Troubleshooting

So far I have built the cloud chamber and have moved on to testing. It came as no surprise that it didn’t work first time and the problem is obvious, cooling. The heat sink I am using is not up to the job of cooling the Peltier coolers, again no surprise as it is about 6 years old.

I attempted to solve this with more fans.

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The heat sink still reaches about 40 degrees which is about 10 degrees to much, the next step will be to clean the 6 years worth of dust from it and if that fails a new(er) heat sink may be in order.

Progress Update

Previous Post

So finally enough of my parts arrived to start building 🙂

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So far I have:

An old cpu fan, a 500ml pot, thermal paste, a TEC1-12710 cooler, a TEC1-12709 cooler, an old ATX power supply (450W), glue, a knife, some metal, some uranium glass, a torch, scissors, nuts and bolts.

If you are interested in building this project yourself I would recommend waiting until I have it working properly. 🙂

This first part is the same as the the first part of the Instructables link in my first post and has been proven to work.

To start off I measured out a hole for the 12709 in the base of the pot, the coolers are 4cm by 4cm, and put it to one side. Next I cleaned and put thermal paste on the cpu fans heat sink.

Cpu heatsink

The paste should form a complete layer as thin as possible on the heat sink. The cooling is by far the most important and difficult part of this project and is very prone to going wrong. Place the 12710 cooler on top of the thermal paste, with the heat sink orientated as in the picture and the 12710 cooler on top with the wires towards you the red wire should be on the right.

A quick check is now needed, make sure the PSU is unplugged. On the main power connector connect the green cable to one of many black cables, this is the PS on connection and will allow the power supply to fun whilst not connected to a PC.  Plug the CPU red cable to a yellow cable, all yellow cables on all of the plugs are 12V, and connect the black to a black. The same goes for the 12710 cooler, red to yellow, black to black. A useful page http://www.smpspowersupply.com/connectors-pinouts.html

Pin layout

This next part must be done quickly, place a finger on top of the 12710 cooler and plug the power supply in. Make sure air can flow through the fan and turn it on.

If the fan doesn’t spin turn it off and check your wiring, if it still fails to spin unplug the 12710 cooler and use a multimeter to check if there is a voltage being produced by the power supply, if there isn’t make sure the green and black are connected. If there is still nothing then your PSU may be broken check the fuse first though.

If the 12710 cooler gets hot switch it off quick, it is upside down. If it gets noticeably cold then it is set up correctly, turn it off.

Place thermal paste on top of the 12710 cooler same as before as thinly as possible and place the 12709 on top. Both should be orientated the same way, wire colours on the same sides. Now for a check, the set up is the same as before apart from the red wire from the 12709 goes to a red wire in the socket (5V). The cooler should get very cold, around -25 degrees Celsius or better.

Up to this point is the basis of the cloud chamber, from now on this is all experimental and has a high chance of not working properly. Again it is advisable to wait until I have it working before making it yourself.

At this point I went back to my pot, on all the cloud chambers I have seen the dry ice or other coolant is connected to the plastic. This didn’t seem very efficient so I cut a hole in the plastic and mounted it on the cooler.

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I used the glue to keep it sealed.

Following this I made sure pressure was applied and the whole thing couldn’t twist by using some nuts and bolts and I fixed a plate, using thermal paste, to the top cooler to give it a larger surface area.

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I switched it all on for a test and found that water in the atmosphere condensed and froze on the metal plate, I took it as a successful test 😛

Until my Isopropyl alcohol and thermometer arrives I can’t test it any further.

Peltier Coolers

A Peltier cooler is a small device that is usually put in between a CPU and its heat sink. This is because a Peltier cooler is far more efficient at cooling a CPU down than a heat sink alone. The tec1-12710 and 12709 that where mentioned on my previous post are almost identical except that the 12709 is a lower power than the 12710.

The Peltier coolers are named after the  Peltier effect, a product of the thermoelectric effect. I am not going to go  into detail about either but I will give a brief explanation of how the cooler works. When a temperature gradient is applied to a thermoelectric device a voltage is created. As is often the case in physics what works one way also works in reverse. When a voltage is applied to a thermoelectric device a temperature gradient is created causing one side to be cold and the other hot.

from http://www.laserfocusworld.com/articles/print/volume-43/issue-8/features/cmos-detectors-thin-film-tecs-give-new-life-to-cmos-cooling.html

This is the basic overview of how a Peltier cooler functions. I hope this proves useful 🙂

The Cloud Chamber

I am taking my inspiration from this project here http://www.instructables.com/id/Make-a-Cloud-Chamber-using-Peltier-Coolers/. I plan to start by making a few choice modifications to the design. Once I have it up and running then I will make more drastic changes to the project to see what gives the best result.

First off is some basic concepts on how cloud chambers work. There are three main types of radiation alpha, beta and gamma. The two types we are focusing on is the alpha and beta, this is because these are heavily ionising. The alpha particle has the greatest charge and therefore the greatest ionising power, followed by the beta particle with half the charge of the alpha particle. The ionising properties of the radiation is what allows the cloud chamber to work.

Inside the cloud chamber we create a supersaturated vapour of alcohol by cooling evaporated alcohol down to very low temperatures. This is usually achieved with a chamber of dry ice at the base. As a charged particle, like a Helium nucleus (alpha particle) or electron (beta radiation), passes through the vapour at high speeds it ionises the vapour around it leaving a trail. These are the white lines in the image on the link at the start.

Unlike most cloud chambers I’m using Peltier coolers like the one in the link to cool the alcohol. The advantage of this being that you don’t need dry ice every time you want to run your cloud chamber. So I start off with a rather odd shopping list:

A Tec1-12710, A Tec1-12709, Thermal paste, A CPU fan (bigger the better), A clear plastic pot, Some thin scrap metal, Concentrated alcohol (Isopropyl or similar), Some bolts and screws, A light source (a torch to start with), A computer PSU (above 300W) and a radioactive source.

While a radioactive source is not necessary, as you can detect cosmic rays, I thought I would get one for testing. My source is some uranium glass from eBay although others are available this is a nice alpha source, some fire alarms contain americium which is a strong alpha source and can be used. WARNING! handle with care! Although these sources are rarely dangerous ingesting or mishandling a radioactive source is never a good idea, swallowing glass isn’t the best idea even if it isn’t radioactive.  If swallowed consult a doctor immediately, better safe than sorry.

Almost all the things on the list can be found on eBay or in a dump. If your a student it is worth asking around your labs for parts. Fortunately I have most of the parts from old computers and bits lying around. The rest I managed to obtain for £20 including delivery.

If you want to build this yourself  it may be worth waiting until I have a working product before you buy all the parts as I am making this up as I go. I will also add more detailed part lists as I go.

Tools: Aside from the essential tools (screw driver, hammer, duct tape, etc.)  it is probably useful to have a multimeter and a inferred thermometer although they are not essential.

Okay, after that lengthy post I look forward to starting the project as soon as I receive my parts in about a weeks time!