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Author: Subject: low-powered Plasma discharge, for surface-interaction
chief3
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[*] posted on 30-9-2014 at 01:25
low-powered Plasma discharge, for surface-interaction


How would one construct a atmospheric-pressure plasma-burner, as a source of a not too hot plasma ... ... ?
==> Anyone tried ?

What I have in mind is something like this:
==> http://en.wikipedia.org/wiki/Plasma_pencil

The kV are no problem, but the nanoseconds of the pulses ... , how would I achieve those with amateur means ?

Any ideas about whats possible ?

The plasma needed may be hot, even hundereds of [Celsius], but of low power ...

[Edited on 30-9-2014 by chief3]
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hissingnoise
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[*] posted on 30-9-2014 at 05:26


Quote:
The kV are no problem, but the nanoseconds of the pulses ...

Not to mention a frequency in kHz.?

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argyrium
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[*] posted on 30-9-2014 at 10:56


Chief3,

You might find something of interest here:


Conference and workshop on atmospheric plasma and self-diagnostic coatings in restoration
From: Sabrina Buchhorn <s.buchhorn<-a>
Date: Wednesday, August 13, 2014

"Plasma and Nano for New Age soft conservation"
Workshop and Conference
EU-PANNA Project FP7 No. 282998
Berlin
2-4 September 2014

The goal of this project was developing a new plasma torch to clean
cultural heritage objects better than the existing torches and new
protective coatings for different surfaces. The new plasma torch
prototype enables the removal of different materials at very low
temperatures, a new protective coating can be applied and removed by
plasma when/if necessary ("Full-life protocol"). Studied materials
are stone (uncoated or with graffiti), wall paintings (varnish
layers, soot deposition) and metals (oxides on silver and bronzes).

On 2-3 September, 2014 a workshop (limited to 30 participants) on
the use of atmospheric plasma and self-diagnostic coatings in
restoration will be held in the Sammlung Scharf-Gerstenberg,
Staatliche Museen zu Berlin (Museum Scharf-Gerstenberg Collection),
Berlin, Germany. Participants are invited to bring samples for
testing. On 4 September 2014 a conference (limited to 100
participants) will be held in the same venue. Both events are
addressed to conservators, architects, restorers, researchers,
policy makers and museum staff.

During the 2-day workshop, the participants will learn what the
"Full-life protocol" is and how it is applied in practice in the
conservation and restoration of cultural heritage objects. They
will also take part in a demonstration of atmospheric plasma
cleaning using the portable plasma system developed within the PANNA
project. In the conference the results of the project will be
presented and some invited speakers will talk about related subjects
(see detailed program on the PANNA Project website).

Participation is free, but it is mandatory to register until 20
August 2014: s.tesche<-a t->smb< . >spk-berlin< . >de

Both events are organised by the Rathgen-Forschungslabor -
Staatliche Museen zu Berlin.

More information on the project is to be found on

<URL:http://www.panna-project.eu>

Sabrina Buchhorn
Verwaltungsangestellte
Rathgen-Forschungslabor
Staatliche Museen zu Berlin - Preussischer Kulturbesitz
Schlossstr. 1A
14059 Berlin
+49 30 266 42 7120
Fax: +49 30 266 42 7110
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argyrium
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[*] posted on 30-9-2014 at 11:02


Although this and my previous post should be under the soot removal thread, they are both intertwined.

Here is the result of a search I did. If you are unable to get to some of the posts/links, contact me and I probably will be able to access it/them.

http://tinyurl.com/o7v5lnb

Good luck.
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violet sin
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[*] posted on 30-9-2014 at 21:22


Microplasma jet at atmospheric pressure
http://diyhpl.us/~bryan/papers2/Microplasma%20jet%20at%20atm...

" The ac power supplier is a commercially available transformer for neon light operated at 20 kHz"

" Each of the two electrodes is made of an aluminum disk with 20 mm diameter and 3 mm thickness
attached to the surface of a centrally perforated dielectric disk with 1.5 mm thickness. The hole in the
center of the dielectric disk has the same diameter with the electrodes. The dielectric disk can be
made of glass, quartz, Teflon, etc. The assembled electrodes and dielectric disks are inserted in a
dielectric case of the same diameter as that of the dielectric disk. "

"the plasma operated at 6.3 lpm (liters per minute) nitrogen was ejected at the speed of approxi-
mately 535 m/s, producing afterglow at high pressure and cooling down to the room temperature"
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chief3
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[*] posted on 14-10-2014 at 02:49


Thanks to @violet_sin ... ! I find this _very_ interesting, seems easy to build one ... ... ; thinking now about how to make 500-micron holes ...

Inbetween i have ordered and tried some latex-aponge (A K A P A D), it works well ... as long as the surface ist stable enough ... ...
==> Also I have tried more than 10 sorts of erasers, which more or less do also work ; but the latex-sponge is superior ... ... .

The said latex-sponge smells and looks and feels like some material which I have found once ago under a carpet ... , maybe its used in some carpet-adhesives (which glue the carpet to the floor) ... ...
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Harristotle
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[*] posted on 14-10-2014 at 20:57


Hey Chief3.

Try 10pcs Small 0.5mm PCB Drill Mini Press HSS Electrical Twist Drilling
http://www.ebay.com/itm/10pcs-Small-0-5mm-PCB-Drill-Mini-Pre...
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jpsmith123
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[*] posted on 15-10-2014 at 18:03


Also check out US Patent# 8471171.
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Harristotle
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[*] posted on 27-10-2014 at 04:35
Constructing a low power plasma discharge


Greetings all.
I have had a go at making one of these. Here is my write up. Please note that this design is not technically optimised, and frankly I was underwhelmed :( However, I did get a faint plasma jet. Please do not try if you are uncomfortable with high voltages. Please take great care - the flyback circuit here can bite, and it may kill you if misused. The high voltage guys say that flybacks are a safe intro into HV, but those crazies definition of safe and mine are not the same! Please, please be careful, and don't construct this unless you are skilled and trained.

Ok disclaimers and safety over, here is what I did.
The power supply: <a href="http://www.screencast.com/t/5AbAeoDPoy1e">27 oct 2014 plasma 061</a>

The setup running, showing the pump etc:
<a href="http://www.screencast.com/t/SH0XFpKn">27 oct 2014 plasma 064</a>

The shortest video to prove the formation of plasma jet (difference between pump on and off): <a href="http://www.screencast.com/t/tXnj5vytf87">27 oct 2014 plasma 068</a>


Construction description:

Materials: Aquarium pump, old flyback transformer from TV, the beast of a transistor that drives it from the same circuit, 270 ohm and 27 ohm 5 watt resistors, sundry wires and solder, CPU heatsink and fan, old Ferrero Rocher box for electronics, 1.5 300g tubes of neutral cure silicone, 0.8cm tubing and 0.4cm refrigerator copper pipe (from the restriction tube that forces the gas to expand), lead-free solder ('cause we don't want to do anything unsafe now :P ), 0.5mm PCB drill bit and chuck, drill press and blow torch, 8-10cm of 0.8cm glass tubing (flared at the end by blowing a bubble, then sanding), electricians tape, epoxy glue.

Begin by washing a length of straight refrigerator copper pipe in concentrated HCl (for mortar cleaning). Dry, then crimp one end to seal it. Heat with blowtorch, then fill with tin solder. Cool, then cut off a 1cm piece. Sand with 120 grit paper, then drill out with a drill press using 0.5mm drill bit.

Glue the copper pipe to the flared end of the glass tube with 5 minute epoxy. Let it set for a few hours. Take the 4mm copper refrigerator tube and push into the other end of the glass, until you have a 5mm gap. Take out the tube, wrap it appropriately with masking tape so that it forms an airtight seal, then place back in the glass.

Build yourself a power supply. I used the first circuit diagram in http://www.loneoceans.com/labs/flyback/. It is said to be the lowest current and safest. See that site for construction details. When I had finished, I mounted the transistor on the cpu fan and heatsink, drilled 4 holes in the Ferrero Rocher plastic box, and then after everything was bogged up to within an inch of its life with silicone, I placed the whole thing in an electric frypan set to approx 50 degrees C and containing a wet tissue overnight. (The setting of neutral-cure silicones is catalysed by water vapour). The next morning, I connected a power pack (12, 1a, bought for $1 at a thrift shop), and pulled a 0.75 ->1cm spark, indicating 20-30 thousand volts. Watch out for that transistor - it runs very hot. It is probably not a good idea to run it for more than a few minutes. BTW, my fan doesnt work - I used it mostly as a spacer between the heatsink and the ferrero rocher box.


Connect it all up: aquarium pump to 4mm copper tube, power supply to 4mm copper tube and to head piece. Turn on pump, then power supply. You won't easily see the plasma jet - it is very faint, but if you photograph it you will. See my pictures below to see the jet and the set up.

Now my interest is can I try my hand at some microfluidic chips. But little steps first!
Any ideas for improving efficiency (ie get better/more intense plasma jets from the exit hole?).

Cheers,
Harristotle.


UPDATE: I don't seem to be getting a jet from the hole - it appears that what you see in my movie is lens flare. (When I warpped the glass tube with black tape, there is no plasma jet) Interesting that you get more plasma with the air pump running. TODO: try smaller exit disk and higher pressure. Also, I am using air as the dielectric. Maybe I should try a plastic disk? Bummer - this looks like a weekend job!

[Edited on 27-10-2014 by Harristotle]
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Harristotle
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[*] posted on 2-11-2014 at 04:54


Well, a frustrating weekend.
Increasing the velocity of the air leaving the exit hole (until it blew the spark out) did not result in a plasma jet.
The brightness of the discharge increased when air was blown through the chamber compared to when it was not.

Replacing the air with silicone as an insulator was not successful - neutral cure silicone remained liquid in the straw used as a mould, even with only a couple of cm (the idea was to cast then cut), even after being left 3 days for one and left 3 days in a simmer pot at 50 degrees with a saturated water atmosphere in the other. Essentially the bathroom sealer skinned, hardened a bit and appears to be impermeable.

Araldite-type epoxy also doesn't seem to work- there is about a half second of arcing followed by silence and reduced air escape. If I redrill the hole, the same happens again, but the nett effect is no plasma, and charring of the epoxy insulator.

Next attempt will be Sugru, which hopefully might be easier to work than my bathroom sealer.

Anyone else get anything like this to go?

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chief3
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[*] posted on 4-12-2014 at 22:51


Hi @Harristotle ... !
==> I tried it myself too, in the past weeks ... .

I had a flyback-transformer ... connected to a halogen-transformer (electronic type) ; the transformer has now several "windings" (I could insert two additional ones), the combinations of possible voltages range from 2 V to 11 Volts ; but continuously I always would use it at most with 6 Volts, as it doesnt get relly warm then ...

The burner-setup was as in the patent, but with aluminum-foil instead of plates ; the foil was punctered by a medicinic needle, to get the tiny hole . The dielectric was epoxy ... ; basically I puntured the foils and epoxy with the needle, and then kept moving the needle while the epoxy was hardening (3 minutes), so that it was withdrawable ...
(before this i had tried it with a medicinic needle, blowing air through it ... which seems to be somehow the same what you tried ; anyhow I observed that the plama was no plasma but just an arc-discharge, and the air and discharge could not really be "mixed", which would be necessary for any real amounts of plasma to be generated ... )


I used no aquarium-pump, but a 2-liter pressure-bottle for plant-desinfection, one which can be filled with some water and has a pump to pressurize it ... ; this gives some air-stream for half a minute before it must be re-pumped ... ; the flow-rate can be calculated to be somewhat in the region ; the guys who wrote the patent used several hundred m/s of air-velocity ... - thats why I spared the EUR and didnt try the aquarium-pump ... : It hasn't enough pressure to get that much air through a 0.5mm hole ... ; anyhow the 4 bar of the pressure-bottle are in the region ... , also give a constant stream, somewhat adjustable ...


Anyhow my dielectric did quickly burn away, since it was only epoxy ; at start it seemed to give a jet, of maybe 2 or 3 mm, but only for seconds before it burned .

The keys seem to be:
==> _tiny_ hole, so the discharge gets forced _through_ the air, no other ways to escape for the electricity
==> thermally stable dielectric ...

The electricity did need a considerably higher voltage to make a discharge when the air-stream was on, had to use more windings from the halogen-transformer

===================

The next steps will be:
==> better dielectric .. , still looking for one ... since it also has to be workable ... which eliminates quartz-glass ...
==> intermediate-transformer for the power-supply: The halogen-trasnsformer, which operates at 25 kHz, has about 1 winding per Volt ; so a ferrite-transformer may be made which has 12 windings as primary, and some secondary-windings ... ; this should give a better variability of the voltage, which then can drive the flyback ... .

[Edited on 5-12-2014 by chief3]
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chief3
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[*] posted on 4-12-2014 at 22:58


So here the second post, now about the soot: It is at best removable with some latex-sponge ; bubble-gum eraser does work too, but slower ... .

There are interesting techniques to stabilize the painting before using the sponge ; one is to spray it with hydroxypropyl-methylcellulose, dissolved in alcohol (not water; but this may vary from painting to painting ...)

In some cases the guys make the paintings hydrophobic ... with some "Testbenzin", the sort of gasoline which boils at 120 to 140 [Celsius] ; then they use moist towels to wash the painting ... , but I'm not so confident of trying this ...
==> Some even use no gasoline, but menthol: The menthol melts at relatively low temperatures, can be soaked into the surface of the painting ... ; then the painting gets washed ; afterwards the menthol evaporates completely within a month ...
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