Spark Chambers

[Doodlebug]

Anyone ever built one, to show the trajectory of Cosmic rays?

They were used up until the 1960's so it's a vintage instrument/machine.

There is a great deal about them on the net from Universities and I have
obtained the bible on them, 'Bubble and Spark Chambers.' published in 1967.

I am toying with the idea to build but among other odd things required would
be a cylinder of near pure helium or argon bought from
the British Oxygen Company, although air has been used very
inefficiently.

[ppppenguin]

Would ordinary balloon gas helium be adequate? Readily available without cylinder rental, it's a lot cheaper than the good stuff.

[ppppenguin]

I've since found that balloon gas is typically 92% to 95% pure, the remainder being air.

Pure argon readily available as welding gas from many suppliers. For example:
https://www.gas-uk.co.uk/argon-pure-5-litre.html

Make sure you get pure argon, not one of the other welding mixes.

[Ed_Dinning]

Hi Gents, these bits of kit also go under the name of cloud chambers, so may be more hits with that descriptor.

Ed

[Doodlebug]

Thanks for suggestions.
Argon would require a higher working voltage than Helium but that would not be a problem.
As Helium is getting scarce now air is added to balloon Helium for that reason I believe.

[ppppenguin]

One source I read said that balloon helium was a result of wastage when filling medical kit etc with pure helium. Not sure I entirely believe it.

[Doodlebug]

What got me interested in Spark Chambers was this directional cosmic ray detector I am making.
Compared with a Spark Chamber it's easy pessy to make.

3 sets of rotatable Geiger Counter tubes, one shielded in each set with lead so that only Cosmic rays (or Muons)
trigger both detectors together and flash the green led and sing a note!
First of 3 now done.  
The electronics is just simple AND gates and one shot 555's., which is nearly finished.

[Doodlebug]

Oh dear. I've started it !!

Here's the 10 aluminium  discs with 20mm nylon spacers and nylon bolts.
Each alternate one to be connected for HV supply.
This is just a mock up to ensure everything fits together.    

Plates must be even to each other within about 1% so that's .2mm in this case.

Acrylic enclosure shown to have top and bottom plates attached, gas proof
with valves to supply argon and drain chamber of air.

My idea is for a circular shape, although research shows all old ones were
rectangular. I see nothing wrong with circular and its much easier to make and seal.
So fingers crossed.


Non pulsed HV to start with.(that's how the early ones worked).
Trouble with non pulsed HV is one gets spurious sparks in among the cosmic
trace.

If non pulsed is useless I shall have to spend, spend, spend
on scintillators, PMT's, amps and timing ccts. etc.

[Doodlebug]

As there have been over 100 hits on this topic, I shall carry on mapping my progress, just in  case some other idiot wishes to  build one too.  
It is old vintage sparking , so near original radio transmission topic too.

I hunted around for some small valves for gas inlet/air outlet.
As the whole rig is only 200mm dia x 250mm high I didn't
wish for large ones, so I bought two model railway engine valves. (60mm high)

Both mounted on the top acrylic plate where the argon gas is not inclined to escape
anyway as it is heavier than air.

The rig will be tilted to one side to fill the chamber, argon pushing the air up
and out.....I hope.   If a problem I shall have to  pipe the gas to the bottom of the chamber.

Now how to know when the chamber is full?
I shall use a lighted match burning at the exit valve and when it goes out
I should be nearly there !

Is there a better way?

[Doodlebug]

Whilst waiting for more parts I built the power supply on the acrylic base mounted under the base. (It will be covered for safety as the voltage will be up to 25kV.  )
Initially the supply will be from a 15kV 30m/a  NST I stripped from an old SGTC I once built.

Nothing unusual in the power supply, just series HV diodes in a bridge with smoothing caps and bleeders wound around a piece of acrylic tube.
I always use nylon bolts, super glued to bases etc  to make cheap stand off HV insulators.

I ran it up to full o/p to check the voltage and there were no bangs or flash overs.