Anode layer ion source. Operation pictures
- Werner Engel
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Re: Anode layer ion source. Operation pictures
Hi Andrew!
Great that you still work on the fusor! Thanks for all your posts - great pictures and details!
What kind of "laser density probe" do you use in this case?
Interferometry, reflectometry, scattering, refractive index?
BR,
Werner
Great that you still work on the fusor! Thanks for all your posts - great pictures and details!
What kind of "laser density probe" do you use in this case?
Interferometry, reflectometry, scattering, refractive index?
BR,
Werner
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Re: Anode layer ion source. Operation pictures
Hi Werner,
It's going to be a CO2 interferometer.
http://www.rtftechnologies.org/physics/ ... ometer.htm
Andrew
It's going to be a CO2 interferometer.
http://www.rtftechnologies.org/physics/ ... ometer.htm
Andrew
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- Werner Engel
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Re: Anode layer ion source. Operation pictures
Hi Andrew!
Congratulations to your final picture (the one showing the interference pattern)!
It's an enormous amount of work doing this @10,6µm with all the special materials. The carbon-pipe is it really stiff enough? What about vibrations from the roughing pump? Or did you switch off pumping during the measurement? Did you choose the 10,6 due to absorption of the plasma to be expected at that density (plasma frequency) or to reduce vibration induced problems?? Thomson Scattering is done @1064 nm (Nd:YAG) at the Tokamak in Garching. It seems they do not care about wavelength. But other refractive index measurements try to use as large as possible wavelengths.
I just built a “normal” HeNe-Michelson to get comfortable with optics. But this will be adapted in several steps.
Attached a Picture of my Michelson and one of the Nd:YAGs in Garching.
BR,
Werner
Congratulations to your final picture (the one showing the interference pattern)!
It's an enormous amount of work doing this @10,6µm with all the special materials. The carbon-pipe is it really stiff enough? What about vibrations from the roughing pump? Or did you switch off pumping during the measurement? Did you choose the 10,6 due to absorption of the plasma to be expected at that density (plasma frequency) or to reduce vibration induced problems?? Thomson Scattering is done @1064 nm (Nd:YAG) at the Tokamak in Garching. It seems they do not care about wavelength. But other refractive index measurements try to use as large as possible wavelengths.
I just built a “normal” HeNe-Michelson to get comfortable with optics. But this will be adapted in several steps.
Attached a Picture of my Michelson and one of the Nd:YAGs in Garching.
BR,
Werner
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Re: Anode layer ion source. Operation pictures
New modifications to the anode layer ion source:
The old flat anode ring has been replaces with a conical anode ring (6.6 degree inward) for better beam focusing. this should have the focal point about 3" in front of the face of the source, right at the focal point of the fusor. In reality there still is the effect from space charge repelling the beam so it doesn't focus to a point, though the beam is considerably better defined with a tighter focus.
The NdFeB magnet has also been replaced with a SmCo magnet for higher temperature operation(up to 300C instead of 80C for the NdFeB)
Stainless Steel Belleville Disc Spring (mcmaster 9713K437) (6.6 degree inward angle) and jig to bore to correct ID New and old anode rings SmCo magnet installed Modified injector re-assembled Ion beam Video of operation
https://www.youtube.com/watch?v=DbfmR5t ... e=youtu.be
https://www.youtube.com/watch?v=UDQ1BAH ... e=youtu.be
The old flat anode ring has been replaces with a conical anode ring (6.6 degree inward) for better beam focusing. this should have the focal point about 3" in front of the face of the source, right at the focal point of the fusor. In reality there still is the effect from space charge repelling the beam so it doesn't focus to a point, though the beam is considerably better defined with a tighter focus.
The NdFeB magnet has also been replaced with a SmCo magnet for higher temperature operation(up to 300C instead of 80C for the NdFeB)
Stainless Steel Belleville Disc Spring (mcmaster 9713K437) (6.6 degree inward angle) and jig to bore to correct ID New and old anode rings SmCo magnet installed Modified injector re-assembled Ion beam Video of operation
https://www.youtube.com/watch?v=DbfmR5t ... e=youtu.be
https://www.youtube.com/watch?v=UDQ1BAH ... e=youtu.be
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
Additional pole pieces have been tested to determine the effect of the magnetic field position on beam focusing
Numbers 1,2,and 3 from left, pole piece 1 was the one used in all previous tests
The version 1 has a 1/8" step of 0.5" dia, then a 1/16" step of 0.625" dia, then a 45degree taper over 1/16"
The version 2 has a1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/16"
The version 3 has a 1/16" step of 0.5" dia, then a 15degree taper over 0.1875" Version 2 pole piece and plasma focus Version 2 pole piece recessed and plasma focus Version 3 pole piece and plasma focus Version 3 pole piece recessed and plasma focus
Numbers 1,2,and 3 from left, pole piece 1 was the one used in all previous tests
The version 1 has a 1/8" step of 0.5" dia, then a 1/16" step of 0.625" dia, then a 45degree taper over 1/16"
The version 2 has a1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/16"
The version 3 has a 1/16" step of 0.5" dia, then a 15degree taper over 0.1875" Version 2 pole piece and plasma focus Version 2 pole piece recessed and plasma focus Version 3 pole piece and plasma focus Version 3 pole piece recessed and plasma focus
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
Further pole pieces tested
Numbers 1,2,and 3 from left, pole piece 1 was the one used in all previous tests
The version 1 has a 1/8" step of 0.5" dia, then a 1/16" step of 0.625" dia, then a 45degree taper over 1/16"
The version 2 has a 1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/16"
The version 3 has a 1/16" step of 0.5" dia, then a 15degree taper over 0.1875"
The version 4 is 7.5mm long 14mm dia
The version 5 has a 1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/8"
Version 4 and 5 have a pump out groove milled in the base to vent the trapped volume inside the magnet
Version 4 pole piece and plasma focus Version 5 pole piece and plasma focus Version 5 is going to be the final version used to upgrade the ion sources, it seems to hold the best focus
Numbers 1,2,and 3 from left, pole piece 1 was the one used in all previous tests
The version 1 has a 1/8" step of 0.5" dia, then a 1/16" step of 0.625" dia, then a 45degree taper over 1/16"
The version 2 has a 1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/16"
The version 3 has a 1/16" step of 0.5" dia, then a 15degree taper over 0.1875"
The version 4 is 7.5mm long 14mm dia
The version 5 has a 1/16" step of 0.5" dia, then a 1/16" step of 0.58" dia, then a 15degree taper over 1/8"
Version 4 and 5 have a pump out groove milled in the base to vent the trapped volume inside the magnet
Version 4 pole piece and plasma focus Version 5 pole piece and plasma focus Version 5 is going to be the final version used to upgrade the ion sources, it seems to hold the best focus
Andrew Seltzman
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- Steven Sesselmann
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Re: Anode layer ion source. Operation pictures
Andrew,
Once again I commend you on your engineering skills and systematic approach to solving a problem, this work on your anode layer source would be worth writing a paper on.
It will be interesting to see if the narrower beam increases the fusion rate or efficiency.
Steven
Once again I commend you on your engineering skills and systematic approach to solving a problem, this work on your anode layer source would be worth writing a paper on.
It will be interesting to see if the narrower beam increases the fusion rate or efficiency.
Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
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Re: Anode layer ion source. Operation pictures
Performance curves for the anode layer ion source
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
I finally got around to converting all the drawing for the ion source from my old cad program (KeyCad, made in 1992) into a modern program (Autodesk Inventor) and made some 3D models:
Andrew Seltzman
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- Werner Engel
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Re: Anode layer ion source. Operation pictures
Did you allready try to focus the beam? Maybe with a Wehnelt cylinder or an einzellens?
Or is this even planned?
Higher luminosity would be nice - I think.
Or is this even planned?
Higher luminosity would be nice - I think.
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Re: Anode layer ion source. Operation pictures
I've only tried to focus the beam by varying the pole pieces. I might try electrostatic/magnetic focusing later on, but my next step will probably be getting the injectors producing short pulses of ions (<100us).
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
There has been some success with pulse work on the injectors
The injectors were run at 10mTorr with an air plasma. HV bias to the anode ring was supplied using a behlke GHTS60(opt1) high speed mosfet pulser http://www.behlke.com/pdf/ghts.pdf capable of delivering up to 15A pulses at 6kV with down to 100ns pulse width. The injectors were found to require a few ms to ionize once HV bias was applied to the anode ring, with a couple of ms jitter. The pulser has 250ohm in series with the output. A 1k resistor was placed in series with the anode ring, a 1k resistor was placed in series with the injector case to monitor injector current, and a 1k resistor was placed in series with the faraday cup to measure beam current. A high speed camera was used to observe the plasma discharge.
On the oscilloscope trace, ch1 is the gate signal to the HV pulser, ch2 is 1v/ma injector current monitor, ch3 is 1v/ma beam current monitor, ch4 is anode HV. beam current peaks at 0.3A A high speed camera was used to observe the plasma discharge. These are from ~3ms long discharges
at 420fps at 1000fps With the 1k resistor in series with the anode removed at 10mTorr, beam current peaks at 0.55A for about 10us with a subsequent exponential decay. (average of 16 pulses) Jitter in the ionization delay is currently limiting the minimum pulse width, but work is in progress on that front as well.
By the way does anyone know where to get krytron tubes?
The injectors were run at 10mTorr with an air plasma. HV bias to the anode ring was supplied using a behlke GHTS60(opt1) high speed mosfet pulser http://www.behlke.com/pdf/ghts.pdf capable of delivering up to 15A pulses at 6kV with down to 100ns pulse width. The injectors were found to require a few ms to ionize once HV bias was applied to the anode ring, with a couple of ms jitter. The pulser has 250ohm in series with the output. A 1k resistor was placed in series with the anode ring, a 1k resistor was placed in series with the injector case to monitor injector current, and a 1k resistor was placed in series with the faraday cup to measure beam current. A high speed camera was used to observe the plasma discharge.
On the oscilloscope trace, ch1 is the gate signal to the HV pulser, ch2 is 1v/ma injector current monitor, ch3 is 1v/ma beam current monitor, ch4 is anode HV. beam current peaks at 0.3A A high speed camera was used to observe the plasma discharge. These are from ~3ms long discharges
at 420fps at 1000fps With the 1k resistor in series with the anode removed at 10mTorr, beam current peaks at 0.55A for about 10us with a subsequent exponential decay. (average of 16 pulses) Jitter in the ionization delay is currently limiting the minimum pulse width, but work is in progress on that front as well.
By the way does anyone know where to get krytron tubes?
Andrew Seltzman
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- Richard Hull
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Re: Anode layer ion source. Operation pictures
Krytrons are dual use devices and are not long lived. Hydrogen thyratrons might be better and more available surplus and can repetitively handle pulses over a long period with 100 amp pulses easily to be had in the 4C35 and the 5C22 can handle hundreds of amps. The one or two krytrons I have were obtained at hamfests over the years as well as the 40-50 hydrogen thyratrons I now have. You probably could not even dream of acquiring either the Krytrons or the H2 Thyratron new. I note the 5C22 was over $1000.00 in an old Newark catalog. Most of the 5C22's I have were under $5.00 at hamfests.
Many of the surplus H2 thyratrons are timed pulls from radars and special precision pulsed energy setups where temporal jitter is crucial. Once the jitter gets out of spec for their app, the perfectly functioning, (save for jitter), tube is pulled.
You may buy a "pig in a poke" at a hamfest in a $5.00, 5C22. I will note I have never found a burned out filament in one of these monsters. Shake the tube and see if stuff rattles around in the tube. (metal particles). Note it is perfectly normal to see a blackened ring inside the envelope around the screened area near the top. All have green transitional uranium glass flat tops where the anode exits. Check the long glass anode stem for cracks that have let out the magic.
If you are not constantly pulsing at a high rep rate in formal daily service, I have pumped 1kiloamp pulses through these puppies and they can take it on the chin.
Specs on 5C22
http://www.relltubes.com/filebase/en/sr ... tional.pdf
I note e-bay has a ton for sale ranging from $10.00 to this brand new National Electronics tube which is what you get from Newark sold here for only $750!
http://www.ebay.com/itm/NATIONAL-ELECTR ... _33wt_1361
Richard Hull
Many of the surplus H2 thyratrons are timed pulls from radars and special precision pulsed energy setups where temporal jitter is crucial. Once the jitter gets out of spec for their app, the perfectly functioning, (save for jitter), tube is pulled.
You may buy a "pig in a poke" at a hamfest in a $5.00, 5C22. I will note I have never found a burned out filament in one of these monsters. Shake the tube and see if stuff rattles around in the tube. (metal particles). Note it is perfectly normal to see a blackened ring inside the envelope around the screened area near the top. All have green transitional uranium glass flat tops where the anode exits. Check the long glass anode stem for cracks that have let out the magic.
If you are not constantly pulsing at a high rep rate in formal daily service, I have pumped 1kiloamp pulses through these puppies and they can take it on the chin.
Specs on 5C22
http://www.relltubes.com/filebase/en/sr ... tional.pdf
I note e-bay has a ton for sale ranging from $10.00 to this brand new National Electronics tube which is what you get from Newark sold here for only $750!
http://www.ebay.com/itm/NATIONAL-ELECTR ... _33wt_1361
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
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: Anode layer ion source. Operation pictures
I'm almost out of the welded version anode rings (which were left over from the initial injectors made for my fusor) since the ion sources have been selling well. The anode ring on the ion source had to be re-designed due to problems finding a machine shop willing to mass produce the TIG welded version(0-80 threaded rods tig welded into a ring) on the mass production ion source.
The resulting design uses three 0-80 flat head screws countersunk flush into a custom machined anode ring. The new design is much easier to mass produce and just as stable(in mounting position) as the older version. I ordered 60 anode rings shown below and have assembled the next batch of ion sources.
Anode ring top/bottom Ion source with new anode design Ion source with new anode design Batch of 6 new ion sources using the new design
The resulting design uses three 0-80 flat head screws countersunk flush into a custom machined anode ring. The new design is much easier to mass produce and just as stable(in mounting position) as the older version. I ordered 60 anode rings shown below and have assembled the next batch of ion sources.
Anode ring top/bottom Ion source with new anode design Ion source with new anode design Batch of 6 new ion sources using the new design
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
I have a quick question about the design. What is the purpose for the central rod to be bored? Is it so it can be used as a gas inlet? Or does it influence the magnetic circuit?
There _is_ madness to my method.
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Re: Anode layer ion source. Operation pictures
The central "rod" is actually a screw, the hole is a vent to prevent trapped gas from forming a virtual leak when the source is screwed into a conflat base plate.
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
Oh I see. It's a "virtual" vent.
There _is_ madness to my method.
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Re: Anode layer ion source. Operation pictures
I recently started a company to sell these ion sources, spread the word to anyone who is interested. For amateurs on fusor.net, I will extend a discount for now, and sell these for $250ea.
https://www.techplasmas.com/
https://www.techplasmas.com/
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
I have recently developed a technique to allow narrow pulse width, high current ion pulse generation with reduced jitter and delay in an anode layer ion source by adding a keep alive electrode into the discharge channel. I have a patent pending on this design, and a paper on this technique under review in Review of Scientific Instruments(attached below)
RSI paper(under review)
https://drive.google.com/open?id=0B28CX ... nkxQXdkS1U
Keep alive electrode cross section KA electrode closeup
RSI paper(under review)
https://drive.google.com/open?id=0B28CX ... nkxQXdkS1U
Keep alive electrode cross section KA electrode closeup
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
Cool - I assume that runs a "simmering" low current discharge?
- Finn Hammer
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Re: Anode layer ion source. Operation pictures
Andrew,
Please excuse my presence in this very advanced thread, but I have been looking for an opportunity, for a while, to ask why the anode was supported by only 3 screws, leaving the 4th. hole vacant.
I guess this post answers that.
Cheers, Finn Hammer
Please excuse my presence in this very advanced thread, but I have been looking for an opportunity, for a while, to ask why the anode was supported by only 3 screws, leaving the 4th. hole vacant.
I guess this post answers that.
Cheers, Finn Hammer
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Re: Anode layer ion source. Operation pictures
Finn,
The original reason for the vacant hole was to allow a gas feed to come in through the back of the ion source, also the first ion source prototypes were hand machined, so the looser tolerances made the fasteners more likely to bind with the lower machining tolerances; only having three mounts reduced this probability. The original anode ring was also welded to threaded rods, so this would have been one less weld.
The original reason for the vacant hole was to allow a gas feed to come in through the back of the ion source, also the first ion source prototypes were hand machined, so the looser tolerances made the fasteners more likely to bind with the lower machining tolerances; only having three mounts reduced this probability. The original anode ring was also welded to threaded rods, so this would have been one less weld.
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
A patent has been granted on the use of a keep alive electrode to decrease startup time:
http://pdfpiw.uspto.gov/.piw?PageNum=0& ... LRPgD8lPts
http://pdfpiw.uspto.gov/.piw?PageNum=0& ... LRPgD8lPts
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
I have a mass-producible base-plate design for the anode layer ion source using an aluminum cutout from Front Panel Express
2.75" blank conflat flange outline for Front Panel Express if anyone wants to make their own custom feedthrough flanges
http://www.frontpanelexpress.com
A hermeticallly sealed Pasternack PE4077 BNC connector is used as the HV feedthrough. It's rated to 500v with a dielectric withstanding voltage of 1500v, however I have run it for extended time at 1000v and shortly to 1700v without problems
Ion source mounted on testbed
ion source running with baseplate
2.75" blank conflat flange outline for Front Panel Express if anyone wants to make their own custom feedthrough flanges
http://www.frontpanelexpress.com
Andrew Seltzman
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Re: Anode layer ion source. Operation pictures
Interesting that those Pasternack connectors work as high vacuum feedthroughs.
Can one realistically run one of these types of sources off an NST?
Can one realistically run one of these types of sources off an NST?