DIY Dry Ice Free Cloud Chamber

The cloud chamber is known as the first particle detector of history. Nowdays it's still used in physics classes as a simple particle/radiation detector.

It is usually made with dry ice, but because of storing issues we made a version that uses freezed gel ice packs (a compound that reaches -18°C if stored in a regular domestic freezer).

DISCLAIMER: measures are arbirary, we're indicating ours just for reference. Keep in mind that making a bigger chamber will improve your chances of seeing particles, but it will be much harder to maintain the right temperature gradient in it.

For the BASE:

• 1x Aluminium plate (13×13)cm

• Polystyrene

• 1× Gel ice pack

• 9x Heat sinks (4x4)cm

• Insulating tape

• Aluminum sheets

For the CHAMBER:

• 5x Plexiglas squares (15×15)cm

• 2x Wool felt squares (15×15)cm

• Hot glue

• Heat-resistent glue

• Nickel-chrominium wire (0.5mm diameter)

• Isopropyl alcohol 99%

• Silicone

• 1x Led stripe 60cm

• 4x Wooden rectangles (16×2)cm

Cut the polystyrene pieces to create an empty box.

In order to build the cooling system, cover the plystyrene box with aluminium sheets.

Then, on an aluminium plate, glue together the heat sinks and we wrap them up with other aluminium sheets

After putting the gel from the gel ice packs in-between the heat sinks, put the whole system created into the empty isolating box with the aluminum plate on the bottom of the polystyrene box. Put and press the second plate (with MUST be black colored; we used insulating tape to make it black) on top of the gel/heat sinks pack: the plate must close the hole of the empty polystyrene box and be at the same height as the polystyrene corners.

Put the base in a freezer and wait for it to reach -18°C.

In order to create the heating system, build a serpentine using the nickel-chrominium wire and glue it onto one felt square, leaving two strands threads longer than the plexiglass box itself, which will be connected to the current supply. Glue the second felt square on top of the first one: you must obtain a felt square containing a wire serpentine with long ends coming outside of the square itself (WARNING: the felt must be wool felt and not acrylic. Acrylic felt will light on fire when heated, while wool felt is totally fireproof and safe).

Use a hot glue gun to stick the five plexiglas squares in order to create a cube without one of its faces.

Using a heat-resistent glue, glue the heating component inside the box on the top of the chamber (the missing face must face downwards). Drill two tiny holes: one on the upper part of one of the side faces of the box and one one the same position on the opposite face. Make the wires of the resistance go through the holes and seal them using silicone.

Glue a polystyrene frame on the top of the box to insulate the heating system and to make the chamer stronger.

Create a wooden frame and glue the led strip into it, then surround the bottom part of the box with it.

After the base has reached the lowest temperature possible, place it on a plain surface.

Soak the felt with little isopropyl alcohol and put the box on top of the black plate of the cooling system.

Connect one of the heating system wires to ground and one to VIN (your wire must reach a temperature of 30°C maximum; depending on the lenght of the wire, the necessary voltage to reach this temperature will vary).

Turn the led strip on and every light in the room off: you must be in total darkness to see the particles.

After some minutes, an alcohol cloud will form over the black base and you should see stripes moving through it: if you do see them, congratulations, you just built your own dry ice free cloud chamber!

If you don't, you may have commited some of the following mistakes:

• the chamber isn't fully sealed
• the chamber and the base let air flow inside of the plexiglas box
• too much alcohol
• the resistance is too hot (alcohol MUST NOT boil)
• the base is not enough cool

After checking for this mistakes, you can try inserting some radiactive samples into the chamber (you should see weird clouds forming); some of the radioactive samples you could use are:

• a piece of a plate made with lead oxide
• a piece of thorium welding rod

You can also try inserting an incandescent wire: you should see electrons excaping from it as a big heavy cloud.