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A Novel Electrostatic Accelerator Concept Developed By Siemens

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jpsmith123

Fri Aug 12 2011, 02:29AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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I don't know if anyone here (besides me) is interested in particle accelerators, but if there is, check this idea out:

Ash Small

Fri Aug 12 2011, 08:38AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

There has been some talk on other forums regarding putting a multiplier inside the vacuum system, but the main obstacle was seen as the problem of outgassing from the dielectric, etc.. This seems to overcome those limitations.

Personally, I'm 'only' aiming for ~650keV (633keV, to be precise). Thanks for posting it, JP.

EDIT: other foils can be used for electron stripping, eg aluminium oxide, etc., around 3 microns thick, if my memory is correct. (EDIT: maybe 0.3, I'll have to check, It's probably <2 years since I read up on it)

Alternatively, using just one set of parallel (or hemi-spherical) plates to achieve half the maximum acceleration wouldn't require H- ions or electron stripping.

Just a proton source, which is pretty straightfoward. An RF or magnetron based ion source, hydrogen, and a couple of magnets (or electrostatics) to separate the monatomic ions (protons) from the diatomic ions. (Using Penning trap technology, basically deflection yokes that bend the protons in the beam more than the diatomic ions)

jpsmith123

Sat Aug 13 2011, 01:34AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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Although at present I'm only interested in accelerating electrons, I have pondered the problem of "sourcing" protons and deuterons.

My first thoughts on the subject started with the issue of how to get the gas into the vacuum envelope of the ion source (or accelerator), and to that end, I came up with the idea of using a thin-walled palladium-silver alloy tube from a hydrogen purifier (of which I have a few laying around here somewhere).

Although, instead of using it in the conventional manner, where it's heated up, my idea was to make the PdAg tube itself the cathode of an electrolytic cell...hoping that with low pressure (vacuum) on one side, and a high "electrochemical pressure" on the other side, that the hydrogen or deuterium would diffuse through at a rate proportional to the cell current. And then maybe the bulk of the H2 or D2 that doesn''t diffuse through could get recombined with the O2 before leaving the cell to avoid waste.

Then, realizing that the H or D diffuses through the PdAg membrane as ions, not molecules, I went a step further and wondered whether a very high electric field in combination with a source of strong UV light, might be able to overcome the "workfunction" (or whatever you would call it) and pull the protons and deuterons off the surface of the PdAg directly as ions, and not molecules that still need to be ionized.

I don't know if any of those ideas would work or not, but it would be interesting to try, and if it actually did work, you could probably save some time and money.

Ash Small

Sat Aug 13 2011, 07:14AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

That sounds over complicated, although it may be worth trying if you have everything you need.

There are a few methods usually used by the amateur community, the first (and best) is the 'commercial' option of using MFC's (mass flow controllers, of which I have a few) with the relevant valving and plumbing, and a small tank (lecture bottle?) of H or D, which are both readily available at reasonable prices.

The most common method used by amateurs is a valve and capillary tube, relying on the vacuum guages and throttle valves of the vacuum system to monitor/control pressure.

Some people have achieved reasonable results using electrolysis of water/heavy water, but the main challenge, apart from obtaining suitable electrodes, is to dry the gas completely, as water vapour is the vacuum system's 'worst enemy'.

It sounds like the method you suggest may overcome this problem (I have heard of something similar, I've been researching this for a couple of years now, on and off, and now have a pretty much complete vacuum system, with automatic pressure control, RF generators, etc. I'm still working on the HV supply, as you are aware, and I'm hoping to be in a position to obtain some initial results by early next year, as I've some other priorities (fixing my truck, and moving house) over the next few months.

~90% monatomic H ions can easily be achieved using both RF and magnetron plasma sources, although some 'tricks' need to be employed (basically lots of power into a small amount of gas).

My main interest is in protons, although the idea of electron beam welding sounds fun. Once everything is 'up and running' I may get hold of some D and some detectors and join the 'neutron club' too, but my main interests are 'playing with protons' and PECVD.

EDIT: I imagine that the kind of DC electric field described above would probably be sufficient in itself to ionize the gas on it's own, but using a separate ion source and separating monatomic ions from diatomic ions before feeding protons in probably has advantages in most situations.

jpsmith123

Thu Aug 25 2011, 11:26PM

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

I found a couple of patents regarding electrostatic accelerators, apparently similar in concept to the one mentioned in my original post. I haven't had time to thoroughly examine them yet, so I don't know if they have much merit, but here they are in case anyone else finds this stuff interesting:

Ash Small

Thu Aug 25 2011, 11:47PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

jpsmith123 wrote ...

I found a couple of patents regarding electrostatic accelerators, apparently similar in concept to the one mentioned in my original post. I haven't had time to thoroughly examine them yet, so I don't know if they have much merit, but here they are in case anyone else finds this stuff interesting:

Thanks for posting, JP. I'm still reading them myself, but this thread has certainly shown me how to build a multiplier inside a vacuum system.

jpsmith123

Sat Aug 27 2011, 09:41PM

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

So you ultimately want to build some sort of a small particle accelerator based on a Cockcroft-Walton voltage multiplier? And is that why you mentioned wanting to get 50 kv ac off the transformer?

Ash Small

Sat Aug 27 2011, 10:30PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

jpsmith123 wrote ...

So you ultimately want to build some sort of a small particle accelerator based on a Cockcroft-Walton voltage multiplier? And is that why you mentioned wanting to get 50 kv ac off the transformer?

I'm aiming for 50kV initially. I feel that the only way an amateur is going to stand a reasonable chance of getting 400-650kV (or keV) is to construct some sort of vacuum capacitor/accelerator arrangement.

I've been told on 'another forum' that it's impossible for an amateur to achieve these energy levels.

I'd started to think about using vacuum capacitors to avoid the outgassing problem, but this thread has given me more ideas about constructing the plates.

EDIT: Although 50kV @ 50mA = ~4mA @ 650kV at best.

jpsmith123

Sun Aug 28 2011, 12:57AM

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

As far as the HV AC drive is concerned, I think Siemens actually uses a series resonant circuit between the transformer and the multiplier, to step the voltage up. This way, the transformer design is easier.

Edit:

Here's the paper I was looking for that shows the use of a "series resonant loop" between the transformer and the multiplier:

Ash Small

Fri Sept 02 2011, 10:53PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I think I'll probably have to consider increasing the proposed frequency of the transformer, as the limiting factor in this design will be the size of the capacitor plates.

The only way to increase current will be to increase frequency.

I think this now means I'm in the market for some much faster cores, but I might carry on with the N27 cores for now, while developing the GDT's etc.

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