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Picture of Make a Cloud Chamber using Peltier Coolers

Cloud chambers let you see vapor trails left by radioactive particles!

A version of this cloud chamber is now available for purchase (fully assembled and tested) from http://www.nothinglabs.com

Discuss cloud chamber assembly and radioactive samples at http://forum.nothinglabs.com




Cloud chambers work by creating a supersaturation of alcohol vapor.  Vapor trails are then formed when the radiation ionizes the alcohol.

Cloud chambers need to be very cold (about -15f) - so most designs require dry ice.

This design uses inexpensive electrical "Peltier" coolers instead!  No need to buy / store dry ice!

It's fairly easy to construct - and should only cost about $100.

This chamber design cools down very quickly - you can see vapor trails within a few minutes.

On the downside - it's not as cold as a dry ice chamber - so the supersaturated area isn't as thick.

 
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Step 1: Stuff You'll Need (Part 1)

Picture of Stuff You'll Need (Part 1)
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Peltier Coolers (need 2)
- Model 12709 (138 watts "max") for "top" cooler ($8 on ebay)
- Model 12710 (168 watts "max") for "bottom" cooler (also $8 on ebay)
- Search eBay -descriptions- to find specific models
- Often listed as "TEC", "Thermoelectric" or "Peltier" coolers and have TEC1 or CP1 as a prefix to the model number
- Other models with similar wattage ratings can likely be used (bottom cooler should have a slightly higher wattage rating than the bottom)
- Coolers look identical - put a piece of tape on a wire of the 12710 so you can identify it later
- Larger coolers are not necessarily better
- Fragile wires tend to break - avoid bending (might want to buy a spare or two)
- Do -NOT- connect a peltier to power backwards or without a heatsink!
- See the bottom of this page for info on a single-Peltier option

Power Supply #1
- 12v and at least 8 amps (good results between about 11v and 15v)
- Used to power 'bottom' peltier cooler
- www.allelectronics.com part # PS-1512 is a good option for $25

Power Supply #2
- 5 volts and at least 2.5 amps (good results between about 4v and 8v)
- Used to power 'top' peltier cooler
- D-Link JTA0302C power supply on ebay for about $10
- Alternative: Use a PC ATX power supply for both 12v and 5v sources (Google for more info)

CPU Cooler / Fan
- Look for "heat pipes" and a 120mm fan
- Design that can be run "upside down" with good airflow
- The Cooler Master Hyper 212 works well and is cheap (under $30 on ebay)
- Cooler Master V8 works well and looks cool (about $50)
- The Corsair H50 (liquid cooling) works a little better - but is more expensive / complicated (about $70)
- See http://www.frostytech.com/ for other possible coolers

Alternative Single Peltier / Single Power Supply Configuration
- This project can also be built using a single dual-stage peltier cooler
- The 19012-5L31-06CQQ from Custom Thermoelectric ($53) has been tested and works well (order with Moisture Sealing option)
- Requires a 12V power supply capable of 6 amps (5V power supply is not needed)
- Other project details stay the same

Step 2: Stuff You'll Need (Part 2)

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Small Plastic Container
- Relatively flat bottom (doesn't need to be perfect)
- Fairly thin plastic (1/16th" or less)
- Good Transparency
- Good results with Rubbermaid Premier 473ml (about $5)

Arctic Silver 5 Thermal Compound
- $10 at Radio Shack for 3.5 grams
- Should probably get 2 tubes (if you're efficient you may get away with 1)
- Arctic Silver "Ceramique" provides good results for less money (22 grams for about $10 at Fry's)
- Other thermal compounds / paste can work
- Have -not- had good luck with Radio Shack's "house brand" thermal paste

Alcohol
- 99% rubbing (isopropyl) alcohol works best ($5 at drug store)
- Denatured ethyl alcohol is another option (hardware store paint section)
- 91% rubbing alcohol can also work (maybe not as well)

Misc. electrical connectors to hook stuff up
- Soldering is another option
- Don't use thin-wired gator clips - they'll melt

LED flashlight (the cheap 9-LED ones work well)

Black Sharpie felt pen

Step 3: Stuff You'll Need (Part 3)

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1/4" x 1" nut + bolt (size doesn't really matter)

1" x 1" piece of kitchen sponge

Styrofoam cup (or other static source - a balloon also work well)

Infrared / non-contact thermometer (optional)
- Optimally can read to at least -28f
- Cen-tech Pocket Thermometer goes for about $20 on ebay
- Cheaper ones may give erratic results

Multimeter (optional)
- For verifying power supply polarity / troubleshooting

Step 4: Obtaining a Radioactive Source

Picture of Obtaining a Radioactive Source
There are many easily obtained inexpensive (and legal) radioactive sources available online.

See video samples / discuss radioactive sources at http://forum.nothinglabs.com

Certain years of Fiestaware dishes featured a "radioactive red" color that actually contained uranium!

A small chip can make an excellent cheap cloud chamber source - try searching ebay for "fiestaware sample"

Small Autunite samples commonly sell for about $20 on ebay (contains uranium).

Search ebay descriptions for "geiger" and "cpm" to see other possibilities.



Alternately - the cloud chamber can be used without a radiation source to view cosmic rays.  They typically appear once every 1-2 minutes.

Take precautions appropriate for your sample!  The provider of your specimen may be able to provide further information on its safety.

To be extra safe - use gloves when handling.  Wash your hands after if you should touch it.


Step 5: Add Thermal Paste to the Heatsink

Picture of Add Thermal Paste to the Heatsink
Position the CPU cooler with the heatsink surface facing up.

Spread a small amount of Arctic Silver on top of the heatsink using a credit card or thin piece of plastic.

Spread it thinly and evenly (thinner is better). Cover an area the size of a peltier cooler.

Step 6: Mount the Bottom Peltier Cooler

Picture of Mount the Bottom Peltier Cooler
Place the 12710 peltier cooler on top of the heatsink.

Important: The wires should be facing you and the red wire should be on your right.

This should assure that the peltier is positioned with the cold side up.

Push the peltier down - and move it around slightly to assure good contact with the thermal paste.


Step 7: Connect the Bottom Peltier and Fan to Power

Picture of Connect the Bottom Peltier and Fan to Power
First - Make sure the 12v power supply is unplugged!

Electrically connect the CPU cooler's fan and the peltier to the 12v power supply.

Red goes to positive, black to negative.

Ignore any unused connections for the fan.

Step 8: Test the Fan and Bottom Peltier

Picture of Test the Fan and Bottom Peltier
These steps need to be performed quickly!  If the peltier is connected backwards or is upside down - it'll burn up in a very short period unless it's disconnected.

1. Plug in the 12v power supply (fan should spin up)

2. Quickly touch the top of the peltier (or measure it with a thermometer)

3. Is it warm? UNPLUG THE POWER NOW! (peltier is backwards or upside down)

4. Is it cold? Good! (unplug the power)

Step 9: Spread Thermal Paste, Attach the Second Peltier and Connect it

Picture of Spread Thermal Paste, Attach the Second Peltier and Connect it
Thinly spread a small amount of Arctic Silver over the top of the peltier you've already placed on the heatsink.

Place the other peltier (12709) on top of the existing one.  Push it down a bit to assure good contact.

Important: The wires should be facing you and the red wire should be on your right.

Connect the top peltier to the 5v power supply (leave power supply unplugged).

Step 10: Test the Top Peltier

Picture of Test the Top Peltier
Same drill as before - these steps need to be performed quickly!

1. Plug in the 5v power supply

2. Quickly touch the top of the peltier (or measure it with a thermometer)

3. Is it warm? UNPLUG THE POWER NOW! (peltier is backwards or upside down)

4. Is it cold? Good! (unplug the power)


Step 11: Test Both Peltiers Simultaneously

Picture of Test Both Peltiers Simultaneously
Plug in the 5v and 12v power supplies.

Marvel at how cold the top peltier gets!

If you have a thermometer - hopefully it reads -18f or colder!

If not - something might be wrong - or it could just be your thermometer isn't that accurate (this is common).

Unplug both power supplies.  If any condensation has formed on the top peltier - wipe it off.



Step 12: Black Out the Bottom of the Cloud Chamber

Picture of Black Out the Bottom of the Cloud Chamber
Use the Sharpie to black out the -outside- bottom of the plastic container.

This will help the vapor trails appear more clearly.

Step 13: Attach the Sponge to the Container's Top

Picture of Attach the Sponge to the Container's Top
Drill a hole in the top of the container for the bolt.

Poke a small hole in the sponge using a pencil.

Use the nut and bolt to attach the sponge to the inside top of the container.

Don't worry about the seal not being perfect. A small leak at the top of the chamber won't hurt performance.

Step 14: Apply Thermal Compound to the Top Peltier

Picture of Apply Thermal Compound to the Top Peltier
Apply Arctic Silver to the top of the top peltier.

This time - apply it fairly liberally.  Use enough so that good contact can be made with the bottom of the container (accounting for any imperfections like raised text).

Yes - normally less is better with thermal paste - but this is an exception.

This may be the point where you have to run to Radio Shack to buy another tube of Arctic Silver.

Step 15: Attach the Container to the Top Peltier Cooler

Picture of Attach the Container to the Top Peltier Cooler
Place the container on top of the top peltier.  Push it down - and squish things around a little.

If it doesn't seem to be making good contact - try adding more Arctic Silver.

Try to make a tight seal - you don't want condensation getting between the container and the peltier.


Step 16: Test Everything with Container Attached / Troubleshooting

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Plug both power supplies in.

The bottom of the container should get very could within several minutes minutes.

If you have a thermometer - hopefully it reads -14f or better!  (Don't worry if the entire surface doesn't read this cold.)

If so - your cloud chamber is now ready for use!

If you aren't getting this cold:

- Don't place too much faith in your thermometer - if you're getting significantly below 0f - it may make sense to proceed and see if things work

- This article originally suggested Tec1-12709's top and bottom - this will work - but using a Tec1-12710 on the bottom works better.  If you're using two Tec1-12709's and having poor results - you may want to switch out the bottom one with the CP1-12710.

- Check your thermal paste application - this is probably the most common issue.  The layers between the peltiers and the heatsink should be thin.  The final layer between the top peltier and the chamber may need to be fairly thick to make good contact.  As a last resort - you may find that removing all thermal paste using alcohol - and then re-applying solves the issue.

- Are the peltier coolers and container all centered over the middle of the heatsink?

- Is your heatsink getting even a little warm?  If so - it may not be good enough.

- If your heatsink is getting warm - one option is to remove the fan - and place it in a container of cold water (maybe even with ice).  This will provide extremely effective cooling - at least until the water warms up.

- Verify your electrical connections are good (warm wires indicate they are too thin).

- Try applying a small amount of weight / pressure to the top of the chamber - this might help close up any gaps in the thermal paste.

- Re-test the peltiers.  You can also check them against their specified resistance values using your multimeter (they shouldn't read any higher than 4 ohms). 

- Try waiting a few hours - some thermal pastes will "set up" and become more conductive over time

Step 17: Using the Chamber

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Place your radioactive sample inside the cloud chamber.

Add about 1 teaspoon of alcohol to the sponge.

Put the top on the container.

Plug in both power supplies.

Hold the LED flashlight behind the chamber.

Within a minute or two you should be able to see a fine mist covering the bottom 1/8th inch or so of the container.

Try changing your viewing angle / flashlight position to best see the mist.

Rub the styrofoam cup (or other static thingy such as a balloon) in your hair - then place it over the container.

Within 2-10 minutes - you should start seeing vapor trails from the radiation!

IMPORTANT: "Recharge" the styofoam cup / balloon (rubbing it in your hair) periodically.  Try removing it / repositioning it to see what provides the best visibility of radiation trails.  This is key to being able to see alpha particles!

If you don't see trails - revisit the troubleshooting section in step 16.

Performance may improve as things cool.

Step 18: Tips

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Important: Periodically check to make sure the peltiers / chamber aren't sliding away from the center of the heatsink (this is bad).  Gently reposition them if this happens.

Without a radiation source - you'll be able to see cosmic rays every few minutes.  Definitely try this!

Get help / share your cloud chamber with others at http://forum.nothinglabs.com

It's possible to run the chamber with the top slightly off (or with a hole cut in it) for direct viewing.  This can be great for shooting photos and video.

If you're not getting trails - or they seem to vanish quickly - try re-applying a static source (styrofoam cup / etc) as mentioned in the prior step. This is key to getting good results!

If you like playing with high voltage - you can try attaching a 1kv or higher DC source to the screw on top of the chamber.  This will provide the same ion-clearing / performance-boosting effect the styrofoam cup does - but is way cooler because it's high voltage.

If too much alcohol builds up on the bottom of the container - it may hurt performance (wick it up with a paper towel).

If your sample becomes wet with alcohol - some radiation will get blocked (again - a paper towel can solve this issue).  This is a very common issue with small Americium samples.

The rubbing alcohol on the sponge should last a long time - but if you stop seeing trails - it may be time to add more.

If you only see trails / mist over a small portion of the container - you may want to try applying more thermal paste between the container and top peltier.

Other directional light sources besides LEDs (like spotlights) can also provide good lighting results.  Standard incandescent or florescent bulbs may even work at certain angles (especially if in a desk lamp or other fixture)- experiment!

To improve viewing contrast - black out the -inside- of the container with the black permanent marker.  The downside of this is that eventually the alcohol will dissolve the ink - making a bit of a mess.

Depending on a number of variables you may find that increasing / decreasing the voltage for either cooler may improve results.

However - do -not- try running the top peltier at 12v instead of 5v.  It won't work (at least not well) - trust me.

(The quick explanation is that each peltier needs to pump all the heat pumped by the one above it -plus- any heat the upper peltier generated itself.  Since peltiers are not very efficient - this head adds up pretty quickly - and becomes a problem.  Trying to stack two peltiers running at the same total power level will result in -less- cooling than a single peltier at the same power.)


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AdnanN121 days ago

Why two separate power supply for peltier and fan while both can run in 12 V ??

BillM73 months ago

Hello

I've read the various comments - the solutions are simple

Develop a kit - under 200.00 - add some free tech assistance - I'll buy two

One for home - one for office - makes a great conversational piece.

Have a good presentation - easy to assembly kit - go to work

I'm waiting to buy one now -

ThomasJ17 months ago

Hi Rich,

I finished building mine and I get a good supersaturated layer over a 5x5" black anodized aluminium plate. I suspect the chamber is working well since I get really good "fake trails" whenever I place/remove/recharge my static source (balloon). however, I don't seem to get trails coming from cosmic rays. Is there a trick with the static source regarding cosmic rays?

nothinglabs (author)  ThomasJ17 months ago
Hi Thomas -

It's most likely you aren't actually getting cold enough to see traces.

From my experience - the kind of "ghost trails" that occur when moving the static source around can occur at higher temperatures than needed to see traces from particles.

The peltier setup for this project has fairly modest cooling power - and can really only cool a small area down to the -15f or so needed to see traces.

Using thin plastic for a surface causes a small area to be cooled directly above the peltier (due to low thermal conductivity). Using aluminum will attempt to cool a larger area - and will counter-inuitively produce less cooling.

I had some luck extending the saturation area with an aluminum base-plate - but only using much larger peltiers - and insulating the bottom of the plate.

My general advice to anyone trying this project is to start with a thin plastic base-plate - get that working - and then experiment from there.

Good luck!

-Rich

Rich, you were absolutely right !

I removed the aluminium plate and used a thin transparent plastic sheet blackened from under with a sharpie. After a few minutes of cooling, I reached between -45F to -50F (compared to -10F previously). I can now see about 5 to 10 trails per seconds above the peltier area.

Thanks for the advice !

Thomas

nothinglabs (author)  ThomasJ17 months ago

glad it's working for you. now for some real fun - go get some uranium ore on ebay!

-Rich

PopsicleGhoul7 months ago

Wow! I love your detailed instructions! I also like how you used easy-to-find Peltier coolers instead of difficult-to-acquire dry ice. Hopefully I can try this out soon!

kamhagh9 months ago

mine gets cold on the upper side, but how can i know that the connection to heatsink is ok? i used kinda less grease ! im worreid that overtime it will get hot ! or my thermal connection is not good :|

nothinglabs (author)  kamhagh9 months ago
If things work (ie - you can see traces) then you're getting good contact.

Other way to test is to use an infrared or contact thermometer that can go down to -20f or colder.

In general - less grease is better assuming you get full coverage.

Good luck!

-Rich

I have a dumb question about powering the CPU fan. I bought the Cooler Master Hyper 212 for my chamber, which has a 4pin output. I tried looking up which pins to connect to my 12V 8A power supply, but I can't seem to get a straight answer online. Did anyone else use this fan that can help me out?

nothinglabs (author)  cmerrill3141 year ago

It's been a while - but I believe this is correct:

http://www.pavouk.org/hw/fan/en_fan4wire.html

short answer - black = gnd, yellow = 12v

julio792 years ago
So I've constructed a cloud chamber using this article and have run into a slight problem. Everything works but I don't think the chamber is getting cold enough. I haven't had a chance to buy a thermometer yet but I'm fairly certain it will only confirm what I think I know. The alcohol is condensing on top of the cooler forming a thin square layer to form on the base, but no mist at all. The voltages are 12 for the bottom and 5.6 for the top cooler, so are there any other things I might need to adjust? I have already removed and reapplied some arctic silver but no dice. There is a good amount of frost buildup underneath the container by the coolers so maybe the container is too thick? I bought one similar to the one used here however. Any troubleshooting advice would be greatly appreciated!
nothinglabs (author)  julio792 years ago
Sorry for taking so long to reply.

What kind of light are you using? (LED light is pretty much mandatory to see the traces)

Also - have you painted / used a magic marker to make the surface black? That's also critical to see anything.

The exact container I used seemed almost custom-made for cloud chamber user with it's thin bottom. It's definitely possible the one your trying is too thick at the base.

One option is to use some thin black plastic (1/16th" or so is best) for the chamber base - and then use a water glass for the chamber itself (don't worry too much if the seal isn't totally perfect). This is the approach I usually use on chambers now.

A local plastics retailer might have something that would work. Can also try something like a plastic picnic plate. Either way - paint or magic-marker it black.

The alcohol pool itself will inhibit traces - so if it forms - wipe it off with a paper towel.

Hope this helps!

-Rich
I am going the route using the single dual stage peltier cooler you listed. I bought a 12V 6A 72W power supply for it. Just a stan dard AC DC transformer. I am worried about the Power rating on it. Should it be enough for the peltier. It will be used to power the TEC only. I am experienced with electronics but I have not worked with TECs much at all.Thanks for the help in advance!
tacoredneck2 years ago
what kind of plastic do you use on your commercial chamber? id like to know the thickness too. the plastics i have used are about an 1/8th of an inch thick but i think it has insulating properties. if you don't mind me asking,i know your trying to sell them.
nothinglabs (author)  tacoredneck2 years ago
i don't really keep a lot of secrets any more - happy to share.

I use 1/16" delrin plastic (check mcmaster.com) in the commercial cloud chamber. delrin is a bit flexy though - so I support it with some thicker plastic around the edge.

my suggestion for others would be to use 1/16th" garolite. mcmaster.com had this in nice 6"x6" pieces in black last i checked.

I like garolite because it's stiffer than most plastic. iif the material is too flexible - the temperature differential will cause major flex that can be a problem.

for any kind of plastic I recommend getting black if possible to avoid having to paint it.

I wouldnt worry too much about how insulating the plastic is.
tacoredneck2 years ago
i have a problem. im not getting a fine mist but the alcohol is pooling over the peltier. i have abandoned my aluminum plate for now and am using a Tupperware container
nothinglabs (author)  tacoredneck2 years ago
do you have a temperature reading?

Is the surface black? It's pretty much impossible to see the traces / mist against a light background.

What kind of light are you using? If you are using something other than an LED - probably won't work.

Good luck,

-Rich
tacoredneck2 years ago
what about something like this... The peltier would fit in the square hole. then the aluminum plate would mount to the cpu cooler. insulation would fit between the peltier and the plate. a square plate would fit over the pelteir to protect it from the alchohol
baseplate.jpg
nothinglabs (author)  tacoredneck2 years ago
Maybe? Couldn 't really say for sure.

My suspicion is that you'd only get super-saturation (trace visibility) over the actual peltier.

Might want to try getting everything working with a plastic sheet first - then experiment - but good luck with whatever path you try!

-Rich
tacoredneck2 years ago
how do you feel about metal base plates for the chamber instead of plastic?
nothinglabs (author)  tacoredneck2 years ago
Certainly can be done - but don't recommend it.

I get about an email a month from people trying to use metal - and not having it work.

Metal tends to conduct heat -too well- - so you end up with a larger cooled area - but doesn't end up being as cold.

IE - 8 sq inches at 0f (no worky) as opposed to 3 sq inches at -30f.

-Rich
myakka2 years ago
OK. Sorry to bother again. I have an ATX power supply rated at 650 watts, a cooler master V8, one 12709, one 12710 and its all hooked up. I get a reading around -7 through -10 degrees Fahrenheit on the bare top peltier. I did not use arctic silver, I used the thermal paste that came with the cooler master. Do you think i would get much better results with arctic silver? I am also using a laser thermometer same as yours. I have read the trouble shooting section but i feel that I need your opinion...
nothinglabs (author)  myakka2 years ago
suspect the included thermal grease is fine. Generally the stuff included with coolers is reasonable quality.

are you powering the 12709 (top) at 5v and the 12710 (bottom) at 12v?

sometimes the IR thermometers can be a bit flaky (try holding it closer to the surface to see if that gets you a colder reading).

If you think everything else is right - might be worth just trying it out.

-Rich
thank you. i tried it again this morning and it got to around -20. maybe, like you said, the paste might have to set in.
myakka2 years ago
never mind. i just found a brand new cooler master v8 on eBay for $20.
05leftlj2 years ago
What is the reason the second peltier cooler is at 5V not 12V?
nothinglabs (author)  05leftlj2 years ago
see end of step 18
myakka2 years ago
I bought this from ebay, do you think it will work? http://www.ebay.com/itm/190712915267?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
nothinglabs (author)  myakka2 years ago
Can't say for sure if that'll work - but it seems reasonable.

Good luck with your fully-automated build! I toyed with that idea - but never got around to it. Seems very do-able though.

-Rich
myakka2 years ago
I plan on building one of these to be fully automatic. meaning of course that a pump will supply the alcohol to the felt and a hv source to clear out static. i want to just leave it on my desk at work an watch the look on peoples faces as they walk by.
mamzypig2 years ago
What is a 12v 8 amp power supply? I googled it and it came up with a " Ac " or "Dc adapter"
Is that the right thing.
nothinglabs (author)  mamzypig2 years ago
It means a power supply that can produce 12 volts (DC) at 8 amps of current. (from AC wall power).

8 amps is a minimum - more is fine.

This would be an example:

http://www.amazon.com/Power-Adapter-Prong-Output-3224-12V/dp/B0057KIHAI
jae10282 years ago
I'm 14years old student in Korea and Im working on building a peltier cloud chamber. Our science teacher asked me to build one for a competition. I ordered tec 12012 and 12010 since 12009 is not available in our country. I also ordered an atx psu. Can I ask what voltage I should put on each module?
Also I was wondering if the heatsink in the link below and 120mm fan can withstand heat. Otherwise I have to buy a cpu cooler.
www.79ne.co.kr/goods/view.php?seq=628
Thanks for help.^^
nothinglabs (author)  jae10282 years ago
I suspect the 12012 and 12010 will work for you. I would run them at 12v for the bottom (12012) - and around 5v for the top (12010).

Since the 12012 is higher rated than the 12010 typically used for the bottom - you might try a little lower votlage - maybe 10v.

I can't say for sure if that heatsink will work or not. I typically have had best luck higher performance heatsinks including "heatpipes"

If you already have the heatsink - there shouldn't be any harm in trying though.

Good luck!

-Rich
toblorone3 years ago
i have an excess of 300 v flash charging circuits.(they actually gave them to me for about a month. then the larger stores refused to give me any.) will these be a suitable substitute for the static?
nothinglabs (author)  toblorone3 years ago
I don't think the static is a more-is-better type thing. I've found too much static can disturb the supersaturation layer - and prevent tracing from showing up.

A constant low-level source of static like a balloon has worked really well for me (using a maybe 1.5k-3k DC source is another option).
i would just use a balloon, but i am building one as part of my applied science class, so i aim to reduce as many variables as possible. can you recommend anywhere that would sell a dc source like that?
nothinglabs (author)  toblorone3 years ago
I've used an AC power supply like this one:

http://www.ebay.com/itm/DELUXE-12VDC-INPUT-2KV-AC-OUTPUT-GAS-TUBE-POWER-SUPPLY-w-3-way-switch-clips-/380404425635?pt=LH_DefaultDomain_0&hash=item5891dee3a3

But you of course need to rectify it (you can do this using a single diode)

Please be careful with high voltage!

Even though I have the HV supply - I still generally use the balloon as it seems to give a bit better results (sure there are variables I haven't pinned down).
OK, thanks. just one more thing: how long would a design similar to the one here take to build?
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