Anode layer ion source. Operation pictures

For the design and construction details of ion guns, necessary for more advanced designs and lower vacuums.
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Finn Hammer
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Re: Anode layer ion source. Operation pictures

Post by Finn Hammer » Wed Nov 01, 2017 6:56 am

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

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Re: Anode layer ion source. Operation pictures

Post by Andrew Seltzman » Wed Nov 01, 2017 2:12 pm

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.
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Re: Anode layer ion source. Operation pictures

Post by Andrew Seltzman » Wed Jan 02, 2019 6:54 pm

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
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Re: Anode layer ion source. Operation pictures

Post by Andrew Seltzman » Sat Mar 23, 2019 7:48 pm

I have a mass-producible base-plate design for the anode layer ion source using an aluminum cutout from Front Panel Express
IMG_20190320_235610180a.jpg
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
IMG_20190320_235626288_HDRa.jpg
Ion source mounted on testbed
IMG_20190320_234942510a.jpg
ion source running with baseplate
IMG_20190320_235000977a.jpg

2.75" blank conflat flange outline for Front Panel Express if anyone wants to make their own custom feedthrough flanges
http://www.frontpanelexpress.com
2.75CF_outline.zip
(391 Bytes) Downloaded 232 times
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Re: Anode layer ion source. Operation pictures

Post by ian_krase » Sun Oct 27, 2019 7:53 am

Interesting that those Pasternack connectors work as high vacuum feedthroughs.

Can one realistically run one of these types of sources off an NST?

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Re: Anode layer ion source. Operation pictures

Post by Andrew Seltzman » Sun Oct 27, 2019 12:48 pm

The pasternack BNC connectors are hermetically sealed and will hold a vacuum, though not UHV since they use an elastomer o-ring to seal to the base plate; not a real issue in the vacuum ranges that fusors/shuttering/deposition runs at though.

If rectified to DC then yes an NST would work, though make sure not to drive it with too much current.
I would not recommend an NST though since they tpically can supply much more current than the ion source can handle and can drive arcs that could damage the source.

I would recommend using an EMCO F40 high voltage DC-DC converter, it has an HV output proportional to the DC input voltage and can be controlled with a DC-DC buck converter
https://www.ebay.com/itm/EMCO-F40-High- ... xycmBSrONF
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Richard Hull
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Re: Anode layer ion source. Operation pictures

Post by Richard Hull » Sun Oct 27, 2019 7:27 pm

I once found a fist full o' these little gems at a hamfest on small old surplus circuit boards in a giant box for a buck a board. I sold a lot of them once I removed and tested them. Most went with the huge lot of EMI PMTs I sold years ago here in our trading post. These are perfect little bias supplies as long as you need only microamps as in PMT work.

Where did I get the PMTs? At Ed Wingate's N.Y. Teslathon! (no longer held) A guy had a giant gamma camera head with about 40 or more EMI PMTs still attached with sockets wiring and preamps to a 2 foot diameter NaI:tl crystal. It think he was asking for $100 but I got it for about $80. I finally got rid of the crystal at one of my HEAS fleamarket events a few years back.

Hang around enough hamfests over the years and you find stuff like this. This will be my 41st year of hamfesting. I used to hit 13 fests a year. Alas, now it is only about 6 plus HEAS. Some of the best goodies are at HEAS as relates to my needs. (vacuum, HV, bizarre cool stuff)

I sold a bunch of these types of small bias supplies that were 0-3000v negative output at this just completed HEAS fleamarket. They all went fast. I forgot to give the schematics out. If who ever got them contacts me I will try and scan the info sheet and e-mail it to them. Just PM me.

Richard Hull
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Re: Anode layer ion source. Operation pictures

Post by ian_krase » Thu Oct 31, 2019 6:56 am

OK.

What would be the mechanism of failure? Heating the magnets to demagnetization?

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Richard Hull
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Re: Anode layer ion source. Operation pictures

Post by Richard Hull » Thu Oct 31, 2019 7:25 pm

I would imagine, like many such magnets that ferrite or Alnico would be used as opposed to rare earth where heating is an issue. Samarium cobalt can take a little bit of heat. Of course, rare earth NeFeB can be used if their energy product is high enough to put the needed field strength in the working gap where air cooling at stand-off distances can be maintained. On a commercial production basis, custom shapes can be made that would take advantage of the lowest cost type that would do the job. Ferrite tends to win out in most cases of custom formed magnets where moderate fields are demanded around hot environments to avoid additional cooling systems.

Amateurs are at the mercy of extant shapes and types of permanent magnets for experiment which are usually kludged affairs such that the resultant field shape and strength is less that optimum to just plain terrible. Still, we tend to persevere. Externally powered electromagnetic structures can, with some forethought, be fashioned to produce a good field if one doesn't mind throwing that energy away to get a good field.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: Anode layer ion source. Operation pictures

Post by John Futter » Fri Nov 01, 2019 5:49 am

i'm sure that i posted a pic of our NW25 that has the required BNC thread to test on our helium leak tester
I'm talking about the Pasternak hermetic BNC's
Out of 20 BNC's we accepted 17 to go into stock leak rates less than 10^-14 litres per sec
viton o-ring a must with the slightest wipe of grease to aid seal

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