude almost did it -

it is sad he abandoned the project.
and you're insisting that this is maximum what we can get at home:

Fdc40139fb274daa9ceb8779db7692fe

right?

"yea, but there is a ton of new ones, which were unheard of at the time of that book."
>Please provide a link proving the existence of a working microtron that is technologically so far advanced in some meaningful sense, compared with the microtrons described in the book by Kapitza, as to be reasonably described as "unheard of."

i was talking about principles, not about devices - are you saying that any and every new principle means instant huge technological leap forward? that's not the case of course. been busy studying Dolbilin's patents, so can't tell right now, but if i remember correctly they work on other modes of acceleration nowadays, the modes that guys from old era wasn't considering optimal/workable, or something like that.

btw - all 3 Dolbilin's patents are total bs - they work on paper, but require insane materials/semiconductors in reality.

" they build microtrons on neodymium magnets these days, with iron core weight about 20 kilos only."
>Who does? This sounds like somebody's research proposal, not a description of a working microtron. To the extent it's possible in the first place that's not something you're going to build.

these dudes -

it's the device from that "research proposal", the magnet weight is only 40kg - electromagnet, can be reduced to 20 kilos by swapping copper on neodymium.

jpsmith123

Wed Aug 14 2019, 01:55AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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"this dude almost did it - it is sad he abandoned the project."

If he "almost" did it he probably wouldn't have abandoned the project after all the time and money spent. Apparently he abandoned it because it was a total failure. Most likely he didn't do enough research beforehand to appreciate what he was getting into.

"and you're insisting that this is maximum what we can get at home:right?"

No not at all. The device in that picture apparently has nothing to do with the approach I suggested. (And there are other possibilities that I didn't even mention).

"i was talking about principles, not about devices"

Principles don't make electron beams and/or x-rays; you need hardware for that.

"are you saying that any and every new principle means instant huge technological leap forward? that's not the case of course."

Huh? That's what you seem to be saying. You seem to be implying that the existence of a research proposal that suggests the possibility of an x band microtron with a relatively small magnet makes Kapitza's book obsolete. It doesn't. Moreover, even if someone was able to make a practical portable x band microtron with a relatively small magnet, all the other design and construction issues are still there so the book is not outdated/obsolete by any means.

"been busy studying Dolbilin's patents, so can't tell right now, but if i remember correctly they work on other modes of acceleration nowadays, the modes that guys from old era wasn't considering optimal/workable, or something like that.btw"

Show me a working example of the hardware that makes everything in Kapitza's book outdated/obsolete.

BTW books could be written about various accelerator concepts that seemed plausible, were tried, but never worked out in practice; e.g. the "megatron" (plasma betatron); the "nested high voltage accelerator"; the "electron auto-accelerator"; the "high current betatron"; are a few that come to mind.

"- all 3 Dolbilin's patents are total bs - they work on paper, but require insane materials/semiconductors in reality."

No; you're looking at it all wrong. A patent is nothing more than a legal record of somebody's idea; it's not a "how to" article. It doesn't have to show merit and it often doesn't have to be very detailed.

"these dudes - it's the device from that "research proposal", the magnet weight is only 40kg - electromagnet, can be reduced to 20 kilos by swapping copper on neodymium."

I don't know how it works in Russia but in the U.S. there's something called the "Small Business Innovation Research" program whereby people submit
various proposals to the government and many times they get funding to do the research. I've followed some of these projects and I think some of these people are in a sense "scammers." They proffer some facially plausible but very high risk ideas that get funded with a grant but nothing ever comes of it. I think they use it as a way to fund a start-up company.

An example is a high current betatron proposed by the Adelphi company. IIRC they proposed to design and build a high current betatron using ferrite instead of silicon steel. The simple and straightforward idea was that if the operating frequency was scaled up - everything else being the same - they could get a much higher average current. (I was so interested in this project that I corresponded with the principal investigator on the project asking things like what kind of ferrite was being used, etc.) They got funding for it but for some reason the high current betatron was never created, AFAIK.

I can imagine the same kind of thing happening with the proposal for the x-band portable microtron: It seems plausible at first but they start building it and then discover that they can't get the magnetic field uniformity they need so they start adding shims and/or coils and then another power supply. And then it turns out to be too temperature sensitive so now they have to add a cooling system and pretty soon it looks nothing like what they originally imagined and it never happens.

father dest

Wed Aug 14 2019, 07:38AM

Registered Member #54795 Joined: Mon Apr 06 2015, 11:55AM
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>If he "almost" did it he probably wouldn't have abandoned the project after all the time and money spent. Apparently he abandoned it because it was a total failure. Most likely he didn't do enough research beforehand to appreciate what he was getting into.

i can't understand - are u being so damn sceptical about almost anything, or are u so damn good at accelerators theory that u know everything in advance? lol, jk.

>The device in that picture apparently has nothing to do with the approach I suggested. (And there are other possibilities that I didn't even mention).

can u speak some more about those "other" variants too? coz i don't like the author of that helical thing already - i see him like some sort of a troll.
btw - he wrote in his next patent than helical thing had some drawbacks so he replaced it with that "tesla-like" thing i posted above.

"are you saying that any and every new principle means instant huge technological leap forward? that's not the case of course."
>Huh? That's what you seem to be saying. You seem to be implying that the existence of a research proposal that suggests the possibility of an x band microtron with a relatively small magnet makes Kapitza's book obsolete. It doesn't.

idk - maybe it's translation problems (english is no my 1st or even 2st language), or maybe it is my fault in the way of formulating thougts - just forget about it.
let's just accelerate! forward : D

father dest

Wed Aug 14 2019, 06:40PM

Registered Member #54795 Joined: Mon Apr 06 2015, 11:55AM
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Posts: 28

jpsmith123 wrote ...

I came to the conclusion that a voltage-scaled-up version of the "multibeam accelerator" described by G.V. Dolbilov et al. might be one approach (there are a few other possibilities, IMO).

This design eliminates the problem of a big and bulky vacuum feedthrough insulator and associated problems.

i think this guy is a troll

look at it:

BZ SJRmJGK0

17 cm dia ferrite cores inside the secondary - lol? : )

This device apparently uses a multi-turn primary driven with 500 volt pulses at 18 khz or something like that. But to scale up the voltage without making it too big, I think you'd need to drive the primary at a much higher voltage with a very short pulse (sub-microsecond), and use a lower turns ratio.

the inverter drives resonance transformer. at it's resonance frequency. but you can't just drive tesla with square wave at Fres - your primary current would rise infinitely as far as i remember. in the case of no load atleast.
and no real pictorials as always, even at conference:

R4eHoZVC3 M

the guys you thinkin were trying to get money for microtron startup company had posted real photos of their working prototype at conference, unlike this jockey : D

jpsmith123

Thu Aug 15 2019, 04:37PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Unfortunately the several published papers on the "multibeam accelerator" are seriously lacking in detail, but I don't think it's fair to call the inventor a "troll."

Anyway, I also had questions about how the primary was being driven. One of the papers mentioned something about an "inverter" made by a company in Bulgaria.

I tried to research that but I couldn't find anything. But I did find the following linked paper which apparently shows a 300 kv unit installed in Japan. It also shows a block diagram of the "inverter" comprised of a DC power supply and a "modulator" (See figures 1,2 and 3).

So from this I assume the accelerator exists and must be fairly rugged and reliable.

BTW here's another interesting accelerator idea that seemed promising, but then I never heard anything more about it ever again:

father dest

Fri Aug 16 2019, 09:33AM

Registered Member #54795 Joined: Mon Apr 06 2015, 11:55AM
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Posts: 28

jpsmith123 wrote ...

BTW here's another interesting accelerator idea that seemed promising, but then I never heard anything more about it ever again:

hurmmm - how bout dat?

it's from 2010 -

Conundrum

Sat Aug 17 2019, 06:30AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062

No, Nd magnets are not used because the Curie point is far too low.

Incidentally some hobbyists are trying ReBCO based superconducting magnets as LN2 is easy to get hold of.
Obviously the problem is getting a good enough physical structure and for high field magnets cooling is less of a problem than making something that can withstand the huge forces trying to blow it apart.

I did look into making a basic HTSC magnet, as building a concentric design is barely doable.
This would be analogous to a Tesla Coil primary and as such not capable of much field except in the bore, and I'd need to use a conventional magnet to boost it. Incidentally Nd magnets are well known to get stronger with low temperature!
Maybe combine the two and use an optimized NdFeB magnet to get maximum possible field at say 200K which is doable using solvent + dry ice.

jpsmith123

Sat Aug 17 2019, 02:36PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Thanks for the link.

It seems they've changed the design a little bit from that described in the earlier paper.

I'm disappointed that the average current from that device is apparently only a few microamps (although that's more than you'd get with a conventional betatron of a similar size).

Apparently I was overestimating the average current you could get from a frequency scaled betatron. For one thing, it seems that as the frequency increases you'd have less time to inject charge. And the amount of injected charge that would actually be trapped would depend on the type of focusing, the accelerating gradient (volts/turn) and the injection energy, so there are a few variables involved.

hurmmm - how bout dat?

it's from 2010

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